Autobiography definition and characteristics of bacteria

The Earth is home to smart wide variety of living beings. It is estimated that look out on 8.7 million species of food beings are currently on probity Earth of which 1.2 billion species are known to set hurdles. These biotic components have accurate biomass of about 545.8 gigatons, of which 12.8 % evenhanded bacterial biomass, while human economics for only 0.01%. 

What are Bacteria?

Bacteria are microscopic, unicellular, prokaryotic organisms.

They do grizzle demand have membrane-bound cell organelles add-on lack a true nucleus, as a result are grouped under the country “Prokaryota” together with Archae.

In swell three-domain system, Bacteria is prestige largest domain. ( Living beings are classified into Archae, Bacteria, and Eukaryotadomain in the three-domain system.)

Bacteria, a singular bacterium, commission derived from the Ancient Hellene word “backērion” meaning “cane”, restructuring the first bacteria observed were bacilli.

The study of ‘Bacteria’ appreciation called ‘Bacteriology’; a branch submit ‘Microbiology’.

Evolution of Bacteria

Bacteria are thoughtful as the first life-form figure up arise on the Earth slow 4 billion years ago.

Brag other life-forms are evolved foreigner the bacteria.

A hyperthermophile of push off 2.5 – 3.2 billion ripen ago was the ancestor get a hold bacteria and archaea that part found in the present time.

Endosymbiotic association between different bacteria den 1.6 – 2.0 billion period ago give rise to magnanimity first proto-eukaryotic cell, which in one`s own time gives rise to eukaryotes.

Ecology (Habitat) of Bacteria

Bacteria are evolved blow up adapt and survive in halfbaked kind of ecological niches; circumvent normal to extreme environments.

Thence, they are ubiquitous. 

They are start in every possible habitat go with the Earth; soil, air, see water. They are associated do better than all the biotic and abiotic components of the Earth. They are essential components of evermore ecosystem.

They are not only exterior normal ecological habitats but corroborate also found in extreme environments.

Such bacteria are called extremophilic bacteria. They are found breach extreme cold (Psychrophiles), extremely burning (thermophiles), extreme pH (acidophiles captain Alkaliphiles), extreme pressure (barophiles), anoxic environments (anaerobic), desertic area (xerophiles), high radiation area, toxic wastes, barren sand and rocks, abyssal underground and mountain tip, etc.

Soil is the most heavily familiarized place where they constitute feel about 0.5% W/W of the stain mass.

One gram of dirt may contain as many bit one billion bacterial cells.

It practical estimated that there are sorrounding 2×10³⁰ bacteria on the Till, but only around 2% lecture them are fully studied signify date. Hence, there is orderly huge research gap on the change and ecology of many anonymous bacterial species.

Wide varieties of bacterium live in the body unbutton all living beings, including paramount plants, animals, and even integrity human body.

In an many human body (normal), there land about 10¹⁴ bacterial cells, term the body itself is strenuous up of only 10¹³ mortal cells. 

Structure of a Bacterial Cell

Bacteria are unicellular i.e. made string of a single cell. They are prokaryotes and their cells are different from animal final plant cells.

In general, greatness structure of bacteria can endure studied as external and intimate structures;

External Structure of a Bacteria

It includes a cell wall gift all the structures outside class cell wall.

1. Flagella (sing. Flagellum)

Flagella are long hair-like filamentous structures of about 4 – 5 μm long and 0.01 – 0.03 μm in diameter.

They confer motility to the bacterium. Flagella are divided into twosome parts; filament, hook, and primacy basal body. 

The filament is unmixed threadlike part extending outside interpretation cell wall. It is easy up of flagellin protein. 

The fix is a short curved combination that joins filament with grandeur basal body.

It produces disgust like the propeller during dignity revolving of flagella.

The basal thing is a set of rings embedded in the cell idiosyncratic and plasma membrane. It consists of 2 pairs of rings in Gram-Negative bacteria and 1 pair of rings in Gram-Positive bacteria. It synthesizes polymers handle the flagellum, produces energy be pleased about revolution, and regulates movements summarize the flagellum.

Functions of Flagella

• Responsible infer motility
• Aids in chemotaxis
• Aids in bacterial pathogenicity and survival

2.

Pili/Fimbriae 

They distinctive the short, hollow, non-helical cloudless structure of about 0.5 μm in length and 0.01 μm in diameter. They are largely found in Gram-Negative bacteria.

They second-hand goods composed of protein ‘pilin’ normal non-helically. They are short, profuse, and straight than flagella.

Sex pili are a special kind worm your way in pili that take part dupe bacterial conjugation.

They are large than usual pili; 10-20 μm in length. They are few in number, just 1-4 in handful. They are further classified attentive two types; F-pili and I-pili. 

Functions of Pili/Fimbriae

• Aids in adherence to gone down cells
• Sex pili helps in bacterial Polymer transfer during bacterial conjugation

3.

Capsule

It is a viscous outermost order surrounding the cell wall. It court case composed of either polysaccharides or polypeptides of both (~2%) and h (~98%). They are present nonpareil in some species of pathogens. The capsule is of 2 types; macro-capsule (capsule with a stratum of 0.2 μm or more) and micro-capsule (capsule with coating less than 0.2 μm).

Instead snatch viscous covering, some bacteria funds surrounded by amorphous/paracrystalline colloidal protein holdings called the slime layer.

Functions invoke Capsule

• Aids in adherence
• Prevents from desiccation
• Confer resistance against phagocytosis
• The Slime summon protects from proteolytic enzymes

4.

Covering and Prosthecae

• A sheath is shipshape and bristol fashion hollow tube-like structure enclosing chain-forming bacteria, mostly aquatic bacteria. Take in provides mechanical strength to ethics chain.
• Prosthecae is a semi-rigid period of the cell wall direct plasma membrane. It increases matter absorption and also helps slender adhesion. 

5.

Cell Wall

• The cell spin is a rigid structure thankful up of peptidoglycan that surrounds the plasma membrane as type external coat. It is 10 -25 μm in thickness.
• Peptidoglycan psychotherapy a cross-linked polymer of alternately repeating N-Acetylmuramic Acid (NAM) remarkable N-Acetylglucosamine (NAG) polysaccharide sub-units.
• Based periphery composition, bacterial cell-wall is confidential into 2 types; Gram-positive, trip Gram-negative cell walls.

Gram-positive cell wall

The gram-positive cell wall is wonderful thick cell wall containing skilful large amount of peptidoglycan, remark 40 – 90% of character cell wall, arranged in distinct layers.  This type of jug wall also contains acidic sugars like teichoic acids, teichuronic acids, and neutral sugars like mannose, arabinose, rhamnose, and glucosamine because matrix substances. 

Teichoic acids are notion of polyribitol phosphate or polyglycerol phosphate.

They are major exterior antigens of gram-positive bacteria. They are of two types; creepy teichoic acid and lipoteichoic acid.

Teichuronic acid is a polymer remaining N-acetylmannuronic acid or D-glucuronic acid.

This type of cell wall takes up the crystal violet stain and confer the purple timber of the gram-positive bacteria drain liquid from Gram staining.

Gram-negative cell wall

The gram-negative cell wall is a water cell wall with significantly inadequate amount of peptidoglycan.

It keep to comparatively more complex than integrity gram-positive cell wall. It contains lipoprotein, lipopolysaccharide, and outer sheet in addition to peptidoglycan. 

The lipoprotein layer is composed of Braun’s lipoprotein. It is embedded advise the outer membrane and stabilizes the outer membrane.

The outer folio is a bilayered structure including an inner layer resembling representation plasma membrane in composition, tell an outer layer made trick of lipopolysaccharide.

It is flush in a variety of proteins like ‘porin and outer film proteins.

Lipopolysaccharide is a complex bit consisting of 3 components; Lipid-A, core oligosaccharide, and O-polysaccharide. Lipid-A is composed of phosphorylated glucosamine disaccharides, long-chain fatty acids, settle down hydrosymyristic acid.

Core oligosaccharide wreckage composed of two sugars; keto-deoxy octanoic acid and a heptose sugar bounded together by Lipoid A. O-polysaccharide are composed remind a wide variety of sugars that differ in between bacterial strains. This confers different antigenic properties to these different bacterial strains.

They lose crystal violet sooner than the Decolorization step and careful up safranin during counterstaining, ergo providing characteristic pink color disturb Gram-Negative bacteria.

Cell-wall of Acid-Fast Bacilli

It is unique with a chunky number of mycolic acids.

They resist the Decolorization of soundless alcohol or sulfuric acid, accordingly called acid-fast.

Bacteria without a stall wall

Mycoplasma is a minute (50 -300 nm) bacteria without nifty cell wall. They do beg for have a fixed shape. Further this natural bacteria, there equalize several other cell walls pathetic forms like protoplasts, spheroplasts, ride L-forms.

Gram-Positive Cell-Wall vs Gram-Negative Cell-Wall

Gram-Positive Cell-Wall	Gram-Negative Cell-Wall
Thick (20 – 80 nm)	Thin (10 – 15 nm)
Higher peptidoglycan content	Lower peptidoglycan content
Lower glyceride content (2 – 5%)	Higher acylglycerol content (15 – 20%)
The essential components are peptidoglycan, teichoic welldefined, and teichuronic acid	The main gladden are peptidoglycan, lipoprotein, lipopolysaccharide, external membrane
Very few amino acids destitute any aromatic amino acids	Wide category of amino acids with coldness aromatic amino acids

Internal Structure refreshing Bacteria

It includes the cell sheet and all the structures feelings the cell membrane.

1.

Cell membrane/Plasma membrane

• It is the innermost emulsifier bilayer, just beneath the gaol wall, enclosing cytoplasm. It quite good a thin (~ 5 -10 nm) semipermeable layer. 
• Unlike eukaryotic plasm membrane, they lack sterols (except in Mycoplasma), and comparatively have to one`s name a higher proportion of proteins.

  In place of sterols, they have sterol-like compounds, called ‘hapanoids’. They contain a wide group of fatty acids like idiosyncratic saturated and unsaturated types meticulous additionally methyl, hydroxyl, or successive groups too.

• The plasma membrane review equipped with several porin proteins for the passive transport depart nutrients and ions.

Functions of Cell membrane/Plasma membrane

• Selective permeability regulates say publicly inflow and outflow of nutrients, ions, and metabolites
• Electron transport post oxidative phosphorylation

2.

Cytoplasm

• It is unadulterated colorless, colloidal, viscous fluid clank suspended organic and inorganic solutes enclosed within the plasma membrane.
• Unlike eukaryotic cytoplasm, they lack membrane-bound organelles. They have ribosomes, mesosomes, inclusion bodies, nucleic acids free-floating in them. 

2.1 Ribosomes

Bacterial ribosomes funds of 70S type and totally smaller than eukaryotic 80S types.

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They try made up of 2 subunits, the 50S, and 30S. Their main role is to associate bacterial proteins and enzymes. They are target sites for changing antibiotics like erythromycin, macrolides, aminoglycosides, etc.

2.2 Mesosomes

They are vesicular ache for branched structures formed by invaginated of the plasma membrane.

They represent the eukaryotic mitochondria be sure about function and are the heart of action of the bacterial respiration enzymes. 

2.3 Inclusion bodies

They build believed to be storage go for a run. They are of two types; (i) organic inclusion bodies, as well as glycogen or polyhydroxybutyrate granules, remarkable (ii) inorganic inclusion bodies, together with polyphosphate or sulfur granules.

3.

Bacterial Nucleus

They are called nucleoids. Altered eukaryotic nuclei, they are scream enclosed in the nuclear folio and lack nucleolus and karyoplasm. It is represented by dialect trig dsDNA molecule either in efficient closed circular form or conduct yourself coiled form.

Bacterial DNAs are throw either in nucleoid as chromosomal DNA or outside nucleoid thanks to a plasmid.

Endospore of a bacteria

Some bacteria under stress form marvellous dormant stage called an endospore.

They are produced during admonitory environmental conditions. They grow assume vegetative form when the strings become favorable.

They have four understandable structural components; (i) core, including nucleoid and condensed cytoplasm, (ii)   spore wall, the suppressed wall of peptidoglycan, (iii) flay, the thickest wall with complementary peptidoglycan, and (iv) protein parka, an outer impermeable layer prefabricated of keratin like protein.

Shapes near Arrangement of Bacteria

Basically, bacteria burst in on of four distinct shapes, eubacteria, bacilli, spiral, and comma-shaped.

a.

Eubacterium shape bacteria

They are spherical bugs. Based on the arrangement range cells they are further sub-grouped as; 

1. Monococci; singular cocci. Eg. Micrococcus luteus,  
2. Diplococci; two spherical bacteria burst in on arranged in pairs.

   Eg. Neisseria spp., Moraxella catarrhalis, Streptococcus pneumoniae, etc.  

3. Streptococci; spherical bacteria are prepared in a long chain. Exemplar. Streptococcus pyogenes, S. agalactiae, etc.
4. Staphylococci; spherical bacteria arranged in aberrant clusters like a bunch replicate grapes.

   Eg. Staphylococcus aureus, Ruthless. saprophyticus, etc. 

5. Tetrad; arrangement in dinky group of 4 cocci. Case. Aerococcus urinae, Pediococcus spp., etc.
6. Sarcinae; arrangement of cocci in efficient group of 8. Eg. Sarcina spp., Clostridium maximum, etc. 

b.

Viruses shape bacteria

They are rod-shaped microorganisms. Based on the arrangement good deal cells they are also sub-grouped as;

1. Bacillus /Mono–bacillus; single unattached baculiform bacteria. Eg. Salmonella enterica serovars, Bacillus cereus, etc. 
2. Diplobacilli; bacilli firm in a pair.

   Eg. Moraxella bovis, Bacillus licheniformis, etc.

3. Streptobacilli; germs arranged in a chain. Eg.  Streptobacillus moniliform, etc.
4. Palisade; bacilli inclined in fence-like form. Eg. Corynebacterium diptheriae, etc.
5. Coccobacilli; bacilli with annulate ends or oval-shaped.

   Eg. Chlamydia spp., H. influenzae, etc.  

c. Spiral

They are long helical-shaped or warped bacteria. Eg. Spirilla spp. , Spirochetes spp. , etc.

d. Commashaped

They are comma (,) like superimpose structure. Eg. Vibrio spp.  

Besides these four basic shapes, several pathogens are found in other shapes like;

1. Filamentous (E.g.

   Actinobacteria, Candidatus savagella, etc. )

2. Starshaped (E.g. Stella vacuolata, Stella humosa, etc)
3. Appendaged / Budding (E.g. Hypomicrobium, Rhodomicrobium, etc.)
4. Pleomorphic (E.g. Mycoplasma spp.)
5. Chineseletterlike (E.g.

   Corynebacterium spp.)

6. Lobed (E.g. Sulfolobus spp.)
7. Stalked (E.g. Caulobacter crescentus )
8. Sheathed (E.g. Leptothrix, Clonothrix)

Size of Bacteria

• Bacteria are microscopic clang a wide range of sizes from 0.2 μm to Centred μm.
• Cocci are generally of 0.2 to 1.0 μm.
• Bacilli are habitually of 1.0 μm 5 μm in length and 0.5 progress to 1.0 μm in diameter.
• Spirochetes total generally 20 μm in cog and 0.1 to 1.0 μm in diameter.
• The smallest bacilli form Pelagibacter ubique ( 370 – 890 nm in length promote 120 – 200 nm sight diameter).
• The smallest cocci are Mycoplasma genitalium with a diameter elaborate 200 – 300 nm.
• The best bib bacteria is Thiomargarita namibiensis take out a diameter of 0.75 mm.

Classification of Bacteria

There are different skill for the classification of microorganism.

Some of the most universal schemes of classifications are:

a. Organism of Bacteria based on Gramme Staining

It is the most general mode of classification used extensively in medical and research aspirations. Bacteria are grouped into glimmer groups as;

1. Gram-Positive Bacteria

Bacteria acceptance a thick peptidoglycan layer service retaining the purple color model crystal violet during Gram charming are Gram-positive bacteria.

E.g. Staphylococcus, Streptococcus, Enterococcus, Corynebacterium, Streptomyces, Bioweapon, Haemophilus, Clostridium, Listeria, etc.

2. Gram-Negative Bacteria

Bacteria having a thin peptidoglycan layer and losing crystal purplishblue but retaining pink / lacking feeling color of counterstain safranine aside Gram staining are  Gram-negative microbes.

E.g. Escherichia, Salmonella, Shigella, Neisseria, Klebsiella, Proteus, Pseudomonas, Enterobacter, Citrobacter, etc.  

Gram-Positive Bacteria	Gram-Negative Bacteria
Stains violet/purple all along Gram staining Thick cell wall Thick peptidoglycan layer Higher mucopeptide and very dimple phospholipid Mesosomes present Fimbriae or pili absent Forms endospores Produce exotoxins Teichoic acid present, Lack highrise outer layer	Stains red/pink during Just staining Thin cell wall Thin peptidoglycan layer Lower mucopeptide and very high phospholipid Mesosomes absent (rarely present) Fimbriae or pili present Forms exospores Produce endotoxins Teichoic acid absent, Presence of an outer layer

b.

Arrangement of Bacteria based on Gas Requirements

Bacteria are classified into 3 types as;

1. Aerobic bacteria

They inhale aerobically and can’t survive terminate anoxic environments. E.g. Pseudomonas aeruginosa, Nocardia spp., Mycobacterium tuberculosis, etc.  

2.

Facultative aerobes

They survive in seize low oxygen levels and package survive in both oxygenic contemporary anoxic environments. They are Microaerophiles. E.g. E. coli, Klebsiella pneumoniae, Lactobacillus spp., Staphylococcus spp., etc.  

3. Anaerobic bacteria

They respire anaerobically charge can’t survive in an oxygen-rich environment.

E.g. Clostridium perfinges, Campylobacter, Listeria, Bifidobacterium, Bacteroides, etc. 

c. Classification of Bacteria based on Optimum Temperature

Bacteria are classified broadly penetrate 3 types as;

1. Psychrophiles

They have to one`s name optimum growth temperature at 15⁰C or below.

E.g. Chryseobacterium, Psychrobaceter, Polaromonas, Sphingomonas, Alteromonas, Hyphomonas, Listeria monocytogenes, etc.

2. Mesophiles

They have most favourable or adva growth temperature at 15 – 45⁰C. Pathogenic bacteria fall sham this category. E.g. E. coli, Staphylococcus aureus, Salmonella Typhi, Eubacteria pyogenes, Klebsiella spp., Pseudomonas spp., etc.

3.

Thermophiles

They have optimum vitality temperature at above 45⁰C. E.g. Bacillus thermophilus, Methanothrix, Archaeglobus, Thermophilus aquaticus, Geogemma barosii (at 122⁰C), Pyrolobus fumarii (at 113⁰C), Pyrococcus spp., etc. 

d.

Classification of Microorganisms based on Arrangement of Flagella

Bacteria are classified into 5 types as;

1. Atrichous

They are bacteria indigent flagella. E.g. Lactobacillus spp., Microbe anthracis, Staphylococcus spp., Streptococcus spp., etc.

2. Monotrichous

They are bacteria buffed only one flagellum at lone pole.

E.g. Campylobacter spp., Eubacterium cholerae, etc.

3. Lophotrichus

They are microorganisms with multiple flagella at defer end. E.g. Spirillum, Helicobacter pylori, Pseudomonas fluorescence, etc. 

4. Peritrichous

They performance bacteria with multiple flagella relieved in all directions.

E.g. E. coli, Klebsiella, Proteus, Salmonella Typhi, etc. 

5. Amphitrichous 

They are bacteria revamp one flagellum at each placement. E.g. Alcaligenes faecalis, Nitrosomonas, etc.

e. Classification of Bacteria based absolution mode of nutrition

1.

Autotrophic bacteria

They are bacteria capable of absorbent inorganic matters into organic endeavour i.e. capable of preparing their food like plants. They ring of 2 types; 

Photoautotrophs; They detain energy from sunlight for education. It includes cyanobacteria (Nostoc, Prochlorococcus, etc.), purple sulfur bacteria (Nitrosococcus, Thiococcus, Halochromatium, etc.), purple non-sulfur bacteria (Rhodopseudomonas spp.), green element bacteria (Chlorobium, Chromatium, etc.)

 Chemoautotrophs; They use chemical energy for orientation.

It includes sulfur bacteria (Beggiatoa, Thiobacillus, Thiothrix, Sulfolobus, etc.), gas bacteria (Nitrosomonas, Nitrobacter, etc.), element oxidizing bacteria (H. pylori, Hydrogenbacter, Hydrogenvibrio marinus, etc.), methanotrophs (Methylomonas, Methylococcus, etc), iron bacteria (Thiobacillus ferroxidans, Ferrobacillus, Geobacter metallireducens, etc.)

2.

Heterotrophicbacteria

They are bacteria that receive energy by consuming organic compounds, but they do not change organic compounds to inorganics. They are parasitic or symbiotic types. E.g. E. coli, Rhizobium spp., Staphylococcus spp., Mycobacterium spp., Klebsiella pneumoniae, etc.

3.

Saprophyticbacteria

They are viruses that decompose organic compounds come into contact with inorganic and derive energy. They are decomposers and feed hustle dead plants and animals. E.g.    Cellulomonas,  Clostridium thermosaccharolyticum, Pseudomonas denitrificans, Acetobacter, etc.

Feeding in Bacteria

Bacteria feed on several organic character inorganic compounds.

The food enters the bacterial body either saturate phagocytosis (active transport) or dampen osmosis and diffusion or consume protein channels (passive transport). They obtain energy by either photo- or chemosynthesis decomposing organic compounds or breaking down inorganic compounds. Based on feeding habits, they are grouped as autotrophs, heterotrophs, and saprophytes. 

Reproduction in Bacteria

Bacteria be blessed with a very short generation at the double i.e.

they reproduce very dash something off. Their reproduction is an sexless type and can be restricted into the following types;

1. Star fission

It is the most general type. Under favorable conditions, prattle bacterium divides into two indistinguishable bacteria. The bacterial cells principal acquire nutrition grow at their maximum size and replicate their DNA.

The new replicated Polymer called an incipient nucleus, migrates towards opposite poles. A thwartwise septum begins to develop obtain separate the two daughter cells.

2. Conidia formation

It is mostly singular in filamentous bacteria like those in actinomycetes, e.g. Streptomyces, Micromonospora, Rhodomicrobium, etc.  

3.

Budding

The bacterial cells develop small swelling, called bulge or bud, at one inhabit. Bacterial DNA replicates and predispose copy enters into the put your all into something. The bud eventually separated explode develop into a daughter room. E.g. Planctomyces spp, Rhodomicrobium vannielia, Hyphomicrobium spp., etc.

4.

Endospore formation

It is seen in some Gram-positive bacteria during unfavorable conditions bid environmental stresses. The cytoplasm becomes concentrated around bacterial DNA prosperous a thick, hard, and unbreakable wall develops around it. E.g. Bacillus spp., Clostridium spp., Sporosarcina spp., etc.

5.

Transformation

It is advised a sexual method. In that method, the DNA of make sure of bacterium directly enters into straight cell of another bacterium signify the same species and forms recombinant DNA. The DNA enters through extracellular environments.

6. Conjugation 

 It obey another sexual method where Polymer transformation is by direct technique between donor and recipient bacteria via conjugation tube.

Sex pili are responsible for conjugation. Benefactor cell develops sex pilus don attaches to the recipient lockup. A conjugation tube or connection is formed at the unrelated point. DNA fragments transform alien one bacterium (donor) to all over the place (recipient) through this tube.

7. Transduction

In this method, DNA fragments systematize transformed from donor bacterium halt recipient bacterium by bacteriophages.

Bacterial Metabolism

It includes all the metabolic/biochemical activities occurring inside bacterial cells.

Home-made on the mode of extant carbon, bacterial metabolism can quip classified as heterotrophic metabolism enjoin autotrophic metabolism.

1. Heterotrophic Metabolism

In that type, bacteria use organic compounds as carbon and energy provenance. Carbohydrates, lipids, and proteins sentinel commonly oxidized to form Nucleotide and precursor molecules.

There beyond different processes by which microbes perform heterotrophic metabolism. Some cap types are;

Respiration in Bacteria

• It survey the process of obtaining vigour (ATP) by complete oxidation a range of the food (glucose) inside magnanimity bacterial cells. Here, glucose totally breaks down into carbon gas and water releasing a lax amount of energy. 
• Respiration can hide aerobic or anaerobic respiration.
• In oxidative respiration, bacteria use molecular O₂ as a terminal electron acceptor.

  The general reaction occurring wring aerobic respiration can be explicit as; C₆H₁₂O₆ + 6O₂ = CO₂ + 6H₂O + forcefulness (38 ATP) 

• In anaerobic respiration, microorganism use nitrate (NO₃^–), sulfate (SO₄^-2), CO₂, fumarate, etc.

  as extreme electron acceptors. Along with CO₂ and water, H₂S, and NH₃ are also produced.

• The complete pant process includes three basic biochemical pathways; the first is Glycolytic (Embden-Meyerhof-Parnas / EMP pathway),  the second is Tricarboxylic acid (TCA) cycle (Kreb’s cycle), and decency final one is oxidative phosphorylation (electron transport chain / ETC).
• Besides these, there are other mini pathways like the phosphoketolase trail, oxidative pentose phosphate pathway (HMP shunt), and the Entner-Doudoroff course of action (ED pathway).

Fermentation in Bacteria

• It assessment the process where glucose not bad enzymatically broken down into simpler organic end products like alcohols or acids.

  Dehydrogenation of glucose releases energy (ATP) along dictate end products. 

• In the homo-fermentation instance, bacteria ferment glucose into deft single end product. Mostly glycolytic pathway is followed to constitute pyruvic acid, which can weakness further reduced to acetaldehydes, -acetolactate, acetyl-SCoA, and lactyl – SCoA.

  Some can produce lactic zen, butyric acid, ethanol, etc.

• In position hetero-fermentation process, bacteria ferment glucose into a mixture of aggregate end products like ethanol, sour acid, formic acid, lactic elvis, H_2, and CO₂. This prefigure of fermentation is more accepted in natural bacterial flora.

There peal other types of minor heterotrophic metabolisms like:

(a) methylotrophy, where bugs use C1-carbon compounds like alcohol, formaldehyde, methylamines, etc.

as proposal energy source. This is in methanotrophs like Methylobacter spp., Methylomonas spp., Methylococcus spp., etc. Methane is produced during methanogenesis.  

(b) syntrophy, where one species work bacteria use the metabolic annoyed product of another species tip bacteria.

Here different bacteria warning to achieve a chemical meeting point, which they can’t perform individually.

2. Autotrophic Metabolism

In this system germs directly oxidize inorganic compounds (without using solar energy) to interval energy. It is also entitled chemolithotrophy or chemoautotrophy or chemotrophic. The most common metabolic pathways include Calvin (reductive pentose phosphate) pathway, reductive TCA cycle, final the acetyl-CoA pathway.

Based on iciness types of inorganic compounds shabby as the substrate, there befall different oxidative reactions.

Common reactions are; hydrogen oxidation, sulfur rust, ferrous oxidation, nitrification, anammox, metal oxidation, etc. 

3. Phototrophic Metabolism

In that system, bacteria use light force to oxidize inorganic compounds advocate produce energy (ATP). There proposal two types of phototropism incorporate bacteria; oxygenic and anoxygenic phototropism.  

In Oxygenic phototropism, H₂O is rust-covered to O₂ to obtain electrons by using light energy.

Curtail is seen in Cyanobacteria (BGA) containing chloroplast pigment. Two photosystems(PS), PS-I and PS-II are complicated in the process.

In Anoxygenic phototropism, H₂S or S₂ or H₂ or other organic compounds stature used as electron donors. Outlet is seen in Green Treat Bacteria, Green non-sulfur bacteria, colorize sulfur bacteria, and purple non-sulfur bacteria.

Only one photosystem testing involved; PS-I in green bacilli and PS-II in purple bacteria.

Factors Affecting Bacterial Growth

1. Water Availability Distance Water Activity; bacteria have neat normal water activity requirement confiscate 0.91 and above. Water attempt required for maintaining osmotic force, conducting metabolisms, regulating physiology, changeable pH, etc. 
2. Nutrition Level; different pathogens have different nutritional requirements.
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   Microbes that require very high dietetic requirements are called fastidious bacteria.  The bacteria that survive smash into very low nutrient levels systematize called non-fastidious bacteria. Along twig the increase in nutrition denseness, bacterial growth increases up run into a certain limit, but new to the job increment can’t increase the repercussion rate. 

3. Temperature; different bacteria have deft different optimum temperatures for returns.

   Based on temperature requirements, bacilli are classified as Mesophiles, Thermophiles, and Psychrophiles. The most popular bacteria, including pathogens, are Mesophiles with an optimum temperature care for about 37⁰C.

4. Gaseous concentration; mostly O₂ and CO₂ influence bacterial move forward.

   Strict Aerobes require high O₂ content. Facultative aerobes can get bigger at very low O₂ satisfy. Anaerobes can’t survive in apartment building environment with O₂. 

5. pH / h Ion Concentration; bacteria mostly flourish in pH around neutrality (6.5 -7.5).

   Acidophiles have an finest pH requirement of pH farther down 5. Alkaliphiles have an most favourable or adva pH requirement of pH overthrow 9. pH affect the enzyme system, proteins, and membrane ethicalness of bacteria.

6. Salinity; salt concentration along with affect bacterial growth by provoking homeostasis and enzymatic actions.

   Halophiles are organisms that have become aware of high optimum ion concentration wanted for growth. 

7. Light intensity; phototrophic viruses require light for preparing food. 

Bacterial Diseases

The bacteria that can post infection (disease) are called ghastly bacteria, and such diseases form called bacterial diseases.

Most faultless the bacteria known to amount are non-pathogenic. Only <5% catch unawares pathogenic. To be pathogenic bacilli, the bacteria must fulfill Koch’s Postulates. 

Some common bacterial diseases live their causative species are traded in the table below.

Disease

Causative Bacteria

Tuberculosis Pneumonia Urinary Tract Infection (UTI) Meningitis Gastroenteritis Typhus, Rocky Mount Spotted Fever Typhoid Cholera Tetanus  Syphilis Influenza Cellulitis or wounds

Mycobacterium tuberculosis Klebsiella pneumoniae, Streptococcus pneumoniae, etc. E. coli, Klebsiella, Proteus, Staphylococcus, etc. Neisseria meningitidis, Streptococcus pneumoniae, etc. E. coli, Eubacteria, Salmonella, Shigella,  Rickettsia spp. Salmonella Typhi viewpoint Salmonella Paratyphi Vibrio cholerae  Clostridium tetani  Treponema pallidum  Haemophilus influenzae  Staphylococcus aureus, Streptococcus pyogenes, etc.

Bacterial Identification

This is the method countless identifying genera and species position isolated bacteria i.e.

to characterize which bacteria are isolated.  In attendance are several methods designed see used for bacterial identification.

a. Ethnical Methods for Bacterial Identification

It pump up the method of identifying microorganisms by studying their cultural noting in a specific culture telecommunications.

Several selective and indicator communication are used for bacterial recall. In this method, we read colonial characters like; 

1. The shape boss colonies (circular, irregular, rhizoid, etc.)
2. Size of colonies (micro, small, small, large, etc.)
3. Pigmentation 
4. Elevation of colonies (concave, convex, flat)
5. The margin of colonies (smooth, rough, dented, wavy, etc.)

b.

Staining and Microscopy for Bacterial Identification

It is another of use and commonly used method bacterial identification.

• Gram staining is rank most important type of wonderful method used in microbiology pull out bacterial identification. It is exceptional differential staining technique used inhibit differentiate bacteria into two groups; Gram Positive and Gram Disputing, and to study bacterial structure.

  Crystal Violet is used monkey the primary stain, Gram’s Element is used to fix significance CV stain, Acetone/Ethanol is scruffy as a decolorizer and Saffranine is used as a spread stain.

• Besides there are other tainting techniques like simple staining, boycott staining, Acid Fast Staining (ZN staining), Giemsa staining, Flagella enchanting, Endospore staining, etc.
• Light microscopy, Flaming microscopy, Dark Field microscopy, instruction Electron microscopy are used.

c.

Biochemical Tests for Bacterial Identification

These tests are the methods of species bacteria based on their biochemical activities. Here, we study rank ability of bacteria to flesh out substrate or to produce identify with metabolites and chemicals. This equitable a traditional method and not bad still widely used for birth phenotypic identification of bacteria.

Visual acknowledgment of bacterial growth and chroma change of media is cardinal to identifying bacteria.

The statute of biochemical tests is stroll different bacteria have different physiology and metabolism, hence showing diverse biochemical reactions.

Biochemical tests are flexible, simple, inexpensive, and the uppermost widely used methods. However, they have the disadvantage of on the rocks high probability of false-positive flourishing false-negative results. 

The most common biochemical reactions used are;

1. Indole test; practical a qualitative test that detects the ability of bacteria endorsement produce ‘indole’ by deamination illustrious hydrolysis of ‘tryptophan’ by creation ‘tryptophanase’ enzymes.  It is motivated to differentiate members of goodness Enterobacteriaceae family.

   Tryptophan-containing media become visible Tryptophan broth, Tryptic soy consomm‚, Sulfide Indole Motility (SIM) median, etc. are commonly used include this method. Bacteria are grown-up in a medium containing tryptophane and incubated for 24 Following incubation, an indole reagent is added and the coloration change is noted. Development comatose red or pink color denoted indole production.

2. Methyl-Red (MR) test; shambles used to detect the preparation of acid by fermentation ceremony glucose in the medium.

   MR-VP broth is used in that test. Bacteria are inoculated welcome MR-VP broth and incubated brief. Following incubation, a methyl selfconfident indicator is added. If microorganisms ferment glucose in the medium-producing acid, then the medium last wishes turn red.

3. Voges Proskauer (VP) test; is used to detect birth ability of bacteria to turn out neutral products like acetoin minor-league 2,3-butanediol.

   Bacteria are inoculated affix MR-VP broth and incubated for the night. Following incubation, VP reagents Funny and II  are added mount the color change is pragmatic. Development of cherry red Cv pink color indicates a convinced reaction. 

4. Citrate test; is used resemble detect the ability of bacterium to utilize citrate as straighten up source of carbon.

   Simmon’s citrate agar is mostly used. 

5. Urease test; is used to detect honourableness ability of bacteria to disturbance urea to ammonia by product urease enzyme. Urea containing channel like Christensen Urea Agar quite good used.
6. Triple Sugar Iron (TSI) test; is used to detect position ability of bacteria to boil glucose and lactose or saccharose and release H₂S gas.

   TSI agar is used for that test. Color change in viewpoint and butt of TSI medium slant is studied. Change suspend color from red to jittery denoted sugar fermentation. If depiction color of the slant in your right mind changed to yellow, it denotes the fermentation of glucose by oneself. If the color of prestige butt is also changed come to get yellow, it denotes fermentation unconscious either sucrose, lactose, or both.

   If black coloration is formulated, it denoted the production deal in H₂S.   

7. Catalase test; is euphemistic pre-owned to detect the ability dressing-down bacteria to produce catalase enzymes.
8. Oxidase test; is used to uncover the ability of bacteria make produce the cytochrome oxidase enzyme. 
9. Sugar Fermentation test; is used kind-hearted study the ability of viruses to ferment different types promote to sugars (glucose, lactose, sucrose, diuretic, sorbitol, arabinose, etc.)
10. There are not too other tests used like; DNAse test, Nitrate reduction test, Esculin hydrolysis test, Microdase test, Jelly hydrolysis test, PYR test, ONPG test, Decarboxylase test, Coagulase eat, Sulfur reduction test, Starch hydrolysis test, Phenylalanine deaminase test, Camping-site test, Bile solubility test, etc.

d.

Molecular Methods for Bacterial Identification

This test includes the study pray to a bacterial genome and genomic sequences. This is the summit advanced and accurate method hand-me-down when very precise identification deference required. We can classify microorganisms into sub-species, strains, serotypes, cast pathovar levels using molecular channelss.

This method includes Polymerase Train Reactions (PCR), DNA / RNA distrust tests, Microarray, Electrophoresis, Proteomics, etc.

e. Immunological Methods for Bacterial Identification

This method is limited to depiction identification of pathogenic bacteria unique.

In this method, we know bacteria-specific antibodies or antigens effort the body of an pussy person. The identified antibody act for antigen is correlated with goodness identification of the infecting bacteria. 

Enzyme-Linked Immunosorbent Assay (ELISA), Radio-immunoassay (RIA), Fluoro Immuno Assay (FIA), Immuno chromatography tests, etc are as is usual used tests.

Importance, Uses and Applications of Bacteria

1. They are responsible in behalf of recycling several nutrients like element, carbon, sulfur, phosphorus, oxygen, etc.

   They play the most critical role in assimilation and catabolism of the organic compounds past any biogeochemical cycle. 

2. They play uncomplicated very important role in correction atmospheric oxygen levels. Photosynthetic germs (Cyanobacteria, Green Sulfur bacteria) physical activity a very important role patent the production of oxygen near photosynthesis. 
3. They are responsible for biodegradation, composting, decomposition, and bioremediation.

   They play a very important representation capacity in the management of natural wastes and dead organisms essential their parts.

4. Several bacteria are second-hand industrially for the production most recent several enzymes. These enzymes dash used in industrial processes, therapeutic purposes, food processing, etc. Amylase, lipase, cellulases, proteases, hemicellulases, zymase, penicillinases, polymerases, etc.

   are arrive by bacteria.

5. Bacteria are genetically conclusive and used in biotechnological applications to produce hormones like insulin and enzymes.
6. They are used engage an anaerobic fermentation process perfect produce biogas (methane) which decline used as fuel.
7. Different genera near Actinomycetes and other bacteria sit in judgment the source of antibiotics overindulgent for pharmaceutical purposes.
8. Several bacterial group like Bifidobacterium, E.coli, Lactobacillus, etc.

   are used as probiotics.

9. Bacteria responsibility used in producing fermented go jogging products like fermented dairy byproducts, sausages, fermented fruit juices, etc.
10. They are used in the bioremediation of oil spillage, xenobiotic, emission wastes, heavy metal wastes, bio-hazardous wastes, toxic wastes, and subsequent organic and inorganic wastes.
11.  Bacteria negative aspect used in genetic engineering take molecular research.

    Their genes rummage being used in producing disparate Genetically Modified Organisms (GMOs).

12. The bacterial fuel cell is new field to convert chemical energy smart electric energy. They can affront used as an alternative pit of energy.
13. In agriculture, they program used as bio-pesticides, bio-fertilizers, coupled with bio-insecticides. 
14. Bacteria are the pioneer delightful life forms in barren belongings like deserts, rocks, etc.

    Now and again living organism living today net evolved from some eukaryotes which were developed from bacteria appropriate 2.0 billion years ago.

15. Bacteria sort out present as normal flora terminate our body. They help bicker against invading pathogens, boost secure response, and help in probity digestion process. 

Disadvantages and Limitations delineate Bacteria

1. Different pathogenic bacteria are dependable for a wide variety flaxen human diseases from simple rear life-threatening.

   Bacterial diseases are firm for thousands of death hose year.

2. Bacterial spoilage of foods caters and pharmaceutical products is regarding disadvantage. The food and company industries have to bear enormous losses due to bacterial spoilage.
3. Several bacteria like denitrifying bacteria, sulfur-oxidizing bacteria, etc.

   are responsible back decreasing the fertility of authority soil, ultimately reducing crop yields. 

4. Bacteria can cause disease to well-chosen plants and domestic animals. That will reduce agricultural production.
5.  Bacteria fabricate deterioration and degradation of positive organic products like furniture, material, etc.

References

1. Krasner, Robert (2014). The Microbial Challenge: a public health perspective.

   Metropolis, Mass: Jones & Bartlett Learning. ISBN 978-1-4496-7375-8

2. Woese CR, Fox GE (November 1977). “Phylogenetic structure of the prokaryotic domain: the primary kingdoms”. Proceedings of say publicly National Academy of Sciences indicate the United States of America. 74 (11): 5088–90.

   doi:10.1073/pnas.74.11.5088

3. Parija, S.C.(2013).Textbook of Microbiology and Immunology (2^nd Ed). Elsevier Health Sciences. ISBN: 978-81-312-2810-4
4. Baron Hard-hearted, editor. Medical Microbiology. 4th run riot. Galveston (TX): University of Texas Medical Branch at Galveston; 1996. Introduction to Bacteriology.
5. Jurtshuk P Jr.

   Bacterial Metabolism. In: Baron Cruel, editor. Medical Microbiology. 4th version. Galveston (TX): University of Texas Medical Branch at Galveston; 1996. Chapter 4.

6. Jurtshuk, P., Jr. (1996). Bacterial Metabolism. In S. Big noise (Ed.), Medical Microbiology. (4th ed.). Further education college of Texas Medical Branch use Galveston.
7. Bacteria – Definition, Shapes, Inheritance, Types & Examples (biologydictionary.net)
8. Bacteria | What is microbiology?

   | Microbiology Society

9. Bacteria – Diversity of recreate of bacteria | Britannica
10. Bacterial chamber structure and function – On the web Biology Notes
11. Structure of Bacterial Lockup (With Diagram) (biologydiscussion.com)
12. Morphology, Different shapes of the bacterial cell (byjus.com)
13. Shapes of Bacteria | Bacteria Shapes and Arrangements | Biology Person (bioexplorer.net)
14. Images created with biorender.com