Classification of Bacteria microbiology

Classification of Bacteria

Presented by:Vinay Kumar Dhiman (F-2016-45-M)

Principles of Microbiology MICRO-501

Bergey’s Manual of Systematic Bacteriology

Published in 1984 Particularly based on phylogenetic

analysisPhylogenetic analysis is

basically depends on Sequencing of rRNA, DNA

and proteins

1.Archaea

2.Proteobacteria

3.Low G+C Gram(+) bacteria

4.High G+C Gram(+) bacteria5.Spirochaetes, Fusobacteria,

Plancomycetes,Bacteroidetes & Fibrobacters

The second edition was divided into 5 volumes

Vol 1. Archaea, cyanobacteria, phototrophs and deeply branched genera This volume has 3 important groups out of which,

one is in different domain(Domain - Archaea) 1. Archaea

Four important sections are present in the archaea. a. Hyperthermophiles - Ex. Thermococcus,

Sulfolobus, Thermosphaerab. Methanogens - Ex. Methanobacterium, Methanococcus, Methanosarcinac. Halobacteria - Ex. Halobacterium, Halococcus, Natronomonasd. Thermoplasma - Ex. Thermoplasma

2. Cyanobacteria Filamentous, oxygenic photosynthetic bacteria.

They have special cells called heterocyst in which nitrogenase enzyme is present. The nitrogenase enzyme is responsible for fixing atmospheric N2 into ammonia.Cyanbobacteria exist in three forms

Single celled - Chrococcus, Gleotheca, Gleocapsa Filamentous non-heterocystous - Oscillatoria,

Lyngbya Filamentous heterocystous - Anabaena, Nostoc,

Tolypothrix

3. Anoxygenic phototrophs Single celled, sulphur required bacteria. They use

H2S as electrondonor. Ex. Green sulphur bacterium Chlorobium

Characteristics of Major Groups of Gram-Negative Photosynthetic Bacteria Anoxygenic Phototrophic Bacteria Oxygenic

Photosynthetic Bacteria

Characteristic

Green Sulfur Green Nonsulfur

Purple Sulfur Purple NonSulfur

Aerobic Anoxygenic Photrophic

Cyanobacteria

Pigments Bacteriochlorophylls a,c,d,e

Bacteriochlorophylls a,c

Bacteriochlorophylls a,b



Chlorophyll a,phycobiliproteins

Morphology of photosynthetic membranes

PS partly in chlorosomes(independent of plasma membrane

Chlorosomes only under anaerobic conditions

PS present in lamellar membrane complexes with continuous plasma membrane

PS present in lamellar membrane complexes with continuous plasma membrane

Few Thylakoid membranes lined with phycobilisomes

Photosynthetic e- donors

H2,H2S,S0 Photoheterotrophic=sugars,AA,organic acids;Photoautotrophic= H2S,H2

H2,H2S,S0 Organic molecules,also S compounds,H2

Photoheterotrophic=sugars,AA, organic acids

Sulfur deposition

Outside of the cell

Inside of cell Sometimes outside of the cell

Nature of photosynthesis

Anoxygenic Anoxygenic Anoxygenic Anoxygenic Anoxygenic Oxygenic/facultative anoxygenic

Motility Non Motile Gliding Motile-polar flagella,peritrichous

Motile-polarflagella;non motile-gas vesicles

Some are motile-few polar flagella

Non motile or gliding

The Deinococci , Mollicutes, and Non-proteobacterial Gram-Negative Bacteria

Deinococci The phylum Deinococcus-Thermus contains the orders Deinococcales. Ribosomal RNA sequences reveals- Deinococcus, closely relates

with Thermus. Shape:- spherical or rod, in pairs or tetrads. Aerobic and catalase positive(catalase enzyme prevent cell from

oxidative damage by reactive oxygen species) Non motile. Most are mesophilic. Cell wall

Peptidoglycan:- L- ornithine present. Plasma membrane- Palmitoleic acid present.

S-layer present- resist extraordinarily oxidative stress, desiccation & radiation.

Deinococcus radiodurans Is an extremophilic bacterium. Natural habitat is still unknown because of the vast

amount of differing environments that it has been found. Capacity to repair massive DNA damage efficiently and

accurately.Gram positive, red pigmented, non motile.Most radiation-resistant organism known.Polyextremophile :-Can survive cold, dehydration, vacuum,

and acids.Cell wall:-5 layers with a total thickness of 150 nm & is

unique.

Spherical tetrad shape of D. radiodurans.

D. radiodurans has been isolated include meat, sewage, filtered air, animal feces, soil, weathered granite in Antarctica, and room dust.

It grow best in 30°C & cease at 4°C. D. radiodurans is an obligatory heterotroph. Its main source of energy production uses the vacuolar

type of proton ATP synthase. D. radiodurans is Gram positive, the cell envelope is

resembles of Gram-negative bacteria due to its multilayered structure and lipid composition.

D. radiodurans can withstand 5,000 Gy with no loss of viability, making it the most radiation resistant organism known.

RecA-dependent homologous recombination DNA repair plays a vital role in the genome restitution of this organism.

Mollicutes Bacteria lack walls (peptidoglycan precursors

absent). Called as Mycoplasmas(smallest bacteria):-

small genomes,simplifed metabolic pathways. Only plasma membrane present. Shape:-Pleomorphic,appears spherical or pear-

shaped to slender branched,helical. Mostly facultative anaerobes, few obligate

anaerobes. Ex:-Mycoplasma genitalium, M. pneumoniae, andUreaplasma urealyticum .

Mycoplasmas. A scanning electron micrograph ofMycoplasma pneumoniae shows its pleomorphic nature (X 26.000).

Mycoplasma Colonies. Note the fried egg appearance;colonies stained before photographing (X100).

Properties of Some Members of the Class Mollicutes

Genus Sterol Requirement Habitat Other distinctive Features

Mesoplasma No Insects, plants Optimum growth 30оC,sustained

growth in serum-freemedium only with

0.04%detergent

Mycoplasma Yes Humans, animals Optimum growth 37оC, Cholesterol in

the plasma membrane

Spiroplasma Yes Insects, plants Helical filaments; Optimum growth 30-

37оC

Ureaplasma Yes Humans, animals Urea hydrolysis

Characteristics of Nitrifying BacteriaSpecies Cell

MorphologyReproduction Motility Cytomembranes Habitat

NH3-Oxidizing BacteriaNitrosomonas europaea(β-proteobacteria)

Rod Binary fission - Peripheral,lamellar

Soil,sewge,freshwater,marine

Nitrococcus oceani(γ-proteobacteria)

Coccoid Binary fission +;subpolar flagella

Centrally,lamellar

Obligately marine

NO2--Oxidizing Bacteria

Nitrobacter winogradskyi(α-proteobacteria)

Rod Budding +or-;1 polar flagellum

Periphary-flattened vesicles

Soil,freshwater,marine

Nitrococcus mobilis(γ-proteobacteria)

Coccoid Binary fission +or-;1or 2 polar flagellum

Tubular cytomembranes

Marine

Vol 2. Proteobacteria This volume has gram negative bacteria. They were further divided into 5 subgroups as

Phylum Proteobacteria A major lineage (phyla) of Bacteria

Includes many of the most commonly encountered bacteria

Most metabolically diverse of all domain Bacteria

E.g., Chemolithotrophy, Chemoorganotrophy, Phototrophy

Morphologically diverse

Divided into five classes

Alpha-, Beta-, Gamma-, Delta-, Epsilon

Proteobacteria Alpha: Parasitic bacteria

Tick borne diseases Flea vector

Beta:Gram negative cocci

Gamma

Largest Group

Enterics

Delta

Sulfur reducing bacteria in soli/water

Predatory(attack other bacteria)

Epsilon:Gastro intertine

α-Proteobacteria

S.No. Important Bacteria

Characters Example

1. Purple bacteria Anoxygenic Photosynthetic - sulphur

Rhodospirillum, Rhodobacter,Chromatium

2. Associative Nitrogen fixing bacteria

These bacteria present in the rhizosphere of graminaceous plants andsymbiotically fix atmospheric nitrogen.

Azospirillum

S.No.

Important Bacteria Characters Example

3. Symbiotic Nitrogen fixing bacteria

Form nodules in legume roots and fix atmospheric nitrogen.

Rhizobium, Bradyrhizobium

4. Free living Nitrogen fixing bacteria

Present in the soil as heterotrophs – use verity of carbon sources in soil and fix atmospheric nitrogen

Azotobacter, Beijerinkia

5. Pseudomonas group Some are Plant Growth Promoting

Pseudomonas

Some are pathogens

Xanthomonas

Some produce alcohol

Zymomonas

S.No.

Important Bacteria Characters Example

6. Rickettsia Endoparasites Rickettsia

7. Sulphur oxidizing bacteria Uses S as electron donor - Chemolithotrophs - Strict aerobes

Thiobacillus

8. Acetic acid producing bacteria Fermentative bacteria

Acetobacter,Gluconobacter

9. Budding bacteria Reproduction by budding like yeast

Caulobacter

10. Hydrogen bacteria Hydrogen producing bacteria

Alkaligenes


Characters Example

β-Proteobacteria

1. Nitrifying bacteria Chemolithotroph - strict aerobe - soil bacteria - important form N cycle

Ammonia to nitrite-Nitrosomonas,Nitrite to nitrate -Nitrobacter

2. Neisseria & relatives Parasitic bacteria,pairs as tetrads

Neisseria

3. Spirillum Large,elongate, spiral, rigid cells,lophotricous

Spirillum sp.

4. Sheathed bacteria Enclosed within a tube or extracellualr material

Sphaerotilus


Characters Example

γ-Proteobacteria

1. Purple sulphur bacteria Anoxygenic photosynthetic – sulphur bacteria

Thiobacillus,Thiospirillum

2. Methylotrophs Uses methane and methanol as carbon source

Methylomonas,Methylobacter,methylococcus

δ-Proteobacteria

1. Sulphur reducing bacteria Anaerobes - use S as terminal electron acceptor

Desulfovibrio,Desulfomonas

2. Gliding bacteria Gliding movement

Myxobacteria

3. Vibrio group Most are pathogenic

Vibrio, Erwinia

Alphaproteobacteria

Alphaproteobacteria includes most of the oligotrophic proteobacteria (those capable of growing at low nutrient levels).

α-proteobacteria have unusual metabolic modes such as methylotrophy-the ability to grow using methane as a carbon source (Methylobacterium), chemolithotrophy (Nitrobacter), and the ability to fix nitrogen (Rhizobium).

Characteristic of selected α-proteobacteria

Genus Morphology Oxygen Requirement

Other Distinct Characteristics

Agrobacterium Motile,peritrichous,nonsporulating,rods

Aerobic Chemoorganotroph,invade & cause tumor in plants

Rhizobium Motile with flagella,rods Aerobic Invade plants for N-fixing root nodules

Rickettsia Short non motile rods Aerobic Obligate intracellular parasite

Rhizobium radiobacter (crown gall) symptoms

EM of Rickettsia popilliae growing in a vacuole in the host beetle

Betaproteobacteria β-proteobacteria are similar to the a-proteobacteria metabolically but tend to use

substances that di use from organic decomposition in anoxic habitats.ff Some of these bacteria use hydrogen, ammonia, volatile fatty acids, and similar

substances. As with a-proteobacteria, there is considerable metabolic diversity; β-proteobacteria

may be chemoorganotrophs, photolithotrophs, and chemolithotrophs.

Characteristic of selected β-proteobacteria Genus Morphology Genome

Size(Mb)Oxygen Requirement

Other Distinct Characteristics

Burkholderia

Straight rods,single flagella/tuft at pole

4.1-7.2 Aerobic,facultative anaerobe respiration with Nitrate

Poly-β-hydroxybutyrate as reserve

Nitrosomonas

Size varies,ellipsoidal cells,intacytoplasmic membrane

2.8 Aerobic Chemolithotropic convert Ammonia to nitrite

Thiobacillus Rods with polar flagella 2.09 Aerobic All chemolithotropic(oxidize S compounds to sulphates),some chemoorganotropic

Nitrosomonas sp. Burkholderia cepacia

Gammaproteobacteria

Gammaproteobacteria is composed of several deeply branching groups.

Gammaproteobacteria include an exceeding number of important pathogens, e.g. Salmonella, Yersinia, Pseudomonas aeruginosa.

Gammaproteobacteria are Gram-negative. Some Gammaproteobacteria are methane oxidizers, and

many of them are in symbiosis with geothermic ocean vent dwelling animals.

Gammaproteobacteria is a class of several medically, ecologically and scientifically important groups of bacteria, such as the Enterobacteriaceae (Escherichia coli), Vibrionaceae and Pseudomonadaceae.

Vibrio cholerae

Characteristicgs of selected γ-Proteobacteria


Distinct Characteristic

Azotobacter Ovoid,pleomorphic,peritrichous flagella or non motile

Aerobic Cysts, Fix N-nonsymbiotically

Escherichia Straight rods,peritrichous flagella or non motile

Facultative anaerobic

Mixed acid fermenter,convert H2 to CO2

Pseudomonas

Straight/slightly curved rods,polar flagella

Aerobic/Facultative anaerobic

Respiration with oxygen or nitrate as acceptor

Vibrio Straight/slightly curved rods,sheathed polar flagella

Facultative anaerobic

Fermentative/respiratory metabolism

Azotobacter vinelandii

Cysts (3 um)

Cells (2 um)

Mixed acid and butanediol fermentation Mixed acid

Some G(-) facultative anaerobic bacteria including species of Escherichia, Salmonella, Shigella and Enterobacter ferment glucose, producing various products including lactate, acetate, succinate, formate, CO2 and H2.

Strictly anaerobes such as Anaerobiospirillum succiniciproducens and Actinobacillus succinogenes ferment carbohydrate mainly to succinate.

Butanediol fermentation Some Erwinia, Klebsiella, Serratia, Bacillus and LAB species

produce 2,3-butanediol (2,3-BDO) in addition to lactate and ethanol from pyruvate.

In these bacteria, pyruvate is the substrate for three enzymes such as lactate dehydrogenase, pyruvate:formate lyase and 2-acetolactate synthase.

Deltaproteobacteria

δ-proteobacteria are chemoorganotrophs. Predators-Bdellovibrios and Myxobacteria. Also anaerobes SO4

-and S terminal e- acceptor. Multiprotein machines in their periplasms & outer membrane. SO4

-reducing δ-proteobacteria metabolize H for proton gradient by e-transport.

The predicted highly expressed genes from delta genomes reflect their different ecologies, metabolic strategies, and adaptations.

SO4-reducing -Desulfovibrio, Desulfobacter, Desulfococcus,

Desulfonema, etc. S-reducing bacteria (e.g. Desulfuromonas spp. ).

Characteristicgs of selected δ-Proteobacteria



Bdellovibrio Comma shaped rods,sheathed polar flagellum

Aerobic Preys Gram negative bacteria & grows in periplasm

Desulfovibrio Curved,may be straight rod,polar flagella

Anaerobic Oxidise Organic compoundsCH3COO-

& reduce SO4-/S to H2S

Myxococcus Slender rods,taper ends,gliding motility

Anaerobic Fruiting bodies with microcysts

BdevellovibrioDesulfovibrio vulgaris Myxobacteria with fruiting bodies

Bdellovibrio Life Cycle

Epsilonproteobacteria Slender, Gram-negative rods,straight, curved, or helical. Are chemolithoautotroph. Most inhabit extreme environments such as the acidic gastric mucosa,

hydrothermal vents, and sulfdic caves. Mostly thermophilic and chemolithoautotrophic. Some chemoorganotrophic or chemolithoheterotrophic inorganic

compounds(use H2& S2- as e- donor). Characteristicgs of selected ε-ProteobacteriaGenus Morphology Oxygen

RequirementDistinct Characteristic

Campylobacter Spirally curved,polar flagella at one or both ends

Microaerophilic Found in intestinal tract,reproductive organs,oral cavity in animals

Helicobacter Helicle,curved,straight with rounded ends,sheathed flagella

Microaerophilic Found in gastric mucosa in humans & other animals

Helicobacter Habitat:- Inhabit the surface of stomach mucosa,gastric

epithelial cells. Optimal growth-37οC & pH 6. At least 23 species of Helicobacter all isolated from the stomachs

and upper intestines of humans, dogs, cats and other mammals. Human pathogen Helicobacter pylori causes gastritis and peptic

ulcer disease. H. pylori are a slow growing organisms. H. pylori obligate microaerophile. Helicobacter pylori is a Gram-negative organism that has a helical

or spiral shape and has 6-8 flagella at one end.

Helicobacter pylori Campylobacter jejuni bacteria, SEM

The name was changed from Campylobacter pylori to Helicobacter pylori as specific morphologic, structural, and genetic features indicated that it should be placed in a new genus.

Vol 3. Low G+C gram positives S.No Group Characters Example

1. Clostridia group Strict anaerobes – mostly fermentative nutrition - fewthermo tolerant - endosporeproducers

Clostridium,Thermoanaerobacteriu,Thermoanaerobium

2. Mycoplasma group Absence of cell wall

Mycoplasma, Mesoplasma,Spiroplasma

3. Bacilli and Lactobacilli group

Lactic acid producing bacteria - endospore producers - aerobes - aerotolerant - fermentative nutrition

Leuconostoc, Lactococcus, Streptococcus

Firmicutes: The Low G + C Gram-Positive Bacteria

Most Firmicutes have cell walls, and these bacteria can be found in a great variety of habitats.

They are grouped in the Class Bacilli or Class Clostridia. Diverse Firmicutes include Staphylococcus, Micrococcus,Streptococcus and Lactobacillus.

Some Firmicutes can form an endospore, a resistant differentiated cell produced under special, usually stressful, conditions.

Endospore-forming bacteria such as Bacillus and Clostridium species can be classified by their aerotolerance.

Characteristics of Selected Members of the Class Clostridia



Clostridium Rod,also pleomorphic,non motile or peritrichous flagella

Anaerobic Usually chemoorganotropic,oval or spherical endospore,catalase negative

Heliobacterium Rods,gliding motility Anaerobic Photoheterotropic some form endospore,bacteriochlorophyll

Gram stain of Clostridium septicum, from culture growth of soft tissue infection.

Heliobacterium modesticaldum

Characteristics of Members of the Class Bacilli Genus Morphology Oxygen

RequirementDistinct Characteristic

Bacillus Straight rods,peritrichous flagella,spore-forming

Aerobic,facultative Catalase positive,chemoorganotropic

Lactobacillus Long,regular rods,nonsporeing,rarely motile

Facultative,microaerophilic

Catalase negative,ferment carbohydrates to lactate

Enterococcus Spherical,ovoid,pairs,chains,nonsporing,may be motile

Facultative Ferment carbohydrates to lactate,catalase negative,complex nutritional requirements

Lactococcus Spherical,ovoid,nonmotile, non sporing Facultative Chemoorganotrophic with fermentativemetabolism,catalase negative; complexnutritional requirements

Leuconostoc Spherical,ovoid,pairs or chain,nonmotile,nonsporing

Facultative Require fermentable carbohydrate andnutritionally rich medium for growth;fermentation produces lactate,catalase negative

Staphylococcus Spherical,irregular clusters,nonmotile,nonsporing

Facultative Chemoorganotrophic,catalase positive;associated with skin and mucousmembranes of vertebrates

Streptococcus Spherical,ovoid,in pairs or chains,nonmotile,nonsporing

Facultative Fermentative,catalase negative,complex nutritional,commensals or parasiteson animals

LACTIC ACID BACTERIAThey share a number of common features: they are Gram-positive non-spore forming rods or cocci non-motile resistant to acid and high fermentative ability Most are aerotolerant anaerobes,catalase- and

oxidase-negative Some do take up oxygen through the mediation

of flavoprotein oxidases and this is used to produce hydrogen peroxide and/or to re-oxidize NADH produced during the dehydrogenation of sugars.

Vol 4. High G+C gram positives S.No Group Characters Example

1. Actinomycetes Filamentous - sporangiospores - conidiospores - soil habitat - antibiotics producers

Actinomyces, Nocardia, Sreptomyces

2. Mycobacterium Presence of mycolic acid in the cell wall - acid fast staining - human pathogens

Mycobacterium lepri

3. Corynebacterium Human pathogens, club-shaped

Corynebacteriumdiptheriaea

Vol 5. Plancomycetes, Spirochetes, Bacteroides and Fusobacteria

S.No Group Characters Example

1. Chlamydia group Obligate parasites to man, animal and birds

Chlamydia

2. Bacteroides Obligate anaerobes, non-endospore forming

Bacteroides

3. Spirochete Gram negative - flexile - endoflagellapresence

Spirocheta, Leptospira

Education

Classification of Bacteria microbiology