classification of bacteria microbiology
TRANSCRIPT
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Classification of Bacteria
Presented by:Vinay Kumar Dhiman (F-2016-45-M)
Principles of Microbiology MICRO-501
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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
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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
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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
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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
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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
Bacteriochlorophylls a,b
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
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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.
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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.
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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.
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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).
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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
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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
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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
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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
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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
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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
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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
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S.No. Important Bacteria
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
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S.No. Important Bacteria
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
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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
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Rhizobium radiobacter (crown gall) symptoms
EM of Rickettsia popilliae growing in a vacuole in the host beetle
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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
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Nitrosomonas sp. Burkholderia cepacia
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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
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Characteristicgs of selected γ-Proteobacteria
Genus Morphology Oxygen Requirement
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
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Azotobacter vinelandii
Cysts (3 um)
Cells (2 um)
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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.
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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. ).
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Characteristicgs of selected δ-Proteobacteria
Genus Morphology Oxygen Requirement
Distinct Characteristic
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
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BdevellovibrioDesulfovibrio vulgaris Myxobacteria with fruiting bodies
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Bdellovibrio Life Cycle
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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
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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.
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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.
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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
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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.
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Characteristics of Selected Members of the Class Clostridia
Genus Morphology Oxygen Requirement
Distinct Characteristic
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
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Gram stain of Clostridium septicum, from culture growth of soft tissue infection.
Heliobacterium modesticaldum
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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
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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.
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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
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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
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