CLASSIFICATION OF BACTERIA

1. Speaker: Aishwarya Chauhan (F-2017-427-M)
n of Bacteria
Principles of
Microbiology
Course No:-MICRO-501
Classification
of bacteria

2. Bergey’s Manual of Systematic
Bacteriology
Published in 1984
Particularly based on phylogenetic
analysis
Phylogenetic analysis is
basically depends on
Sequencing of rRNA, DNA and
proteins

3. 1.Archaea
2.Proteobacteria
3.Low G+C Gram(+) bacteria
4.High G+C Gram(+) bacteria
5.Spirochaetes, Fusobacteria,
Plancomycetes,
Bacteroidetes & Fibrobacters
The Second Edition was divided into 5
Volumes
1. Archaea
2. Protobacteria
3. Low G+C Gram Positive Bacteria
4. High G+C Gram Positive Bacteria
5. Spirochaetes, Fusobacteria, Plancomycetes,
Bacteriodetes & Fibrobacters

4. 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
General characterstics of archaea
Cell walls :Virtually all bacteria contains peptidoglycan in their
cell wall, however, archaea and eukaryotes lack peptidoglycan.
Various types of cell walls exist in the archaea. Therefore, the
absence or presence of peptidoglycan is a distinguishing
features between the archaea and bacteria.

5. Cont.
 Fatty acid: Bacteria and eukaryotes produce membrane lipids
consisting of fatty acids linked by ester bonds to a molecules of
glycerol. In contrast, the archaea have ether bonds connecting fatty
acids to molecules of glycerol. Although a few bacteria also contain
ether linked lipids, no archaea have been discovered that contains
ester linked lipids
 Protein synthesis: Various features of proteins synthesis in the archaea
are similar to those of eukaryotes but not of bacteria. A prominent
difference is that bacteria have an tRNA that has a modified methionine,
whereas eukaryotes and archaea have an intiator tRNA with an
unmodified methionine.

6. Crenarchaeot
-a
A kingdom in the domin
Archaea compried of
thermoacidophilic, sulfur
dependent organism. The order
are Sulfolobales and
thermoproteales.
In the taxonomy of microorganism
the euryarchaeota are a phylum of
the Archaea. Euryarchaeota include
the methogens, which produce
methane and are often found in
intestines, the halobacteria,which
survive extreme conc. Of salt

7. Four important sections are present in the
archaea.
 Hyperthermophiles :-an organisms that thrives in
extremely hot environments from 60˚C upwards -
Example. Thermococcus,Thermosphaera
Thermoplasma –It belong to the Thermoplasmata,
which thrives in acidic and high temperature
environments.Example. Thermoplasma

8. Methanogens
Methanogens are microorganisms that produce methane as a
metabolic byproduct in anoxic conditions ( low amount of oxygen).
Example. Methanobacterium, Methanococcus, Methanosarcina
General characterstics of methanogens:-
They uniquely belong to the domin of archaea.
They are common in wetlands, where they are responsible for marsh
gas.
Methanogens are coccoid (spherical shaped) or bacilli (rod shaped).
Methanogens lack peptidoglycan, a polymer that is found in the cell
walls of bacteria but not in those of Archaea.
They are very sensitive to the presence of oxygen even at trace level.

9. Halobacteria
Halobacteria consists of several species of the archaea with an aerobic
metabolism which requires an environment with a high concentration of
salt. Example. Halobacterium, Halococcus
General characterstics of Halobacteria:-
They grow on amino acids in their aerobic conditions.
Their cell walls are quite different from those of bacteria, as
ordinary lipoprotein membranes fails in high salt concentrations.
In shape, they may be either rods and cocci, in colour, either red or
purple.
They reproduce using binary fission (by construction), and are
motile.
Halobacterium grows best in a 42˚C environment.

10. IMPORTANT SECTIONS ARE PRESENT IN THE ARCHAEA
HYPERTHERMOPHILES

11. 2. Cyanobacteria
Filamentous, oxygenic photosynthetic bacteria. They have
special cells called heterocyst( nitrogen fixing cells) in which
nitrogenase enzyme is present. The nitrogenase enzyme is
responsible for fixing atmospheric N2 into ammonia.
Cyanbobacteria exist in three forms
a. Single celled - Chrococcus, Gleocapsa
b. Filamentous non-heterocystous - Oscillatoria,
c. Filamentous heterocystous -Anabaena, Nostoc
3. Anoxygenic phototrophs
Single celled, sulphur required bacteria. They use H2S as
electron
donor. Example.:- Green sulphur bacteriumChlorobium

12. 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 Bacteriochlorophyl
ls a,c,d,e
Bacteriochloroph
ylls a,c
Bacteriochloroph
ylls a,b
Bacteriochloroph
ylls a,b
Bacteriochloroph
ylls a,b
Chlorophyll
Morphology of
photosynthetic
membranes
PS partly in
chlorosomes(inde
pendent 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
Photosynthetic
e- donors
H2,H2S,S0 Photoheterotroph
ic=sugars,AA,org
anic acids;
Photoautotrophic
= H2S,H2
H2,H2S,S0 Organic
molecules,also S
compounds,H2
Photoheterotrop
hic=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
 

13. 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, 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.

14.  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.
Spherical tetrad shape of D. radiodurans.

15. D. radiodurans has been isolated from meat,
sewage, filtered air, animal feces (excreta),
soil.
It grow best in 30°C temperature.
D. radiodurans is an obligatory heterotroph.
Its main source of energy production uses the
vacuolar type of proton ATP synthase.
 Cell wall:-5 layers with a total thickness of 150 nm & is
unique.

16. Why is Deinococcus so resistant to ionizing
radiation?
 Their resistance to radiation results from their
ability to repair a severely damaged genome,
which consists of circular chromosomes, a
megaplasmid, and small plasmid.
 When they are exposed to high level of
radiations, radical oxygen species are
generated and the genome is broken down into
hundred of fragments.
 Amazingly, within 12 to 24 hours, the genome
is pieced back together, ensuring viability.

17. Cont.
 Evidence suggests that while D. radiodurans DNA is not
especially radiation resistant, its proteins are.
The ability to accumulate high level of Maganese helps
the microbes from damage caused by radiation
induced toxic oxygen species.
Maganese ions selectively protect proteins, rather than
DNA.
Thus, unlike other microbes D. radiodurans DNA repair
enzymes survive severe oxidative stress.

18. 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.
Examples :-Mycoplasma genitalium,
Mycoplasma pneumoniae.

19. Properties of Some Members of the Class Mollicutes
Genus Sterol Requirement Habitat Other distinctive
Features
Mesoplasma No Insects, plants Optimum growth
30оC
Mycoplasma Yes Humans, animals Optimum growth 37оC,
Spiroplasma Yes Insects, plants Optimum growth 30-
37оC
Ureaplasma Yes Humans, Urea hydrolysis

20. 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
 Most metabolically diverse of all domain Bacteria
 E.g., Chemolithotrophy, Chemoorganotrophy, Phototrophy
 Morphologically diverse
 Divided into five classes
 Alpha-, Beta-, Gamma-, Delta-, Epsilon
Proteobacteria

21. Proteobacteria
 Alpha : Parasitic bacteria
 Tick borne diseases
 Flea( small flightless insects) vector
 Beta :Gram negative cocci
 Gamma
 Largest Group
 Enterics (occurring in the intestine)
 Delta
 Sulfur reducing bacteria in soli/water
 Predatory(attack other bacteria)
 Epsilon: Gastro intestine

22. Some images of(a) alpha, (b) beta, (c)gamma,
(d) delta and (e)epsilon proteobacteria
respectively.
b.
c.
d.
a.
e.

23. α-Proteobacteria
S.No. Important Bacteria Characters Example
1. Purple bacteria Anoxygenic Rhodospirillu
m,
Rhodobacter
2.
Associative Nitrogen
fixing bacteria
These bacteria
present in the
rhizosphere of
graminaceous
plants (herbaceous
or
woody plants with
hollow jointed
stems and long
narrow leaves) and
Azospirill
um

24. S.N
o.
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
Azotobacter,
Beijerinkia
5. Pseudomonas group Some are Plant
Growth Promoting
Pseudomonas
Some are
pathogens
Xanthomonas
Some produce Zymomonas

25. Characterstics of Rhizobium
 Rhizobium is a genus of gram negative soil bacteria that fix nitrogen.
 Rhizobium species forms an endosymbiotic nitrogen fixing association with
roots of legumes.
 The bacteria colonize plant cells within root nodules, where they convert
atmospheric nitrogen into ammonia and then provide organic nitrogenous
compounds such as glutamine in plant.
 The plant, in turn, provides the bacteria with organic compound made by
photosynthesis.
 This mutually beneficial relationship is true of all of the rhizobia, of which
rhizobium genus is a typical example.

26. Characterstics of Nitrifying bacteria
 Able to grow chemolithotrophically at the expense of inorganic
nitrogen compounds
 Found in Alpha-, Beta-, Gamma- and Deltaproteobacteria.
 Nitrification:- (oxidation of ammonia to nitrates) two separate
reactions by different groups of bacteria.
Ammonia oxidizer (nitrosifyers) ( e.g., Nitrococcus)
Nitrites oxidizer (nitrifyer) (e.g,nitrobacter)
• Ammonia Monooxygenase : oxidizes NH 𝑡𝑜 𝑁𝐻2𝑂𝐻

27. 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 Alkaligenes

28. 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
Spirillum sp.
4. Sheathed bacteria Enclosed within a
tube or extracellualr
Sphaerotilus

29. 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

30. 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,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

31. Characterstics of Agrobacterium
 Soil borne, gram negative, rod shaped, motile bacteria
in rhizosphere.
 Encodes a large ( 250 kbp) plasmid called tumor
inducing (Ti) plasmid, a vector which can transfer its
T-DNA region into genome of host plant.
 Causative agents of “ Crown gall” disease of
dicotyledons.
 Have ability to transfer bacterial genes plant genome.

32. β- Proteobacteria
 β-proteobacteria are similar to the α-proteobacteria metabolically but
tend to use substances that diffuse from organic decomposition in
anoxic habitats.
 Some of these bacteria use hydrogen, ammonia, volatile fatty acids,
and similar substances.
 As with α-proteobacteria, there is considerable metabolic diversity;
β-proteobacteria may be chemoorganotrophs, photolithotrophs, and
chemolithotrophs.

33. Betaproteobacteria
 β-proteobacteria are similar to the a-proteobacteria metabolically but tend to use
substances that diffuse from organic decomposition in anoxic habitats.
 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
Burkholder
ia
Straight rods,single
flagella
4.1-7.2 Aerobic,facultativ
e anaerobe
respiration with
Nitrate
Poly-β-hydroxybutyrate as
reserve
Nitrosomo
nas
Size varies,cytoplasmic
membrane
2.8 Aerobic Chemolithotropic convert
Ammonia to nitrite
Thiobacillu
s
Rods with polar flagella 2.09 Aerobic All chemolithotropic(oxidize
S compounds to
sulphates),some
chemoorganotropic

34. Gammaproteobacteria
 Gammaproteobacteria is composed of several deeply
branching groups.
 Gammaproteobacteria include an exceeding number of
important pathogens, e.g. Salmonella, Pseudomonas.
 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.
Vibrio
cholerae

35. Characteristicgs of selected γ-Proteobacteria
Genus Morphology Oxygen
Requirement
Distinct
Characteristic
Azotobacter pleomorphic and non motile Aerobic Cysts, Fix N-
nonsymbiotically
Escherichia Straight rods and non motile Facultative
anaerobic
Mixed acid
fermenter,convert H2 to
CO2
Pseudomon
as
Straight/slightly curved rods,polar
flagella
Aerobic Respiration with oxygen or
nitrate as acceptor
Vibrio Straight/slightly curved
rods,sheathed polar flagella
Facultative
anaerobic
Fermentative

39. Deltaproteobacteria
 δ-proteobacteria are chemoorganotrophs.
 Predators-Bdellovibrios and Myxobacteria.
 Also anaerobes SO4
-and S terminal e- acceptor.
 SO4
-reducing δ-proteobacteria metabolize H for proton gradient
by e-transport.
 The predicted highly expressed genes from delta genomes reflect
their SO4
-reducing -Desulfovibrio, Desulfobacter, Desulfococcus,
Desulfonema, etc.
 S-reducing bacteria (e.g. Desulfuromonas spp. ).

40. Characteristics 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
compounds
Myxococcus Slender rods,taper
ends,gliding motility
Anaerobic Fruiting bodies with
microcysts

41. Epsilonproteobacteria
 Slender, Gram-negative, rods,straight, curved, or helical.
 Are chemolithoautotroph.
 Most inhabit extreme environments such as the acidic gastric
mucosa, hydrothermal vent.
 Mostly thermophilic and chemolithoautotrophic.
 Some chemoorganotrophic or chemolithoheterotrophic
inorganic compound.

42. 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).
Characteristics of selected ε-
Proteobacteria
Genus Morphology Oxygen
Requirement
Distinct
Characteristi
c
Campylobacter Spirally
curved,polar
flagella at one or
both ends
Microaerophilic Found in intestinal
tract,reproductive
organs,oral cavity
in animals
Helicobacter Helicle,curved,stra
ight with rounded
ends,sheathed
Microaerophilic Found in gastric
mucosa in humans
& other animals

43. 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 (requiring little free oxygen).
 Helicobacter pylori is a Gram-negative organism that has a

44. How does H.pylori survive the acidic condition of the
stomach?
 H.pylori survives the acidic environment of the stomach by a few
mechanisms.
 Firstly, it secretes urease which produces ammonia as a byproduct
and neutralize the acidity.
Secondly, H.pylori posses flagella, which enables it to ‘swim’. They
swim towards the less acidic environment of the mucosal surface
on your stomach linings.
 Without flagella they will be unable to escape the acid and won’t
be pathogenic even with urease.
There is evidence that H.pylori alters the stomach lining and

45. Vol 3. Low G+C gram positive bacteria
S.No Group Characters Example
1. Clostridia group Strict anaerobes –
mostly fermentative
nutrition - few
thermo tolerant -
endospore
producers
Clostridium,
Thermoanaerobacterium,
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

46. 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.

47. Characteristics of Selected Members of the Class Clostridia
Genus Morphology Oxygen
Requirement
Distinct Characteristic
Clostridium Rod,also pleomorphic,non
motile
Anaerobic Usually
chemoorganotropic,oval or
spherical endospore,catalase
negative
Heliobacteriu
m
Rods,gliding motility Anaerobic Photoheterotropic some form
endospore,bacteriochlorophyll

48. Characteristics of Members of the Class Bacilli
Genus Morphology Oxygen
Requirement
Distinct Characteristic
Bacillus Straight rods, spore-forming facultative Catalase positive,chemoorganotropic
Lactobacillus regular rods,nonsporeing,rarely
motile
Facultative Catalase negative,ferment carbohydrates
to lactate
Enterococcus Spherical,nonsporing, may be motile Facultative Ferment carbohydrates to lactate,catalase
negative,complex nutritional requirements
Lactococcus Spherical,nonmotile, non sporing Facultative Chemoorganotrophic with fermentative
metabolism,catalase negative; complex
nutritional requirements
Leuconostoc Spherical ,nonmotile,nonsporing Facultative Require fermentable carbohydrate and
nutritionally rich medium for growth;
fermentation produces lactate,catalase negative
Staphylococcus Spherical,nonmotile,nonsporing Facultative Chemoorganotrophic,catalase positive;
associated with skin and mucous
membranes of vertebrates
Streptococcus Spherical,nonmotile,nonsporing Facultative Fermentative,catalase negative,complex
nutritional or parasites
on animals

49. Vol 4. High G+C gram positive bacteria
S.No Group Characters Example
1. Actinomycetes Filamentous -
sporangiospores -
conidiospores - soil
habitat -
antibiotics producers
Actinomyces,
Sreptomyces
2. Mycobacterium Presence of mycolic
acid in the cell wall -
acid fast staining -
human pathogens
Mycobacterium lepri
3. Corynebacterium Human pathogens,
club-shaped
Corynebacterium
diptheriaea

50. 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 - Spirocheta

51. Difference between Rickettsia and Virus
S.No. Property Rickettsia/
typical bacteia
chlamydia Virus
1. DNA/RNA Both Both Any one
2. Multiplication by
binary fission
Yes Yes No
3. Cell wall with
muramic acid
Yes Yes No
4. ribosomes Yes Yes No
5. Metabolically active
enzymes
Yes Yes No
6. Inhibition by
antibacterial
enzymes
Yes Yes No