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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 ofSystematic 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 inthe 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 sectionsare 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 microorganismsthat 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 ofseveral 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 AREPRESENT IN THE ARCHAEA HYPERTHERMOPHILES
- 11. 2. Cyanobacteria Filamentous, oxygenicphotosynthetic 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 MajorGroups 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 hasbeen 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 Deinococcusso 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 suggeststhat 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 lackwalls (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 SomeMembers 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 Thisvolume 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 BacteriaCharacters 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 CharactersExample 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 Nitrifyingbacteria 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 CharactersExample 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 BacteriaCharacters 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 BacteriaCharacters 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 includesmost 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-proteobacteriaare 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 aresimilar 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 iscomposed 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 selectedγ-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 arechemoorganotrophs. 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 selectedδ-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-negativerods,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:- Inhabitthe 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.pylorisurvive 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. LowG+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 LowG + 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 SelectedMembers 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 Membersof 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. HighG+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 Rickettsiaand 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