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Proteobacteria
Proteobacteria is a major phylum of gram-negative bacteria consisting of over 460 genera and 1600 species, including significant pathogens like Escherichia and Salmonella. These bacteria exhibit diverse morphologies, metabolic strategies, and habitats, ranging from free-living forms to intracellular endosymbionts and essential contributors to the nitrogen cycle. Key representatives include nitrogen-fixing rhizobia, phototrophic purple bacteria, and various important pathogens like Rickettsia.
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Proteobacteria
- 1. Proteobacteria Prepared by Dharmesh N.Sherathia CCSIT, Junagadh(BKNMU) [email protected]
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- 5. The Proteobacteriaare a major group (phylum) of bacteria Include a wide variety of pathogens, such as Escherichia, Salmonella, Vibrio, Helicobacter, and many other notable genera Proteobacteria are Gram-negative, with an outer membrane mainly composed of lipopolysaccharides move about using flagella, but some are nonmotile or rely on bacterial gliding The last include the myxobacteria
- 6. many differentshapes, to reflect the enormous diversity of morphologies and physiologies observed within this bacterial phylum In 2002, the Proteobacteria consist of more than 460 genera and more than 1600 species, scattered over 5 major phylogenetic lines of descent known as the classes “Alphaproteobacteria,” “Betaproteobacteria,” “Gammaproteobacteria,” “Deltaproteobacteria”
- 7. Habitat Organisms thatcan be found in different habitats ranging from plant roots (Rhizobium and Azospirillum) inside the cells of a host (rickettsias) and as free living bacteria in the environment such as Methylobacteriaum species Found in virtually any environment across the globe Some of the species in the phyla can survive extreme environments with very little to no oxygen.
- 8. Diversity ofmorphological and physiological types: besides rods and cocci, curved, spiral, ring-shaped, appendaged, filamentous and sheathed bacteria occur among this phylum Most Proteobacteria are mesophilicphilic,but some thermophilic (e.g., Thiomonas thermosulfata and Tepidomonas) and psychrophilic (e.g., Polaromonas) representatives have been described
- 9. A greatnumber of Proteobacteria are motile by means of polar or peritrichous flagella, whereas the myxobacteria (belonging to the “Deltaproteobacteria”) display a gliding type of motility and show highly complex developmental lifestyles, whereby often remarkable multicellular and macroscopic structures (so-called “fruiting bodies”) are formed
- 10. Most ofthe known Proteobacteria are free-living; some (such as the rhizobia) enter in symbiotic associations with specific leguminous plants, where they fix nitrogen in root or stem nodules Others live as intracellular endosymbionts of protozoa and invertebrates (mussels, insects and nematodes), whereas the rickettsiae are obligate intracellular parasites of humans or mammals
- 11. The extremediversity of energy generating mechanisms is a unique biochemical characteristic of the Proteobacteria: some are chemoorganotrophs (e.g., Escherichia coli), others are chemolithotrophs (e.g., the sulfuroxidizing bacteria such as the thiobacilli and the ammonia-oxidizing bacteria such as Nitrosomonas) or phototrophs (e.g., the purple colored Chromatium, Rhodospirillum and many others)
- 12. Concerning theirrelationship towards oxygen, the Proteobacteria include strictly aerobic and anaerobic species as well as facultative aerobes and microaerophiles Denitrifiers are reported among the “Alphaproteobacteria,” “Betaproteobacteria,” “Gammaproteobacteria,” and the “Epsilonproteobacteria.
- 13. Types of organisms Purple Phototrophic Bacteria Nitrifying Bacteria Sulphur and Iron Oxidising Bacteria Hydrogen Oxidising Bacteria Methanotrophs Acetic Acid Bacteria Bioluminescent and Related Bacteria
- 14. Classification 1987, CarlWoese established- ribosomal RNA (rRNA) sequences The Proteobacteria are divided into six sections, referred to by the Greek letters alpha through zeta alpha, beta, delta, epsilon sections are monophyletic. Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, Deltaproteobacteria, Epsilonproteobacteria and Zetaproteobacteria
- 15. HISTORY 1987, CarlWoese established this grouping called it the "purple bacteria and their relatives“ great diversity of forms found in this group Proteobacteria are named after Proteus Greek god of the sea Capable of assuming many different shapes, and it is therefore not named after the genus Proteus
- 16. Great biologicalimportance, as they include the majority of the known Gram negatives of medical, veterinary, industrial and agricultural interest Because they play key roles in the carbon, sulfur and nitrogen cycles on our planet e.g rhizobium, green purple sulphur bacteria
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- 18. Oligotrophic proteobacteria-those capable of growing at low nutrient levels Some have unusual metabolic modes such as Methylotrophy (Methylobacterium), Chemolithotrophy (Nitrobacter) fix nitrogen (Rhizobium) Members of genera such as Rickettsia and Brucella are important pathogens Many genera are characterized by distinctive morphology such as prosthecae
- 20. A prostheca(pl., prosthecae) is an extension of the cell, including the plasma membrane and cell wall, that is narrower than the mature cell A stalk is a nonliving appendage produced by the cell and extending from it. Budding is distinctly different from the binary fission normally used by bacteria.
- 21. The Purple Nonsulfur Bacteria Noxygenic photosynthesis, possess bacteriochlorophylls a or b, All purple nonsulfur bacteria are – proteobacteria (exception Rhodocyclus) Trap light energy and employ organic molecules as both electron and carbon sources(photoorganoheterotrophs)- Nonsulfur Bacteria(do not oxidize elemental sulfur to sulfate) During absence of light- devoid colour- grow like chemoorganotrophs
- 23. Representatives of PurpleNonsulfur Bacteria Figure 15.6
- 24. Prevalent inthe mud and water of lakes and ponds with abundant organic matter and low sulfide levels
- 25. Family: Rhodospirillaceae Rhodospirillumand Azospirillum Cyst formation is unique feature of this family Cyst is for 1. Protect cell from dessication 2. Less protective against UV and heat 3. Made in response to nutrient limitations
- 26. Rickettsia and Coxiella These bacteria are rod-shaped, coccoid, or pleomorphic with typical gram-negative walls and no flagella. Although their size varies, they tend to be very small. For example, Rickettsia is 0.3 to 0.5 m in diameter and 0.8 to 2.0 m long; . All species are parasitic or mutualistic.
- 27. The parasiticforms grow in vertebrate erythrocytes, macrophages , and vascular endothelial cells. Often they also live in blood-sucking arthropods such as fleas, ticks, mites, or lice, which serve as vectors or primary hosts. This order contains many important pathogens. Rickettsia prowazekii and R. typhi are associated with typhus fever, and R. rickettsii, with Rocky Mountain spotted fever. Coxiella burnetii causes Q fever in humans.
- 28. Rickettsias arevery different from most other They lack glycolytic pathways and do not use glucose as an energy source, but rather oxidize glutamate The rickettsial plasma membrane has carrier-mediated transport systems host cell nutrients and coenzymes are absorbed and directly used
- 31. The Caulobacteraceae and Hyphomicrobiaceae These bacteria can have at least one of three different features: a prostheca, a stalk, or reproduction by budding The genus Hyphomicrobium contains chemoheterotrophic, aerobic, budding bacteria that frequently attach to solid objects in freshwater, marine, and terrestrial environments About 0.5 to 1.0 by 1 to 3 m- vegetative cell size Prostheca 0.2 to 0.3 um in diameter, that grows to several um in length
- 32. Bud isfinally released as an oval- to pear-shaped swarmer cell,
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- 35. Distinct metabolism-> Sugars and most amino acids do not support abundant growth https://www.tandfonline.com/doi/pdf/10.1 080/00021369.1982.10865468 Hyphomicrobium grows on ethanol and acetate and flourishes with one-carbon compounds such as methanol, formate, and formaldehyde facultative methylotroph and can derive both energy and carbon from reduced one carbon compounds Hyphomicrobium may comprise up to 25% of the total bacterial population in
- 36. Caulobacter Possess aprostheca and holdfast Material secreted at the end of the Caulobacter holdfast is the strongest biological adhesion molecule known-superglue Freshwater and marine habitats with low nutrient levels Adhere to bacteria, and got nutrient from them Here prostheca contain only cytoplasm of cell can enlarge 10 time larger than vegetative cells Caulobacter can survive in diluted medium by enlarging their size
- 38. Family:Rhizobiaceae Order Rhizobialesof the -proteobacteria contains 11 families This includes the family Hyphomicrobiaceae Important family in this order is Rhizobiaceae which includes rhizobium and agrobacterium Cells often contain poly—hydroxybutyrate inclusions. They grow symbiotically within root nodule cells of legumes as nitrogen-fixing bacteroids Live with leguminous plant symbiotically within the nodule it fix atmospheric nitrogen
- 39. Agrobacterium isplaced in the family Rhizobiaceae but differs from Rhizobium agrobacteria invade the crown, roots, and stems of many plants and transform plant cells into autonomously proliferating tumor cells Responsible genes are located on plasmid best-studied species is A. tumefaciens, which enters many broad-leaved plants through wounds and causes crown gall disease Presence of a large Ti (for tumor inducing) plasmid
- 40. Nitrifying Bacteria Nitrifiersmay be rod-shaped, ellipsoidal, spherical, spirillar or lobate, and they may possess either polar or peritrichous flagella Nitrifying bacteria make important contributions to the nitrogen cycle
- 41. most ofthe proteobacteria that are capable of growth at very low levels of nutrients Some have unusual morphology, including protrusions such as stalks or buds known as prosthecae. also include agriculturally important bacteria capable of inducing nitrogen fixation in symbiosis with plants, and several plant and human pathogens
- 42. List of microbesincluded in alpha proteobacteria
- 43. Magnetococcus marinus abilityto form a structure called a magnetosome a membrane encased single-magnetic- domain mineral crystals formed by biomineralisation allows the cells to orientate along the Earth’s geomagnetic field
- 44. Magnetotactic bacteria(or MTB) are a polyphyletic group of bacteria discovered by Richard P. Blakemore in 1975 The biological phenomenon of microorganisms tending to move in response to the environment's magnetic characteristics is known as magnetotaxis Blakemore realised that these microorganisms were following the direction of Earth's magnetic field, from south to north, and thus coined the term "magnetotactic“
- 45. The MTBscan be subdivided into two categories, according to whether they produce particles of magnetite (Fe3O4) or of greigite (Fe3S4) Many MTB are able to survive only in environments with very limited oxygen, and some can exist only in completely anaerobic environments
- 46. Some typesof magnetotactic bacteria can produce magnetite even in anaerobic conditions, using nitric oxide, nitrate, or sulfate as a final acceptor for electrons. The greigite mineralising MTBs are usually strictly anaerobic It has been suggested MTB evolved in the early Proterozoic Era
- 47. order: Rickettsiales Mostof those described survive only as endosymbionts of other cells Some are notable pathogens, including Rickettsia, which causes a variety of diseases in humans Studies support the endosymbiotic theory according to which mitochondria and related organelles developed from members of this group
- 48. owing largelyto difficulties in cultivating them The Rickettsiales has a sister order the Pelagibacterales
- 49. Order: Pelagibacterales Alphaproteobacteriacomposed of free- living bacteria It was first placed in the Rickettsiales, but was later raised to the rank of order, and then placed as sister order to the Rickettsiales Pelagibacter ubique and related species are oligotrophs—scavengers—and feed on dissolved organic carbon and nitrogen
- 50. They areunable to fix carbon or nitrogen, but can perform the TCA cycle with glyoxylate bypass and are able to synthesise all amino-acids, except glycine It is non-photosynthetic Possesses proteorhodopsin (incl. retinol bi osynthesis) for ATP production from light
- 51. Parvularcula bermudensis Parvularculaisolates are Gram-negative, strictly aerobic, chemoheterotrophic, slightly motile short rods with a single flagellum. Colonies on marine agar are very small (0·3–0·8 mm in diameter), yellowish-brown and very hard. They are oxidase positive and catalase negative.