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Transcript
Chapter 15 (2) Bacteria: The Proteobacteria 15.12 Vibrio, Alivibrio, and Photobacterium The Vibrio Group Cells are motile, straight or curved rods Facultative aerobes Possess a fermentative metabolism Best known genera are Vibrio, Alivibrio, and Photobacterium Most inhabit aquatic environments The Vibrio Group (cont’d) Some are pathogenic Some are capable of light production (bioluminescence) Catalyzed by luciferase, an O2-dependent enzyme Regulation is mediated by population density (quorum sensing) * NADH + H+ + FMN → NAD+ + FMNH2 FMNH2 + O2 + RCHO → FMN + RCOOH + H2O + light NAD+ + RCOOH → NADH + H+ + RCHO Bioluminescent Bacteria Blue light Aliivibrio fischeri MJ-1 Green light Aliivibrio fischeri Y-1 Photobacterium phophoreum Bioluminescent Bacteria as Light Organ Symbionts Bioluminescent bacteria 15.13 Rickettsias Rickettsias Small, coccoid or rod-shaped cells Most are obligate intracellular parasites Causative agent of several human diseases Rickettsias Growing Within Host Cells Rickettsia rickettsii in tunica vaginalis cells of the vole. Rickettsias Growing Within Host Cells vacuole EM of cells of Rickettsiella popilliae within a blood cells of a beetle. Characteristics of Rickettsias Wolbachia Genus of rod-shaped Alphaproteobacteria Intracellular parasites of arthropod insects Affect the reproductive fitness of hosts - parthenogenesis - killing of males - feminization (the conversion of male insects into females) Wolbachia pipientis Small genome: 1.5 Mbp Does not cause disease in either vertebrates or its invertebrates host Cause disease only in insects Passed from infected females to her offspring through the egg infection - colonize the insect egg (e.g. wasp) Wolbachia Wolbachia induced parthenogenesis Occurs in a number of species of wasps Male normally arise from unfertilized eggs and female arise from fertilized eggs Walbachia in unfertilized eggs triggers a doubling of the chromosome number - yields only females Wolbachia induced killing of males In lady beetles and butterflies Walbachia infection results in the death of male offspring Wolbachia induced feminization In certain species of woodlice (= pillbugs) Walbachia causes male to develop as females due to the damage in the male hormone-producing glands Wolbachia is essential for survival In the nematode worms causing the diseases elephantiasis and river blindness Antibiotics kill the worms, apparantly by killing their Walbachia symbionts IV. Morphologically Unusual Proteobacteria 15.14 Spirilla 15.15 Sheathed Proteobacteria: Sphaerotilus and Leptothrix 15.16 Budding and Prosthecate/Stalked Bacteria 15.14 Spirilla Spirilla Group of motile, spiral-shaped Proteobacteria Key taxonomic features include Cell shape and size Number of polar flagella Metabolism Physiology Ecology Spirilla : Spirillum volutans Spirillum volutans Spirilla: An intestinal spirillum Spirilla: Cells of Ancyclobacter aquaticus Ancyclobacter aquaticus Characteristics of the Genera of Spiral-Shaped Bacteria Spirilla A few are magnetotactic, demonstrating directed movement in a magnetic field A Magnetotactic Spirillium, M. magnetotacticum Magnetosome (particles of Fe3O4) Spirilla Bdevellovibrio Prey on other bacteria Obligate aerobes Members of Deltaproteobacteria Widespread in soil and water, including marine environments Very thick flagellum Attachment and Penetration of a Prey Cell by Bdellevibrio bdelloplast Developmental Cycle of Bdellevibrio bacteriovorus 15.15 Sheathed Proteobacteria: Sphaerotilus & Leptothrix Sheathed bacteria Filamentous Betaproteobacteria Unique life cycle in which flagellated swarmer cells form within a long tube or sheath Under unfavorable conditions, swarmer cells move out to explore new environments Sheath: a complex of protein and polysaccharides Common in freshwater habitats rich in organic matter Sphaerotilus Nutritionally versatile Able to use simple organic compounds Obligate aerobes Cells within the sheath divide by binary fission Eventually swarmer cells are liberated from sheaths Sphaerotilus natans Sphaerotilus natans Sphaerotilus natans Swarmer cells with polar flagellar tuft Sphaerotilus and Leptothrix are able to precipitate iron oxides on their sheath Leptothrix also can oxidize Mn2+ to Mn4+ ■ the protein responsible for the oxidation process resides in the sheath Leptothrix and Iron Precipitation Protuberance of the cell envelope contacting the sheath 15.16 Budding and Prosthecate/Stalked Bacteria Budding and Prosthecate/Stalked Bacteria Large and heterogeneous group Primarily Alphaproteobacteria Form various kinds of cytoplasmic extrusions bounded by a cell wall (collectively called prosthecae) Features of Stalked, Appendaged and Budding Bacteria Prosthecate Bacteria Asticcacaulis biprosthecum Ancalomicrobium adetum Stella sp. Cell Division Budding Bacteria Divide as a result of unequal cell growth Two well-studied genera Hyphomicrobium (chemoorganotrophic) Rhodomicrobium (phototrophic) Stages in the Hyphomicrobium Cell Cycle Morphology of Hyphomicrobium Prosthecate and Stalked Bacteria Appendaged bacteria that attach to particulate matter, plant material, and other microbes in aquatic environments Appendages increase surface-to-volume ratio of the cells Stalked Bacteria A Caulobcater rosettes Caulobacter Chemoorganotroph Produces a cytoplasm-filled stalk Often seen on surfaces in aquatic environments with stalks of several cells attached to form rosettes Holdfast structure present on the end of the stalk used for attachment Model system for cell division and development Growth of Caulobacter Gallionella Chemolithotrophic iron-oxidizing bacteria Possess twisted stalk-like structure composed of ferric hydroxide Common in waters draining bogs, iron springs, and other environments rich in Fe2+ Neutrophilic Ferrous Iron Oxidizer, Gallionella ferruginea V. Delta- and Epsilonproteobacteria 15.17 Gliding Myxobacteria 15.18 Sulfate- and Sulfur-Reducing Proteobacteria 15.19 The Epsilonproteobacteria 15.17 Gliding Myxobacteria Gliding A form of motility exhibited by some bacteria Gliding Bacteria Are typically either long rods or filaments Lack flagella, but can move when in contact with surfaces Classification of the Fruiting Myxobacteria Myxobacteria Group of gliding bacteria that form multicellular structures (fruiting bodies) and show complex developmental life cycles Deltaproteobacteria Chemoorganotrophic soil bacteria Lifestyle includes consumption of dead organic matter or other bacterial cells Most are obligate aerobes - exception: a facultative aerobe Anaeromyxobacter that can grow by anaerobic respiration Fruiting myxobacteria exhibit complex behavioral patterns and life cycles Vegetative cells are simple, nonflagellated rods that glide across surfaces and obtain their nutrients primarily by lysing other bacteria and utilizing released nutrients Under appropriate conditions, vegetative cells aggregate, construct fruiting bodies, and undergo differentiation into myxospores Myxococcus xanthus A vegetative cell Myxococcus xanthus Myxospore with multilayered outer wall Stigmatella aurantiaca Stigmatella aurantiaca Fruiting Bodies of Myxococcus fulvus Fruiting Body of Myxococcus stipitatus Fruiting Body of Chondromyces crocatus The life cycle of fruiting myxobacterium is complex (e.g.) glycerol Life cycle of Myxococcus xanthus Swarming in Myxococcus Fruiting Body Formation in Chondromyces crocatus 15.18 Sulfate- and Sulfur-Reducing Proteobacteria Dissimilative sulfate- and sulfur-reducing bacteria Over 40 genera of Deltaproteobacteria Use SO42- and So as electron acceptors and organic compounds or H2 as electron donors H2S is an end product Most obligate anaerobes Widespread in aquatic and terrestrial environments Characteristics of Sulfate- and Sulfur-Reducing Bacteria Physiology of sulfate-reducing bacteria Group I Oxidize lactate, pyruvate, or ethanol to acetate and excrete fatty acid as an end product Group II Oxidize fatty acids, lactate, succinate, and benzoate to CO2 Sulfate- and Sulfur- Reducing Bacteria: Desulfovibrio desulfuricans Sulfate- and Sulfur-Reducing Bacteria: Desulfonema limicola Sulfate-and Sulfur-Reducing Bacteria: Desulfobulbus propionicus Sulfate- and Sulfur-Reducing Bacteria: Desulfobacter postgatei Sulfate- and Sulfur-Reducing Bacteria: Desulfosarcina variabilis Sulfate- and Sulfur-Reducing Bacteria: Desulfuromonas acetoxidans Enrichment Culture of Sulfate-Reducing Bacteria Sterile medium Positive enrichment showing black FeS Colonies of sulfatereducing bacteria 15.19 The Epsilonproteobacteria Epsilonproteobacteria Abundant in oxic–anoxic interfaces in sulfur-rich environments e.g., hydrothermal vents Many are autotrophs Using H2, formate, sulfide, or thiosulphate as electron donor (nitrite, oxygen, or elemental sulfur as electron acceptor) Pathogenic and non-pathogenic representatives Campylobacter and Helicobacter All Gram-negative, microaerophilic, motile spirilla Most are pathogenic to humans or other animals e.g., Campylobacter sp. - acute enteritis leading to usually bloody diarrhea e.g., Helicobacter pylori - chronic and acute gastritis, leading to peptic ulcers (Barry Marshall and Robin Warren: 2005 Nobel Prize in Physiology and Medicine) Helicobacter pylori Arcrobacter Unusually wide diversity of habitats Some are pathogenic to humans and other animals, infecting the reproductive and intestinal tract of humans and other animals Cause reproductive failures in animals, diarrhea-like diseases in a wide range of animals, and gastroenteritis and appendicitis in humans Infection route: fecal-to-water-to-oral (?) Sulfurospirillum and Thiovulvum Sulfurospirillum Non-pathogenic, free-living microaerophiles Freshwater and marine habitats Use elemental sulfur, selenate, or arsenate as an electron acceptor Thiovulvum Microaerophilic Freshwater and marine habitats in which sulfide-rich muds interface with oxygen-containing waters Forms large internal sulfur granules No pure culture is available yet Secretes a slime stalk Wolinella Wolinella succinogenes Anaerobic, isolated from the bovine rumen Anaerobic respiration using fumarate or nitrate as electron acceptors with hydrogen or formate as electron donors Contains genes for nitrogen fixation Characteristics of Key Genera of Epsilonproteobacteria