Chapter 20 Nonproteobacterial Gram-Negative Bacteria PDF

Because learning changes everything.® Chapter 20 Nonproteobacterial Gram-Negative Bacteria Prescott’s Microbiology Twelfth edition Joanne Willey, Kathleen Sandman, Dorothy Wood © 2023 McGraw Hill, LLC. All rights reserved. Authorized only for instructor use in the classroom....

Because learning changes everything.® Chapter 20 Nonproteobacterial Gram-Negative Bacteria Prescott’s Microbiology Twelfth edition Joanne Willey, Kathleen Sandman, Dorothy Wood © 2023 McGraw Hill, LLC. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw Hill, LLC.  Cell Envelope Monoderm—have only a plasma membrane. Common to stain gram positive. Diderm—have two membranes. Plasma membrane Outer membrane Common to stain gram negative Cell envelops are continuously studied and reveal diverse structures. © McGraw Hill, LLC 2  Microbial Hyperthermophiles Grow above 80°C. Two phyla are Aquificota and Thermotogota. Genus Aquifex Chemolithoautotrophs that capture energy by oxidizing hydrogen, thiosulfate, and sulfur with oxygen as the terminal electron acceptor. Aquifex pyrophilus Microaerophilic rod Growth optimum 85°C and a maximum 90°C. © McGraw Hill, LLC 3  Genus Thermotoga Rods with an outer sheathlike envelope that can extend or balloon out from ends of the cell enclosing a large periplasmic space. Outer membrane lacks LPS and is enriched in protein. Grow in active geothermal areas in marine hydrothermal systems and terrestrial ©Karl O. Stetter solfataric springs. Chemoorganotrophs © McGraw Hill, LLC 4  Phylum Deinococcota Two families, Deinococcaceae and Thermaceae. Deinococci Spherical or rod-shaped and non-motile, often seen in pairs or tetrads. Stain Gram positive (outer membrane has LPS). (a) Michael J. Daly/Science Source; (b) ©Dr. Robert G.E. Murray/University of Western Ontario Access the text alternative for slide images. © McGraw Hill, LLC 5  Deinococci Characteristics Extraordinarily resistant to desiccation and radiation. Survive 3 to 5 million rad of radiation (100 rad lethal to humans). Mechanism of radiation resistance involves protection from ROS- induced oxidation. (a) Michael J. Daly/Science Source Access the text alternative for slide images. © McGraw Hill, LLC 6  Characteristics of Photosynthetic Bacteria Major photosynthetic pigments Morphology of photosynthetic membranes Photosynthetic electron donors Sulfur deposition Nature of phototrophy General metabolic type Motility Taxonomic distribution © McGraw Hill, LLC 7  Photosynthetic Bacteria Cyanobacteria carry out oxygenic photosynthesis. Have two photosystems. Use water as an electron donor. Generate oxygen during photosynthesis. Purple bacteria, green bacteria, and AAnPs have only one photosystem and carry out anoxygenic photosynthesis. © McGraw Hill, LLC 8  Photosynthetic Microbes Differences in photosynthetic pigments and oxygen requirements are important ecologically. Pigments collect light of different wavelengths and transfer it to Chl or Bchl, where it is converted to chemical energy. Access the text alternative for slide images. © McGraw Hill, LLC 9  Green Sulfur Bacteria Phylum Bacteroidota. Obligate anaerobic photolithoautotrophs. Use H2S, elemental sulfur, and H2 as electron sources. Elemental sulfur deposited outside cell. Live in sulfide-rich areas. (b) ©Dr. Vasil Gaisin, Professor Martin Pilhofer, Dr. Romain Kooger Access the text alternative for slide images. © McGraw Hill, LLC 10  Green Sulfur Bacteria Structures Chlorosomes Ellipsoidal vesicles attached to plasma membrane that contain photosynthetic pigments. Lipid monolayer Reaction center Complex of proteins and cofactors that capture light energy from photons and transfer it to electrons. Access the text alternative for slide images. © McGraw Hill, LLC 11  Phylum Chloroflexota: Green Nonsulfur Bacteria Chloroflexus ssp. Some are facultative anaerobes, others are anaerobic. Some are chemoorganotrophic, most are photoheterotrophic. When growing autotrophically, they use the 3-hydroxypropionate bi-cycle to fix CO2. Access the text alternative for slide images. © McGraw Hill, LLC 12  Phylum Cyanobacteria: Oxygenic Photosynthetic Bacteria Largest and most diverse group of photosynthetic bacteria. Endosymbiotic cyanobacteria are thought to have evolved into chloroplasts. Resembles photosynthesis of eukaryotes. Have photosystems I and II Have chlorophyll a Oxygenic photosynthesis © McGraw Hill, LLC 13  Photosynthesis in Cyanobacteria—Carbon Fixation Phycobilisomes—contain electron-transport chain components in thylakoid membrane. Contain phycobiliproteins, particularly phycocyanin and phycoerythrin. (a) Joanne M. Willey, Ph.D. Access the text alternative for slide images. © McGraw Hill, LLC 14  Cyanobacterial Pigmentation Blue-green color due to presence of phycocyanin. Presence of phycoerythrin in many ocean isolates gives them red or brown coloration. Chromatic acclimation—modulation of pigment concentrations in different light. Maximizes energy capture for ambient light conditions. Mechanism involves changing gene expression. Phototaxis—use of gas vacuoles to position themselves in in optimum illumination. © McGraw Hill, LLC 15  Cyanobacteria Cellular Processes Employ CO2-concentration mechanisms to facilitate high rates of carbon fixation. Carboxysomes—microcompartments that contain carbonic anhydrase and RuBisCO. During daylight, cyanobacteria synthesize glycogen as a reserve carbohydrate for respiration at night. Cyanophycin—polymers of arginine and aspartic acid that store nitrogen. © McGraw Hill, LLC 16  Cyanobacteria Morphology Can be unicellular, exist as colonies of many shapes or form filaments. Trichome—row of bacterial cells in close contact with one another over a large area. Individual plasma membrane, but share outer membrane and periplasmic space. (a) M.I. Walker/Science Source; (b) Don Rubbelke/McGraw Hill; (c) Gerd Guenther/SPL/Science Source; (d) ©Dr. Burkhard Büdel Access the text alternative for slide images. © McGraw Hill, LLC 17  Cyanobacteria Motility Gliding Used by microbes in microbial mats. Swimming Lack flagella Used to move toward simple nitrogenous compounds. © McGraw Hill, LLC 18  Cyanobacteria Reproduction Binary fission Budding Fragmentation Multiple fission Baeocytes—small progeny from an enlarged cell that divides. Disperse by gliding. Hormogonia—motile filaments. Akinetes—dormant, thick-walled resting cells resistant to desiccation. © McGraw Hill, LLC 19  Heterocysts Specialized cells used for nitrogen fixation. Produced when organism is nitrogen deprived. Differentiate from individual cells in filament. Thick heterocyst wall prevents O2 diffusion into heterocyst which would inactivate nitrogenase. (a) Jason K. Oyadomari; (b) Biophoto Associates/Science Source Access the text alternative for slide images. © McGraw Hill, LLC 20  Prochlorophytes Cyanobacteria in genera Prochloron, Prochlorococcus, and Prochlorothrix. Distinguished by presence of chlorophyll a and b and lack of phycobilins. Are the only prokaryotes to possess chlorophyll b. Makes them candidates as ancestors of endosymbionts that give rise to chloroplasts. © McGraw Hill, LLC 21  Cyanobacterial Ecological Relationships Prochlorococcus spp. Flourish in marine plankton. Prochlorococcus marinus globally distributed, so it is the most abundant photosynthetic organism on Earth. Synechococcus and Prochlorococcus Profound effect on global CO2 fixation. Coevolved to take advantage of incident light, not competing for the for light source. © McGraw Hill, LLC 22  Phylum Planctomycetes Anammoxosome membrane bound organelle that occupies much of cell volume. Anammox reaction— localized anaerobic ammonia oxidation. Cell wall lacks peptidoglycan. Genus Planctomyces Attach to surfaces through stalk and holdfast. Most have life cycles in which sessile cells bud to produce motile swarmer cells. Access the text alternative for slide images. © McGraw Hill, LLC 23  Phylum Verrucomicrobiota Includes Human Symbionts and Obligate Intracellular Parasites Verrucomicrobiota Akkermansia muciniphila Makes up 1 to 5% of human gut microbiome. Diminishes obesity-related inflammation. Consumes mucus; obligate anaerobe with fermentative metabolism. Nonmotile and coccobacillus in shape. © McGraw Hill, LLC 24  Phylum Chlamydiae: Obligate Intracellular Parasites Gram-negative. Obligate intracellular parasites. Must grow and reproduce inside host cells. Although their ability to cause disease is widely recognized, many species grow within protists and animal cells without adverse effects. Genus Chlamydia is best studied. © McGraw Hill, LLC 25  Genera Chlamydiae and Chlamydophila Nonmotile, coccoid, and Gram-negative. Range in size from 0.2 to 1.5 μm. Limited metabolically, relying on host cells for metabolites. Have very small genomes. Unique reproduction Elementary body (EB) attaches to host cell. Reticulate body (RB) reproduction by binary fission. Differentiate back into mature EB. (b) SPL/Science Source © McGraw Hill, LLC 26  The Chlamydial Life Cycle Access the text alternative for slide images. © McGraw Hill, LLC 27  Chlamydial Metabolism Cannot catabolize carbohydrates. Cannot synthesize ATP or NAD+. Energy parasites—completely dependent on host for ATP. RBs have biosynthetic capabilities when supplied precursors from host; can synthesize some amino acids. © McGraw Hill, LLC 28  Phylum Spirochaetota Chemoorganotrophic bacteria with distinctive shape and motility. Slender, long with flexible helical shape. Periplasmic flagella—extend from both ends of the cylinder and wrap around the peptidoglycan. Rotation enables motility. Corkscrewlike movement. Flexing and crawling on solid surface. (b) Science Source Access the text alternative for slide images. © McGraw Hill, LLC 29  Symbiotic Associations Between Spirochetes and Other Organisms Free living Symbiotic associations Hindguts of termites and wood-eating roaches. Digestive tracts of mollusks and mammals. Oral cavities of animals. Cause disease Lyme disease Phase variation—changes during an infection to hide from immune clearance. © McGraw Hill, LLC 30  Phase Variation in Borrelia Detailed mechanism remains to be discovered. vlsE expression cassette Modular genetic organization. High rate of spontaneous mutation. Access the text alternative for slide images. © McGraw Hill, LLC 31  Phylum Bacteroidota Diverse, includes photolithoautotrophic green sulfur bacteria and chemoheterotrophs. Many contribute to digestion of cellulose, agar and chitin. Common in terrestrial and marine environments, and in sewage treatment plants where they contribute to the treatment process. © McGraw Hill, LLC 32  Genus Bacteroides Anaerobic, diderm, and non- spore-forming rods. Motility is rare. Often found in human intestinal tract and animal rumens. Benefit host by degrading cellulose, pectins and complex carbohydrates. Constitute up to 30% of bacteria from human feces. Some cause disease. Access the text alternative for slide images. © McGraw Hill, LLC 33  Gliding Motility Characteristic of Sporocytophaga Gliding mechanism not well understood. F. johnsoniae use glide (gld) proteins. Gld proteins harvest energy of the proton motive force. Gld proteins propel large, filamentous surface proteins called SprB. Access the text alternative for slide images. © McGraw Hill, LLC 34  Advantages of Gliding Motility Enables cells to encounter insoluble nutrient sources and digest them with cell bound digestive enzymes. Works well in drier habitats and within solid masses (i.e., soil, sediments, and rotting wood). Enables cells to position themselves optimally for light intensity, [O2], [H2S], temperature, etc. © McGraw Hill, LLC 35  Fusobacteriota Characteristic spindle, or football, shape. Obligate or facultative anaerobes. Inhabit both anoxic sediments and oral and intestinal habitats of mammals and insects. Can cause opportunistic infections in humans. © McGraw Hill, LLC 36  Sulfur-Reducing Bacteria (SRB) Reduce sulfur and other oxidized sulfur compounds to hydrogen sulfide during anaerobic respiration. Dissimilatory sulfate reduction—sulfur atoms not incorporated into biomass. Oxidize lactate, formate, butyrate, propionate, pyruvate, and aromatic compounds to acetate. © McGraw Hill, LLC 37  Dissimilatory Sulfate Reduction Access the text alternative for slide images. © McGraw Hill, LLC 38  SRB Important in Sulfur Cycling within Ecosystems Sulfate is present in aquatic and terrestrial habitats. Dissimilatory sulfate reduction—sulfur atoms not incorporated into biomass. Oxidize lactate, formate, butyrate, propionate, pyruvate, and aromatic compounds to acetate. Negative impact on industry because primary role in anaerobic corrosion of iron in pipelines. © McGraw Hill, LLC 39  Family Geobacteraceae Strict anaerobes with respiratory or fermentative metabolism. The capacity of Geobacter spp. to conserve energy from dissimilatory metal reduction is of great interest to environmental microbiologists. These bacteria can reduce toxic and radioactive metals. Nanowires—enable electron transport to solid phase acceptors that a physically distant from the microbe. © McGraw Hill, LLC 40  Cable Bacteria Ubiquitous in aquatic sediments. Aerobic sulfide oxidizers E-cables are a multicellular system with 2 different cell types. Access the text alternative for slide images. © McGraw Hill, LLC 41  Genus Bdellovibrio Aerobic, Gram-negative, curved rods with polar flagella. Distinctive lifestyle Pray on other diderm bacteria. Swims rapidly until it collides with prey and makes a hole in the host for entry. Alternate between nonreplicating predatory phase and intracellular reproductive phase. Access the text alternative for slide images. © McGraw Hill, LLC 42  Genus Bdellovibrio Controls Host Host cell loses shape and becomes spherical. Host plasma membrane is disrupted and cytoplasmic constituents leak out of the cell. Bdellovibrio uses host amino acids as carbon, nitrogen and energy source. (b) Katy Evans, Chi Aizawa and Liz Sockett © McGraw Hill, LLC 43  Myxobacteria Gram-negative and aerobic soil bacteria. Rods, slender or stout. Gliding motility. Complex life cycle that includes fruiting bodies and formation of spores (myxospores). Predators that do not rely on predation for reproduction. Lytic enzymes and antibiotics released to kill prey. Access the text alternative for slide images. (a) Eye of Science/Science Source © McGraw Hill, LLC 44  Myxobacteria Life Cycle Fruiting bodies—range in size and are characteristic to each species. Myxospores—dormant and desiccation-resistant. Access the text alternative for slide images. © McGraw Hill, LLC 45  Genus Campylobacter Pathogens C. fetus causes reproductive disease and abortions in cattle and sheep. Some use molecular mimicry to cause the immune system to mistakenly attack the host’s nervous system. Some non-pathogenic strains do exist. © McGraw Hill, LLC 46  Genus Helicobacter Helicobacter pylori Causes gastritis, peptic ulcer disease, and gastric cancer. Microaerophile Cannot grow under pH 4.5 In gut, it the microbe burrows within gastric mucosa, to avoid the acidity of the stomach lumen. Produces the enzyme urease, which converts urea to CO2 and NH3 which drives up local pH. © McGraw Hill, LLC 47