Transcript Chapter 20
Chapter 20 The Archaea Archaea • highly diverse with respect to morphology, physiology, reproduction and ecology • best known for growth in anaerobic, hypersaline and high-temperature habitats • also found in marine arctic temperature and tropical waters Archaeal Cell Walls • lack muramic acid • walls found in group are diverse – pseudomurein (peptidoglycan-like polymer) found in some methanogenic species – complex polysaccharides, proteins or glycoproteins found in some other species Archaeal Membrane Lipids • differ from Bacteria and Eucarya in having branched chain hydrocarbons attached to glycerol by ether linkages • sulfolipids and glycolipids are also found in archaeal membranes Archaeal Lipids and Membranes Bacteria/Eucaryotes • fatty acids attached to glycerol by ester linkages Archaea • branched chain hydrocarbons attached to glycerol by ether linkages • some have diglycerol tetraethers Archaeal Genetics and Molecular Biology • exhibit some similarities to Bacteria or Eucarya • ~30% of genes shared exclusive between archeons and eucaryotes code for proteins involved in transcription, translation or DNA metabolism • many genes shared only with bacteria are involved in metabolic pathways – there is evidence for lateral (horizontal) gene transfer between archeons and bacteria More about Archaeal Genetics and Molecular Biology • DNA replication and transcription have both bacterial and eucaryotic features • archael mRNA appears to be similar to that of bacteria rather than eucaryotic mRNA • Like bacteria circular chromosome • Like eucarya – histone proteins Genus Sulfolobus • irregularly lobed, spherical shaped – cell walls contain lipoproteins and carbohydrates • thermoacidophiles – 70-80°C – pH 2-3 • metabolism – lithotrophic on sulfur using oxygen (usually) organotrophic on sugars and amino acids Fig. 20.7a Sulfolobus Habitats of methanogens • anaerobic environments rich in organic matter – e.g., animal rumens – e.g., anaerobic sludge digesters – e.g., within anaerobic protozoa – Swamps and marshes Ecological and practical importance of methanogens • important in wastewater treatment • can produce significant amounts of methane – can be used as clean burning fuel and energy source – is greenhouse gas and may contribute to global warming • can oxidize iron (mathanogen) – contributes significantly to corrosion of iron pipes Examples of Halobacteria Figure 20.12 e.g., Halobacterium salinarium (H. halobium) • has unique type of photosynthesis – not chlorophyll based – uses modified cell membrane (purple membrane) • contains bacteriorhodopsin – absorption of light by bacteriorhodopsin drives proton transport, creating PMF for ATP synthesis Chapter 21 Bacteria: The Deinococci and Nonproteobacteria Gram Negatives Cyanobacteria • largest, most diverse group of photosynthetic bacteria • many are obligate photolithoautotrophs; some can grow slowly in dark as chemoheterotrophs Photosynthesis in cyanobacteria • resembles that of eucaryotes – oxygenic photosynthesis Photosynthesis in cyanobacteria • use phycobiliproteins as accessory pigments • phycobilisomes, which line thylakoid membranes, contain phycocyanin and phycoerythrin – use Calvin cycle to fix CO2 Cyanobacterial Thylakoids and Phycobilisomes Figure 21.6 contains phycobilin pigments nitrogen storage Polymer Arginine, Aspartic acid Figure 21.7 (a) typical gramnegative cell wall site of photosynthesis Figure 21.7b More About Cyanobacteria • range in diameter from ~1 to 10 mm • may be unicellular, colonial or form filaments called trichomes (a row of cells in close contact with each other) • pigmentation – most appear blue-green due to presence of phycocyanin – presence of phycoerythrin in many ocean isolates gives them red or brown coloration Chromatic Adaptation • many use gas vacuoles to optimally position themselves in optimal illumination in water column – considered a form of phototaxis Heterocysts • specialized cells used for nitrogen fixation – produced when organism is nitrogen deprived – differentiate from individual cells in filament • involves reorganization of photosynthetic membranes – thick heterocyst wall prevents O2 diffusion into heterocyst which would inactivate nitrogenase, enzyme responsible for nitrogen fixation Fig.21.8b Ecology of cyanobacteria • tolerant of environmental extremes – thermophilic species can grow at temperatures up to 75°C – often are primary colonizers • can cause blooms in nutrient-rich ponds and lakes – some produce toxins • often form symbiotic relationships – e.g., are phototrophic partner in most lichens – e.g., symbionts with protozoa and fungi – e.g., nitrogen-fixing species form associations with plants Figure 21.11 Chlamydia • gram-negative • obligate intracellular parasites – although known for ability to cause disease, many grow within hosts such as protists, vertebrate and invertebrate cells without adverse effects. • genus Chlamydia is best studied Genus Chlamydia • nonmotile, coccoid, gram-negative bacteria – cell walls lack muramic acid and peptidoglycan – have very small genomes • obligate intracellular parasites with unique developmental cycle – involving formation of elementary body (EB) and reticulate body (RB) or initial body – found mostly in mammals and birds – some recently isolated from spiders, clams, and freshwater invertebrates Figure 21.13b Chlamydial metabolism • appear to be energy parasites, obtaining ATP from host – do have genes for substrate-level phosphorylation, electron transport, and oxidative phosphorylation • reticulate bodies have biosynthetic capabilities when supplied precursors from host; can synthesize some amino acids • elementary bodies seem to be dormant forms Important pathogens • C. trachomatis – infects humans and mice – causes trachoma (blindness), nongonococcal urethritis, and other diseases in humans • C. psittaci • Associated with birds - parrots – infects humans and many other animals – causes psittacosis in humans • C. pneumoniae – common cause of human pneumonia Spirochetes • gram-negative bacteria with distinctive structure and motility – slender, long with flexible helical shape – creeping (crawling) motility due to a structure called an axial filament • chemoheterotrophs • ecologically diverse Figure 21.14 axial filament = complex of axial fibrils (periplasmic flagella) Figure 21.15 (a1) and (a2) Symbiotic Associations between Spirochetes and Other Organisms • broad range of organisms • found in a variety of locations, for example – hindguts of termites – digestive tracts of mollusks and mammals – oral cavities of animals • Treponema pallidum – syphilis STD • Ulcer, rash, latent stage, Tertiary stage Bacteroides • gram-negative rods of various shapes – do not form endospores – motile or nonmotile • anaerobic chemoheterotrophs – fermentative • often found in oral cavity and intestinal tract of humans and other animals and the rumen of ruminants – often benefit host by degrading complex carbohydrates, providing extra nutrition to host – can constitute up to 30% of bacteria from human feces genus Cytophaga • slender rods, often with pointed ends • aerobic metabolism – degrade complex polysaccharides • e.g., cellulose, chitin, pectin, keratin, agar – significant component of bacterial population in sewage treatment plants – most are free-living; some are pathogenic in vertebrate hosts • e.g., Cytophaga columnaris – pathogen of fish Chapter 22 Bacteria: The Proteobacteria Rickettsia • rod-shaped, coccoid, or pleomorphic – typical gram-negative cell walls – no flagella – very small • Rickettsia – 0.3 to 0.5 by 0.8 to 2.0 mm • Obligate intracellular parasites. – Grow in vertebrate erythrocytes, macrophages, and vascular endothelial cells • also live in blood-sucking arthropods, which serve as vectors or primary hosts • Rickettsia rickettsii – rocky mountain spotted fever • Transmitted by ticks • Rash on palms Rickettsia metabolism • lack glycolytic pathway – do not use glucose as energy source • oxidize glutamate and TCA cycle intermediates (e.g., succinate) • take up and use ATP and other materials from host cell Important pathogen • Rickettsia rickettsii – Rocky Mountain Spotted Fever Genus Caulobacter • in class Caulobacteraceae • may be polarly flagellated rods or may possess prostheca and holdfast(end of the stem like stucture. – used to attach to solid substrata with what is known as the strongest biological adhesion molecule (superglue) – prostheca lacks cytoplasmic components Genus Caulobacter • usually found in oligotrophic aquatic and terrestrial habitats – often adhere to other microorganisms • may absorb nutrients released from hosts – long prosthecae – stalk (extension of the cell, but narrower) may improve nutrient uptake Caulobacter Figure 22.7 (b) and (c) Figure 22.8 Genus Rhizobium • gram-negative, motile rods – often contain poly-b-hydroxybutyrate granules – become pleomorphic under adverse conditions • grow symbiotically as nitrogen-fixing bacteroids within root nodule cells of legumes • Form nodules in the roots and convert nitrogen gas to ammonia • Plants use ammonia to make protein Figure 22.9 Figure 22.11 Nitrification • ammonianitritenitrate • conversion of ammonia to nitrate by action of two genera – e.g., Nitrosomonas – ammonia to nitrite – e.g., Nitrobacter – nitrite to nitrate • fate of nitrate – easily used by plants – Chemolithotrophs – get electrons from inorganic substance Genus Neisseria • nonmotile, gram-negative cocci – most often occur in pairs with adjacent sides flattened – may have capsules and fimbriae • aerobic chemoorganotrophs • inhabitants of mucous membranes of mammals – some human pathogens • Neisseria gonorrhoeae – gonorrhea - STD • Neisseria meningitidis – meningitis - aerosol Genus Bordetella • gram-negative coccobacilli – some have capsules • aerobic chemoorganotrophs – respiratory metabolism – require organic sulfur and amino acids for growth • mammalian parasites that multiply in respiratory epithelial cells • e.g., Bordetella pertussis – – – – nonmotile, encapsulated species causes whooping cough Cough violently gasp for air DTP pertussis - vaccine has heat killed bacteria Thiobacillus – well studied chemolithotroph – prominent member of colorless sulfur bacteria • chemolithotrophs that oxidize sulfur compounds • Gram negative rod, soil Genus Thiobacillus • found in soil and aquatic habitats – production of sulfuric acid can cause corrosion of concrete and metal structures – may increase soil fertility by releasing sulfate Figure 22.18 Chromatium • typical purple sulfur bacteria • strict anaerobes • usually photoautolithotrophs – use H2S as electron donor • deposit sulfur granules internally • often eventually oxidize sulfur to sulfate – may also use hydrogen as electron donor • usually found in anaerobic, sulfide-rich zones of lakes – can cause large blooms in bogs and lagoons • Fig. 22.19a Figure 22.20 (a) Fig. 22.20b Pseudomonas • chemoheterotrophs with respiratory metabolism – usually use oxygen as electron acceptor – sometimes use nitrate as electron acceptor – have functional TCA cycle Practical importance of pseudomonads • metabolically versatile – degrade wide variety of organic molecules – mineralization • microbial breakdown of organic materials to inorganic substrates • important experimental subjects • some are major animal and plant pathogens • some cause spoilage of refrigerated food – can grow at 4°C – Pseudomonas aeruginosa – opportunist – Wound and burn infections Vibrio cholerae • causes cholera • genome has been sequenced – has two circular chromosomes – copies of some genes present on both chromosomes – Contaminated water – Cholera toxin – stimulates the cell to release – Water and electrolytes – profuse and watery diarrhea- rice water stools Vibrio cholerae • • • • • • • G-, bent rod, single flagellum Intestine, toxin Cholera Cells lining the intestine Stimulate them to release water and electrolytes Profuse and watery diarrhea Rice water stools – mucus, epithelia cells, bacteria Escherichia coli • probably best studied bacterium • inhabitant of intestinal tracts of many animals • used as indicator organisms for testing water for fecal contamination • some strains are pathogenic – gastroenteritis – urinary tract infections – E. coli O157:H7 – dysentery – contaminated undercooked hamburgers Important pathogenic enteric bacteria • Salmonella – typhoid fever and gastroenteritis • Shigella – bacillary dysentery • Klebsiella – pneumonia • Yersinia - plague Salmonella typhi • • • • • G- rod, typhoid fever Found in humans Carriers – gall bladder Fluoroquinilones, chloramphenicol Contaminated food or water Salmonella enteritidis • • • • • • Salmonellosis Poultry and cattle Undercooked, contaminated food Fever, abdominal pain, diarrhea Fluid and electrolyte therapy Cooking the meat thoroughly Shigella dysenteriae • • • • • • G- rod, shigellosis Humans Contaminated food Produces toxin Damage to the intestinal wall Fluoroquinilones Yersinia pestis • • • • • G- rod, plague Fleas from rats Southwestern – squirrels, chipmunks Direct contact Proliferate in the blood stream Y. pestis • Buboes – swelling of lymph nodes. Bubonic plague • Mortality – 50 to 75% • Streptomycin and tetracycline – prophylaxis • Pneumonic plague – aerosol • Mortality rate 100% Bdellovibrio pathogenic to other bacteria Figure 22.23 Figure 22.34 (a) Myxococcus • gram-negative, rod-shaped gliding bacteria • aerobic chemoorganotrophs with respiratory metabolism – most are micropredators or scavengers that lyse bacteria and yeasts by secretion of digestive enzymes • most use amino acids as major source of C, N, and energy Myxobacteria • distinctive life cycle which resembles that of cellular slime molds • in presence of food form a swarm and migrate on solid surfaces • form a fruiting body when nutrients are exhausted – involves at least 5 extracellular signaling molecules which allow cells to communicate with each other Figure 22.36 Fruiting Bodies • formation requires gliding motility and involves at least 5 extracellular signaling molecules which allow cells to communicate with each other • range in height from 50 to 500 mm • colored by carotenoid pigments • vary in complexity • some cells develop into dormant myxospores Myxospores • frequently enclosed in walled structures called sporangioles (sporangia) • dormant and desiccation-resistant – may survive up to 10 years Figure 22.37 Chapter 23 Bacteria: The Low G + C Gram Positives Endospores – have a complex structure containing a coat, cortex, and inner spore membrane surrounding the protoplast – dipicolinic acid is present – heat resistant – dormant and viable for long periods of time Figure 23.6 Important species of Clostridium • C. botulinum – food spoilage (especially canned foods); botulism • C. tetani – tetanus • C. perfringens – gas gangrene Figure 23.7 Clostridium • • • • • Gram + Obligate anaerobe Endospores Soil 3 pathogenic species Clostridium tetani - tetanus • • • • • • • • Infects deep puncture wounds Endospores become vegetative cells Neurotoxin – spastic paralysis Stiffness of the muscles Lockjaw DTP vaccine – tetanus toxoid Antitoxin – antibodies Tetanus immune globulins (TIG) Clostridium botulinum - botulism • • • • • Improperly canned food Neurotoxin Flaccid paralysis Double vision, drooping eyelids Toxin is heat labile Clostridium perfringens • Gas gangrene • Gangrene – death of a tissue due to the loss of blood supply • Ferments carbohydrates and releases gas • Toxins kill cells • Bullet wounds, frost bites • Amputation Bacillus subtilis • type species • used as model organism for cellular differentiation, division and other processes • various species produce antibiotics Other important species of Bacillus • B. cereus – food poisoning • B. anthracis – anthrax • B. thuringiensis – used as insecticide Bacillus anthracis - anthrax • Sheep, cattle – endospores are ingested from the soil – septicemia • People at risk – work with animals • Cutaneous anthrax – cuts and breaks in the skin. • Inhalation anthrax – wool sorter’s disease • Dangerous form of pneumonia • Tetracycline Figure 23.9 Figure 23.13 Pathogenic Staphylococcus • Staphylococcus epidermidis – common skin resident – sometimes responsible for endocarditis and for infections of patients with lowered resistance • e.g., wound infections, surgical infections, and urinary tract infections Antibiotic Resistant Staphylococci • resistance to methicillin – Methicillin-Resistant Staphylococcus aureus (MRSA) • obtained from genetic elements received from other organisms • resistance to vancomycin, the “drug of last resort” Staphylococcus aureus • produces the virulence factor coagulase – causes blood plasma to clot • produces hemolysin – toxin which lyses cells • major cause of food poisoning – recently >1,000 school children in Texas had staphylococcal food poisoning caused by eating improperly handled chicken • found on nasal membranes and skin, and in gastrointestinal and urinary tracts Genus Lactobacillus • widely distributed in nature – on plant surfaces – in dairy products, meat, water, sewage, beer, fruits, and other materials – normal flora of mouth, intestinal tract, and vagina • usually not pathogenic Figure 23.14 Figure 23.17 Important streptococci, enterococci, and lactococci • Streptococcus pyogenes – streptococcal sore throat, • • • • acute glomerulonephritis, and rheumatic fever Streptococcus pneumoniae – lobar pneumonia and otitis media Streptococcus mutans – dental caries Enterococcus faecalis – opportunistic pathogen (urinary tract infections and endocarditis) Lactococcus lactis – production of buttermilk and cheese Chapter 24 Bacteria: The High G + C Gram Positives Corynebacterium • many are animal and human pathogens – e.g., C. diphtheriae - diphtheria Genus Mycobacterium – straight or slightly curved rods that sometimes branch or form filaments Figure 24.10 Mycobacterial cell walls • contain waxes with 60 to 90 carbon mycolic acids • acid-fast – basic fuchsin dye cannot be removed from cell by acid alcohol treatment Important species of Mycobacterium • M. bovis – tuberculosis in cattle and other ruminants • M. tuberculosis – tuberculosis in humans • M. leprae – leprosy Impact of Nocardia • most are free-living saprophytes – can degrade many molecules • e.g., petroleum hydrocarbons, detergents, benzene • involved in biodegradation of rubber joints in water and sewage pipes • some are opportunistic pathogens causing nocardiosis – usually infect lungs; can infect central nervous system Streptomycetes • are 1 to 20% of culturable soil microbiota – produce geosmin • volatile substance that is source of moist earth odor – important in mineralization process • aerobically degrade many resistant substances (e.g., pectin lignin, and chitin) • produce vast array of antibiotics • most are nonpathogenic saprophytes Streptomyces • aerial hyphae that divide in single plane to form chains of 3-50 nonmotile spores Figure 24.15