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Chapter 11 The Prokaryotes: Domains Bacteria and Archaea Part 2 The Nonproteobacteria GramNegative Bacteria • Not closely related to the gram-negative proteobacteria • Several physiological and morphologically distinctive photosynthesizing bacteria • Phyla Cyanobacteria, Chlorobi (green sulfur bacteria) & Choloroflexi (green nonsulfur bacteria) The Nonproteobacteria GramNegative Bacteria Photosynthetic Bacteria Photosynthetic Bacteria • Phyla Cyanobacteria, Chlorobi, Chloroflexi, photosynthetic purple sulfur bacteria (proteobacteria), and purple nonsulfur bacteria (-proteobacteria) • Photoautotrophs and chemoheterotrophs • Photosynthetic purple and green sulfur bacteria are generally anaerobic and usually found in deep sediments of lakes and ponds Cyanobacteria • Oxygenic (oxygen-producing) photosynthetic bacteria – Produce O2 from H2O using light energy • Characteristic blue-green (cyan) pigmentation • Gliding motility or gas vacuoles • Fix nitrogen (into ammonium) from atmosphere in specialized cells called heterocysts • Morphologically varied (Unicellular to colonial form) Cyanobacteria Figure 11.12a-c Purple and Green Photosynthetic Bacteria • Anoxygenic photosynthesis (does not produce O2) – carry out photosynthesis to make carbohydrates – Possess chlorophyll Oxygenic 2H2O + CO2 light (CH2O) + H2O + O2 Anoxygenic (purple sulfur and green sulfur bacteria) 2H2S + CO2 light (CH2O) + H2O + 2S0 Phylum Chlamydiae • Do not contain peptidoglycan in cell walls – Chlamydia: intracellular parasite; a unique developmental cycle (elementary body is the infective agent); gram-negative coccoid – Transmitted via interpersonal contact or by airborne respiratory routes • C. trachomatis • C. pneumoniae • C. psittaci Trachoma, STD, urethritis Mild form of pneumoniae Causes psittacosis (ornithosis) In Bergey's Manual, Volume 5 Figure 11.22a In Bergey's Manual, Volume 5 Figure 11.22b Phylum Spirochaetes • Coiled morphology; outer sheath; axial filaments (endoflagella) for motility – many are found in oral cavity • Borrelia Relapsing fever and Lyme disease • Leptospira leptospirosis • Treponema syphilis (T. pallidum) Figure 11.23 Phylum Bacteroidetes • Anaerobic Bacteria – Bacteroides: nonmotile; in mouth (gingival crevice) and large intestine; also recovered frequently from deep tissue infections – Cytophaga: degrade cellulose and chitin in soil; gliding motility Phylum Fusobacteria • Often pleomorphic, may be spindleshaped – Fusobacterium: found in mouth (gingival crevice); may be involved in dental diseases Figure 11.24 Gram-Positive Bacteria • Two groups: – high G + C ratios (above 50%) e.g. Phylum Actinobacteria (mycobacteria, corynebacteria,and actinomycetes) – low G + C ratios (below 50%) e.g. Phylum Firmicutes (common soil bacteria, lactic acid producing bacteria, and several human pathogens) Phylum Firmicutes • Low G + C • Gram-positive Order Clostridiales • Clostridium – Form endospores – Obligate anaerobes • C. botulinum Botulism • C. tetani Tetanus • C. perfringens Gas gangrene Food diarrhea • C. difficile Severe diarrhea • Epulopiscium – Giant prokaryote; symbiotic in the gut of surgeonfish Figure 11.14 & 15 Order Bacillales • Important genera of grampositive rods and cocci • Bacillus – Rod-shaped bacteria that form endospores – Common in soils • B. anthracis: Anthrax • B. thuringiensis: Microbial insect pathogen • B. cereus: Occasional food poisoning Figure 11.16b Order Bacillales • Staphylococcus – Cocci in clusters • S. aureus: facultative anaerobes; can tolerate high osmotic pressure and low moisture; produce many toxins (e.g. enterotoxin); toxic shock syndrome, food poisoning Figure 1.17 Order Lactobacillales • Generally aerotolerant anaerobes, lack an electron-transport chain • Lactobacillus – produce lactic acid (industrial and commercial application); found in vagina, intestinal tract, and oral cavity • Enterococcus – facultative anaerobes; found in GI tract, vagina, and oral cavity; leading cause of nosocomial infection Order Lactobacillales – E. faecalis & E. faecium: infect surgical wounds & urinary tract • Listeria: facultative anaerobes – L. monocytogenes: contaminate food (dairy products); can grow in refrigeration temperature • Streptococcus – Usually cocci in chains; human pathogens – Have hemolytic activity (alpha hemolysis, beta hemolysis, and no hemolysis) Order Lactobacillales – S. pyogenes: scarlet fever, pharyngitis, impetigo, and rheumatic fever – S. mutans: dental carries – S. pneumoniae: most common cause of pneumonia Figure 11.18 Order Mycoplasmatales • Wall-less and highly pleomorphic • Very small (0.1 - 0.25 µm) • Degenerative evolution – M. pneumoniae: common form of mild pneumonia – Spiroplasma: plant pathogens and common parasites of plantfeeding insects Figure 11.19a, b Actinobacteria • High G + C • Gram-positive; highly pleomorphic; tend to be filamentous; very common inhabitants in soil Phylum Actinobacteria • Mycobacterium – Aerobic, acid-fast (contains mycolic acids which forms waxy, water resistant layer in cell wall); slow grower (may take weeks for visible colonies to appear) – Found in soil and water; occasional pathogens – Human pathogens • M. tuberculosis • M. leprae Tuberculosis Leprosy Phylum Actinobacteria • Nocardia – Aerobic; filamentous morphology – Reproduction by forming rudimentary filaments which fragment into short rods – Cell wall resemble mycobacteria; often acidfast • N. asteroides Mycetoma and occasionally cause a chronic, difficult-to-treat pulmonary infection Phylum Actinobacteria • Corynebacterium – Tend to be pleomorphic; morphology varies with the age of the cells • C. diphtheriae Diphtheria • Propionibacterium – Form propionic acid; fermentation of Swiss cheese • P. acnes Common on human skin, cause acne • Frankia – Form nitrogen-fixing nodule in alder tree roots Phylum Actinobacteria • Gardenella – Gram-variable; highly pleomorphic – Cause of one of the most common forms of vaginitis • Actinomyces – Facultative anaerobe; filamentous morphology – Found in the mouth and throat of humans and animals • A. israelii actinomycosis Phylum Actinobacteria • Streptomyces – One of the most commonly isolated bacteria from soil; responsible for the musty odor of soil – Strict aerobes; filamentous bacteria – Produce most of our commercial antibiotics Figure 11.20b Microbial Diversity • Bacteria size range – Thiomargarita (750 µm) to nanobacteria (0.02 µm) in rocks Figure 11.26 Microbial Diversity • PCR indicates up to 10,000 bacteria/gm of soil. Many bacteria have not been identified or characterized because they: – Haven't been able to culture (need to develop special media/nutrients and cultivation condition) – Are part of complex food chains requiring the products of other bacteria – Need to be cultured to understand their metabolism and ecological role Chapter Review • Prokaryotic organisms are classified into 2 domains: Archaea & Bacteria based on rRNA sequences – Each domain is further subdivided into phylum, class, order, family, genus, and species • Domain Bacteria – Relatively few species cause disease in humans, animals, plants or any other organisms – Essential part of life on Earth Domain Bacteria • Phylum: Proteobacteria (gram-negative bacteria) 1) Alpha- (α-) proteobacteria – Includes most of the proteobacteria that are capable of growth at very low levels of nutrients; nitrogen –fixing bacteria & several plant & human pathogens – Some bacteria with unusual morphology such as prosthecae – Prosthecae: a stalk or bud protruding from a prokaryotic cell Domain Bacteria 2) Beta- (-) proteobacteria – Often use nutrient substances that diffuse away from areas of anaerobic decomposition of organic matter – Considerable overlap between the α- & proteobacteria, especially among the nitrifying bacteria; some human pathogens in this group – Spirillum helical shaped bacteria, but use flagella for motility (not axial filament) Domain Bacteria 3) Gamma- (-) proteobacteria – Constitute the largest subgroup of proteobacteria; many are human & plant pathogens (e.g. Order Pseudomonadales, Legionellales, Vibrionales, Enterobacteriales, & Pasteurellales) 4) Delta (-) proteobacteria – Include some bacteria that are predators of other bacteria and important contributors to the sulfur cycle (e.g. Bdellovibrio, Desulfovibrio, and Myxococcus) – Myxococcus form fruiting bodies under low nutrients condition Domain Bacteria 5) Epsilon- (-) proteobacteria – Slender gram-negative rods that are helical or vibrioid (e.g. Campylobacter & Helicobacter) – Vibrioid: helical bacteria that do not have a complete turn • Gram-negative Nonproteobacteria – Include several photosynthetic bacteria: Phyla cyanobacteria, green sulfur bacteria, & green nonsulfur bacteria (Table 11.2) Domain Bacteria – Purple sulfur (α-proteobacteria) & purple nonsulfur (-proteobacteria) also included in this section – Cyanobacteria carry out oxygenic (oxygenproducing) photosynthesis and fix nitrogen gas (in specialized cell called heterocyst) from the atmosphere into ammonium – Green & purple photosynthetic bacteria carry out anoxygenic photosynthesis (generally anaerobic) Domain Bacteria • Gram-positive bacteria – 2 groups based on G + C ratio 1) Firmicutes (low G + C ratio) – Includes important endospore forming bacteria (e.g. Bacillus & Clostridium), medically important bacteria (e.g. Staphylococcus, Enterococcus, & Streptococcus), industrially important bacteria (e.g. Lactobacillus), and wall-less Mycoplasma Domain Bacteria 2) Actinobacteria (high G + C ratio) – Highly pleomorphic, but tend to be fimalentous – Common inhabitants in soil – e.g. acid-fast group (e.g. Mycobacterium & Nocardia), and antibiotic producing Streptomyces. • Assorted Phyla – Chlamydiae: no peptidoglycan in cell wall; intracellular parasite (human pathogen); has unique developmental cycle (elementary body = infectious) Domain Bacteria – Spirochaetes: coiled morphology; motility by axial filament; many found in human oral cavity & in environment; some human pathogens – Bacterioidetes: several genera of anaerobic bacteria – Fusobacteria: anaerobic bacteria, spindleshaped (often pleomorphic); can cause dental diseases Domain Archaea • Cell wall lacks peptidoglycan; a few lack cell wall • Frequent inhabitants of exceptional extreme environment (heat, cold, acidity, & pressure) • 3 major groups: – Extreme halophiles: survive in very high concentrations of salt; found in Great Salt Lake, solar evaporating ponds, salinas, & Dead Sea Domain Archaea – Extreme thermophiles: thrive in high temperature (above 70 oC) or sulfur rich environment; found in acidic, sulfur rich hot springs or deep ocean hydrothermal vents – Methanogens: obligately anaerobic methane producing bacteria; found in human intestines and used in sewage-treatment processes • Microbial Diversity – Various sizes: nanobacteria (0.02 – 0.03 μm) to giant bacteria (750 μm) Microbial Diversity • Many bacteria in the environment have not been identified or characterized due to: – Lack of culture method – Some bacteria are part of complex food chains and can only grow in the presence other microbes that provide specific growth requirements • PCR can be used to reveal the presence of bacteria that cannot be cultured in the laboratory Chapter Review • Know these terms: prosthecae, vibrioid, and oxygenic • Know different groups of proteobacteria (and some examples) given in the chapter review section • Know the names of different photosynthesizing bacteria and their mode of photosynthesis Chapter Review • Know characteristics of 2 groups of grampositive bacteria and some of the examples listed in the chapter review • Know characteristics of Arhaea, and its 3 major groups (characteristics and where they are found) given in the chapter review • Know why many bacteria have not been classified and identified (2 main reasons) & use of PCR to detect them without culturing them