The Prokaryotes: Domains Bacteria and Archaea

Transcription

1 PowerPoint Lecture Presentations prepared by Bradley W. Christian, McLennan Community College C H A P T E R 11 The Prokaryotes: Domains Bacteria and Archaea

2 Table 11.1 Classification of Selected Prokaryotes*

3 Proteobacteria From the mythological Greek god Proteus, who could assume many shapes Gram-negative Chemoheterotrophic Largest taxonomic group of bacteria Five classes

4 The Gammaproteobacteria Pseudomonadales Pseudomonas Opportunistic pathogens; nosocomial infections Metabolically diverse Polar flagella; common in soil P. aeruginosa: wound and urinary tract infections

5 The Gammaproteobacteria Pseudomonadales (cont'd) Azotobacter and Azomonas Nitrogen-fixing Moraxella M. lacunata: causes conjunctivitis Acinetobacter A. baumanii: respiratory pathogen; resistant to antibiotics

6 The Gammaproteobacteria Legionellales Legionella Found in streams, warm-water pipes, and cooling towers Causes legionellosis Coxiella C. burnetii: causes Q fever; transmitted via aerosols or milk

7 The Gammaproteobacteria Vibrionales Found in aquatic habitats V. cholerae causes cholera V. parahaemolyticus causes gastroenteritis

8 The Gammaproteobacteria Enterobacteriales Commonly called enterics inhabit the intestinal tract; ferment carbohydrates Facultative anaerobes Peritrichous flagella

9 The Gammaproteobacteria Enterobacteriales (cont'd) Escherichia E. coli: indicator of fecal contamination; causes foodborne disease and urinary tract infections Salmonella 2400 serovars Common form of foodborne illness Salmonella typhi causes typhoid fever

10 The Gammaproteobacteria Enterobacteriales (cont'd) Proteus Swarming motility; colonies form concentric rings Yersinia Y. pestis causes plague Transmitted via fleas Erwinia Plant pathogens

11 The Epsilonproteobacteria Helical or curved; microaerophilic Campylobacter One polar flagellum C. jejuni causes foodborne intestinal disease Helicobacter Multiple flagella Cause peptic ulcers and stomach cancer

12 Cyanobacteria (The Oxygenic Photosynthetic Bacteria) Carry out oxygenic photosynthesis Many contain heterocysts that can fix nitrogen Gas vesicles that provide buoyancy Unicellular or filamentous

13 The Phyla Chlorobi and Chloroflexi (The Anoxygenic Photosynthetic Bacteria) Carry out anoxygenic photosynthesis Green sulfur: phylum Chlorobi Green nonsulfur: phylum Chloroflexi Purple sulfur and purple nonsulfur photosynthetic bacteria are proteobacteria

14 Table 11.2 Selected Characteristics of Photosynthesizing Bacteria

15 Chlamydiae No peptidoglycan in the cell wall; grow intracellularly Chlamydia and Chlamydophila Form an elementary body that is infective Chlamydia trachomatis causes trachoma and urethritis Chlamydophila psittaci causes respiratory psittacosis

16 Figure 11.15a Chlamydias. The elementary bodies are released from the host cell. Elementary body The bacterium's infectious form, the elementary body, attaches to a host cell. The reticulate bodies begin to convert back to elementary bodies. Host cell Nucleus The host cell phagocytizes the elementary body, housing it in a vacuole. Vacuole forming Vacuole Reticulate body The reticulate body divides successively, producing multiple reticulate bodies. The elementary body reorganizes to form a reticulate body. Life cycle of the chlamydias, which takes about 48 hours to complete

17 Deinococci Deinococcus radiodurans More resistant to radiation than endospores Thermus aquaticus Found in a hot spring in Yellowstone National Park Source of Taq polymerase

18 The Gram-Positive Bacteria Firmicutes (low G + C ratios) Actinobacteria (high G + C ratios)

19 Firmicutes (Low G + C Gram-Positive Bacteria) Clostridiales Clostridium Endospore-producing Obligate anaerobes Includes disease-causing C. tetani, C. botulinum, C. perfringens, and C. difficile Epulopiscium Can be seen with the unaided eye Daughter cells form within the parent cell; no binary fission

20 Firmicutes (Low G + C Gram-Positive Bacteria) Bacillales Bacillus Endospore-producing rods B. anthracis causes anthrax B. thuringiensis is an insect pathogen B. cereus causes food poisoning Staphylococcus Grapelike clusters S. aureus causes wound infections, is often antibiotic resistant, and produces an enterotoxin

21 Firmicutes (Low G + C Gram-Positive Bacteria) Lactobacillales (cont'd) Streptococcus Spherical in chains Produce enzymes that destroy tissue Beta-hemolytic streptococci hemolyze blood agar; includes S. pyogenes Non-beta-hemolytic streptococci include S. pneumoniae and S. mutans, which causes dental caries

22 Firmicutes (Low G + C Gram-Positive Bacteria) Lactobacillales (cont'd) Enterococcus Found in intestinal tract; hospital contaminants E. faecalis and E. faecium infect surgical wounds and the urinary tract Listeria L. monocytogenes contaminates food

23 Firmicutes (Low G + C Gram-Positive Bacteria) Mycoplasmatales Lack a cell wall; pleomorphic M. pneumoniae causes mild pneumonia

24 Actinobacteria (High G + C Gram-Positive Bacteria) Often pleomorphic; branching filaments Often common inhabitants of soil Mycobacterium Outermost layer of mycolic acids that is waxy and waterresistant Often slow-growing M. tuberculosis causes tuberculosis M. leprae causes leprosy

25 Diversity Within the Archaea Distinct taxonomic grouping; lack peptidoglycan Extremophiles Halophiles Require salt concentration >25% Thermophiles Require growth temperature >80 C Methanogens Anaerobic and produce methane

26 Microbial Diversity Bacteria size range Thiomargarita (diameter of 750 µm) Carsonella ruddii (182 genes) PCR indicates up to 10,000 bacterial species per gram of soil Many bacteria have not been identified Have not been cultured Are a part of complex food chains requiring the products of other bacteria