Review of Key Microbial Groups

1. Review of Key Microbial Groups • Domain Bacteria • Domain Archaea • Domain Eucarya

2. Domain Bacteria: General Features • Prokaryotic cell structure • DNA organized in nucleoid; no nuclear membrane, nucleolus, or histones • No complex membranous organelles (e.g. endoplasmic reticulum, golgi apparatus) • Cell walls containing peptidoglycan found in most groups of bacteria • Some features of gene expression (mRNA, tRNA, RNA polymerase, ribosomes) are more similar to archaea; some are more similar to eucarya

3. Domain Bacteria:General features • Metabolic strategies found in Bacteria: • Chemoheterotrophy • Chemolithotrophy • Photosynthesis

4. Domain Bacteria:General features • Cell Wall Structures in Bacteria • Gram-negative cell wall • Outer membrane containing lipopolysaccharide • Thin layer of peptidoglycan • Periplasmic space • Gram-positive cell wall • Thick layer of peptidoglycan • Teichoic acids • “Acid-fast” bacteria • Bacteria in Phylum Actinomycetes with high concentrations of mycolic acid • Detected by acid-fast staining • Mycoplasmas • Bacteria in Phylum Firmicutes with no cell wall

5. Domain Bacteria:General features • Other structural features found in Bacteria • Plasma membrane • Capsules • Pili or Fimbrae • Cytoplasmic inclusions • Bacterial DNA • Ribosomes • Flagella • Spores http://science.kennesaw.edu/~jhendrix/bio3340/handouts/microcells.ppt

6. Domain Bacteria:General features • Identification of the Bacteria • Colony morphology • Cell shape & arrangement • Cell wall structure (Gram staining) • Special cellular structures • Biochemical characteristics • Serological tests • G+C content • DNA hybridization • DNA fingerprinting • Nucleic acid sequencing http://science.kennesaw.edu/~jhendrix/bio3340/handouts/microtaxonomy.ppt

7. Domain Bacteria:Major Groups • Phylum Proteobacteria • “Gram-negative” type cell wall architecture • Outer membrane with lipopolysaccharide and porin protein • Thin layer of peptidoglycan • Notable periplasmic space containing transport proteins and hydrolases • A very large and metabolically diverse phylum; various groups utilizing chemoheterotrophy (both respiration & fermentation), chemolithotrophy, photosynthesis

8. Domain Bacteria:Major Groups • Phylum Proteobacteria (cont.) • Major groups of proteobacteria • Enterobacteriacea: “Gram-negative enterics;” common intestinal flora and pathogens; both respiratory and fermentative metabolisms; facultatively anaerobic; oxidase negative; includes genera Escherichia, Klebsiella, Enterobacter, Citrobacter, Serratia, Proteus, Salmonella, Shigella, Yersinia • Pseudomonadaceae: Genus Pseudomonas and related genera; common soil and aquatic organism; usually aerobic; oxidase positive; use Entner-Douderoff glycolysis instead of EMP glycolysis; often can metabolize unusual carbon substrates such as aromatic hydrocarbons

9. Domain Bacteria:Major Groups • Phylum Proteobacteria (cont.) • Major groups of proteobacteria (cont.) • Purple nonsulfur photosynthetic bacteria, e.g. Rhodospirillum • Green sulfur photosynthetic bacteria, e.g. Chlorobium • Nitifying bacteria: Nitrosomonas (oxidizes ammonium to nitrite) and Nitrobacter (oxidizes nitrite to nitrate) • Nitrogen fixing bacteria: Rhizobium (symbiotic in root nodules); Azotobacter (free-living) • Various human pathogens in phylum Proteobacteria: Neisseria, Vibrio, Haemophilus, Rickettsia, Coxsiella, Bordetella, Legionella, Camphylobacter, Helicobacter

10. Domain Bacteria:Major Groups • Phylum Firmicutes • “Low G-C” Gram-positive bacteria • Cell walls consist of thick layers of extensively crosslinked peptidoglycan (exception: Mycoplasma) • Notable genera • Clostridium: Strictly anaerobic, spore-forming rods; common in soil; includes botulism & tetanus; significant contaminant in food industry & medicine • Bacillus: Facultatively anaerobic, spore-forming rods; common in soil; frequent contaminant; includes Bacillus anthracis • Mycoplasma: Have no cell walls; respiratory tract flora & pathogens of humans & other animals

11. Domain Bacteria:Major Groups • Phylum Firmicutes • Notable genera • Lactobacillus: Facultatively anaerobic nonsporeforming rods; oral or intestinal flora; found in sevral dairy products such as yogurt • Staphylococcus: Catalase-positive cocci; common skin flora; virulent strains of Staph. aureus are associated with skin infections, food poisoning, and toxic shock syndrome • Streptococcus, Enterococcus, Lactococcus: Catalase-negative cocci; diverse group with numerous skin, oral, and intestinal flora as well as several important pathogens such as Streptococcus pyogenes (Group A pyogenic strep)

12. Domain Bacteria:Major Groups • Phylum Actinomycetes • “High G-C” Gram-positive bacteria • Cell walls consist of thick layers of extensively crosslinked peptidoglycan • Notable genera • Corynebacterium: Facultatively anaerobic, irregular rods; coryneform arrangement; common soil & skin flora; common laboratory contaminant • Micrococcus: Facultatively anaerobic cocci; tetrads or sarcinae; yellow or pink pigmentation; common soil flora;common laboratory contaminants • Actinomyces, Streptomyces; Common soil organism; filamentous growth often mistaken for mold

13. Domain Bacteria:Major Groups • Phylum Actinomycetes • Notable genera • Mycobacterium: Acid-fast rods; high concentration of mycolic acid in the cell wall make them difficult to gram stain; certain species are skin and soil flora; includes tuberculosis and leprosy

14. Domain Bacteria:Major Groups • Phylum Bacteroidetes • A group of gram-negative, strictly anaerobic bacteria • Most are intestinal and oral flora in humans and animals; some are pathogens • Example: genus Bacteroides

15. Domain Bacteria:Major Groups • Phylum Cyanobacteria • The “blue-green algae” • Carry out oxygenic photosynthesis • Have thylakoid membranes, chlorophyll a, and photosystem II

16. Domain Bacteria:Major Groups • Phylum Chlamydiae • A group of gram-negative, obligately intracellular parasites • Genus Chlamydia • Phylum Spirochaetes • Characterized by flexible helical-shaped cells • Cells covered by an outer sheath and are motile by a modified flagellar structure called an axial filament • Example: Treponema pallidum (syphillis)

17. Domain Archaea: General Features • Prokaryotic cell structure • Cell walls have no peptidoglycan; some archaea have pseudomurein or other polymers • Some features of gene expression (mRNA, tRNA, RNA polymerase, ribosomes) are more similar to bacteria; some are more similar to eucarya • Metabolic strategies found in Archaea: • Chemoheterotrophy • Chemolithotrophy

18. Domain Archaea:Major Groups • Methanogenic archaea • Methanobacterium, Methanococcus • Extremely thermophilic archaea • Sulfate reducers, Archaeoglobus • Sulfur reducers, Desulfurococcus, Sulfolobus • Extremely halophilic archaea • Halobacterium, Halococcus • Cell wall deficient archaea • Thermoplasma

19. Domain Eucarya: General Features • Eukaryotic cell structure • Cell walls vary; none in “animal-like” cells; cellulose in algae most others, with additional polysaccharides in different groups (e.g., chitin in many fungi) • Some features of gene expression (mRNA, tRNA, RNA polymerase, ribosomes) are more similar to bacteria; some are more similar to archaea • Metabolic strategies found in Eucarya: • Chemoheterotrophy (respiration in mitochondria) • Photosynthesis (in chloroplasts)