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

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

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)