Bacteria, Viruses, and ProtistsBacteria Basics |
How many groups are identified in the domain Bacteria? |
Biologists recognize at least a dozen different groups of bacteria. The following lists the major groups to date (for the explanation of a Gram reaction, see above):
Major Group |
Gram Reaction |
Characteristics |
Examples |
Actinomycetes |
Positive |
Produce spores and antibiotics; live in soil environment |
Streptomyces |
Chemoautotrophs |
Negative |
Live in soil environment; important in the nitrogen cycle |
Nitrosomonas |
Cyanobacteria |
Negative |
Contain chlorophyll and are capable of photosynthesis; live in aquatic environment |
Anabaena |
Enterobacteria |
Negative |
Live in intestinal and respiratory tracts; ability to decompose form spores; pathogenic |
Escherichia, Salmonella, Vibrio |
Gram-positive cocci |
Positive |
Live in soil environment; inhabit the skin and mucous membranes of animals; pathogenic to humans |
Streptococcus, Staphylococcus |
Gram-positive rods |
Positive |
Live in soil environment or animal intestinal tracts; anaerobic; disease-causing |
Clostridia, Bacillus |
Lactic acid bacteria |
Positive |
Important in food production, especially dairy products; pathogenic to animals |
Lactobacillus, Listeria |
Myxobacteria |
Negative |
Move by secreting slime and gliding; ability to decompose materials |
Chondromyces |
Pseudomonads |
Negative |
Aerobic rods and cocci; live in soil environment |
Pseudomonas |
Rickettsiae and Chlamydia |
Negative |
Very small, intracellular parasites; pathogenic to humans |
Rickettsia, chlamydia |
Spirochetes |
Negative |
Spiral-shaped, live in aquatic environment |
Treponema, Borrelia |