|
Microbiologists broadly classify bacteria according to their shape: spherical, rod-shaped, and spiral-shaped. Pleomorphic bacteria can assume a variety of shapes. Bacteria may be further classified according to whether they require oxygen (aerobic or anaerobic) and how they react to a test with Gram’s stain. Bacteria in which alcohol washes away Gram’s stain are called gram-negative, while bacteria in which alcohol causes the bacteria’s walls to absorb the stain are called gram-positive.
| Acetic acid |
Rod-shaped, gram-negative, aerobic; highly tolerant of acidic conditions; generate organic acids |
| Actinomycete |
Rod-shaped or filamentous, gram-positive, aerobic; common in soils; essential to growth of many plants; source of much of original antibiotic production in pharmaceutical industry |
| Coccoid |
Spherical, sometimes in clusters or strings, gram-positive, aerobic and anaerobic; resistant to drying and high-salt conditions; Staphylococcus species common on human skin, certain strains associated with toxic shock syndrome |
| Coryneform |
Rod-shaped, form club or V shapes, gram-positive, aerobic; found in wide variety of habitats, particularly soils; highly resistant to drying; include Arthrobacter, among most common forms of life on earth |
Endospore-
forming |
Usually rod-shaped, can be gram-positive or gram-negative; have highly adaptable, heat-resistant spores that can go dormant for long periods, possibly thousands of years; include Clostridium (anaerobic) and Bacillus (aerobic) |
| Enteric |
Rod-shaped, gram-negative, aerobic but can live in certain anaerobic conditions; produce nitrite from nitrate, acids from glucose; include Escherichia coli,Salmonella (over 1000 types), and Shigella |
| Gliding |
Rod-shaped, gram-negative, mostly aerobic; glide on secreted slimy substances; form colonies, frequently with complex fruiting structures |
| Lactic acid |
Gram-positive, anaerobic; produce lactic acid through fermentation; include Lactobacillus, essential in dairy product formation, and Streptococcus, common in humans |
| Mycobacterium |
Pleomorphic, spherical or rod-shaped, frequently branching, no gram stain, aerobic; commonly form yellow pigments; include Mycobacterium tuberculosis, cause of tuberculosis |
| Mycoplasma |
Spherical, commonly forming branching chains, no gram stain, aerobic but can live in certain anaerobic conditions; without cell walls yet structurally resistant to lysis; among smallest of bacteria; named for superficial resemblance to fungal hyphae (myco- means 'fungus') |
| Nitrogen-fixing |
Rod-shaped, gram-negative, aerobic; convert atmospheric nitrogen gas to ammonium in soil; include Azotobacter, a common genus |
| Propionic acid |
Rod-shaped, pleomorphic, gram-positive, anaerobic; ferment lactic acid; fermentation produces holes in Swiss cheese from the production of carbon dioxide |
| Pseudomonad |
Rod-shaped (straight or curved) with polar flagella, gram-negative, aerobic; can use up to 100 different compounds for carbon and energy |
| Rickettsia |
Spherical or rod-shaped, gram-negative, aerobic; cause Rocky Mountain spotted fever and typhus; closely related to Agrobacterium, a common gall-causing plant bacterium |
| Sheathed |
Filamentous, gram-negative, aerobic; 'swarmer' (colonizing) cells form and break out of a sheath; sometimes coated with metals from environment |
| Spirillum |
Spiral-shaped, gram-negative, aerobic; include Bdellovibrio, predatory on other bacteria |
| Spirochete |
Spiral-shaped, gram-negative, mostly anaerobic; common in moist environments, from mammalian gums to coastal mudflats; complex internal structures convey rapid movement; include Treponemapallidum, cause of syphilis |
Sulfate- and
Sulfur-reducing |
Commonly rod-shaped, mostly gram-negative, anaerobic; include Desulfovibrio, ecologically important in marshes |
Sulfur- and
iron-oxidizing |
Commonly rod-shaped, frequently with polar flagella, gram-negative, mostly anaerobic; most live in neutral (nonacidic) environment |
| Vibrio |
Rod- or comma-shaped, gram-negative, aerobic; commonly with a single flagellum; include Vibrio cholerae, cause of cholera, and luminescent forms symbiotic with deep-water fishes and squids |
 |
|
Hotmail
Messenger
My MSN
MSN Directory
