Obligate Anaerobic Bacteria

Bacteroidaceae

• All are strict anaerobes; ferment sugars and produce acids
• Peritrichously rod shaped Bacteroides; produce succinic &/or propionate; gastrointestinal tract; transform bile acids & sterols to carcinogenic metabolites (bowel cancer causing ??)
• Spindle-shaped rods viz Fusobacterium & comma-shaped Butyvibrio (produce butyric acid)
• Coccal shaped Veillonell; rumen, mouth & intestine; some produce toxins & may be involved in periodontal diseas of the mouth & gums

Sulfate Reducing Bacteria

• Morphologically diverse (rods, cocci, vibrio, non-flagellated, polar or peritrichous flagella
• Ecological- metabolic single group; anaerobic respiration of organic acids with sulfate as the terminal electron acceptor (hydrogen sulfide excreted by the cells [not assimilated] is toxic to fish, bad odor & corrodes metal pipes)
• Anaerobic habitats with high organic matter & sulfates (polluted lakes, sewagw digestors, rumen, intestine); physiological types psychrophilic, thermophilic, mesophilic, thermophilic & halophilis.
• No spores formed (Desulfotomaculum = spore-forming Gram +ve]; Desulfovibrio, Desulfuromonas