Peptococcus: A genus of gram-positive, anaerobic, coccoid bacteria that is part of the normal flora of the mouth, upper respiratory tract, and large intestine in humans. Its organisms cause infections of soft tissues and bacteremias.Peptostreptococcus: A genus of gram-positive, anaerobic, coccoid bacteria that is part of the normal flora of humans. Its organisms are opportunistic pathogens causing bacteremias and soft tissue infections.Peptococcaceae: A family of bacteria found in the mouth and intestinal and respiratory tracts of man and other animals as well as in the human female urogenital tract. Its organisms are also found in soil and on cereal grains.Anaerobiosis: The complete absence, or (loosely) the paucity, of gaseous or dissolved elemental oxygen in a given place or environment. (From Singleton & Sainsbury, Dictionary of Microbiology and Molecular Biology, 2d ed)Bacteria, AnaerobicFerredoxins: Iron-containing proteins that transfer electrons, usually at a low potential, to flavoproteins; the iron is not present as in heme. (McGraw-Hill Dictionary of Scientific and Technical Terms, 5th ed)Eubacterium: A genus of gram-positive, rod-shaped bacteria found in cavities of man and animals, animal and plant products, infections of soft tissue, and soil. Some species may be pathogenic. No endospores are produced. The genus Eubacterium should not be confused with EUBACTERIA, one of the three domains of life.