Growth of a facultative anaerobe under oxygen‐limiting conditions in pure culture and in co‐culture with a sulfate‐reducing bacterium

Abstract

The occurrence and properties were studied of glucose‐metabolizing bacteria present in the anaerobic sediment 5–10 cm below the surface of an estuarine tidal mud‐flat. Of all these bacteria (104– 105 per g wet sediment) 80–90% were facultatively anaerobic species. Chemostat enrichments on glucose under aerobic, oxygen‐limited and alternately aerobic‐anaerobic conditions also yielded cultures dominated by facultative anaerobes. One of the dominant species, tentatively identified as a Vibrio sp., was studied in more detail under oxygen‐limiting conditions. Fermentative and respiratory metabolisms were found to operate simultaneously, and the ratio between the two was regulated by the extent of oxygen limitation. A small fraction of the acetate formed under such growth conditions was shown to be subsequently respired. A co‐culture was established of the Vibrio sp. and a sulfate‐reducing bacterium (Desulfovibrio HL21 ) in an aerated chemostat. The importance of these observations is discussed in relation to the role of facultative anaerobes in anaerobic habitats