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 (10 4 – 10 5 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.