CHARACTERISTICS OF ANAEROBIC MIXED CULTURES ISOLATED FROM ALKALINE AND OLIGOTROPHIC HABITATS

Anaerobic microorganisms were isolated from rock cores of Valanginian marl from Oberbauenstock (Switzerland) and from samples of sediments of soda lakes in California. Enrichments from the marl were made under fermenting, sulfate-reducing, and methanogenic conditions with concentrations of organic carbon ranging from 8.4 mg/L to 0.84 g/L, 2.1 mg/L to 0.21 g/L, and 2.6 mg/L to 0.26 gn, respectively, at neutral and alkaline pH. Organisms from sediment samples were isolated under the same conditions with carbon contents of 8.4, 2.1, and 2.6 g/L, respectively, at alkaline pH. Growth and activity of the mired cultures obtained were investigated at different values of pH and with limiting carbon source. All cultures obtained were obligate alkaliphilic with an optimum for growth at pH 9.0 for sulfate-reducing and methanogenic cultures, and pH 10.0 for the fermenting culture. Ar these pH values the cultures also grew under carbon-lim)ited conditions (<10 mg carbon/L). Under eutrophic conditions no activity of the fermenting organisms was observed above pH 12, for the sulfate-reducing culture the limiting pH was 11, and for the methanogenic culture about pH 10.5.