Synthesis of intracellular storage polymers by Amaricoccus kaplicensis, a tetrad forming bacterium present in activated sludge

Aims: The study investigated the physiology of Amaricoccus kaplicensis to d etermine whether it could outcompete polyphosphate accumulating bacteria in activated sludge systems removing phosphorus, by preferentially assimilati ng substrates in the anaerobic stages of these processes. Methods and Results: The storage processes were investigated under anaerobi c, anoxic and aerobic conditions in both batch and periodically fed culture s in an aerobic sequencing batch reactor (SBR). Amaricoccus kaplicensis sho wed a high capacity for storing aerobically large amounts of acetate as pol y beta -hydroxybutyrate (PHB) at high rates. However, no acetate assimilati on under anaerobic conditions and very slow assimilation under anoxic condi tions could be detected. Conclusions: Amaricoccus kaplicensis in pure culture does not behave as pol yphosphate accumulating bacteria competitor; therefore it is difficult to u nderstand why anaerobic/aerobic systems often contain such large numbers of Amaricoccus cells. Significance and Impact of the Study: Amaricoccus kaplicensis is probably n ot responsible for the failure of activated sludge systems removing phospho rus, and other organisms capable of anaerobic substrate assimilation should be sought.