IN SITU GROWTH ACTIVITY of ACINETOBACTER SPECIES WITH VARIABLE EXPOSURE TO ELECTRON DONOR AND ELECTRON ACCEPTOR

Increasingly, molecular biology-based tools targeting ribosomal ribonucleic acids are used to identify, enumerate, and determine the spatial organization of microbial populations in a variety of environments including biological wastewater treatment systems. Although these approaches provide an increased understanding of microbial community structure, they may not adequately describe the IN SITU function of microbial populations. Recently, we developed a new approach to quantify the IN SITU levels of precursor 16S rRNA (Oerther et al., Appl. Environ. Microbiol. 66:2154-2165). Transient changes in precursor 16S rRNA abundance have been shown to be related to the growth of Acinetobacter spp. In the current study, we used precursor 16S rRNA-targeted oligonucleotide hybridization probes to measure changes in the abundance of precursor 16S rRNA in Acinetobacter spp. exposed to variable concentrations of electron donor or electron acceptor. Acinetobacter spp. experienced increases in precursor 16S rRNA levels (and thus increases in IN SITU growth activity) when the concentrations of excess available electron donor were rapidly increased in the presence of available electron acceptor, but not in the absence of available electron acceptor. When excess available electron donor was available, the addition of available electron acceptor stimulated transient increases in precursor 16S rRNA levels in both strains examined in this study. These results have broad implications for biological wastewater treatment – suggesting that molecular biology-based tools can be used successfully to measure the IN SITU growth activity of microbial populations directly in the environment.