| Herein, we have adapted, developed, and implemented novel technologies from molecular microbial ecology to understand the role of Acinetobacter spp. as a model phosphorus accumulating organisms in biological phosphorus removal. Oligonucleotide hybridization probes targeting the 16S ribosomal ribonucleic acid of various phylogenetic groups of microorganisms including the beta-subclass Proteobacteria, gamma-subclass Proteobacteria, the genus Acinetobacter, Acinetobacter johnsonii, Acinetobacter lwoffii , and Acinetobacter strain ED were designed and experimentally characterized for radiolabeled oligonucleotide hybridizations of membrane immobilized cellular extracts as well as whole cell fluorescence in situ hybridizations. In addition, a novel class of oligonucleotide probes targeting the precursor 16S ribosomal ribonucleic acid of the genus Acinetobacter were developed. Subsequently, these molecular tools were used to identify, enumerate, quantify long-term (with a characteristic time-frame of hours to days) growth activity, and monitor short-term (with a characteristic time-frame of minutes to hours) changes in growth activity of Acinetobacter spp. in laboratory- and full-scale activated sludge wastewater treatment systems. Our results suggest that Acinetobacter spp. are a high ribosome containing, low abundance microbial population in activated sludge systems. Furthermore, the addition of idle stages at the end of the decant phase of fill-and-draw reactor operation stimulated transient increases in both the abundance and growth activity of Acinetobacter spp. Precursor 16S ribosomal ribonucleic acid levels were a sensitive indicator of rapid changes in the in situ growth activity of Acinetobacter spp, and Acinetobacter spp. responded to dynamic changes in the operation of activated sludge systems including the rapid addition of fresh influent. Although we failed to find any correlation between the abundance and growth activity of Acinetobacter spp. and biological phosphorus removal, the results of our work have demonstrated a proposed role for Acinetobacter spp. in activated sludge wastewater treatment systems. We propose that Acinetobacter spp. occupy an ecological niche that includes dynamic operating conditions in activated sludge systems. We hypothesize that Acinetobacter spp. have an ecological advantage in wastewater treatment systems that are not at steady-state. Thus, the role of Acinetobacter spp. in activated sludge systems could include transient removal of organic pollution during fluctuations in the operation of bioreactors. |
