Sponsored by: the Office of Research and Sponsored Projects, VU
The objective of this study was to investigate gene expression under stress conditions that lead E. coli into a viable but non--culturable (VBNC) state during anaerobic digestion process. Gene expression of E. coli under stress conditions was studied in biosolids samples obtained from full-scale mesophilic and thermophilic anaerobic digesters. Two full-scale anaerobic digestion plants, one mesophilic and one thermophilic, that were sampled have experienced the reactivation phenomenon after centrifuge dewatering of their digested biosolids, suggesting that the E. coli in their biosolids go into a VBNC state in their digesters. Laboratory-scale studies were performed to determine the E. coli density before and after centrifugation and to investigate the reactivation using standard culturing methods. The first step of this study involved the development and optimization of an RNA extraction protocol. The second step of the study was to determine the specific stress genes that lead E. coli to VBNC state using GeneChip ® E. coli Genome 2.0 Array.