Assessing the transcriptional responses of E. coli in co-culture with K. pneumoniae and E. faecalis in relation to quorum sensing and entrance into viable but nonculturable state

• Main Author: Ranjani Nadarajan
• Other Authors: Sze Chun Chau
• Format: Final Year Project
• Language: English
• Published: 2011
• Subjects: DRNTU::Science::Biological sciences::Microbiology::Bacteria
• Online Access: http://hdl.handle.net/10356/45130
• Institution: Nanyang Technological University

In this study, the influences of two non-Escherichia coli species – Klebsiella pneumoniae and Enterococcus faecalis, on the regulation of VBNC and quorum sensing- related gene expression were assessed in a co-culture context by analyzing the differential promoter activities of a subset of genes. The study evaluated the transcriptional responses of these genes in two culture conditions in both the planktonic and biofilm mode of growth. Further investigations were performed to evaluate if the influences exerted by the non- E. coli species were dependent on physical presence of the partner species or their secreted factors. The downregulation of PompR and PpolB observed in co-cultures suggests that the presence of non-E. coli species could possibly interfere with the adaptive responsiveness of E. coli. It was also observed that AI-2 synthesis in E. coli was inhibited in the co-cultures with the non- E. coli species through the downregulation of PluxS. Furthermore, results also indicate that the influences exerted by both the non- E. coli species were dependent on physical presence and that quorum sensing and the entrance into the VBNC state by E. coli were more pronounced in biofilms.