Abstract
Salmonella Enteritidis is a non-typhoidal serovar of great public health significance worldwide. The RpoE sigma factor and CpxRA two-component system are the major regulators of the extracytoplasmic stress response. In this study, we found that the CpxR has highly significant, but opposite effects on the auto-aggregation and swarming motility of S. Enteritidis. Auto-aggregation was negatively affected in the ∆cpxR mutant, whereas the same mutant significantly out-performed its wild-type counterpart with respect to swarming motility, indicating that the CpxR plays a role in biofilm-associated phenotypes. Indeed, biofilm-related assays showed that the CpxR is of critical importance in biofilm development under both static (microtiter plate) and dynamic (flow cell) media flow conditions. In contrast, the RpoE sigma factor showed no significant role in biofilm development under dynamic conditions. Transcriptomic analysis revealed that the cpxR mutation negatively affected the constitutive expression of the operons critical for biosynthesis of O-antigen and adherence, but positively affected the expression of virulence genes critical for Salmonella-mediated endocytosis. Conversely, CpxR induced the expression of curli csgAB and fimbrial stdAC operons only during biofilm development and flagellar motAB and fliL operons exclusively during the planktonic phase, indicating a responsive biofilm-associated loop of the CpxR regulator.
Highlights
Non-typhoidal Salmonella (NTS) are the leading cause of food-borne gastroenteritis worldwide [1]
The growth assay revealed no significant differences in growth kinetics between the wild type and ∆cpxR mutant strains (Figure 1)
Besides genes associated with cell appendages and O-antigen biosynthesis, the ∆cpxR mutant underwent significant down-regulation of genes encoding for proteins involved in carbohydrate uptake (malEFKPQSMZG—maltose metabolic processes; frwBCD—phosphotransferase system (PTS fructose-specific transporter), peptide uptake (oppABCDF—oligopeptide ATP-binding cassette transporters (ABC transporter); dppABCDF – dipeptide ABC transporter), thiamine synthesis, glycolysis and leucine synthesis (Figure 7), clearly indicating that the cpxR deletion significantly affected anabolic processes during sessile growth of S
Summary
Non-typhoidal Salmonella (NTS) are the leading cause of food-borne gastroenteritis worldwide [1]. Enteritidis) is one of the most common serovars associated with human salmonellosis [1] This zoonotic pathogen owes its great public health importance to an unusually broad host range [2]. The Cpx regulon is involved in protein translocation across the inner membrane [8] along with the biogenesis of bacterial appendages [9]. These two extracytoplasmic stress-response regulators are involved in the most important biological processes where bacterial cells interact with their surroundings; survival [10,11] and pathogenicity [12,13]. Enteritidis cells grown under planktonic and biofilm conditions, enhancing our understanding of the regulatory role of the Cpx regulon during biofilm development
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
