Gene regulation of rhamnolipid production in Pseudomonas aeruginosa – A review

Abstract

Pseudomonas aeruginosa produces abundant levels of rhamnolipid biosurfactants which exhibit remarkable chemical and physical characteristics, making these compounds attractive targets for biotechnology research. The complex gene regulation network involved in rhamnolipids' biosynthesis represents a challenge to industrial production, which has been the object of a growing number of studies. This article provides a comprehensive review of the known gene regulatory factors involved in rhamnolipid production within P. aeruginosa. The regulatory factors include quorum sensing systems proteins and environmental response, and global regulatory systems within basal bacterial physiology, acting either at transcriptional or post-transcriptional level. The multilayer gene regulation responds to a wide variety of environmental and physiologic signals, and is capable of combining different signals in unique and specific responses.

Spatially dependent alkyl quinolone signaling responses to antibiotics in Pseudomonas aeruginosa swarms

“…Although cells exposed to carbenicillin exhibit a dramatic morphology change, we found that exposure to tobramycin, but not carbenicillin, resulted in profile shifts of both PQS and AQNO families during swarming. This is in contrast to reports that have suggested a general PQS response to antimicrobials (22,26,27). Our findings are consistent with the hypothesis that AQ modulations following tobramycin exposure during pre-biofilm swarming should contribute to antibiotic tolerance (22,25,38), however, other factors must control P. aeruginosa tolerance to carbenicillin.…”

“…Our findings reveal a role for the PQS subclass in response to tobramycin exposure, but not carbenicillin exposure. Thus, we conclude that the PQS stress response (22,27) is not a universal response mechanism to all antibiotics. Additionally, AQs belonging to the general PQS pathway appear to be under distinct regulatory control mechanisms, since modulations to the PQS and targeted AQNOs subclasses are observed to be independent of one another.…”

“…Of the molecules that belong to these subclasses, the roles of HHQ, PQS, and HQNO are particularly well-documented. The AQs belonging to the PQS pathway participate in processes as diverse as intercellular quorum sensing signaling, virulence regulation, biofilm development, iron chelation, antimicrobial activity, stress response, and control of cell death (15,(18)(19)(20)(21)(22)(23)(24)(25)(26)(27). In the Pseudomonas literature, AQs are generally presented to contain 7-Carbon (C7) side chains (HHQ, PQS, and HQNO), yet 9-Carbon (C9; NHQ, C9-PQS, and NQNO) and 11-Carbon (C11; UHQ, C11-PQS, and UQNO) side chain variants of these molecules are also common (16,17).…”

Microbiotechnology Based Surfactants and Their Applications

“…Biosurfactants production is known to be controlled by a sophisticated and highly organized regulatory network at both the transcriptional and post-transcriptional level (Dusane et al, 2010;Reis et al, 2011). Factors that were shown to play a key role in biosurfactants production include quorum sensing and stress conditions like nutrients deprivation.…”

“…For instance, biosurfactants production increases under nitrogen-limiting conditions Reis et al, 2011). The nitrogen source indirectly affects the rhlAB operon via the nitrogen metabolism sigma factor regulator RpoN.…”