Biology subjects

Guckes, K. R.

Publications and source records attributed to Guckes, K. R..

3 recordsLinked to original sources

bioRxiv2023

The QseB response regulator imparts tolerance to positively charged antibiotics by controlling metabolism and minor changes to LPS

The modification of lipopolysaccharide (LPS) in Escherichia coli and Salmonella spp. is primarily controlled by the two-component system PmrAB. LPS modification allows bacteria to avoid killing by positively charged antibiotics like polymyxin B. We previously demonstrated that in uropathogenic E. coli (UPEC), the sensor histidine kinase PmrB also activates a non-cognate transcription factor, QseB, and this activation somehow augments polymyxin B tolerance in UPEC. Here, we demonstrate - for the first time - that in the absence of the canonical LPS transcriptional regulator, PmrA, QseB can direct some modifications on the LPS. In agreement with this observation, transcriptional profiling analyses demonstrate regulatory overlaps between PmrA and QseB in terms of regulating LPS modification genes. However, both PmrA and QseB must be present for UPEC to mount robust tolerance to polymyxin B. Transcriptional and metabolomic analyses also reveal that QseB transcriptionally regulates the metabolism of glutamate and 2-oxoglutarate, which are consumed and produced during the modification of lipid A. We show that deletion of qseB alters glutamate levels in the bacterial cells. The qseB deletion mutant, which is susceptible to positively charged antibiotics, is rescued by exogenous addition of 2-oxoglutarate. These findings uncover a previously unknown mechanism of metabolic control of antibiotic tolerance that may be contributing to antibiotic treatment failure in the clinic. IMPORTANCEAlthough antibiotic prescriptions are guided by well-established susceptibility testing methods, antibiotic treatments oftentimes fail. The presented work is significant, because it uncovers a mechanism by which bacteria transiently avoid killing by antibiotics. This mechanism involves two closely related transcription factors, PmrA and QseB, which are conserved across Enterobacteriaceae. We demonstrate that PmrA and QseB share regulatory targets in lipid A modification pathway and prove that QseB can orchestrate modifications of lipid A in E. coli in the absence of PmrA. Finally, we show that QseB controls glutamate metabolism during the antibiotic response. These results suggest that rewiring of QseB-mediated metabolic genes can lead to stable antibiotic resistance in subpopulations within the host, thereby contributing to antibiotic treatment failure.

microbiology↗

bioRxiv2022

Two enhancer binding proteins activate σ54 -dependent transcription of a quorum regulatory RNA in a bacterial symbiont

To colonize a host, bacteria depend on an ensemble of signaling systems to convert information about the various environments encountered within the host into specific cellular activities. How these signaling systems coordinate transitions between cellular states in vivo remains poorly understood. To address this knowledge gap, we investigated how the bacterial symbiont Vibrio fischeri initially colonizes the light organ of the Hawaiian bobtail squid Euprymna scolopes. Previous work has shown that the small RNA Qrr1, which is a regulatory component of the quorum-sensing system in V. fischeri, promotes host colonization. Here, we report that transcriptional activation of Qrr1 is repressed by the regulator BinK, which inhibits cellular aggregation by V. fischeri prior to light organ entry. We show that Qrr1 expression depends on the alternative sigma factor {sigma}54 and the transcription factors LuxO and SypG, which function together as an OR logic gate, thereby ensuring Qrr1 is expressed during colonization. Finally, we provide evidence that this regulatory mechanism is widespread throughout the Vibrionaceae family. Together, our work reveals how coordination between the signaling pathways underlying aggregation and quorum sensing promotes host colonization, which provides insight into how integration among signaling systems facilitates complex processes in bacteria.

microbiology↗

bioRxiv2020

A Bacterial Signaling Network Controls Antibiotic Resistance by Regulating Anaplerosis of 2-oxoglutarate

Antibiotic resistance has become a global threat. In addition to acquiring resistance via horizontal gene transfer, bacteria can evade killing by temporarily modifying their cell envelope to prevent antibiotic-bacterial interactions. A critical gap in knowledge is how bacteria balance the metabolic needs of altering the cell envelope with the constant need to generate energy. Cross-regulation between two signaling networks in Escherichia coli increases resistance to positively charged antibiotics. We show that increased resistance is supported by metabolic re-wiring controlled by the QseB transcription factor. QseB controls the increase in 2-oxoglutarate required for lipid A modification, by upregulating three anaplerotic pathways that feed acetyl Co-A, succinate and fumarate into the TCA cycle. Exogenous addition of 2-oxoglutarate restores antibiotic resistance in the qseB deletion mutant. Antibiotic resistant clinical isolates bear mutations within QseB-mediated anaplerotic pathways. These findings are significant, because they uncover a previously unknown mechanism of metabolic control of antibiotic resistance.

microbiology↗