Our research program seeks answers to a fundamental biological question:
How does an organism know when, where and for long to turn a gene on or off?
We address this question by investigating bacterial species
that establish intimate interactions with animal hosts.
Visit our Research page and Groisman Lab News for more information.
Dietary sugar silences a colonization factor in a mammalian gut symbiont.
Dietary components are believed to influence the composition of the gut microbiota by serving as nutrients to a subset of microbes, thereby favoring their expansion. However, we now report that dietary fructose and glucose, which are prevalent in the Western diet, specifically silence a protein that is necessary for gut colonization, but not for utilization of these sugars, by the human gut commensal Bacteroides thetaiotaomicron. Our findings underscore a role for dietary sugars that escape absorption by the host intestine and reach the microbiota: regulation of gut colonization by beneficial microbes independently of supplying nutrients to the microbiota.
RNA secondary structures regulate three steps of Rho-dependent transcription termination within a bacterial mRNA leader.
The corA leader RNA controls three steps of Rho-dependent transcription termination.
Sequestration from Protease Adaptor Confers Differential Stability to Protease Substrate.
We report that the Salmonella adaptor ClpS binds to the N terminus of the regulatory protein PhoP, resulting in PhoP degradation by ClpAP. The identified mechanism provides a simple means to spare specific substrates from an adaptor-dependent protease.
Navigating the Gut Buffet: Control of Polysaccharide Utilization in Bacteroides spp.
Metabolic flux controls chondroitin sulfate utilization in Bacteroides thetaiotaomicron.
Protein synthesis controls phosphate homeostasis.
Free cytoplasmic Mg2+ inhibits Pi starvation response.
Reduction in adaptor amounts establishes degradation hierarchy among protease substrates.
A reduction in adaptor amounts creates a hierarchy among substrates delivered to a protease by an adaptor. The ClpAP protease degrades certain substrates directly but requires the adaptor ClpS to degrade others.
A protein that controls the onset of a Salmonella virulence program.
Under non‐inducing conditions for the master virulence regulator PhoP (gray), the anti‐virulence protein CigR is expressed independently of PhoP, and the virulence protein MgtC is not expressed (left). At early times under inducing conditions (pink), PhoP promotes expression of MgtC, which, sequestered by CigR, does not inhibit the F1Fo ATP synthase (ATPase) or protect PhoP from degradation (middle). At late times under inducing conditions (blue), MgtC amounts supersede CigR amounts, which result in MgtC binding to and inhibition of the ATPase (right). In addition, MgtC protects PhoP from degradation, thereby increasing PhoP amounts and enabling transcription of a subset of PhoP‐activated genes (right).
When Too Much ATP Is Bad for Protein Synthesis.
Cells' energy and protein synthesis potentials depend on the availability of Mg2+. Bacteria sense and respond to various degrees of Mg2+ limitation. Non-physiological increase in ATP disrupts essential Mg2+-dependent processes. Cell restores free Mg2+ levels by shutting down synthesis of ATP and ribosomes.
Reducing ribosome biosynthesis promotes translation during low Mg2+ stress.
A cell maximizes its translation capacity by matching the rate of ribosome synthesis to the levels of ATO available for consumption. Here, we uncover a stress response pathway that supersedes this regulation and, unexpectedly, aids translation by decreasing ribosome production.