Biology subjects

Reichardt, S.

Publications and source records attributed to Reichardt, S..

3 recordsLinked to original sources

bioRxiv2023

The RNA-binding protein RbpB is a central regulator of polysaccharide utilization in gut Bacteroides

Paramount to human health, symbiotic bacteria in the gastrointestinal tract rely on the breakdown of complex polysaccharides to thrive in this sugar-deprived environment. Gut Bacteroides are metabolic generalists and deploy dozens of polysaccharide utilization loci (PULs) to forage diverse dietary and host-derived glycans. The expression of the multi-protein PUL complexes is tightly regulated at the transcriptional level. However, how PULs are orchestrated at translational level in response to the fluctuating levels of their cognate substrates is unknown. Here, we identify the RNA-binding protein RbpB and a family of noncoding RNAs as key players in post-transcriptional PUL regulation. Ablation of RbpB in Bacteroides thetaiotaomicron displays compromised colonization in the mouse gut in a host diet-dependent manner. Current dogma holds that individual PULs are regulated by dedicated transcriptional regulators. We demonstrate that RbpB acts as a global RNA binder that directly interacts with several hundred cellular transcripts. This includes a paralogous noncoding RNA family comprised of 14 members, the FopS (family of paralogous sRNAs) cluster. Through a series of in-vitro and in-vivo assays, we reveal that FopS sRNAs repress the translation of a SusC-like glycan transporter when substrates are limited--an effect antagonized by RbpB. Together, this study implicates RNA-coordinated metabolic control as an important, yet previously overlooked, factor contributing to the in-vivo fitness of predominant microbiota species in dynamic nutrient landscapes.

microbiology↗

bioRxiv2023

Global analysis of the RNA-RNA interactome in Acinetobacter baumannii AB5075 uncovers a small regulatory RNA repressing the virulence-related outer membrane protein CarO

Acinetobacter baumannii is an opportunistic Gram-negative pathogen that infects critically ill patients. The emergence of antimicrobial resistant A. baumannii has exacerbated the need to functionally characterise environmental adaptation, antibiotic resistance and pathogenicity of this organism and their genetic regulators to inform intervention strategies. Critical to rapid adaptation to changing environments in bacteria are small regulatory RNAs (sRNAs), however, the role that sRNAs play in the biology of A. baumannii is poorly understood. To assess the regulatory function of sRNAs and to uncover their RNA interaction partners in A. baumannii, we employed an RNA proximity ligation and sequencing method (Hi-GRIL-seq) in three different environmental conditions. We found that 40 sRNA candidates were ligated to sRNA-RNA chimeric sequencing reads, suggesting that sRNA-mediated gene regulation is pervasive in A. baumannii and that sRNAs act as direct regulators of mRNA molecules through antisense base-pairing. In-depth characterisation uncovered the sRNA Aar to be a post-transcriptional regulator of four mRNA targets including that of the outer membrane protein CarO and the siderophore receptor BfnH. We show that Aar initiates base-pairing with these mRNA molecules using a conserved seed region of nine nucleotides, sequestering the ribosome binding sites and inhibiting translation. Aar is differentially expressed in response to multiple stress stimuli suggesting a role in fine-tuning translation of the Aar-target molecules in A. baumannii under hostile conditions. Together, our study provides mechanistic insights into sRNA-mediated gene expression control in A. baumannii and represents a valuable resource for future RNA-centric research endeavours in this ESKAPE pathogen.

microbiology↗

bioRxiv2023

Improved RNA stability estimation through Bayesian modeling reveals most bacterial transcripts have sub-minute half-lives

RNA decay is a crucial mechanism for regulating gene expression in response to environmental stresses. In bacteria, RNA-binding proteins (RBPs) are known to be involved in post-transcriptional regulation, but their global impact on RNA half-lives has not been extensively studied. To shed light on the role of the major RBPs ProQ and CspC/E in maintaining RNA stability, we performed RNA sequencing of Salmonella enterica over a time course following treatment with the transcription initiation inhibitor rifampicin (RIF-seq) in the presence and absence of these RBPs. We developed a hierarchical Bayesian model that corrects for confounding factors in rifampicin RNA stability assays and enables us to identify differentially decaying transcripts transcriptome-wide. Our analysis revealed that the median RNA half-life in Salmonella in early stationary phase is less than 1 minute, a third of previous estimates. We found that over half of the 500 most long-lived transcripts are bound by at least one major RBP, suggesting a general role for RBPs in shaping the transcriptome. Integrating differential stability estimates with CLIP-seq revealed that approximately 30% of transcripts with ProQ binding sites and more than 40% with CspC/E binding sites in coding or 3 untranslated regions decay differentially in the absence of the respective RBP. Analysis of differentially destabilized transcripts identified a role for ProQ in the oxidative stress response. Our findings provide new insights into post-transcriptional regulation by ProQ and CspC/E, and the importance of RBPs in regulating gene expression. Significance StatementTogether with transcription and translation, RNA decay is one of the major processes governing protein production. Here, we have developed a new statistical approach that corrects for confounding effects when estimating RNA decay rates from RNA-seq in bacteria. Our more accurate decay rate estimates indicate that Salmonella transcripts have half-lives about three times shorter than previously thought. This approach allowed us to measure the effects of RNA-binding proteins (RBPs) on decay rates, identifying large cohorts of transcripts with changes in stability following RBP deletion and conditions where post-transcriptional regulation affects survival. Our method should lead to a reevaluation of RNA stability estimates across diverse bacteria and new insights into the role of RBPs in shaping the transcriptome.

microbiology↗