Biology subjects

Lalaouna, D.

Publications and source records attributed to Lalaouna, D..

6 recordsLinked to original sources

bioRxiv2026

Peptidoglycan remodeling prevents antibiotic resistance during oxidative stress

ABSTRACT: The bacterial small RNA (sRNA) OxyS is expressed in Escherichia coli during oxidative stress. The sRNA OxyS enhances cell survival by controlling genes involved in the regulation of hydrogen peroxide (H2O2) and iron-sulfur (Fe-S) cluster formation. Here, we used the MS2 affinity purification coupled with RNA sequencing (MAPS) technique to identify new target mRNAs of the sRNA OxyS. Our analysis revealed a significant enrichment of mepS mRNA, which encodes a peptidoglycan endopeptidase that promotes cell growth. Our results confirm a previous report on the sRNA OxyS repressing the translation of mepS. We also found that an {Delta}oxyS background facilitates the emergence of mutations, conferring increased resistance to the last-resort antibiotics polymyxin B and E (colistin), but only in the presence of the target mepS gene. This suggests that the translation repression of mepS by OxyS could prevent mutations in bacterial DNA during H2O2-induced oxidative stress. Moreover, we show that adding the antioxidant thiourea or sequestering iron in the {Delta}oxyS background effectively reduces the emergence of resistance against both polymyxin B and colistin. These results suggest that reactive oxygen species (ROS), in conjunction with intracellular iron, play a key role in driving the emergence of antibiotic resistance. Overall, our work underlines a mechanism of antimicrobial emergence implicating oxidative stress, intracellular Fe, and cell wall remodeling in E. coli. IMPORTANCE: This study uncovers an underexplored link between peptidoglycan remodeling and oxidative stress responses during exposure to antibiotics. By elucidating how MepS and the sRNA OxyS interact in the presence of polymyxins and oxidative stress, our study suggests that MepS may exert an anti-mutator function. The repression of mepS translation by OxyS seems to limit the emergence of antibiotic resistance driven by DNA mutations. Together, these findings suggest cell wall remodeling and oxidative stress response pathways as promising targets to enhance antibiotic efficacy and limit the emergence of resistance.

microbiology↗

bioRxiv2025

A Zur-dependent regulatory RNA involved in maintaining zinc homeostasis in Staphylococcus aureus

Small regulatory RNAs (sRNAs) are key drivers of bacterial adaptation to environmental fluctuations, including iron and manganese restriction imposed by the host. This study explored the repertoire of sRNAs produced by the human pathogen Staphylococus aureus in response to metal limitation. Two sRNAs, S1077 and ZinS (RsaX20), regulated by zinc (Zn) availability, were identified. Further investigations revealed that, similar to the cnt operon from which it derives, S1077 synthesis is controlled by the transcription factors Zur and Fur. In contrast, zinS transcription is solely repressed by Zur. Amongst the ZinS targets are several Zn-dependent enzymes, such as the alcohol dehydrogenase Adh, whose synthesis is negatively regulated by ZinS. Loss of ZinS does not alter staphylococcal metal accumulation, suggesting a role in a Zn-sparing response. Remarkably, zinS also encodes a small peptide, ZinP. Genomic analysis suggests that the regulatory portion of ZinS emerged from the 3 untranslated region of zinP in S. aureus and closely related species after horizontal gene transfer from phylogenetically distant organisms. All our findings demonstrate that sRNAs also facilitate bacterial adaptation to Zn limitation, and that genetic exchange and subsequent neofunctionalization have enabled S. aureus to adapt to metal-restricted environments.

microbiology↗

bioRxiv2024

An unprecedented small RNA-riboswitch interaction controls expression of a bifunctional pump that is essential for Staphylococcus aureus infection

Maintaining manganese and iron homeostasis is critical for the human pathogen Staphylococcus aureus. To counteract metal-based host defense strategies (e.g., nutritional immunity, metal poisoning), S. aureus uses a combination of metal-sensing transcription factors and regulatory RNAs to maintain metal homeostasis. In this study, we uncovered an unprecedented interaction between a cis- and a trans-acting regulatory RNA controlling a conditionally essential gene, mntY, encoding a Mn efflux pump. This broadly conserved RNA-RNA interaction between a Fe-responsive sRNA and a Mn-sensing riboswitch allows the integration of Feand Mn-related stresses, notably encountered at the infection site, to fine-tune mntY expression. Remarkably, deletion of the mntY gene is strongly pleomorphic, causing growth defects, altering virulence factor expression, immune evasion, and survival during infection. We demonstrated that MntY is critical for the adaptation of S. aureus to both low and high Mn environments, due to its dual role in metalation of Mn-dependent exoenzymes and Mn detoxification. These findings point to MntY as a promising new therapeutic target to combat multidrug-resistant staphylococcal infections.

microbiology↗

bioRxiv2024

The Staphylococcus aureus small non-coding RNA IsrR regulates TCA cycle activity and virulence

Staphylococcus aureus has evolved mechanisms to cope with low iron (Fe) availability in host tissues. S. aureus uses the ferric uptake transcriptional regulator (Fur) to sense titers of cytosolic Fe. Upon Fe depletion, apo-Fur relieves transcriptional repression of genes utilized for Fe uptake. We demonstrate that an S. aureus {Delta}fur mutant has decreased expression of acnA, which codes for the Fe-dependent enzyme aconitase. Decreased acnA expression prevented the {Delta}fur mutant from growing with amino acids as sole carbon and energy sources. Suppressor analysis determined that a mutation in isrR, which produces a regulatory RNA, permitted growth by decreasing isrR transcription. The decreased AcnA activity of the {Delta}fur mutant was partially relieved by an {Delta}isrR mutation. Directed mutation of bases predicted to facilitate the interaction between the acnA transcript and IsrR, decreased the ability of IsrR to control acnA expression in vivo and IsrR bound to the acnA transcript in vitro. IsrR also bound to the transcripts coding the alternate TCA cycle proteins sdhC, mqo, citZ, and citM. Whole cell metal analyses suggest that IsrR promotes Fe uptake and increases intracellular Fe not ligated by macromolecules. Lastly, we determined that Fur and IsrR promote infection using murine skin and acute pneumonia models. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=80 SRC="FIGDIR/small/601953v1_ufig1.gif" ALT="Figure 1"> View larger version (19K): org.highwire.dtl.DTLVardef@1ec27b2org.highwire.dtl.DTLVardef@1224b64org.highwire.dtl.DTLVardef@83cd49org.highwire.dtl.DTLVardef@11a9cea_HPS_FORMAT_FIGEXP M_FIG C_FIG

microbiology↗

bioRxiv2023

The 3'UTR of vigR is required for virulence in Staphylococcus aureus and has expanded through STAR sequence repeat insertions

Staphylococcus aureus is an adaptable human pathogen causing life-threatening endocarditis and bacteraemia. Methicillin-resistant S. aureus (MRSA) is alarmingly common, and treatment is confined to last-line antibiotics. Vancomycin is the treatment of choice for MRSA bacteraemia and vancomycin treatment failure is often associated with vancomycin-intermediate S. aureus strains termed VISA. The regulatory 3 UTR of vigR mRNA contributes to vancomycin tolerance in the clinical VISA isolate JKD6008 and upregulates the lytic transglycosylase IsaA. Using MS2-affinity purification coupled with RNA sequencing (MAPS), we find that the vigR 3 UTR also interacts with mRNAs involved in carbon metabolism, amino acid biogenesis, cell wall biogenesis, and virulence. The vigR 3 UTR was found to repress dapE, a succinyl-diaminopimelate desuccinylase required for lysine and cell wall peptidoglycan synthesis, suggesting a broader role in controlling cell wall metabolism and vancomycin tolerance. Deletion of the vigR 3 UTR increased VISA virulence in a wax moth larvae model, and we find that an isaA mutant is completely attenuated in the larvae model. Sequence and structural analysis of the vigR 3 UTR indicates that the UTR has expanded through the acquisition of Staphylococcus aureus repeat insertions (STAR repeats) that partly contribute sequence for the isaA interaction seed and may functionalise the 3 UTR. Our findings reveal an extended regulatory network for vigR, uncovering a novel mechanism of regulation of cell wall metabolism and virulence in a clinical S. aureus isolate.

microbiology↗

bioRxiv2019

CcnA, a novel non-coding RNA regulating the bacterial cell cycle

Bacteria are powerful models for understanding how cells divide and accomplish global regulatory programs. In Caulobacter crescentus, a cascade of essential master regulators supervises the correct and sequential activation of DNA replication, cell division and development of different cell types. Among them, the response regulator CtrA plays a crucial role coordinating all those functions. Here, for the first time we describe the role of a novel factor named CcnA, a cell cycle regulated ncRNA located at the origin of replication, presumably activated by CtrA and responsible for the accumulation of CtrA itself. In addition, CcnA may be also involved in the inhibition of translation of the S-phase regulator, GcrA, by interacting with its 5 untranslated region (5-UTR). Performing in vitro experiments and mutagenesis, we propose a mechanism of action of CcnA based on liberation (ctrA) or sequestration (gcrA) of their ribosome-binding site (RBS). Finally, its role may be conserved in other alphaproteobacterial species, such as Sinorhizobium meliloti, representing indeed a potentially conserved process modulating cell cycle in Caulobacterales and Rhizobiales.

microbiology↗