Biology subjects

Chourashi, R.

Publications and source records attributed to Chourashi, R..

3 recordsLinked to original sources

bioRxiv2026

RsmW is an iron-responsive 3 UTR derived small regulatory RNA that contributes to biofilm formation and virulence of Pseudomonas aeruginosa

Pseudomonas aeruginosa is an opportunistic Gram-negative pathogen that causes acute and chronic opportunistic infections. Progression to chronic infection requires upregulation of the Rsm small regulatory RNAs (sRNAs), which in turn induce the expression of virulence factors to promote chronic virulence phenotypes, including biofilm formation. Iron is a critical nutrient for survival and virulence of Pa, and host-mediated iron limitation leads to the induction of key virulence factors driving infection. Prior work showed that the RsmY and RsmZ sRNAs are modestly upregulated due to iron limitation in static growth conditions via PqsR. Here, we show that another Rsm sRNA, RsmW, is strongly induced by iron limitation, likely in a Fur-dependent manner. We identified an RNA processing event, which appears to be mediated by the RNAse E, resulting in cleavage of RsmW from the 3 UTR of pa4570 mRNA. We also report that RsmW is more stable than the full length pa4570-rsmW transcript as well as the processed pa4570 mRNA. Surprisingly, we found that RetS, which down-regulates RsmY and RsmZ expression, enhances expression of RsmW under iron limiting conditions. We further demonstrate that RsmW plays a key role in biofilm formation under iron limiting conditions and is required for full pathogenesis in a Galleria mellonella infection model. Lastly, we observed similar iron-dependent regulation of RsmW in chronic infection isolates from cystic fibrosis (CF) sputum, underlining the potential importance of this regulation in the CF lung. Taken together, the results outline a new paradigm for sRNA-dependent iron regulation of P. aeruginosa pathogenesis.

microbiology↗

bioRxiv2024

The Pseudomonas aeruginosa PrrF sRNAs promote biofilm formation at body temperature

Pseudomonas aeruginosa is a Gram-negative opportunistic pathogen that causes both acute and chronic infections in vulnerable populations. Treatment of P. aeruginosa infections is increasingly challenging due to multi-drug resistance as well as biofilm formation that further increases antibiotic tolerance. Iron, which is sequestered by the host innate immune system, is also a key nutrient that required for P. aeruginosa biofilm formation. Previous work showed that the iron-responsive PrrF small regulatory RNAs (sRNAs), which are key to P. aeruginosas iron starvation response and required for virulence in murine lung infection, are dispensable for biofilm formation. However, these studies were performed using flow-cell biofilms at room temperature. Here we demonstrate a temperature dependency for PrrF in P. aeruginosa biofilm formation - the genes for these sRNAs are required for optimal biofilm formation at 37{degrees}C but not 25{degrees}C. We further show that the {Delta}prrF mutant lacks a yet-to-be identified surface appendage that is produced at 37{degrees}C but not 25{degrees}C. These studies demonstrate that the importance of the PrrF sRNAs in P. aeruginosa biofilm formation at body temperature and reveal a previously under-appreciated role of temperature in iron homeostasis and P. aeruginosa biofilm physiology. IMPORTANCEBiofilm formation is a critical aspect of pathogenesis for many microbial pathogens as it confers increased tolerance to the host immune system and antimicrobial treatments. Pseudomonas aeruginosa is an opportunistic pathogen that forms biofilms during infection, resulting in antimicrobial tolerance and treatment failure. Iron is a known requirement for P. aeruginosa biofilm formation, yet the precise role of iron homeostasis in biofilm physiology remains unclear. Here we show that temperature alters the requirement for the PrrF small regulatory RNAs, key components of P. aeruginosas iron starvation response, for biofilm formation. Specifically, PrrF is required for the optimal formation of biofilms in flow cells at 37{degrees}C but not 25{degrees}C, yet most flow-cell biofilm studies are conducted at 25{degrees}C. These results demonstrate a previously under-appreciated role of temperature in P. aeruginosa biofilm physiology.

microbiology↗

bioRxiv2022

Pseudomonas aeruginosa mediates PqsA-dependent iron regulation of the RsmY and RsmZ sRNAs in static conditions

Pseudomonas aeruginosa is an opportunistic Gram-negative pathogen that causes acute and chronic lung infection in compromised hosts. During infection, the host innate immune system restricts iron to limit microbial growth. In response, P. aeruginosa induces expression of numerous virulence genes. Recently, our lab showed that some virulence factors are responsive to iron limitation in static but not shaking growth conditions, the former of which is likely to mimic growth in the chronically-infected lung. One of these novel iron-responsive factors is the HSI-2-type six secretion system (T6SS), which is also induced during chronic infection. Iron regulation of T6SS was partially impacted by deletion of the iron-responsive PrrF sRNA and completely dependent upon the Pseudomonas quinolone signal (PQS) biosynthetic gene pqsA. Here, we analyzed the impact of iron on the expression of two small regulatory RNAs (sRNAs), RsmY and RsmZ, that activate expression of T6SS by sequestering the RsmA translation inhibitor. Our results demonstrate that iron starvation induces expression of RsmY and RsmZ in static but not shaking cultures. We further show that this induction occurs through the rsmY and rsmZ promoters and is dependent upon PqsA. We identified interrupted palindromes in the rsmY and rsmZ promoters as putative PqsR binding sites, and disruption of these sites eliminated iron-dependent regulation of rsmY and rsmZ promoter activity. To determine if iron-dependent regulation of the Rsm sRNAs is likely responsible for iron regulation of HSI-2 T6SS, we constructed translational and transcriptional reporters of the hsiA2 T6SS gene. Analysis of these reporters revealed robust PqsA-mediated iron regulation of the transcriptional reporter, as well as modest PrrF-dependent iron regulation of the translational reporter. Taken together, our results show novel iron regulatory pathways that are promoted by static growth, highlighting the importance of studying regulatory mechanisms in static communities that are likely more representative of chronic P. aeruginosa infections. IMPORTANCEIron is a central component of various bacterial metabolic pathways making it an important host acquired nutrient for pathogens to establish infection. Previous iron regulatory studies primaried relied on shaking bacterial cultures; while these ensure cultural homogeneity they do not reflect growth conditions during infection. We recently showed that static growth of Pseudomonas aeruginosa promotes iron-dependent regulation of a type six secretion system (T6SS), a virulence factor that is induced during chronic infections. In the current study, we found that static growth also promotes iron-dependent regulation of the RsmY and RsmZ sRNAs, which are global regulators that affect T6SS during chronic P. aeruginosa lung infection. Hence, our work demonstrates the Rsm sRNAs as potential effectors of iron regulation during static growth that may also be relevant in chronic infection.

microbiology↗