Biology subjects

Oglesby, A. G.

Publications and source records attributed to Oglesby, A. G..

3 recordsLinked to original sources

bioRxiv2023

The heme-responsive PrrH sRNA regulates Pseudomonas aeruginosa pyochelin gene expression

Pseudomonas aeruginosa is an opportunistic pathogen that requires iron for growth and virulence, yet this nutrient is sequestered by the innate immune system during infection. When iron is limiting, P. aeruginosa expresses the PrrF1 and PrrF2 small regulatory RNAs (sRNAs), which post-transcriptionally repress expression of non-essential iron-containing proteins thus sparing this nutrient for more critical processes. The genes for the PrrF1 and PrrF2 sRNAs are arranged in tandem on the chromosome, allowing for the transcription of a longer heme-responsive sRNA, termed PrrH. While the functions of PrrF1 and PrrF2 have been studied extensively, the role of PrrH in P. aeruginosa physiology and virulence is not well understood. In this study, we performed transcriptomic and proteomic studies to identify the PrrH regulon. In shaking cultures, the pyochelin synthesis proteins were increased in two distinct prrH mutants compared to wild type, while the mRNAs for these proteins were not affected by prrH mutation. We identified complementarity between the PrrH sRNA and sequence upstream of the pchE mRNA, suggesting potential for PrrH to directly regulate expression of genes for pyochelin synthesis. We further showed that pchE mRNA levels were increased in the prrH mutants when grown in static but not shaking conditions. Moreover, we discovered controlling for the presence of light was critical for examining the impact of PrrH on pchE expression. As such, our study reports on the first likely target of the PrrH sRNA and highlights key environmental variables that will allow for future characterization of PrrH function. ImportanceIn the human host, iron is predominantly in the form of heme, which Pseudomonas aeruginosa can acquire as an iron source during infection. We previously showed that the iron-responsive PrrF sRNAs are critical for mediating iron homeostasis during P. aeruginosa infection; however the function of the heme-responsive PrrH sRNA remains unclear. In this study, we identified genes for pyochelin siderophore biosynthesis, which mediate uptake of inorganic iron, as a novel target of PrrH regulation. This study therefore highlights a novel relationship between heme availability and siderophore biosynthesis in P. aeruginosa.

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↗

bioRxiv2021

The human innate immune protein calprotectin elicits a multi-metal starvation response in Pseudomonas aeruginosa

To combat infections, the mammalian host limits availability of essential transition metals such as iron (Fe), zinc (Zn), and manganese (Mn) in a strategy termed "nutritional immunity". The innate immune protein calprotectin (CP) contributes to nutritional immunity by sequestering these metals to exert antimicrobial activity against a broad range of microbial pathogens. One such pathogen is Pseudomonas aeruginosa, which causes opportunistic infections in vulnerable populations including individuals with cystic fibrosis. CP was previously shown to withhold Fe(II) and Zn(II) from P. aeruginosa and induce Fe- and Zn-starvation responses in this pathogen. In this work, we performed quantitative, label-free proteomics to further elucidate how CP impacts metal homeostasis pathways in P. aeruginosa. We report that CP induces an incomplete Fe-starvation response, as many Fe-containing proteins that are repressed by Fe limitation are not affected by CP treatment. The Zn-starvation response elicited by CP seems to be more complete than the Fe-starvation response and includes increases in Zn transporters and Zn-independent proteins. CP also induces the expression of membrane-modifying proteins, and metal-depletion studies indicate this response results from the sequestration of multiple metals. Moreover, the increased expression of membrane-modifying enzymes upon CP treatment correlates with increased resistance to polymyxin B. Thus, response of P. aeruginosa to CP treatment includes both single and multi-metal starvation responses and includes many factors related to virulence potential, broadening our understanding of this pathogens interaction with the host. ImportanceTransition metals are critical for growth and infection by all pathogens, and the innate immune system withholds these metals from pathogens to limit their growth in a strategy termed "nutritional immunity". While multi-metal depletion by the host is appreciated, the majority of metal depletion studies have focused on individual metald. Here we use the innate immune protein calprotectin (CP), which complexes with several metals including iron (Fe), zinc (Zn), and manganese (Mn), and the opportunistic pathogen Pseudomonas aeruginosa to investigate multi-metal starvation. Using an unbiased label-free proteomics response, we demonstrate that multi-metal withholding by CP induces a regulatory response that is not merely additive of individual metal starvation responses, including the induction of Lipid A modification enzymes.

microbiology↗