The Regulatory Protein ChuP Connects Heme and Siderophore-Mediated Iron Acquisition Systems Required for Chromobacterium violaceum Virulence

Lima, Vinicius Marques de; Batista, Bianca Bontempi; Neto, José F. da Silva

doi:10.3389/fcimb.2022.873536

“…Genome analysis revealed the presence of multiple genetic elements within the chromosome, some associated with virulence. These included the type VI secretion system (cellular aggression mechanism [55]), flagella (mobility [56]), chromobacterium haem utilization and aerobactin operons (iron acquisition [57, 58]), as well as a P fimbriae operon (bacterial adhesion [59]). Unfortunately, there was insufficient DNA to perform long-read sequencing [60], and benefit from the improvements in draft assembly and resolving genomic complexity that this would have provided.…”

Section: Discussionmentioning

confidence: 99%

“…Genome analysis revealed the presence of multiple genetic elements within the chromosome, some associated with virulence. These included the type VI secretion system (cellular aggression mechanism [55]), flagella (mobility [56]), chromobacterium haem utilization and aerobactin operons (iron acquisition [57,58]), as well as a P fimbriae operon (bacterial adhesion [59]).…”

Section: Discussionmentioning

confidence: 99%

A discovery down under: decoding the draft genome sequence of Pantoea stewartii from Australia’s Critically Endangered western ground parrot/kyloring (Pezoporus flaviventris)

White,

Taylor,

Klukowski

et al. 2023

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Pantoea stewartii , a plant pathogen, is primarily transmitted through contaminated seeds and insect vectors, with the corn flea beetle (Chaetocnema pulicaria) being the primary carrier. P. stewartii is a bacterium belonging to the order Enterobacterales and can lead to crop diseases that have a significant economic impact worldwide. Due to its high potential for spread, P. stewartii is classified as a quarantine organism in numerous countries. Despite its impact on agriculture, the limited genome sequences of P. stewartii hamper understanding of its pathogenicity and host specificity, and the development of effective control strategies. In this study, a P. stewartii strain (C10109_Jinnung) was discovered in the faecal matter of the Critically Endangered western ground parrot/kyloring (Pezoporus flaviventris) in Australia, which to our knowledge is the first reported P. stewartii genome from a bird source. Whole-genome sequencing and phylogenomic analysis of strain C10109_Jinnung, obtained from a captive psittacine, provides new insights into the genetic diversity and potential transmission route for the spread of P. stewartii beyond insects and plants, where P. stewartii is typically studied. Our findings provide new insights into the potential transmission route for spread of P. stewartii and expand the known transmission agents beyond insects and plants. Expanding the catalogue of P. stewartii genomes is fundamental to improving understanding of the pathogenicity, evolution and dissemination, and to develop effective control strategies to reduce the substantial economic losses associated with P. stewartii in various crops and the potential impact of endangered animal species.

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“…28 In another study, we have demonstrated that C. violaceum uses heme via the ChuPRSRTUV system, and that both siderophores and heme are important iron acquisition strategies during infection. 29 Further work by our group has shown that Fur protects C. violaceum against iron overload and oxidative stress. Also, Fur represses genes related to iron homeostasis and controls virulence in this bacterium.…”

Section: Introductionmentioning

confidence: 97%

A complex regulatory cascade involving quorum sensing regulates siderophore-mediated iron homeostasis inChromobacterium violaceum

Batista,

de Lima,

Picinato

et al. 2023

Preprint

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Iron is a transition metal used as a cofactor in many biochemical reactions. In bacteria, iron homeostasis involves Fur-mediated de-repression of iron uptake systems, such as the iron-chelating compounds siderophores. In this work, we identified and characterized novel regulatory systems that control siderophores in the environmental opportunistic pathogenChromobacterium violaceum. Screening of a 10,000-transposon mutant library for siderophore halos on PSA-CAS plates identified seven possible regulatory systems involved in siderophore-mediated iron homeostasis inC. violaceum. Further characterization revealed a regulatory cascade that controls siderophores involving the transcription factor VitR acting upstream of the quorum sensing (QS) system CviIR. Mutation of the regulator VitR led to an increase in siderophore halos, and a decrease in biofilm, violacein, and protease production. We determined that these effects occurred due to VitR-dependent de-repression ofvioS. Increased VioS leads to direct inhibition of the CviR regulator by protein-protein interaction. Indeed, insertion mutations incviRand null mutation ofcviIandcviRled to an increase of siderophore halos. RNA-seq of thecviIandcviRmutants revealed that CviR regulates CviI-dependent and CviI-independent regulons. Classical QS-dependent processes (violacein, proteases, and antibiotics) were activated at high cell density by both CviI and CviR. However, genes related to iron homeostasis and many other processes were regulated by CviR but not CviI, suggesting that CviR acts without its canonical CviI autoinducer. Our data revealed a complex regulatory cascade involving QS that controls siderophore-mediated iron homeostasis inC. violaceum.ImportanceThe iron-chelating compounds siderophores play a major role in bacterial iron acquisition. Here, we employed a genetic screen to identify novel siderophore regulatory systems inChromobacterium violaceum, an opportunistic human pathogen. Many mutants with increased siderophore halos had transposon insertions in genes encoding transcription factors, including a novel regulator called VitR, and CviR, the regulator of the quorum sensing (QS) system CviIR. We found that VitR is upstream in the pathway and acts as a dedicated repressor ofvioS, which encodes a direct CviR-inhibitory protein. Indeed, all QS-related phenotypes of avitRmutant were rescued in avitRvioSmutant. At high cell density, CviIR activated classical QS-dependent processes (violacein, proteases, and antibiotics production). However, genes related to iron homeostasis and type-III and type-VI secretion systems were regulated by CviR in a CviI- or cell density-independent manner. Our data unveil a complex regulatory cascade integrating QS and siderophores inC. violaceum.

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“…We propose that these siderophores are assembled by the nonribosomal peptide synthetases (NRPS) CbaF and VbaF from the 2,3-DHBA precursor and imported by the TonB-dependent receptors CbuA and VbuA, respectively ( 28 ). In another study, we have demonstrated that C. violaceum uses heme via the ChuPRSTUV system, and that both siderophores and heme are important iron acquisition strategies during infection ( 29 ). Further work by our group has shown that Fur protects C. violaceum against iron overload and oxidative stress.…”

Section: Introductionmentioning

confidence: 99%

A quorum-sensing regulatory cascade for siderophore-mediated iron homeostasis in Chromobacterium violaceum

Batista,

de Lima,

Picinato

et al. 2024

mSystems

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Iron is a transition metal used as a cofactor in many biochemical reactions. In bacteria, iron homeostasis involves Fur-mediated de-repression of iron uptake systems, such as the iron-chelating compounds siderophores. In this work, we identified and characterized novel regulatory systems that control siderophores in the environmental opportunistic pathogen Chromobacterium violaceum . Screening of a 10,000-transposon mutant library for siderophore halos identified seven possible regulatory systems involved in siderophore-mediated iron homeostasis in C. violaceum . Further characterization revealed a regulatory cascade that controls siderophores involving the transcription factor VitR acting upstream of the quorum-sensing (QS) system CviIR. Mutation of the regulator VitR led to an increase in siderophore halos, and a decrease in biofilm, violacein, and protease production. We determined that these effects occurred due to VitR-dependent de-repression of vioS . Increased VioS leads to direct inhibition of the CviR regulator by protein-protein interaction. Indeed, insertion mutations in cviR and null mutations of cviI and cviR led to an increase of siderophore halos. RNA-seq of the cviI and cviR mutants revealed that CviR regulates CviI-dependent and CviI-independent regulons. Classical QS-dependent processes (violacein, proteases, and antibiotics) were activated at high cell density by both CviI and CviR. However, genes related to iron homeostasis and many other processes were regulated by CviR but not CviI, suggesting that CviR acts without its canonical CviI autoinducer. Our data revealed a complex regulatory cascade involving QS that controls siderophore-mediated iron homeostasis in C. violaceum . IMPORTANCE The iron-chelating compounds siderophores play a major role in bacterial iron acquisition. Here, we employed a genetic screen to identify novel siderophore regulatory systems in Chromobacterium violaceum , an opportunistic human pathogen. Many mutants with increased siderophore halos had transposon insertions in genes encoding transcription factors, including a novel regulator called VitR, and CviR, the regulator of the quorum-sensing (QS) system CviIR. We found that VitR is upstream in the pathway and acts as a dedicated repressor of vioS , which encodes a direct CviR-inhibitory protein. Indeed, all QS-related phenotypes of a vitR mutant were rescued in a vitRvioS mutant. At high cell density, CviIR activated classical QS-dependent processes (violacein, proteases, and antibiotics production). However, genes related to iron homeostasis and type-III and type-VI secretion systems were regulated by CviR in a CviI- or cell density-independent manner. Our data unveil a complex regulatory cascade integrating QS and siderophores in C. violaceum .

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The Regulatory Protein ChuP Connects Heme and Siderophore-Mediated Iron Acquisition Systems Required for Chromobacterium violaceum Virulence

Cited by 11 publications

References 68 publications

A discovery down under: decoding the draft genome sequence of Pantoea stewartii from Australia’s Critically Endangered western ground parrot/kyloring (Pezoporus flaviventris)

A discovery down under: decoding the draft genome sequence of Pantoea stewartii from Australia’s Critically Endangered western ground parrot/kyloring (Pezoporus flaviventris)

A complex regulatory cascade involving quorum sensing regulates siderophore-mediated iron homeostasis inChromobacterium violaceum

A quorum-sensing regulatory cascade for siderophore-mediated iron homeostasis in Chromobacterium violaceum

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