ORCID Profile
0000-0002-9780-4130
Current Organisations
University of Newcastle Australia
,
The University of Newcastle
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Publisher: Springer Science and Business Media LLC
Date: 09-02-2023
DOI: 10.1038/S41467-023-36252-2
Abstract: Acinetobacter baumannii and Klebsiella pneumoniae are opportunistic pathogens frequently co-isolated from polymicrobial infections. The infections where these pathogens co-exist can be more severe and recalcitrant to therapy than infections caused by either species alone, however there is a lack of knowledge on their potential synergistic interactions. In this study we characterise the genomes of A. baumannii and K. pneumoniae strains co-isolated from a single human lung infection. We examine various aspects of their interactions through transcriptomic, phenomic and phenotypic assays that form a basis for understanding their effects on antimicrobial resistance and virulence during co-infection. Using co-culturing and analyses of secreted metabolites, we discover the ability of K. pneumoniae to cross-feed A. baumannii by-products of sugar fermentation. Minimum inhibitory concentration testing of mono- and co-cultures reveals the ability for A. baumannii to cross-protect K. pneumoniae against the cephalosporin, cefotaxime. Our study demonstrates distinct syntrophic interactions occur between A. baumannii and K. pneumoniae , helping to elucidate the basis for their co-existence in polymicrobial infections.
Publisher: Microbiology Society
Date: 17-11-2021
Abstract: Competitive behaviours of plant growth promoting rhizobacteria (PGPR) are integral to their ability to colonize and persist on plant roots and outcompete phytopathogenic fungi, oomycetes and bacteria. PGPR engage in a range of antagonistic behaviours that have been studied in detail, such as the production and secretion of compounds inhibitory to other microbes. In contrast, their defensive activities that enable them to tolerate exposure to inhibitory compounds produced by their neighbours are less well understood. In this study, the genes involved in the Pseudomonas protegens Pf-5 response to metabolites from eight erse rhizosphere competitor organisms, Fusarium oxysporum , Rhizoctonia solani , Gaeumannomyces graminis var. tritici , Pythium spinosum , Bacillus subtilis QST713, Pseudomonas sp. Q2-87, Streptomyces griseus and Streptomyces bikiniensis subspecies bikiniensi , were examined. Proximity induced excreted metabolite responses were confirmed for Pf-5 with all partner organisms through HPLC before culturing a dense Pf-5 transposon mutant library adjacent to each of these microbes. This was followed by transposon-directed insertion site sequencing (TraDIS), which identified genes that influence Pf-5 fitness during these competitive interactions. A set of 148 genes was identified that were associated with increased fitness during competition, including cell surface modification, electron transport, nucleotide metabolism, as well as regulatory genes. In addition, 51 genes were identified for which loss of function resulted in fitness gains during competition. These included genes involved in flagella biosynthesis and cell ision. Considerable overlap was observed in the set of genes observed to provide a fitness benefit during competition with all eight test organisms, indicating commonalities in the competitive response to phylogenetically erse micro-organisms and providing new insight into competitive processes likely to take place in the rhizosphere.
Publisher: Research Square Platform LLC
Date: 16-07-2020
DOI: 10.21203/RS.3.RS-40738/V1
Abstract: In bacteria, transcription complexes stalled on DNA represent a major source of roadblocks for the DNA replication machinery that must be removed in order to prevent damaging collisions. Gram-positive bacteria contain a transcription factor HelD that is able to remove and recycle stalled complexes, but it was not known how it performed this function. Here, using cryo-electron microscopy and single-particle analysis, we have determined the structures of Bacillus subtilis RNA polymerase (RNAP) elongation and HelD complexes, enabling analysis of the extraordinary conformational changes that occur in RNAP driven by HelD interaction. HelD has a unique 2-armed structure which penetrates deep into the primary and secondary channels of RNA polymerase. One arm removes nucleic acids from the active site, and the other induces a dramatic conformational change in the primary channel leading to removal and recycling of the stalled polymerase.
Publisher: Wiley
Date: 23-09-2022
DOI: 10.1002/MBO3.1316
Abstract: Antibiotic resistance is becoming increasingly prevalent amongst bacterial pathogens and there is an urgent need to develop new types of antibiotics with novel modes of action. One promising strategy is to develop resistance‐breaker compounds, which inhibit resistance mechanisms and thus resensitize bacteria to existing antibiotics. In the current study, we identify bacterial DNA double‐strand break repair as a promising target for the development of resistance‐breaking co‐therapies. We examined genetic variants of Escherichia coli that combined antibiotic‐resistance determinants with DNA repair defects. We observed that defects in the double‐strand break repair pathway led to significant resensitization toward five bactericidal antibiotics representing different functional classes. Effects ranged from partial to full resensitization. For ciprofloxacin and nitrofurantoin, sensitization manifested as a reduction in the minimum inhibitory concentration. For kanamycin and trimethoprim, sensitivity manifested through increased rates of killing at high antibiotic concentrations. For icillin, repair defects dramatically reduced antibiotic tolerance. Ciprofloxacin, nitrofurantoin, and trimethoprim induce the promutagenic SOS response. Disruption of double‐strand break repair strongly d ened the induction of SOS by these antibiotics. Our findings suggest that if break‐repair inhibitors can be developed they could resensitize antibiotic‐resistant bacteria to multiple classes of existing antibiotics and may suppress the development of de novo antibiotic‐resistance mutations.
Publisher: Elsevier BV
Date: 2022
DOI: 10.1016/J.BIOORG.2021.105481
Abstract: A series of hybrid compounds that incorporated anthranilic acid with activated 1H-indoles through a glyoxylamide linker were designed to target bacterial RNA polymerase holoenzyme formation using computational docking. Synthesis, in vitro transcription inhibition assays, and biological testing of the hybrids identified a range of potent anti-transcription inhibitors with activity against a range of pathogenic bacteria with MICs as low as 3.1 μM. A structure activity relationship study identified the key structural components necessary for inhibition of both bacterial growth and transcription. Correlation of in vitro transcription inhibition activity with in vivo mechanism of action was established using fluorescence microscopy and resistance passaging using Gram-positive bacteria showed no resistance development over 30 days. Furthermore, no toxicity was observed from the compounds in a wax moth larvae model, establishing a platform for the development of a series of new antibacterial drugs with an established mode of action.
Publisher: Springer Science and Business Media LLC
Date: 18-12-2020
DOI: 10.1038/S41467-020-20157-5
Abstract: In bacteria, transcription complexes stalled on DNA represent a major source of roadblocks for the DNA replication machinery that must be removed in order to prevent damaging collisions. Gram-positive bacteria contain a transcription factor HelD that is able to remove and recycle stalled complexes, but it was not known how it performed this function. Here, using single particle cryo-electron microscopy, we have determined the structures of Bacillus subtilis RNA polymerase (RNAP) elongation and HelD complexes, enabling analysis of the conformational changes that occur in RNAP driven by HelD interaction. HelD has a 2-armed structure which penetrates deep into the primary and secondary channels of RNA polymerase. One arm removes nucleic acids from the active site, and the other induces a large conformational change in the primary channel leading to removal and recycling of the stalled polymerase, representing a novel mechanism for recycling transcription complexes in bacteria.
Publisher: Research Square Platform LLC
Date: 08-02-2022
DOI: 10.21203/RS.3.RS-1184776/V1
Abstract: Acinetobacter baumannii and Klebsiella pneumoniae are opportunistic pathogens frequently co-isolated from polymicrobial infections. The infections where these pathogens co-exist can be more severe and recalcitrant to therapy than infections caused by either species alone, however there is a lack of knowledge on their potential synergistic interactions. In this study we characterised the genomes of A. baumannii and K. pneumoniae strains co-isolated from a single human lung infection. We examined various aspects of their interactions through transcriptomic, phenomic and phenotypic assays that form a basis for understanding their effects on antimicrobial resistance and virulence during co-infection. Using co-culturing and analyses of secreted metabolites, we discovered the ability of K. pneumoniae to cross-feed A. baumannii by-products of sugar fermentation. Minimum inhibitory concentration testing of mono- and co-cultures revealed the ability for A. baumannii to cross-protect K. pneumoniae against the cephalosporin, cefotaxime. Our study demonstrates distinct syntrophic interactions occur between A. baumannii and K. pneumoniae , helping to elucidate the basis for their co-existence in polymicrobial infections.
Publisher: Cold Spring Harbor Laboratory
Date: 25-01-2022
DOI: 10.1101/2022.01.24.477632
Abstract: Antibiotic resistance is becoming increasingly prevalent amongst bacterial pathogens and there is an urgent need to develop new types of antibiotics with novel modes of action. One promising strategy is to develop resistance-breaker compounds, which inhibit resistance mechanisms and thus re-sensitise bacteria to existing antibiotics. In the current study, we identify bacterial DNA double-strand break repair as a promising target for the development of resistance-breaking co-therapies. We examined genetic variants of Escherichia coli that combined antibiotic-resistance determinants with DNA repair defects. We observed that defects in the double-strand break repair pathway led to significant re-sensitisation towards five bactericidal antibiotics representing different functional classes. Effects ranged from partial to full re-sensitisation. For ciprofloxacin and nitrofurantoin, sensitisation manifested as a reduction in the minimum inhibitory concentration. For kanamycin and trimethoprim, sensitivity manifested through increased rates of killing at high antibiotic concentrations. For icillin, repair defects dramatically reduced antibiotic tolerance. Ciprofloxacin, nitrofurantoin, and trimethoprim induce the pro-mutagenic SOS response. Disruption of double-strand break repair strongly d ened the induction of SOS by these antibiotics. Our findings suggest that if break-repair inhibitors can be developed they could re-sensitise antibiotic-resistant bacteria to multiple classes of existing antibiotics and may supress the development of de novo antibiotic-resistance mutations.
No related grants have been discovered for Catherine Dawson.