Biology subjects

Sistrom, M.

Publications and source records attributed to Sistrom, M..

4 recordsLinked to original sources

bioRxiv2025

Vibrio harveyi plasmids as drivers of virulence in barramundi (Lates calcarifer)?

Vibrio species are an emerging public and animal health risk in marine environments and the opportunistic bacterial pathogen Vibrio harveyi is a major disease risk for tropical aquaculture. Current understanding of virulence in V. harveyi is limited by strain-specific variability and complex host-pathogen dynamics. This study sought to integrate genomic investigation, phenotypic characterisation and in vivo challenge trials in barramundi (Lates calcarifer) to increase our understanding of V. harveyi virulence. We identified two hypervirulent isolates, Vh-14 and Vh-15 that caused 100% mortality in fish within 48 hours, and that were phenotypically and genotypically distinct from other V. harveyi isolates. Virulent isolates contained multiple plasmids, including a 105,412 bp conjugative plasmid with type III secretion system genes originally identified in Yersinia pestis. The emergence of this hypervirulent plasmid-mediated patho-variant poses a potential threat to the sustainable production of marine finfish in Southeast Asia, the Mediterranean and Australia. In addition, we observed an effect of temperature on phenotypic indicators of virulence with an increase in activity at 28{degrees}C and 34{degrees}C compared to 22{degrees}C. This suggests that temperature fluctuations associated with climate change may act as a stressor on bacteria, increasing virulence gene secretion and host adaptation. Our results utilising a myriad of technologies and tools, highlights the importance of a holistic view to virulence characterisation.

microbiology↗

bioRxiv2023

Comparative genomics of Japanese encephalitis virus shows low rates of recombination and a suite of sites under episodic diversifying selection

Japanese encephalitis virus (JEV) is the dominant cause of viral encephalitis in the Asian region with 100,000 cases and 25,000 deaths reported annually. The genome is comprised of a single polyprotein that encodes three structural and seven non-structural proteins. We collated a dataset of 347 complete genomes from a number of public databases, and analysed the data for recombination, evolutionary selection and phylogenetic structure. There are low rates of recombination in JEV, subsequently recombination is not a major evolutionary force shaping JEV. We found a strong overall signal of purifying selection in the genome, which is the main force affecting the evolutionary dynamics in JEV. There are also a small number of genomic sites under episodic diversifying selection, especially in the envelope protein and non-structural proteins 3 and 5. Overall, these results support previous analyses of JEV evolutionary genomics and provide additional insight into the evolutionary processes shaping the distribution and adaptation of this important pathogenic arbovirus. Author SummaryThis comparative study of Japanese Encephalitis Virus is the largest genomic analysis of the virus to date. We undertake a suite of analyses to investigate phylogenetic relationships, rates of recombination and patterns of genomic selection. We show that recombination is not a significant driver of evolution in JEV, demonstrate support for previous phylogenetic reconstructions of the virus, and find a number of sites across the genome under episodic diversifying selection. These adaptive hotspots of evolution serve as key genomic points for the adaptive evolution of this important vector borne pathogen.

microbiology↗

bioRxiv2021

Going through phages: A Computational approach to Revealing the role of prophage in Staphylococcus aureus

Prophages have important roles in virulence, antibiotic resistance and genome evolution in Staphylococcus aureus. Rapid growth in the number of sequenced S. aureus genomes allows for an investigation of prophage sequences in S. aureus at an unprecedented scale. We developed a computational pipeline to detect and analyze prophage sequences in nearly 10,011 S. aureus genomes, discovering thousands of putative prophage sequences with genes encoding virulence factors and antibiotic resistance. ImportanceBacteriophages (phages) play key roles in bacterial evolution, governing abundance, adaptation and diversity of bacterial communities. Temperate phage can facilitate bacterial adaptation via transduction of novel genes. This study takes advantage of the unprecedented quantity of genomic sequencing in public repositories to analyze viral genes in 10,000 Staphylococcus aureus genomes. We found 196,727 prophage sequences, with an estimated total of 129,935 genes. We determined the function of these genes, identifying a large quantity of novel genes that benefit the host such as beta-lactamase, enterotoxins and cytotoxins. These results will inform studies of bacterial evolution and adaptation, by identifying the mechanism of horizontal transfer of genes that confer adaptive traits to bacteria, especially in the context of antibiotic resistance.

microbiology↗

bioRxiv2021

Antibiotic Resistance in Bacillus-based Biopesticide Products

The crisis of antibiotic resistant bacterial infections is one of the most pressing public health issues. Common agricultural practices have been implicated in the generation of antibiotic resistant bacteria. Biopesticides, live bacteria used for pest control, are non-pathogenic and considered safe for consumption. Application of bacteria-based pesticides to crops in high concentrations raises the possibility of unintentional contributions to the movement and generation of antibiotic resistance genes in the environment. However, the presence of clinically relevant antibiotic resistance genes and their resistance phenotypes are currently unknown. Here we use a combination of multiple bioinformatic and microbiological techniques to define resistomes of widely used biopesticides and determine how the presence of suspected antibiotic resistance genes translates to observable resistance phenotypes in several biopesticide products. Our results demonstrate that biopesticide products are reservoirs of clinically relevant antibiotic resistance genes and bear resistance to multiple drug classes. ImportanceThis is the first study to specifically address antibiotic resistance in widely distributed bacterial strains used as commercial biopesticides. Safety assessments of commercial live bacterial biopesticide products do not include antibiotic resistance phenotype identification. We identify antibiotic resistance genes in all live bacterial strains examined, and resistant phenotypes in all strains tested for antibiotic susceptibility. This work demonstrates that biopesticides potentially play a critical role as reservoirs and vectors of antibiotic resistance in the broader environmental resistome that is to date, unstudied.

microbiology↗