Izzo, V. | Search bioRxiv

bioRxiv2021

Outer membrane vesicles derived from Klebsiella pneumoniae are a driving force for horizontal gene transfer

Gram-negative bacteria release outer membrane vesicles (OMVs) into the extracellular environment. Recent studies recognized these vesicles as vectors to horizontal gene transfer, however the parameters that mediate OMVs transfer within bacterial communities remain unclear. The present study highlights for the first time the transfer of plasmids containing resistance genes via OMVs derived from Klebsiella pneumoniae (K. pneumoniae). This mechanism confers DNA protection and it is plasmid copy number dependent with a ratio of 3.6 time among high copy-number plasmid (pGR) versus low copy number plasmid (PRM) and the transformation efficiency was 3.6 times greater. Therefore, the DNA amount in the vesicular lumen and the efficacy of horizontal gene transfer was strictly dependent on the identity of the plasmid. Moreover, the role of K. pneumoniae-OMVs in interspecies transfer was described. The transfer ability was not related to the phylogenetic characteristics between the donor and the recipient species. K. pneumoniae-OMVs transferred plasmid to Escherichia coli, Salmonella enterica, Pseudomonas aeruginosa and Burkholderia cepacia. These findings address the pivotal role of K. pneumoniae-OMVs as vectors for antimicrobial resistance genes spread, contributing to the development of antibiotic resistance in the microbial communities. Author summaryK. pneumoniae is an important opportunistic pathogen that affects several host districts, in particular respiratory and urinary tracts. Hospital-acquired K. pneumoniae infections lead to a 50% mortality rate correlated with rapid acquisition of antibiotic resistance. Currently, the increasing rate of antibiotic resistance among K. pneumoniae isolates is a major concern worldwide. The spread of multidrug-resistant K. pneumoniae strains renders current therapeutic options ineffective. Like all Gram-negative bacteria, K. pneumoniae secretes OMVs. OMVs are spherical structures, with a diameter between 50-250 nm, originating from the outer membrane. OMVs biogenesis allows bacteria to interact with the external environment, increasing bacterial survival under stressful conditions and regulating microbial interactions within bacterial communities. Few evidence recognized OMVs as vectors for horizontal gene transfer, contributing to the spread of resistance. In this scenario, the present study examines the potential role of K. pneumoniae-OMVs in inter- and intra-species diffusion of {beta}-lactam resistance.

microbiology↗

bioRxiv2017

Origin of pest lineages of the Colorado potato beetle, Leptinotarsa decemlineata

Colorado potato beetle (Leptinotarsa decemlineata Say) is a pest of potato throughout the Northern Hemisphere, but little is known about the beetles origins as a pest. To determine the origins of pest populations of CPB, we sampled the beetle from uncultivated Solanum host plants in Mexico, and from pest and non-pest populations in the U.S. We used mtDNA and nuclear loci to examine three hypotheses on the origin of the pest lineages: 1) the pest beetles originated from Mexican populations, 2) the pest beetles descended from hybridization between previously divergent populations, or 3) the pest beetles descended from populations that are native to the Plains states in the United States. We examined patterns of genetic diversity among geographic regions in order to detect invasion-related genetic information. Mitochondrial haplotypes of non-pest populations from Mexico and southern Arizona differed substantially from beetles collected from the southern plains and potato fields in the U. S., indicating that beetles from Mexico and Arizona did not contribute to founding the pest lineages. Similar results were observed for AFLP and microsatellite data. In contrast, non-pest populations from the southern plains of Colorado, Kansas, Nebraska, New Mexico, and Texas were genetically similar to U. S. pest populations, clearly indicating that they contributed to the founding of the pest lineages. Although some pest populations are less genetically diverse (e.g., Washington, Idaho), most of the pest populations do not show a significant reduction in genetic diversity compared to the plains populations in the U. S. In contrast to the colonization patterns typical of exotic pests, our analyses suggests that a large genetically heterogeneous beetle populations expanded onto potato from native Solanum hosts. As an endemic colonization of a novel host plant, this host range expansion may have contributed to the relatively abundant genetic diversity of contemporary populations, perhaps contributing to the rapid evolution of host range and insecticide resistance in this widely successful insect pest.

evolutionary biology↗