Biology subjects

Kirchberger, P.

Publications and source records attributed to Kirchberger, P..

3 recordsLinked to original sources

bioRxiv2021

Pandemic Vibrio cholerae Acquired Competitive Traits from an Environmental Vibrio Species

BackgroundVibrio cholerae, the causative agent of cholera, is a human pathogen that thrives in estuarine environments. V. cholerae competes with neighboring microbes by the contact-dependent translocation of toxic effectors with the type VI secretion system (T6SS). Effector types are highly variable across V. cholerae strains, but all pandemic isolates encode the same set of distinct effectors. It is possible that acquisition of these effectors via horizontal gene transfer played a role in the development of pandemic V. cholerae. ResultsWe assessed the distribution of V. cholerae T6SS loci across multiple Vibrio species. We showed that the fish-pathogen V. anguillarum encodes all three V. cholerae core loci as well as two of the four additional auxiliary clusters. We further demonstrated that V. anguillarum shares T6SS effectors with V. cholerae, including every pandemic-associated V. cholerae effector. We identified a novel T6SS cluster (Accessory Aux1) that is widespread in V. anguillarum and encodes the pandemic V. cholerae effector TseL. We highlighted potential gene transfer events of Accessory Aux1 from V. anguillarum to V. cholerae. Finally, we showed that TseL from V. cholerae can be neutralized by the V. anguillarum Accessory Aux1 immunity protein and vice versa, indicating V. anguillarum as the donor of tseL to the V. cholerae species. ConclusionsV. anguillarum constitutes an environmental reservoir of pandemic-associated V. cholerae T6SS effectors. V. anguillarum and V. cholerae likely share an environmental niche, compete, and exchange T6SS effectors. Further, our findings highlight the fish as a potential reservoir of pandemic V. cholerae.

genomics↗

bioRxiv2021

Population analysis of Vibrio cholerae in aquatic reservoirs reveals a novel sister species (Vibrio paracholerae sp. nov.) with a history of association with human infections

Most efforts to understand the biology of Vibrio cholerae have focused on a single group, the pandemic-generating lineage harbouring the strains responsible for all known cholera pandemics. Consequently, little is known about the diversity of this species in its native aquatic environment. To understand the differences in the V. cholerae populations inhabiting in regions with varying history of cholera cases and how that might influence the abundance of pandemic strains, a comparative analysis of population composition was performed. Little overlap was found in lineage compositions between those in Dhaka (cholera endemic) located in the Ganges delta, and of Falmouth (no known history of cholera), a small coastal town on the US East Coast. The most striking difference was the presence of a group of related lineages at high abundance in Dhaka which was completely absent from Falmouth. Phylogenomic analysis revealed that these lineages form a cluster at the base of the phylogeny of V. cholerae species, sufficiently differentiated genetically and phenotypically to form a novel species. Strains from this species have been anecdotally isolated from around the world and were isolated as early as 1916 from a British soldier in Egypt suffering from choleraic diarrhoea. In 1935 Gardner and Venkatraman unofficially referred to a member of this group as Vibrio paracholerae. In recognition of this earlier designation, we propose the name Vibrio paracholerae, sp. nov. for this bacterium. Genomic analysis suggests a link with human populations for this novel species and substantial interaction with its better-known sister species. ImportanceCholera continues to remain a major public health threat around the globe. Understanding the ecology, evolution and environmental adaptation of the causative agent Vibrio cholerae and tracking the emergence of novel lineages with pathogenic potential are essential to combat the problem. In this study, we investigated the population dynamics of Vibrio cholerae in an inland locality which is known as endemic for cholera and compared with that of a cholera free coastal location. We found the consistent presence of the pandemic generating V. cholerae in cholera-endemic Dhaka and an exclusive presence of a lineage phylogenetically distinct from other V. cholerae. Our study suggests that this lineage represents a novel species having pathogenic potential and a human link to its environmental abundance. The possible association with human population, co-existence and interaction with toxigenic V. cholerae in the natural environment make this potential human pathogen an important subject for future studies.

microbiology↗

bioRxiv2019

Resurrection of a Global, Metagenomically Defined Microvirus

The Gokushovirinae (family Microviridae) are a group of single-stranded, circular DNA bacteriophages that have been detected in metagenomic datasets from every ecosystem on the planet. Despite their abundance, little is known about their biology or their bacterial hosts: isolates are exceedingly rare, known only from a very small number of obligate intracellular bacteria. By synthesizing circularized phage genomes from prophages embedded in diverse enteric bacteria, we produced viable gokushovirus phage particles that could reliably infect E. coli, thereby allowing experimental analysis of its life cycle and growth characteristics. Revived phages integrate into host genomes by hijacking a phylogenetically conserved chromosome-dimer resolution system, in a manner reminiscent of cholera phage CTX. Sequence motifs required for lysogeny are detectable in other metagenomically defined gokushoviruses, but we show that even partial motifs enable phages to persist in a state of pseudolysogeny by continuously producing viral progeny inside hosts without leading to collapse of their host culture. This ability to employ multiple, disparate survival strategies is likely key to the long-term persistence and global distribution of Gokushovirinae. The capacity to harness gokushoviruses as an experimentally tractable model system thus substantially changes our knowledge of the nature and biology of these ubiquitous phages.

microbiology↗