Biology subjects

Elg, C. A.

Publications and source records attributed to Elg, C. A..

3 recordsLinked to original sources

bioRxiv2025

Not So Mosaic After All? The Core Genomes of IncP-1 Plasmids Evolve Predominantly Through Vertical Trasmission

Broad-host-range plasmids of the incompatibility group IncP-1 play an important role in bacterial evolution by disseminating genes between diverse bacteria. This includes the notable spread of antibiotic resistance genes to bacterial pathogens that increasingly threaten human health. A better understanding of the evolution of genetic elements like IncP-1 plasmids that underwrite bacterial adaptation is required to counter this threat. Here we examined the evolutionary history of IncP-1 plasmids by utilizing the large increase in published genomes and advancing techniques for lineage-based detection of microbial recombination. We specifically tested whether IncP-1 backbone genes evolve primarily (1) through vertical transmission, or (2) horizontally through homologous recombination between distinct plasmids. Our key finding is the IncP-1 plasmid backbone evolves predominantly through vertical transmission, which was supported by a nucleotide-level mapping of backbone recombination. We also showed via a phylogeny of 187 IncP-1 plasmids that established subgroup categories are well-supported. Finally, we examined factors that are potentially associated with IncP-1 subgroup diversification, including a gene related to plasmid-host adaptation and accessory genes like antibiotic and resistance metals. While some IncP-1 subgroups do correlate with certain categories of accessory genes, it remains unknown if these are causes or consequences of subgroup diversification.

evolutionary biology↗

bioRxiv2024

Evolution of a Plasmid Regulatory Circuit Ameliorates Plasmid Fitness Cost

Plasmids play a major role in rapid adaptation of bacteria by facilitating horizontal transfer of diverse genes, most notably those conferring antibiotic resistance. While most plasmids that replicate in a broad range of bacteria also persist well in diverse hosts, there are exceptions that are poorly understood. We investigated why a broad-host range plasmid, pBP136, originally found in clinical Bordetella pertussis isolates, quickly became extinct in laboratory Escherichia coli populations. Through experimental evolution we found that inactivation of a previously uncharacterized plasmid gene, upf31, drastically improved plasmid maintenance in E. coli. This gene inactivation resulted in decreased transcription of the global plasmid regulators (korA, korB, and korC) and numerous genes in their regulons. It also caused transcriptional changes in many chromosomal genes primarily related to metabolism. In silico analyses suggested that the change in plasmid transcriptome may be initiated by Upf31 interacting with the plasmid regulator KorB. Expression of upf31 in trans negatively affected persistence of pBP136{Delta}upf31 as well as the closely related archetypal IncP-1{beta} plasmid R751, which is stable in E. coli and natively encodes a truncated upf31 allele. Our results demonstrate that while the upf31 allele in pBP136 might advantageously modulate gene expression in its original host, B. pertussis, it has harmful effects in E. coli. Thus, evolution of a single plasmid gene can change the range of hosts in which that plasmid persists, due to effects on the regulation of plasmid gene transcription.

microbiology↗

bioRxiv2021

A Broadly Conserved Deoxycytidine Deaminase Protects Bacteria from Phage Infection

The El Tor biotype of Vibrio cholerae is responsible for perpetuating the longest cholera pandemic in recorded history (1961-current). The genomic islands VSP-1 and -2 are two understudied genetic features that distinguish El Tor from previous pandemics. To understand their utility, we calculated the co-occurrence of VSP genes across bacterial genomes. This analysis predicted the previously uncharacterized vc0175, herein renamed deoxycytidylate deaminase Vibrio (dcdV), is in a gene network with dncV, a cyclic GMP-AMP synthase involved in phage defense. DcdV consists of two domains, a P-loop kinase and a deoxycytidylate deaminase, that are required for the deamination of dCTP and dCMP, inhibiting phage predation by corrupting cellular nucleotide concentrations. Additionally, DcdV is post-translationally inhibited by a unique noncoding RNA encoded 5 of the dcdV locus. DcdV homologs are conserved in bacteria and eukaryotes and our results identify V. cholerae DcdV as the founding member of a previously undescribed bacterial phage defense system.

microbiology↗