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Heuristic Mining of Hierarchical Genotypes and Accessory Genome Loci in Bacterial Populations
Published on: December 7, 2021
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Assessing spatial distribution, genetic variants, and virulence of pathogen
Shalyn N Bauschlicher1, Chava L Weitzman2, Victoria Martinez1
1Department of Biology Colorado State University - Pueblo Pueblo Colorado USA.
Ecology and Evolution
|June 7, 2023
Summary
This study investigated virulence genes in Mycoplasma agassizii, a pathogen affecting Mojave desert tortoises. A specific gene (528) correlated with higher bacterial loads, suggesting a role in tortoise respiratory disease.
Area of Science:
- Veterinary Medicine
- Microbiology
- Conservation Biology
Background:
- Mojave desert tortoises (Gopherus agassizii) face chronic respiratory disease caused by Mycoplasma agassizii.
- The virulence and genetic diversity of M. agassizii are poorly understood, hindering effective management of this threatened species.
- Previous attempts to culture and characterize M. agassizii have yielded limited success.
Purpose of the Study:
- To investigate the geographic distribution and genetic variation of putative virulence genes in M. agassizii within Mojave desert tortoise populations.
- To identify specific M. agassizii genes associated with bacterial load and potential virulence.
- To explore evolutionary patterns of M. agassizii virulence in relation to host health and environmental conditions.
Main Methods:
- Development and application of a quantitative polymerase chain reaction (qPCR) assay targeting three exo-α-sialidase genes in the M. agassizii type strain PS6T.
- Analysis of 140 M. agassizii-positive DNA samples collected from Mojave desert tortoises between 2010 and 2012.
- Statistical analysis to correlate the presence and abundance of sialidase genes with M. agassizii bacterial loads.
Main Results:
- Evidence of multiple M. agassizii strains infecting individual tortoises.
- Sialidase-encoding genes were most prevalent in tortoise populations near southern Nevada, the origin of the PS6T strain.
- A specific gene, 528 (exo-α-sialidase), was positively associated with higher M. agassizii bacterial loads, suggesting a role as a growth factor.
- A general trend of sialidase gene loss or reduced presence was observed among strains, even within single hosts.
Conclusions:
- The study identified a potential virulence factor (gene 528) in M. agassizii that may promote bacterial growth in Mojave desert tortoises.
- Observed genetic variation and gene loss suggest complex evolutionary dynamics, including neutral changes, trade-offs between virulence and transmission, and selection against virulence.
- The qPCR approach provides a valuable model for studying host-pathogen dynamics in chronically persisting opportunistic pathogens like M. agassizii.
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