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Temporal changes in the frequency of colicinogeny in Escherichia coli from house mice
David M Gordon1, Margaret A Riley2, Theodora Pinou2
1Division of Botany and Zoology, Australian National UniversityCanberra, ACT 0200Australia.
Abstract:
Escherichia coli was isolated from feral house mice (Mus domesticus) during the course of a mouse plague in the state of Victoria, Australia. The isolates were characterized for the production of colicins and their resistance to the co-occurring colicins. Of the 447 isolates examined, 59% were found to be colicinogenic. Phenotypic and PCR-based genotypic methods were used to determine the types of colicins being produced. Colicin E2 was the most common, representing 27% of the colicin-producing isolates. Colicin Ia was produced by 3% of the colicinogenic isolates. The remaining colicins could not be identified, but phenotypic and PCR data argue that at least nine different colicin types are present in this collection of E. coli. The frequency of colicinogenic isolates declined from 71% to 43% over the 7 months of the study. All colicin types appeared to decline in frequency. Concurrently, the resistance of isolates to colicin E2 increased from about 50% to 70%. Two hypotheses are proposed to explain the decline in the frequency of colicinogeny in this population of E. coli. The first relates to the within-host interactions occurring among colicinogenic, colicin-susceptible and colicin-resistant populations within a host. The second relates to the among-host interactions between susceptible and colicinogenic populations and the effect of host population densities on these interactions.
Insights
Colicin production by Escherichia coli in feral mice declined over time, with increased resistance to common colicins observed. This suggests complex population dynamics influence bacterial interactions during mouse plagues.
Area of Science:
- Microbiology
- Ecology
- Genetics
Background:
- Escherichia coli is a common bacterium found in mammals.
- Colicins are bacteriocins produced by E. coli that inhibit or kill other E. coli strains.
- Understanding colicin production and resistance is crucial for studying bacterial population dynamics.
Purpose of the Study:
- To investigate colicin production and resistance in Escherichia coli isolated from feral house mice during a plague.
- To characterize the types of colicins produced and their prevalence.
- To analyze changes in colicinogenic and colicin-resistant E. coli frequencies over time.
Main Methods:
- Isolation and characterization of Escherichia coli from feral mice (Mus domesticus).
- Phenotypic and PCR-based genotypic methods for colicin typing.
- Quantification of colicinogenic and colicin-resistant isolates over a 7-month period.
Main Results:
- 59% of 447 E. coli isolates were colicinogenic, with Colicin E2 being the most common type.
- Colicinogenic isolate frequency decreased from 71% to 43% over 7 months.
- Isolate resistance to Colicin E2 increased from 50% to 70% during the study period.
Conclusions:
- The study observed a decline in colicin production and an increase in colicin resistance in E. coli populations within feral mice.
- Proposed hypotheses involve within-host and among-host interactions influencing these population dynamics.
- These findings highlight the complex ecological factors affecting bacterial populations in wildlife during disease outbreaks.