I am interested in the emergent properties of social behavior, particularly as they relate to disease transmission occurring within the social context.
Documenting the transmission patterns of bacteria within social groups is notoriously difficult. Simply identifying the presence of a particular bacterial species in multiple socially interacting individuals is not a valid indicator of transmission because those bacterial individuals may differ in their genotype. To determine the fine-grain structure of bacteria transmission, it is necessary to differentiate bacterial genotypes. Standard techniques for differentiating bacterial genotypes involve isolating each cell on a culture plate and sequencing it at multiple loci, which is time-consuming, resource-intensive, and impractical at a large scale (Dias et al., 2010). To reduce the time and resource burden of this multi-locus approach, I developed a differentiation method that uses one highly variable E-coli-specific locus that is appropriate for high throughput sequencing. E. coli is a typically harmless resident of the human gut but its temporal and taxonomic ubiquity among mammals (Hartl and Dykhuizen 1984) and ability to spread through physical contact (Caugant et al. 1984) makes it a powerful system in which to study transmission dynamics in a variety of host species.
One-locus differentiation methods can be extremely powerful, as exemplified by the field of microbiome research, which uses a single locus to differentiate species and genera of bacteria. However, current methods cannot differentiate genotypes of a single species, which is the necessary scale at which to study transmission dynamics. The validation work for my newly-developed one-locus method indicates that it operates with high fidelity and reliably recapitulates known structures of bacteria sharing. This method is now being applied to a real mammalian social system for the first time. I have collected social behavior and fecal data over the course of a year from multiple groups of wild ringtailed lemurs in southwestern Madagascar. Analyses are currently underway to understand the relationship between shared E. coli genotypes and patterns of social behavior. Now that the E. coli differentiation method has been validated, I am building collaborations that will allow the application of this method to other mammalian systems to elucidate how a variety of social and environmental variables contribute to transmission dynamics.
This work is being done in collaboration with Drs. Daniel Dykhuizen, Patricia Wright, and Liliana Davalos.
Caugant, D. A., Levin, B. R., Selander, R. K. 1984. Distribution of multilocus genotypes of Escherichia coli within and between host families. Journal of Hygiene-Cambridge 92: 377-384.
Dias, R. C. S., Moreira, B. M. M., Riley, L. W. (2010). Use of fimH single-nucleotide polymorphisms for strain typing of clinical isolates of Escherichia coli for epidemiologic investigation. Journal of Clinical Microbiology 48: 483-488.
Hartl, D. L., Dykhuizen, D. E. (1984). The population genetics of Escherichia coli. Annual Review of Genetics 18: 31–68.