Biomedical subjects

Dustin Brisson

Publications and source records attributed to Dustin Brisson.

3 recordsLinked to original sources

PubMed2006

A modest model explains the distribution and abundance of Borrelia burgdorferi strains.

The distribution and abundance of Borrelia burgdorferi, including human Lyme disease strains, is a function of its interactions with vertebrate species. We present a mathematical model describing important ecologic interactions affecting the distribution and abundance of B. burgdorferi strains, marked by the allele at the outer surface protein C locus, in Ixodes scapularis ticks, the principal vector. The frequency of each strain in ticks can be explained by the vertebrate species composition, the density of each vertebrate species, the number of ticks that feed on individuals of each species, and the rate at which those ticks acquire different strains. The model results are consistent with empirical data collected in a major Lyme disease focus in New England. An applicable extension of these results would be to predict the proportion of ticks carrying human infectious strains of B. burgdorferi from disease host densities and thus predict the local risk of contracting Lyme disease.

Animals↗

PubMed2004

ospC diversity in Borrelia burgdorferi: different hosts are different niches.

The outer surface protein C (ospC) locus of the Lyme disease bacterium, Borrelia burgdorferi, is at least an order of magnitude more variable than other genes in the species. This variation is classified into 22 ospC major groups, 15 of which are found in the northeastern United States. The frequency distributions of ospC within populations suggest that this locus is under balancing selection. In multiple-niche polymorphism, a type of balancing selection, diversity within a population can be maintained when the environment is heterogeneous and no one genotype has the highest fitness in all environments. Genetically different individuals within vertebrate species and different vertebrate species constitute diverse environments for B. burgdorferi. We examined four important host species of B. burgdorferi and found that the strains that infected each species had different sets of ospC major groups. We found no variation among conspecific hosts in the ospC major groups of their infecting strains. These results suggest multiple niches create balancing selection at the ospC locus.

Animals↗

PubMed2003

The directed mutation controversy in an evolutionary context.

Neo-Darwinists have long held that random mutations produce genetic differences among individuals, and selection increases the frequency of advantageous alleles. In 1988, Cairns et al. claimed that an environmental pressure can cause advantageous mutations to occur in specific genes to alleviate that particular pressure. Directed mutation, as proposed by Cairns, has been all but eradicated from evolutionary thinking. However, more than a decade of research spurred by the Cairns et al. paper has cast doubt on three neo-Darwinian principles: (1) mutations occur independently of the environment, (2) mutations are due to replication errors, and (3) mutation rates are constant. This mini-review explores the history of the controversy and the decade of research that followed so as to place it in an evolutionary context. Several of the cellular mechanisms and models that explain the increased genetic diversity in populations experiencing adverse environmental pressure are described. In most cases it is clear that the increased genetic diversity is due to breakdowns of cellular machinery or alleles evolved for a purpose other than increasing genetic diversity, rather than to cellular systems that have been evolutionarily selected to increase the genetic diversity in times of stress.

Bacteria↗