Dr. Lawrence studies the molecular evolution of bacterial genomes using theoretical, bioinformatic and experimental approaches. The evolutionary pressures on bacterial genomes differ markedly from those affecting eukaryotic genomes. Sexual exchange is limited, interspecies gene transfer is rampant, and miniscule fitness differences overwhelm stochastic variability owing to enormous population sizes. This laboratory examines the roles of selection and recombination in bacterial speciation and the formation of higher taxonomic groups. Current research foci include the role of diversifying selection in maintaining antigenic diversity, the role of pioneer genes in catalyzing temporally fragmented bacterial speciation, the role of codon slection in coupling rates of synonymous and nonsynonymous diversgence, and constraints on the lateral transfer of genes among distantly-related genomes.