Genetic exchange among natural isolates of bacteria: recombination within the phoA gene of Escherichia coli

Abstract

An 1871-nucleotide region including the phoA gene (the structural gene encoding alkaline phosphatase, EC 3.1.3.1) was cloned and sequenced from eight naturally occurring strains of Escherichia coli. Alignment with the sequence from E. coli K-12 made apparent that there were 87 polymorphic nucleotide sites, of which 42 were informative for phylogenetic analysis. Maximum parsimony analysis revealed six equally parsimonious trees with a consistency index of 0.80. Of the 42 informative sites, 22 were inconsistent with each of the maximum parsimony trees. The spatial distribution of the inconsistent sites was highly nonrandom in a manner implying that intragenic recombination has played a major role in determining the evolutionary history of the nine alleles. The implication is that different segments of the phoA gene have different phylogenetic histories.