The Roles of Lateral Gene Transfer and Vertical Descent in Vibrio Evolution

Abstract

This chapter discusses the detection of lateral gene transfer (LGT), from the level of individual genes up to whole-genome and multiple locus analyses. The genetic elements most frequently involved in these gene transfers and the genomic hot spots for such events are also described. Lateral DNA transfer is known to occur through three main modes. Many detection methods are used to detect LGT events. The methods for estimating foreign gene content in a genome give different estimates because they detect different laterally acquired gene subsets. The integron/gene cassette system of vibrios is noteworthy, given the substantial contribution it likely makes to LGT. In addition, other integrons with smaller cassette arrays, usually containing antibiotic resistance genes, are frequently found on vibrio plasmids or other genetic elements. Most efforts in studying the evolution of Vibrios have been devoted to pathogenic species. From these studies, many novel mobile genetic elements have been discovered. Several of these elements have been subsequently found in nonpathogenic environmental vibrios, marking them as general tools for vibrio evolution. Much progress has recently been made in trying to quantify laterally acquired DNA in the genomes of vibrios, although many more taxa need to be examined for accurate representation. Vibrio genome sequences and microarray comparisons, phylomes of vibrio genomes, and multilocus sequence analysis of many strains and species of vibrios, allows for a global picture of Vibrio evolution, from the microevolution of conserved housekeeping genes by recombination to mobile genes traveling rapidly between species.