Gene transfer mechanisms, population genetics/genomics and the evolution of haloarchaea

Abstract

The Halobacteriales were once classified with the Pseudomonadales due to their aerobic, heterotrophic, non-spore forming, and rod-shaped morphological characteristics. Today we know them as Archaea belonging to a distinct order within the Euryarchaeota, the Halobacteria, which appear to have methanogens as an evolutionary sister group. Molecular phylogeny led to this reclassification, and also to a realization of remarkable genetic diversity within haloarchaeal taxa. Over the past few decades, and even more so recently, it has become clear that Halobacteria (referred to as haloarchaea in this chapter) have mechanisms for acquiring genetic information through lateral gene transfer (LGT). Further, we present evidence indicating the evolutionary history of haloarchaea is riddled with gene transfer events and homologous recombination, and discuss the impact of LGT on the evolution of this halophilic group.