Ecology and Evolution of Haloquadratum walsbyi Through the Lens of Genomics and Metagenomics
Lejla Pašić and Francisco Rodríguez-Valera
from: Halophiles: Genetics and Genomes (Edited by: R. Thane Papke and Aharon Oren). Caister Academic Press, U.K. (2014)
In this chapter we summarize the current knowledge on the ecology of natural populations of Haloquadratum walsbyi obtained through genomics and metagenomics. The cells of this enigmatic microbe populate crystallizer brines and deal with a high viral predation pressure. The natural populations of Haloquadratum walsbyi differ in genomic regions known as metagenomic islands that impart environmental adaptation: they are enriched in genes that are involved in transport of nutrients, but also in genes that code for cells surface components that can serve as viral recognition sites. Likewise, similar genomic variability is observed in natural populations of viruses that prey on this species. Natural populations of Haloquadratum walsbyi are not dominated by a single ecologically most successful lineage. Instead, they are composed of numerous (up to 80) clonal lineages that are preserved in space and time. The observed phenomena favors the 'Constant diversity' model of population dynamics which assumes that the expansion of metabolically superior clonal lineages will be selected against by predating viruses in a density-dependent fashion. This way, the microbial population would avoid catastrophic losses due to viral lysis, preserve intragenomic diversity and efficiently exploit niche resources read more ...