Diversity across Seasons of CulturablePseudomonasfrom a Desiccation Lagoon in Cuatro Cienegas, Mexico

Abstract

Cuatro Cienegas basin (CCB) is a biodiversity reservoir within the Chihuahuan desert that includes several water systems subject to marked seasonality. While several studies have focused on biodiversity inventories, this is the first study that describes seasonal changes in diversity within the basin. We sampledPseudomonaspopulations from a seasonally variable water system at four different sampling dates (August 2003, January 2004, January 2005, and August 2005). A total of 70Pseudomonasisolates across seasons were obtained, genotyped by fingerprinting (BOX-PCR), and taxonomically characterized by 16S rDNA sequencing. We found 35 unique genotypes, and two numerically dominant lineages (16S rDNA sequences) that made up 64% of the sample:P. cuatrocienegasensisandP. otitidis. We did not recover genotypes across seasons, but lineages reoccurred across seasons;P. cuatrocienegasensiswas isolated exclusively in winter, whileP. otitidiswas only recovered in summer. We statistically show that taxonomic identity of isolates is not independent of the sampling season, and that winter and summer populations are different. In addition to the genetic description of populations, we show exploratory measures of growth rates at different temperatures, suggesting physiological differences between populations. Altogether, the results indicate seasonal changes in diversity of free-living aquaticPseudomonaspopulations from CCB.