Unravelling the bacterial diversity found in the semi-arid Tablas de Daimiel National Park wetland (central Spain)

Abstract

Our knowledge of microbial diversity in the environment is still limited, and there are many species as yet unidentified in both soil and water. Studies of the microbial diversity of wetland ecosystems have been neglected for years, as is the case of Tablas de Daimiel National Park (TDNP), a Spanish semi-arid wetland system of international importance in terms of waterfowl. We report the bacterial diversity of water column, sediment (upper and lower layers) and biofilm samples from the TDNP system using a 16S rRNA gene library approach. A sequence comparison of the 703 clones obtained revealed a number of bacterial phylogroups unreported to date. Bacterial diversity was high (Shannon values of 3.2 to 4.9), with the highest corresponding to the water sample, followed by the water-sediment interface (upper sediment). The sequences affiliated with the Proteobacteria and Bacteroidetes phyla were the most frequently found. Sequence distribution corresponded closely between the water column and upper sediment layers on the one hand, and the lower sediment and biofilm layers on the other. Gamma- and Deltaproteobacteria were the most dominant groups in the clone libraries from samples of water and upper sediment environments, whereas Alpha- and Betaproteobacteria were dominant in lower sediment and biofilm. In total, 265 new phylogroups were found with less than 97% similarity to the closest taxonomically defined 16S rRNA gene sequences in public sequence repositories.