Anàlisi estructural del biofilm microbià de les llacunes salades dels Monegros

Abstract

Biofilms are structures formed by a group of microorganisms such as bacteria, algae and fungi. These, are surrounded by extracellular polymeric substances which they secrete and are essential for the biofilm structure and stability. Biofilms can be found worldwide in many conditions and in extreme environments, such as salty lagoons of the Monegros Desert (Spain), our sampling area. The aim of this study is determine de content of the microorganisms that define the biofilm structure of four lagoons (La Playa, Salineta, Chiprana 1 and Chiprana 2), to observe if the salinity and the drought gradient affect them significantly. In the laboratory we applied some techniques such as EPS extraction, which is used to estimate the amount of polysaccharides present in the lagoons. It has been also used the DAPI staining to determine bacterial density, based on the staining the bacteria and make a subsequent recount. Another technique used has been ergosterol extraction, which is used to determine fungal biomass, carried out in an solid-phase extraction and separation and a subsequent HPLC reading. We have also analyzed the nitrates, phosphates and ammonium from the water of these lakes, and it has been estimated the water content and the algal biomass too. The results show similar and high values of microorganisms, mainly bacteria, and high EPS content in the four lagoons, but surprisingly, there are also high values of fungi, which were initially expected to be lower due to the lack of water and moisture in some areas and the extreme salinity. The two more salty lagoons and less affected by extreme drought conditions had more fungal biomass but very low algal biomass, in costrast to the two Chiprana lagoons that showed a higher drought extreme conditions and had high algal biomass and very low fungi biomass. In all the lagoons the EPS content was high, but specially in Chiprana 1. This means that some of these microorganisms may adapt to these severe conditions, either becoming stronger or by protection mechanisms such as extracellular polymeric substances. This fact leads to form microorganisms with very special characteristics and which are able to tolerate higher salinities than the Mediterranean Sea