Metagenomic analysis of the microbial community structure in protected wetlands in the Maritza River Basin

Microbial communities drive the biogeochemical cycles in wetlands and provide a number of ecosystem services. They underpin soil function, and are easily impacted by anthropogenic pressure. This study examined the bacterial microbiome in the natural wetland of Zlato Pole and the protected, periodically flooded rice paddies in the Maritsa River Basin using a metagenomic approach, based on high-throughput sequencing. Alpha-diversity analysis showed a significant variation between the three study sites for Chao1 and ACE (abundance based coverage estimator) richness estimators. A positive correlation was established with pH, with highest values detected for the rice paddies and the lowest, for the Zlato Pole sediments. The obtained sequences were assigned into 37 known bacterial phyla with over 97% bacterial sequences classified within only nine of them. The bacterial communities in rice paddies sediments were more evenly distributed, whereas the Zlato Pole sediment was the most biased. The consortiums in the rice paddies were dominated by Proteobacteria, followed by Actinobacteria and Acidobacteria. The bacterial assemblages in those sites could not be distinguished by analysis of similarity. The Zlato Pole sediment community held an isolated position, where Acidobacteria was replaced by Firmicutes and Bacteroidetes and the microbiome showed an extremely high abundance of Gammaproteobacteria and Bacilli. The dominance of Gammaproteobacteria and the presence of Deinococcus-Thermus phylum, along lower nutrient concentration and the absence of correlation with the environmental parameters, is evidence of constant anthropogenic pressure around the area. The obtained results could be applied in the plans for sustainable management of the protected wetlands.