Insights into microbial actions on hydraulic concrete structures: Effects of concrete alkalinity on bacterial community composition and functional expression

摘要

Microbial induced concrete degradation (MICD) has received increased research attention. Nonetheless, microbial actions on hydraulic concrete structures (HCSs) in freshwater are poorly understood compared with those in sewer systems. Knowledge of the effects of the highly alkaline nature of concretes on attached microbial communities on HCSs is especially lacking. Here, we studied the composition and succession of bacterial communities in the deterioration layers of HCSs in response to concrete alkalinity gradients with the pH ranging from 7.88 to 12.08. Furthermore, variation in the functional bacteria potentially related to MICD was explored by functional prediction based on the Kyoto Encyclopedia of Genes and Genome (KEGG) pathways database. The diversities and abundances of most bacterial communities at the phylum and genus level were significantly inhibited by dosed alkalinity, and a positive relationship was observed between the abundance of Cyanobacteria and concrete alkalinity. The bacterial communities in attached biofilms gradually increased in similarity as succession progressed, whereas concrete alkalinity led to slight increases in the similarity in community structure. The main contribution of community assemblage was from a turnover pattern caused by species replacement. A nonlinear relationship was observed between concrete alkalinity and the distributions of functional genes related to nitrogen and sulfur metabolism. The distribution of functional genes was most affected by high alkalinity solutions (pH 11.39-12.08), whereas the distribution of functional genes was least affected by moderate alkalinity conditions (pH 10.88-11.16). The nitrogen cyclic pathways were dominated by partial ammonia oxidation, and self-assimilation was the major process in the sulfur metabolic cycle. As the alkalinity gradients decreased in strength, the biological activities of functional genes related to MICD gradually increased, potentially exacerbating microbial degradation on HCSs. Generally, our work provides new insight into the effects of concrete alkalinity on microbial actions and improves our understanding of the safety and durability of water conservation projects in marine and freshwater environments with high alkalinity. (C) 2021 Elsevier Ltd. All rights reserved.