Abstract
In river sediments, nitrate is a more preferable electron sink for
microbial respiration than oxygen, for its good solubility and high
redox potential. Nitrate amendment has been used to accelerate oxidation
of pollutants but very few studies focused on microbial dynamics during
bioremediation. Here we simulated a nitrate surge and monitored the
microbial responses in a sulfide-rich river sediment. Original
communities were found dominated by methanogens and syntrophic bacteria,
yet nitrate input enriched two chemolithotrophic denitrifiersThiobacillus and Luteimonas , in spite of abundant organic
carbons there. This led to simplified community composition, function
and interactive networks. Similarly, serial dilutions of sediments found
that Thiobacillus thiophilu s dominated 18/30 communities because
of its simultaneous nitrate reduction and sulfide oxidation.
Interestingly, syntrophic bacteria and archaea performing interspecies
cross-feeding rather than the dominant denitrifiers were sustaining
microbial interactions. Therefore, environment perturbations that
inhibit native auxotrophs will very likely disrupt original microbial
interactions.