Composition of humic acid-degrading estuarine and marine bacterial communities

Abstract

We examined the bacterial decomposition of humic acids (HA) in two flowthrough culture experiments, one inoculated by marine and one by estuarine bacterial communities. In both experiments, the cultures were fed with HA media of salinities of 28 and 14, close to their ambient and a distinctly different, foreign salinity. HA were decomposed to > 60% of the initial concentration within 70 days, and the foreign salinity yielded the highest decomposition. A detrended correspondence analysis of denaturing gradient gel electrophoresis (DGGE) banding patterns showed that during incubation, the bacterial community composition underwent distinct changes. A phylogenetic analysis of DGGE bands excised and bacteria isolated at the end on HA as the sole carbon source showed that Alphaproteobacteria and Gammaproteobacteria largely dominated the communities in the marine flow-through cultures, whereas Gammaproteobacteria, Actinobacteria and Alphaproteobacteria dominated the estuarine communities. Eleven of 13 isolates obtained from both experiments were able to grow on HA as the sole carbon source, seven on phenol and three, affiliated to the Roseobacter clade, on various aromatic acids. The bacteria retrieved from the flow-through cultures were closely (96-99%) affiliated to organisms capable of degrading humic matter, aromatic and aliphatic compounds and also to other bacteria reported previously from the Wadden Sea and Weser estuary.

Bacteria Contribute to Sediment Nutrient Release and Reflect Progressed Eutrophication-Driven Hypoxia in an Organic-Rich Continental Sea

“…It has also been reported that Alphaproteobacteria and Gammaproteobacteria have been found in organic-rich sediments, such as those at fish farms, or have been provoked by organic enrichment [58]–[61], and even by complex humic compounds [62]. The abundant decomposing organic matter and oxygenic bacteria detected in our study, and in previous studies, may contribute greatly to nutrient release such as phosphate and ammonium from sediments, either directly from organic matter or indirectly, enhancing hypoxia and hypoxia-induced nutrient release (e.g.…”

When riverine dissolved organic matter (DOM) meets labile DOM in coastal waters: changes in bacterial community activity and composition

“…It was previously reported that Alphaproteobacteria is the main group stimulated when humic acids are specifically added to a marine bacterial community (Rocker et al 2012). …”

Simultaneous Catabolism of Plant-Derived Aromatic Compounds Results in Enhanced Growth for Members of the Roseobacter Lineage

“…Group members are most dominant in coastal environments, including salt marshes heavily influenced by lignocellulosic vascular plant material (28). Roseobacter ubiquity and success in the oceans have been attributed, in part, to their ability to use a large repertoire of growth substrates, including aromatic compounds (29)(30)(31). Ge-nome analyses have identified several ring-cleaving pathways in roseobacters, including the box and pca pathways (30).…”