Diversity and abundance of aromatic catabolic genes in lake sediments in response to temperature change

The abundance and composition of genes involved in the catabolism of aromatic compounds provide important information on the biodegradation potential of organic pollutants and naturally occurring compounds in the environment. We studied catechol 2, 3 dioxygenase (C23O) and benzylsuccinate synthase (bssA) genes coding for key enzymes of aerobic and anaerobic degradation of aromatic compounds in experimental incubations with sediments from two contrasting lakes; humic lake Svarttjarn and eutrophic Vallentunasjon, respectively. Sediment cores from both lakes were incubated continuously for 5months at constant temperatures ranging from 1.0 to 21.0 degrees C. The difference in C23O gene composition of the sediment analyzed at the end of the experiment was larger between lakes, than among temperature treatments within each lake. The abundance of C23O gene copies and measured respiration was positively correlated with temperature in Vallentunasjon, whereas putative C23O genes were present in lower concentrations in Svarttjarn sediments. Putative bssA genes were only detected in Svarttjarn. For both lakes, the two catabolic genes were most abundant in the surface sediment. The results emphasize the important role of temperature and nutrient availability in controlling the functional potential of sediment microorganisms and reveal differences between systems with contrasting trophic status. A better understanding of catabolic pathways and enzymes will enable more accurate forecasting of the functional properties of ecosystems under various scenarios of environmental change.