The Detritusphere as Biogeochemical Interface for Bacterial and Fungal Degradation of MCPA and Phenanthrene

This project aims to clarify microbiological and physicochemical interactions during MCPA and phenanthrene degradation in the detritusphere. The detritusphere offers a unique opportunity to study metabolism and co-metabolism by a bacterial and fungal community along a gradient of decreasing availability of low molecular weight substances within a distance of 10 mm from the soil-litter interface. First, we estimate the MCPA degrading genetic potential by quantitative PCR targeting on tfdA sequences coding MCPA alpha-ketoglutarate dioxygenase. The phenanthrene degrading genetic potential is estimated by targeting on phnC coding for the 3,4-dihydroxy-phenanthrene dioxygenase, phnG coding for the 1-hydroxy 2-naphtoate dioxygenase and nahC coding for the 1,2-dihydroxy-naphthalene dioxygenase. Second, we clarify the fungal and bacterial contribution to degradation by tracing the carbon flow into fungal and bacterial derived 13C PLFAs and 13C ergosterol. Third, we combine 13C/14C techniques to elucidate the time-dependent interplay between biological and physical processes during degradation. Fourth, we model transport and degradation of MCPA and phenanthrene as well as small-scale microbial growth using, for the first time, abundances of functional genes.