Transformation of soil humic acids by Aporrectodea caliginosa earthworm: effect of gut fluid and gut associated bacteria

The decomposition of recalcitrant organic compounds by soil organisms plays an important role in the carbon and nitrogen cycles. Earthworms are assumed as “hot spots”, where humic acids (HAs) are being transformed. In present work the transformation of HAs, extracted from Dystric Albic Planosol soil, was studied in presence of i) sterilized gut fluid (GF) of the earthworm Aporrectodea caliginosa, ii) one of the five bacterial strains (Aeromonas encheleia, Bacillus thuringiensis, Acinetobacter sp., Aeromonas sp. and Streptomyces sp.) isolated from the native GF and iii) simultaneous present of GF and one of the five bacterial strains.