Characterization of cattle manure vermicompost microbial communities and biocontrol potential of associated bacterial isolates

The microbial composition of cattle manure vermicompost (CMV) obtained using Eisenia fetida and E. andrei, was determined by microbiological, molecular, and metabolic analysis. The CMV biocontrol potential and the CMV-associated microorganisms were evaluated against different fungal pathogens by dual culture assay. Fungi were poorly represented conversely to bacteria. On nutrient agar (NA), the bacterial community was determined in 1.37×107 CFU/g of dried CMV, and it was represented by 19 different morphotypes that, according to the BLASTn analysis of the partial 16S rDNA sequence and metabolic profiling, belonged to the classes Actinomycetes (69.5%), Bacilli (21.3%), Gamma proteobacteria (7.8%) and Flavobacteria (1.4%). On starch casein agar (SCA), the bacteria were 5.09×107 CFU/g, and nine different morphotypes belonging to the classes Gamma proteobacteria (91.7%) and Actinomycetes (8.3%) were identified. According to metagenomic analysis, bacteria (95.0%) were confirmed to be the most predominant kingdom, followed by Archaea (3%), Eukaryota (0.22%), and Viruses (0.04%). Preliminary in vitro experiments against Botrytis cinerea suggest a possible biocontrol potential of CMV due to its associated microorganisms. In dual culture, out of the 28 bacteria isolated from NA and SCA, were effective against 13 isolates of Cylindrocarpon destructans, 8 of Fusarium oxysporum f. sp. radicis-lycopersici, 5 of Rosellinia necatrix, 3 of Sclerotinia sclerotiorum and 25 of Verticillium dahliae. Pseudomonas aeruginosa DiSSPA_PA1 showed the best biocontrol potential included in the range 41% (F. oxysporum f. sp. radicis-lycopersici) to 81% (V. dahliae). Results achieved in this work suggest that vermicompost can be an additional tool in integrated and organic pest management.