Prokaryotic Community Structure in Casts of Aporrectodeacaliginosa and Lumbricusterrestris

For the first time, a comparative study of the influence of two species of earthworms ( Aporrectodea caliginosa and Lumbricus terrestris ) on the composition of the prokaryotic complex of Umbric Albeluvisols was carried out using the methods of metagenomics. Prokaryotes in the soil and casts were represented mostly by Acidobacteria, Actinobacteria, Bacteroidetes, Chloroflexi, Gemmatimonadetes, Planctomycetes, Proteobacteria, and Verrucomicrobia phyla. The passage of soil through the earthworm intestines changed significantly the abundance of some taxa in the soil prokaryotic block, but not general indicators of biodiversity. In the casts of earthworms of both species, a decrease in the abundance of Acidobacteria and Gemmatimonadetes phyla, including predominantly oligotrophic bacteria, was observed. Casts of L. terrestris were characterized by an increase in the proportion of Actinobacteria and Firmicutes phyla, which were mainly represented by copiotrophs and hydrolytic bacteria. In addition, the abundance of Clostridiaceae anaerobic bacteria and Flavobacterium capable of nitrate respiration increased in the casts of L. terrestris , which could be due to the appearance of anaerobic conditions in the biogenically transformed soil. Generally, the changes in the taxonomic structure of prokaryotes in the soil treated by L. terrestris were greater than those in the soil treated by A. caliginosa . These differences among casts of different earthworm species could be due to the specificity of functioning of their digestive systems adapted to transformation of different food sources.