Open AccessEffect of Earthworm Feeding Guilds on Ingested Dissimilatory Nitrate Reducers and Denitrifiers in the Alimentary Canal of the Earthworm
Author(s) -
Peter S. Depkat-Jakob,
Maik Hilgarth,
Marcus A. Horn,
Harold L. Drake
Publication year - 2010
Publication title -
applied and environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.552
H-Index - 324
eISSN - 1070-6291
pISSN - 0099-2240
DOI - 10.1128/aem.01373-10
Subject(s) - lumbricus terrestris , earthworm , biology , lumbricus rubellus , actinobacteria , lumbricidae , alphaproteobacteria , soil microbiology , proteobacteria , nitrous oxide reductase , botany , microbiology and biotechnology , nitrate reductase , bacteria , nitrate , nitrite reductase , ecology , 16s ribosomal rna , genetics
The earthworm gut is an anoxic nitrous oxide (N2 O)-emitting microzone in aerated soils.In situ conditions of the gut might stimulate ingested nitrate-reducing soil bacteria linked to this emission. The objective of this study was to determine if dissimilatory nitrate reducers and denitrifiers in the alimentary canal were affected by feeding guilds (epigeic [Lumbricus rubellus ], anecic [Lumbricus terrestris ], and endogeic [Aporrectodea caliginosa ]). Genes and gene transcripts ofnarG (encodes a subunit of nitrate reductase and targets both dissimilatory nitrate reducers and denitrifiers) andnosZ (encodes a subunit of N2 O reductase and targets denitrifiers) were detected in guts and soils. Gut-derived sequences were similar to those of cultured and uncultured soil bacteria and to soil-derived sequences obtained in this study. Gut-derivednarG sequences andnarG terminal restriction fragments (TRFs) were affiliated mainly with Gram-positive organisms (Actinobacteria ). The majority of gut- and uppermost-soil-derivednarG transcripts were affiliated withMycobacterium (Actinobacteria ). In contrast,narG sequences indicative of Gram-negative organisms (Proteobacteria ) were dominant in mineral soil. MostnosZ sequences andnosZ TRFs were affiliated withBradyrhizobium (Alphaproteobacteria ) and uncultured soil bacteria. TRF profiles indicated thatnosZ transcripts were more affected by earthworm feeding guilds than werenosZ genes, whereasnarG transcripts were less affected by earthworm feeding guilds than werenarG genes.narG andnosZ transcripts were different and less diverse in the earthworm gut than in mineral soil. The collective results indicate that dissimilatory nitrate reducers and denitrifiers in the earthworm gut are soil derived and that ingestednarG - andnosZ -containing taxa were not uniformly stimulated in the guts of worms from different feeding guilds.