Abstract
Clones of the WWE1 (Waste Water of Evry 1) candidate division were retrieved during the exploration of the bacterial diversity of an anaerobic mesophilic (35 ± 0.5°C) digester. In order to investigate the metabolic function of WWE1 members, a 16S rRNA gene -based stable isotope probing (SIP) method was used. Eighty-seven percent of 16S r rRNA gene sequences affiliated to WWE1 candidate division were retrieved in a clone library obtained after polymerase chain reaction (PCR) amplification of enriched DNA fraction from anaerobic municipal solid waste samples incubated with (13) C-cellulose, at the end of the incubation (day 63) using a Pla46F-1390R primer pair. The design of a specific WWE1 probe associated with the fluorescence in situ hybridization (FISH) technique corroborated the abundant representation of WWE1 members in our (13) C-cellulose incubations. Secondary ion mass spectrometry-in situ hybridization (SIMSISH) using an iodine-labeled oligonucleotide probe combined with high-resolution nanometer-scale SIMS (NanoSIMS) observation confirmed the isotopic enrichment of members of WWE1 candidate division. The (13) C apparent isotopic composition of hybridized WWE1 cells reached the value of about 40% early during the cellulose degradation process, suggesting that these bacteria play a role either in an extracellular cellulose hydrolysis process and/or in the uptake fermentation products.