title: Technical challenges in metatranscriptomic studies applied to the bacterial communities of freshwater ecosystems.
abstract: Metatranscriptome analysis relates to the transcriptome of microbial communities directly sampled in the environment. Accessing the mRNA pool in natural bacterial communities presents some technical challenges such as the RNA extraction, rRNA depletion, and the choice of the high-throughput sequencing technique. The lack of technical details in scientific articles is a major problem to correctly obtained mRNA from a microbial community and thus the corresponding sequencing data. In our study, we present the methodological procedure that was developed in order to access to the metatranscriptome of the microbial communities during two cyanobacterial blooms successively occurring in a freshwater eutrophic lake. Each procedure step was detailed and discussed with regard to the choices and difficulties encountered and to the recent literature. Finally, the two major limits for metatranscriptomic approaches targeting bacterial communities from natural environments were (i) the removal of rRNA in order to increase the putative mRNA reads number after sequencing, and (ii) for most of the bacterial communities living in natural environments, the lack of reference genomes in databases that leads to the non-assignation of numerous reads. Once these challenges overcome, we managed to access putative mRNA of dominant species, i.e. cyanobacteria (from 6 to 72 % of mRNA assigned), and of the surrounding bacteria (from 1 to 5 % of mRNA assigned).
authors.affiliation: iEES Paris, UMR 7618 UPMC-CNRS-INRA-IRD-Paris 7-UPEC, 4 place Jussieu, 75005, Paris, France.
authors.forename: Noémie
authors.initials: N
authors.lastname: Pascault
authors.forename: Valentin
authors.initials: V
authors.lastname: Loux
authors.forename: Sandra
authors.initials: S
authors.lastname: Derozier
authors.forename: Véronique
authors.initials: V
authors.lastname: Martin
authors.forename: Didier
authors.initials: D
authors.lastname: Debroas
authors.forename: Selma
authors.initials: S
authors.lastname: Maloufi
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Humbert
authors.forename: Julie
authors.initials: J
authors.lastname: Leloup
mesh_terms: D017033:Anabaena; D019295:Computational Biology; D000458:Cyanobacteria / Q000145:classification*; D017753:Ecosystem; D005068:Eutrophication; D005602:France; D005618:Fresh Water / Q000382:microbiology*; D020869:Gene Expression Profiling / Q000379:methods*; D059014:High-Throughput Nucleotide Sequencing / Q000379:methods; D054892:Metagenome; D046931:Microcystis; D012329:RNA, Bacterial / Q000235:genetics / Q000302:isolation & purification; D012333:RNA, Messenger / Q000235:genetics / Q000302:isolation & purification; D017422:Sequence Analysis, DNA / Q000379:methods; D059467:Transcriptome
chemical_list: D012329:RNA, Bacterial; D012333:RNA, Messenger