Open AccessCharacterization of the Community Structure of a Dechlorinating Mixed Culture and Comparisons of Gene Expression in Planktonic and Biofloc-Associated “ Dehalococcoides ” and Methanospirillum Species
Author(s) -
Annette R. Rowe,
Brendan J. Lazar,
Robert M. Morris,
Ruth Richardson
Publication year - 2008
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.00445-08
Subject(s) - biology , 16s ribosomal rna , temperature gradient gel electrophoresis , dehalococcoides , archaea , microbiology and biotechnology , methanogen , ribosomal rna , population , gene , gene expression , genetics , bacteria , chemistry , demography , organic chemistry , vinyl chloride , sociology , copolymer , polymer
This study sought to characterize bacterial and archaeal populations in a perchloroethene- and butyrate-fed enrichment culture containing hydrogen-consuming “Dehalococcoides ethenogenes ” strain 195 and aMethanospirillum hungatei strain. Phylogenetic characterization of this microbial community was done via 16S rRNA gene clone library and gradient gel electrophoresis analyses. Fluorescence in situ hybridization was used to quantify populations of “Dehalococcoides ” andArchaea and to examine the colocalization of these two groups within culture bioflocs. A technique for enrichment of planktonic and biofloc-associated biomass was developed and used to assess differences in population distribution and gene expression patterns following provision of substrate. On a per-milliliter-of-culture basis, mostD. ethenogenes genes (the hydrogenase genehupL ; the highly expressed gene for an oxidoreductase of unknown function,fdhA ; the RNA polymerase subunit generpoB ; and the 16S rRNA gene) showed no statistical difference in expression between planktonic and biofloc enrichments at either time point studied (1 to 2 and 6 h postfeeding). Normalization of transcripts to ribosome (16S rRNA) levels supported that planktonic and biofloc-associatedD. ethenogenes had similar gene expression profiles, with one notable exception; planktonicD. ethenogenes showed higher expression oftceA relative to biofloc-associated cells at 6 h postfeeding. These trends were compared to those for the hydrogen-consuming methanogen in the culture,M. hungatei . The vast majority ofM. hungatei cells, ribosomes (16S rRNA), and transcripts of the hydrogenase genemvrD and the housekeeping generpoE were observed in the biofloc enrichments. This suggests that, unlike the comparable activity ofD. ethenogenes from both enrichments, planktonicM. hungatei is responsible for only a small fraction of the hydrogenotrophic methanogenesis in this culture.