title: Differences in hyporheic-zone microbial community structure along a heavy-metal contamination gradient.
abstract: The hyporheic zone of a river is nonphotic, has steep chemical and redox gradients, and has a heterotrophic food web based on the consumption of organic carbon entrained from downwelling surface water or from upwelling groundwater. The microbial communities in the hyporheic zone are an important component of these heterotrophic food webs and perform essential functions in lotic ecosystems. Using a suite of methods (denaturing gradient gel electrophoresis, 16S rRNA phylogeny, phospholipid fatty acid analysis, direct microscopic enumeration, and quantitative PCR), we compared the microbial communities inhabiting the hyporheic zone of six different river sites that encompass a wide range of sediment metal loads resulting from large base-metal mining activity in the region. There was no correlation between sediment metal content and the total hyporheic microbial biomass present within each site. However, microbial community structure showed a significant linear relationship with the sediment metal loads. The abundances of four phylogenetic groups (groups I, II, III, and IV) most closely related to alpha-, beta-, and gamma-proteobacteria and the cyanobacteria, respectively, were determined. The sediment metal content gradient was positively correlated with group III abundance and negatively correlated with group II abundance. No correlation was apparent with regard to group I or IV abundance. This is the first documentation of a relationship between fluvially deposited heavy-metal contamination and hyporheic microbial community structure. The information presented here may be useful in predicting long-term effects of heavy-metal contamination in streams and provides a basis for further studies of metal effects on hyporheic microbial communities.
authors.affiliation: Microbial Ecology Program, Division of Biological Sciences, The University of Montana, Missoula, Montana 59812, USA.
authors.forename: Kevin
authors.initials: K
authors.lastname: Feris
authors.forename: Philip
authors.initials: P
authors.lastname: Ramsey
authors.forename: Chris
authors.initials: C
authors.lastname: Frazar
authors.forename: Johnnie N
authors.initials: JN
authors.lastname: Moore
authors.forename: James E
authors.initials: JE
authors.lastname: Gannon
authors.forename: William E
authors.initials: WE
authors.lastname: Holben
mesh_terms: D020561:Alphaproteobacteria / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification; D001419:Bacteria / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification*; D001483:Base Sequence; D020562:Betaproteobacteria / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification; D000458:Cyanobacteria / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification; D017931:DNA Primers; D020563:Gammaproteobacteria / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification; D005843:Geography; D019216:Metals, Heavy / Q000032:analysis* / Q000494:pharmacology; D009009:Montana; D016133:Polymerase Chain Reaction / Q000379:methods; D012336:RNA, Ribosomal, 16S / Q000235:genetics / Q000302:isolation & purification; D014871:Water Microbiology; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000494:pharmacology
chemical_list: D017931:DNA Primers; D019216:Metals, Heavy; D012336:RNA, Ribosomal, 16S; D014874:Water Pollutants, Chemical