Seasonal changes in bacterial and archaeal gene expression patterns across salinity gradients in the Columbia River coastal margin.
Through their metabolic activities, microbial populations mediate the impact of high gradient regions on ecological function and productivity of the highly dynamic Columbia River coastal margin (CRCM). A 2226-probe oligonucleotide DNA microarray was developed to investigate expression patterns for microbial genes involved in nitrogen and carbon metabolism in the CRCM. Initial experiments with the environmental microarrays were directed toward validation of the platform and yielded high reproducibility in multiple tests. Bioinformatic and experimental validation also indicated that >85% of the microarray probes were specific for their corresponding target genes and for a few homologs within the same microbial family. The validated probe set was used to query gene expression responses by microbial assemblages to environmental variability. Sixty-four samples from the river, estuary, plume, and adjacent ocean were collected in different seasons and analyzed to correlate the measured variability in chemical, physical and biological water parameters to differences in global gene expression profiles. The method produced robust seasonal profiles corresponding to pre-freshet spring (April) and late summer (August). Overall relative gene expression was high in both seasons and was consistent with high microbial abundance measured by total RNA, heterotrophic bacterial production, and chlorophyll a. Both seasonal patterns involved large numbers of genes that were highly expressed relative to background, yet each produced very different gene expression profiles. April patterns revealed high differential gene expression in the coastal margin samples (estuary, plume and adjacent ocean) relative to freshwater, while little differential gene expression was observed along the river-to-ocean transition in August. Microbial gene expression profiles appeared to relate, in part, to seasonal differences in nutrient availability and potential resource competition. Furthermore, our results suggest that highly-active particle-attached microbiota in the Columbia River water column may perform dissimilatory nitrate reduction (both dentrification and DNRA) within anoxic particle microniches.
Division of Environmental & Biomolecular Systems, Center for Coastal Margin Observation & Prediction, Oregon Health & Science University, Beaverton, Oregon, United States of America.
Maria W
MW
Smith
Lydie
L
Herfort
Kaitlin
K
Tyrol
Dominic
D
Suciu
Victoria
V
Campbell
Byron C
BC
Crump
Tawnya D
TD
Peterson
Peter
P
Zuber
Antonio M
AM
Baptista
Holly M
HM
Simon
D001105:Archaea / Q000235:genetics*; D001419:Bacteria / Q000235:genetics*; D019848:Gene Expression Regulation, Archaeal; D015964:Gene Expression Regulation, Bacterial; D012621:Seasons; D012965:Sodium Chloride; D014871:Water Microbiology
D012965:Sodium Chloride