Phylogenetic and functional heterogeneity of sediment biofilms along environmental gradients in a glacial stream.
We used in situ hybridization with fluorescently labeled rRNA-targeted oligonucleotide probes concurrently with measurements of bacterial carbon production, biomass, and extracellular polymeric substances (EPS) to describe the bacterial community in sediments along a glacial stream. The abundance of sediment-associated Archaea, as detected with the ARCH915 probe, decreased downstream of the glacier snout, and a major storm increased their relative abundance by a factor of 5.5 to 7.9. Bacteria of the Cytophaga-Flavobacterium group were also sixfold to eightfold more abundant in the storm aftermath. Furthermore, elevated numbers of Archaea and members of the Cytophaga-Flavobacterium group characterized the phylogenetic composition of the supraglacial ice community. We postulate that glacial meltwaters constitute a possible source of allochthonous bacteria to the stream biofilms. Although stream water temperature increased dramatically from the glacier snout along the stream (3.5 km), sediment chlorophyll a was the best predictor for bacterial carbon production and specific growth rates along the stream. Concomitant with an increase in sediment chlorophyll a, the EPS carbohydrate-to-bacterial-cell ratio declined 11- to 15-fold along the stream prior to the storm, which is indicative of a larger biofilm matrix in upstream reaches. We assume that a larger biofilm matrix is required to assure prolonged transient storage and enzymatic processing of allochthonous macromolecules, which are likely the major substrate for microbial heterotrophs. Bacteria of the Cytophaga-Flavobacterium cluster, which are well known to degrade complex macromolecules, were most abundant in these stream reaches. Downstream, higher algal biomass continuously supplies heterotrophs with easily available exudates, therefore making a larger matrix unnecessary. As a result, bacterial carbon production and specific growth rates were higher in downstream reaches.
Battin
T J
TJ
Institute of Ecology and Conservation Biology, University of Vienna, A-1090 Vienna, Austria. tbattin@Stroudcenter.org
Wille
A
A
Sattler
B
B
Psenner
R
R
D001105:Archaea / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D018441:Biofilms / Q000254:growth & development*; D018533:Biomass; D002734:Chlorophyll / Q000378:metabolism; D000077194:Chlorophyll A; D003589:Cytophaga / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D005417:Flavobacterium / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D005618:Fresh Water / Q000737:chemistry / Q000382:microbiology*; D014644:Genetic Variation; D019015:Geologic Sediments / Q000737:chemistry / Q000382:microbiology*; D007053:Ice; D017403:In Situ Hybridization; D010802:Phylogeny; D011108:Polymers / Q000378:metabolism
D007053:Ice; D011108:Polymers; D002734:Chlorophyll; D000077194:Chlorophyll A