Sulphate reduction and vertical distribution of sulphate-reducing bacteriaquantified by rRNA slot-blot hybridization in a coastal marine sediment

Citation
K. Sahm et al., Sulphate reduction and vertical distribution of sulphate-reducing bacteriaquantified by rRNA slot-blot hybridization in a coastal marine sediment, ENVIRON MIC, 1(1), 1999, pp. 65-74
Citations number
45
Categorie Soggetti
Environment/Ecology,Microbiology
Journal title
ENVIRONMENTAL MICROBIOLOGY
ISSN journal
14622912 → ACNP
Volume
1
Issue
1
Year of publication
1999
Pages
65 - 74
Database
ISI
SICI code
1462-2912(199902)1:1<65:SRAVDO>2.0.ZU;2-R
Abstract
In the past, enumeration of sulphate-reducing bacteria (SRB) by cultivation -based methods generally contradicted measurements of sulphate reduction, s uggesting unrealistically high respiration rates per cell. Here, we report evidence that quantification of SRB rRNA by slot-blot hybridization is a va luable tool for a more realistic assessment of SRB abundance in the natural environment. The distribution of SRB was investigated in a coastal marine sediment by hybridization of membrane-immobilized rRNA with oligonucleotide probes. As represented by general probe-target groups, SRB rRNA contribute d between 18% and 25% to the prokaryotic rRNA pool. The dominant SRB were r elated to complete oxidizing genera (Desulphococcus, Desulphosarcina and De sulphobacterium), while Desulpho-bacter could not be detected. The vertical profile and quantity of rRNA from SRB was compared with sulphate reduction rates (SRR) measured with (SO42-)-S-35 tracer in whole-core incubations. W hile SRB abundance was highest near the surface, peaking at around 1.5cm, m easured sulphate reduction rates were lowest in this region. A second peak of SRB rRNA was observed at the transition zone from oxidized to reduced se diment, directly above the sulphate reduction maximum. Cell numbers calcula ted by converting the relative contribution of SRB rRNA to the percentage o f DAPI-stained cells indicated a population size for SRB of 2.4-6.1 x 10(8) cells cm(-3) wet sediment. Cellular sulphate reduction rates calculated on the basis of these estimated cell numbers were between 0.01 and 0.09 fmol SO42- cell(-1) day(-1), which is below the rates that have been determined for pure cultures (0.2-50fmol SO42- cell(-1) day(-1)) growing exponentially at near-optimal temperature with a surplus of substrates.