Previous Article | Next Article ![]()
Appl Environ Microbiol, May 1998, p. 1700-1707, Vol. 64, No. 5
Department of Microbial Ecology, Institute of
Biological Sciences, University of Aarhus, DK-8000 Aarhus C,
Denmark
Received 5 September 1997/Accepted 10 February 1998
A greatly improved most-probable-number (MPN) method for selective
enumeration of sulfate-reducing bacteria (SRB) is described. The method
is based on the use of natural media and radiolabeled sulfate
(35SO42
0099-2240/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Improved Most-Probable-Number Method To Detect
Sulfate-Reducing Bacteria with Natural Media and a
Radiotracer
). The natural media used
consisted of anaerobically prepared sterilized sludge or sediment
slurries obtained from sampling sites. The densities of SRB in sediment
samples from Kysing Fjord (Denmark) and activated sludge were
determined by using a normal MPN (N-MPN) method with synthetic
cultivation media and a tracer MPN (T-MPN) method with natural media.
The T-MPN method with natural media always yielded significantly higher
(100- to 1,000-fold-higher) MPN values than the N-MPN method with
synthetic media. The recovery of SRB from environmental samples was
investigated by simultaneously measuring sulfate reduction rates (by a
35S-radiotracer method) and bacterial counts by using the
T-MPN and N-MPN methods, respectively. When bacterial numbers estimated by the T-MPN method with natural media were used, specific sulfate reduction rates (qSO42
) of 10
14
to 10
13 mol of SO42
cell
1 day
1 were calculated, which is within
the range of qSO42
values previously reported
for pure cultures of SRB (10
15 to 10
14 mol
of SO42
cell
1
day
1). qSO42
values calculated
from N-MPN values obtained with synthetic media were several orders of
magnitude higher (2 × 10
10 to 7 × 10
10 mol of SO42
cell
1 day
1), showing that viable counts of
SRB were seriously underestimated when standard enumeration media were
used. Our results demonstrate that the use of natural media results in
significant improvements in estimates of the true numbers of SRB in
environmental samples.
*
Corresponding author. Mailing address: Department of
Microbial Ecology, Institute of Biological Sciences, University of
Aarhus, Ny Munkegade, Building 540, DK-8000 Aarhus C, Denmark. Phone: 45 89423245. Fax: 45 86127191. E-mail:
Kjeld.Ingvorsen{at}biology.aau.dk.
This article has been cited by other articles:
Copyright © 2009 by the American Society for Microbiology. For an alternate route to Journals.ASM.org, visit: http://intl-journals.asm.org | More Info»