Molecular quantification of sulfate-reducing microorganisms (carrying dsrAB genes) by competitive PCR in estuarine sediments

Julie Leloup^a*, Laurent Quillet^a, Cécile Oger^a, Dominique Boust^b, Fabienne Petit^a

FEMS Microbiology Ecology 47 (2004) 207-214

In this study, we describe a competitive polymerase chain reaction (PCR) for the quantification of the sequences of dsrAB in sulfate­reducing microorganisms. We used the dsr1F/dsr4R set of primers, previously designed by Wagner et al. (1998), and a competitor sequence was constructed from the dsrAB genes of Desulfovibrio vulgaris. The detection lirait of competitive PCR corresponded to 45 copies of the dsrAB genes per ng of extracted DNA, and most of the dsrAB sequences amplified and cloned from DNA extracted from Seine estuary sediments were amplified with a similar efficiency. Competitive PCR was then used to assess the abundance of dsrAB genes in the total DNA extracted from the sediment of the Seine estuary mudflats. We observed that the abundance of dsrAB coincided with the variation in the sulfate reduction rate with the depth of the sample, confirming the importance of 'dsrAB' sulfate-reducing microorganisms in sulfidogenesis in anoxic environments. We obtained values ranging from 0.045 x 10³ to 6.63 x 10³ copies of dsrAB per ng of extracted DNA, and values of the sulfate reduction rate ranging from 35 to 158 nmol _CM -3 day ^-1. These results are similar to those obtained in other studies using molecular biology techniques.

a)LMDF-UPRES 2123, Groupe Biodiversité et Environnement, UFR des Sciences, Université de Rouen, 76821 Mont Saint Aignan, France
b) Laboratoire d'études radioécologiques de la façade Atlantique, IRSN, Cherbourg- Octeville, France