Desulfovibrionales-related bacteria in a paper mill environment as detected with molecular techniques and culture.

The aim of the present study was to evaluate the suitability of a nested PCR-DGGE (denaturing gradient gel electrophoresis) method for the detection of Desulfovibrionales-related sulfate-reducing bacteria (SRB) from paper mill samples. The samples were also analyzed with culturing. SRB cause/enhance industrial problems, namely creation of foul-smelling gases (hydrogen sulfide) and biological corrosion, and so far there has not been a simple method to study these bacteria in paper mill laboratories. In our study, culturing was able to detect Desulfovibrionales-related bacteria from two different white waters, two different brokes, pulp, clay, and slime. Out of the isolated Desulfovibrionales, 23 enrichment cultures were further characterized with Desulfovibrionales-selective PCR-DGGE. An identical Desulfovibrio species sequence was found from paper machine I (broke I, slime, and pulp) and from paper machine II (broke II and white water II), suggesting an in-house contamination with the same strain. Desulfovibrionales-selective PCR-DGGE was also performed from DNA templates extracted directly from the paper mill samples. The DGGE profiles derived from the samples without prior enrichment were more diverse and the sequenced amplicons proved to belong to the Desulfovibrionales order. Moreover, molecular techniques were able to detect Desulfovibrionales-related bacteria from calcium carbonate samples whereas culture did not. Altogether, the nested PCR-DGGE method used in this study was suitable for the detection of Desulfovibrionales-related SRB directly from different paper mill samples and it could be used for the rapid identification of SRB-contaminated industrial sites and, when combined with sequencing, for tracing of the contamination routes.