Identification and quantification of acetic acid bacteria in wine and vinegar by TaqMan-MGB probes.

A Real-Time PCR (RT-PCR) assay was developed using TaqMan minor groove binder (MGB) probes for the specific detection and quantification of five acetic acid bacteria (AAB) species (Acetobacter pasteurianus, Acetobacter aceti, Gluconacetobacter hansenii, Gluconacetobacter europaeus and Gluconobacter oxydans) in wine and vinegar. The primers and probes, designed from the 16S rRNA gene, showed good specificity with the target AAB species. The technique was tested on AAB grown in glucose medium (GY) and inoculated samples of red wine and wine vinegar. Standard curves were constructed with the five target species in all these matrices. Quantification was linear over at least 5 log units using both serial dilution of purified DNA and cells. When this technique was tested in GY medium and inoculated matrices, at least 10(2)-10(3) cells/ml were detected. To quantify low populations of AAB in microbiologically complex samples, a PCR enrichment including part of the 16S-23S rRNA gene ITS region was needed to increase the amount of target DNA compared to non-target DNA. The RT-PCR assay used in this study is a reliable, specific and fast method for quantifying these five AAB species in wine and vinegar.

Analysis of several methods for the extraction of high quality DNA from acetic acid bacteria in wine and vinegar for characterization by PCR-based methods.

Acetic acid bacteria (AAB) are fastidious microorganisms with poor recovery in culture. Culture-independent methods are currently under examination. Good DNA extraction is a strict requirement of these methods. We compared five methods for extracting the DNA of AAB directly from wine and vinegar samples. Four matrices (white wine, red wine, superficial vinegar and submerged vinegar) contaminated with two AAB strains belonging to Acetobacter pasteurianus and Gluconacetobacter hansenii were assayed. To improve the yield and quality of the extracted DNA, a sample treatment (washing with polyvinyl pyrrolidone or NaCl) was also tested. DNA quality was measured by amplification of the 16S rRNA gene with conventional PCR. DNA recovery rate was assessed by real-time PCR. DNA amplification was always successful with the Wizard method though DNA recovery was poor. A CTAB-based method and NucleoSpin protocol extracted the highest DNA recoveries from wine and vinegar samples. Both of these methods require treatment to recover suitable DNA for amplification with maximum recovery. Both may therefore be good solutions for DNA extraction in wine and vinegar samples. DNA extraction of Ga hansenii was more effective than that of A. pasteurianus. The fastest and cheapest method we evaluated (the Thermal shock protocol) produced the worst results both for DNA amplification and DNA recovery.