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Aims:  To develop rapid methods allowing enumeration of lactic acid bacteria producing biogenic amines in wines and to analyse wine samples by the methods. Methods and Results:  Methods based on quantitative PCR targeting bacterial genes involved in histamine, tyramine and putrescine production were developed and applied to detect and quantify the bacteria producing these biogenic amines in wine. Analysis of 102 samples revealed low populations of the targeted bacteria in grape must samples, an increased bacteria biomass in wine samples after alcoholic fermentation, reaching the highest population levels (above 106 cells ml−1) during spontaneous malolactic fermentation. A minimum of 103 ml−1 producing cells was required for production of more than 1 mg l−1 of biogenic amines. Accumulation of putrescine in wine was correlated with the presence of bacteria carrying an ornithine decarboxylation pathway. Trials of winemaking showed that the use of selected bacteria for inducing malolactic fermentation was efficient to limit the proliferation of undesirable bacteria and the production of biogenic amines. Conclusion:  Methods using quantitative PCR are efficient to enumerate biogenic amines‐producing cells in wine. Significance and Impact of the Study:  The methods can help to better control and to improve winemaking conditions in order to avoid biogenic amine production.

Aims: This work was carried out to complete the sequence of the arc cluster involved in arginine catabolism in Oenococcus oeni, and particularly to characterize the genes encoding proteins involved in arginine transport. Methods and Results: Using molecular cloning, two loci encoding proteins involved in the arginine-ornithine antiport were isolated. Their expression patterns were monitored by RT-PCR to study the influence of arginine on their transcription. Polycistronic mRNAs were detected. PCR performed directly on colonies with primer pairs specific of arc genes was used to discriminate strains able/unable to degrade arginine. Conclusions: Oenococcus oeni contains two arcD loci encoding similar proteins. Their expression is not influenced by arginine and polycistronic messengers were detected. The inability to use arginine is due to a lack of genetic information encoding proteins of the arginine deiminase pathway. Significance and Impact of the Study: The constitutive expression of arcD genes points to the positive role of arginine on O. oeni cell growth. The occasional presence of all the arc ABCD genes together in O. oeni strains might provide insights into the growth rate variability within this species.

We have characterized a temperate phage (MM1) from a clinical isolate of the multiply antibiotic-resistant Spanish/American 23F Streptococcus pneumoniae clone (Spain 23F -1 strain). The 40-kb double-stranded genome of MM1 has been isolated as a DNA-protein complex. The use of MM1 DNA as a probe revealed that the phage genome is integrated in the host chromosome. The host and phage attachment sites, attB and attP, respectively, have been determined. Nucleotide sequencing of the attachment sites identified a 15-bp core site (5-TTATA ATTCATCCGC-3) that has not been found in any bacterial genome described so far. Sequence information revealed the presence of an integrase gene (int), which represents the first identification of an integrase in the pneumococcal system. A 1.5-kb DNA fragment embracing attP and the int gene contained all of the genetic information needed for stable integration of a nonreplicative plasmid into the attB site of a pneumococcal strain. This vector will facilitate the introduction of foreign genes into the pneumococcal chromosome. Interestingly, DNAs highly similar to that of MM1 have been detected in several clinical pneumococcal isolates of different capsular types, suggesting a widespread distribution of these phages in relevant pathogenic strains.

The polysaccharide content of wine is generally assumed to originate from grapes and yeasts, independent of bacterial metabolism, except for the action of certain spoilage species. This study shows that malolactic fermentation (MLF) significantly modifies the soluble polysaccharide (SP) concentration of various red Bordeaux wines. Wines with the highest initial SP concentration go on to present decreased SP concentration, whereas those with the lowest initial SP concentration rather go on to have a higher SP concentration after MLF. These tendencies were observed whatever the Oenococcus oeni strain (indigenous or starter) used for MLF. Neutral and charged SPs were affected, but to a degree that depended on the microorganisms driving the MLF. The SP modifications were directly linked to bacterial development, because non MLF controls did not present any significant change of SP concentration.