Incidence and transmission of antibiotic resistance in Campylobacter jejuni and Campylobacter coli.

One-hundred and two Campylobacter clinical isolates were characterized for their in-vitro resistance to erythromycin (1.9%), three fluoroquinolones (31.3-34.3%), tetracycline (43.1%), kanamycin (4.8%), ampicillin (18.6%) and other 16 antimicrobial agents. Conjugative transfer of tetracycline and kanamycin resistances among these strains was achieved and small plasmids of 4.3, 4 and 1.9 kb were observed in kanamycin-resistant Campylobacter coli strains.

Genetic evidence of a new flocculation suppressor gene in Saccharomyces cerevisiae.

The flocculation character in strain IM1-8b of Saccharomyces cerevisiae is controlled by a single and dominant gene shown to be allelic to FLO1. Such a gene has been both mitotically and meiotically mapped on the right arm of chromosome I at 4.7 cM from PHO11. The phenotype was suppressed by a single gene of wide distribution among non-flocculent strains (proposed as fsu3) that, however, was unable to suppress other FLO1 genes in other flocculent strains.

Characterization of killer-resistant strains of Saccharomyces cerevisiae isolated from spontaneous fermentations.

A study of 26 killer-resistant wine strains of Saccharomyces cerevisiae, isolated during spontaneous fermentations in three vineyards in NW Spain, was carried out employing several methods that included a spheroplast-killing assay and analysis of chromosomal DNA patterns by pulse-field agarose electrophoresis. The results showed that 92% of the strains were derivatives of K2 killer toxin producing wine strains isolated from the same fermentations, and that they could be grouped into four different karyotypes. The remaining strains were killer-resistant at cell-wall level and were not related to the others, as was demonstrated by the absence of L and M ds-RNAs and by their different karyotypes.

Influence of the curing of the killer phenotype inSaccharomyces cerevisiae wine strains on their fermentative behaviour.

Fermentative behaviour and cell growth have been studied in grape juice inoculated either with two killerSaccharomyces cerevisiae wild strains or with their Acridine Orange-cured isogenic counterparts. The number of viable cells/ml at the beginning of the fermentation, as well as during exponential growth, were higher in grape juices inoculated with the cured strains. The CO2 production, fermentative rate and ethanol and acetic acid production were also higher in the cured strains, particularly during the stage of active fermentation. These differences, however, were minimal at the end of the fermentations.

Production of higher alcohols, ethyl acetate, acetaldehyde and other compounds by 14Saccharomyces cerevisiae wine strains isolated from the same region (Salnés, N.W. Spain).

Fourteen strains of the yeastSaccharomyces cerevisiae were isolated from three wineries in the Salnés wine region (N.W. Spain) at the three different periods of the natural fermentation. Each wild yeast was screened for production of acetaldehyde, ethyl acetate, isobutanol,n-propanol, amylic alcohol and other important enological compounds during laboratory scale fermentations of grape juice. After 25 days at 20°C, the analytical results evidenced variations in the production of acetaldehyde (from 13.1 to 24.3 mg/l), isobutanol (from 27.7 to 51.1 mg/l), amyl alcohols (from 111 to 183 mg/l) and ethyl acetate (from 19.3 to 43.7 mg/l). Although isolated from the same wine region, differences in the wine composition were observed depending on the particular yeast strain used for the vinification experiments.

Improvement of the alcoholic fermentation of grape juice with mixed cultures of Saccharomyces cerevisiae wild strains. Negative effect of Kloeckera apiculata.

Four assays were designed to study the fermentative behaviour of two selected wild strains of Saccharomyces cerevislae when inoculated in sterilized grape juice either alone or in association. In addition, a wild strain of Kloeckera apiculata was employed for studying and characterizing the influence of this micro-organism on the fermentations when associated with Sacch. cerevisiae. Fermentation was improved when the two strains of Sacch. cerevisiae were grown together since the residual sugar fell to 0.12% and ethanol increased up to more than 11% (v/v). In this case, a proliferation of the two strains with successive exponential phases was observed. On the other hand, when Kloeckera apiculata was incorporated into the fermentations, these were incomplete with a residual sugar level of 1.64% and a final ethanol concentration of 6.4%.

Isolation and enological characterization of malolactic bacteria from the vineyards of northwestern Spain.

Thirty-five strains of malolactic bacteria were isolated from grapes and alcoholic and malolactic fermentations in two vineyards from northwestern Spain. These belonged to six species of the genera Lactobacillus and Leuconostoc. The results of their partial enological characterization showed that 47.5% utilized more than 80% of the initial malic acid.