GROWTH-RATE AND PHYSIOLOGY OF YERSINIA-ENTEROCOLITICA INFLUENCE OF TEMPERATURE AND PRESENCE OF THE VIRULENCE PLASMID

The effect of temperature on the growth rate, protein pattern and fatty acid composition of Yersinia enterocolitica strain W22703 pYV(+), its plasmidless isogenic derivative W22703 pYV(-) and four recent field isolates was examined. The growth rate was clearly influenced by presence or absence of the virulence plasmid: pYV(-) strains grew consistently faster than pYV(+) strains. This difference in growth rate was high at 30-35 degrees C, moderate at 1-10 degrees C and 25 degrees C, but hardly significant at 15-20 degrees C. Increasing the growth temperature above 25 degrees C resulted in the induction of the 220 kDa virulence plasmid-encoded Yop1 protein. In the 1-20 degrees C range no obvious temperature- or plasmid-related differences in protein patterns could be detected. The fatty acid composition showed a clear temperature-dependent change: with all strains the degree of saturation was low at 1 degrees C and gradually increased with raising temperatures. All strains had similar fatty acid patterns, except one of the field isolates which showed aberrant C16:1 and cyclic fatty acid contents in the 5-25 degrees C and less than or equal to 15 degrees C ranges respectively. With strain W22703, the presence or absence of the virulence plasmid did not significantly alter the fatty acid pattern.