Response of L. lactis faced to S. cerevisiae. Lactococcus lactis

The response of L. lactis to the presence of S. cerevisiae was analyzed during the exponential growth phase in fermentors in defined growth conditions. Although no growth kinetic difference was observed between the pure and mixed culture of L. lactis, the mRNA level of genes was significantly modified. More particularly, a strong reorientation of pyrimidine metabolism was observed when L. lactis was grown in the mixed culture. Keywords: microbial interaction, time course Overall design: A pure culture of L. lactis was conducted in parallel with a co-culture of L. lactis and S. cerevisiae. For the transcriptomic analysis, the mixed culture (test condition, 2.5 hours of culture, B’) was compared to the pure culture (reference, 2.5 hours of culture, B) on the same slide at the same time. The mRNA level changes between 2 and 3 hours (A and C samples) flanking B sample (2.5 hours) in the pure culture were also determined on another slide. Total RNA was extracted from these samples and labelled cDNA (Cy3/Cy5) were prepared and hybridized on glass slides exhibiting 2004 amplicons specific of Lactococcus lactis IL1403 genes. 3 independent repetitions were performed.