[Flow cytometric analysis of Enterococcus faecalis aph2"(+) response to aph2" (-) strains with high and low gene...

Resistance genes, as aph2" are usually encoded on conjugate plasmids and spread with high rate 2 among Gram-positive cocci. The conjugation is inducted by recipient strains by secreting specific pheromone involved in formation of mating aggregates with donor cells. The project aimed to check if strain with lower rate of gene transfer differ also from strains with high gene transfer in ability to aggregate to donor strains. In our study we used two aph2"(+), three aph2"(-) with low transfer e and three aph2"(-) with high transfer strains. Each time one aph2"(+) and one aph2" strains were cultivated for 18h in BHI. The bacteria was washed, stained with carboksyfluorescein, and analyzed by flow cytometry in FACS BD cytometr. Relative fluorescence and size of aggregation was used to compare influence on particular stains. In result of induction of aph2"(+) strains with aph2" recipients with high transfer rate we observed increase of size and number aggregates. Surprisingly, induction with aph2" recipients with low transfer rate result in two different reaction of aph2"(+) donors. In case of one of the , according to expectation we do not observe increase of aggregation. Second of the donors aggregate with induction with aph2" recipients with low transfer rate, but in contrast to reaction to presence of other recipients, fluorescence of such aggregates increased. The results show that strain with lower rate of gene transfer in fact differ from strains with high gene transfer in ability to aggregate to donor strains ant that analysis of aggregation alone is insufficient to distinguish between recipients of high and low transfer rate.