Medicina Molecular e Genética

Flow Cytometry Monitors Xylitol Metabolism of Streptococcus mitis

Abstract

Prabani Dissanayake, Nardhy Gomez- Lopez, Gail Czarnecki and Sunil Palchaudhuri

In this work we are presenting our novel adaptation of flow cytometry for the determination of change of diplococcic Gram-positive Streptococcus mitis population heterogeneity by their xylitol metabolism. The inherent population heterogeneity of the bacteria due to their growth in-chains of varying lengths was grouped into three different groups by flow cytometric analysis, designated as gates P1, P2 and P3. Gate P1 consists of the bacterial subpopulation with minimum cell wall thickness and therefore the least side scattering, while gate P3 consists of the subpopulation with the most side scattering (corresponding to the thick bacterial cell wall). According to our results gate P1 contains bacteria in long-chains, while P3 contains individual bacteria. When these diplococcic bacteria were grown in the presence of 2% xylitol more homogeneous population was seen as P1 gate was populated with approximately 80% of the total population. These results suggest that once xylitol is metabolized by these bacteria, they stabilize in long chains. These ‘xylitol stabilized’ long chains arose apparently by incomplete bacterial separation, contains individual bacteria with reduced cell wall thickness, resulted less side scattering. The optimum population homogeneity was achieved when these bacteria were grown in 2% xylitol and 300 ppm fluoride containing medium, as measured by the bacterial population percentage in gate P1. Since these bacteria in long chains are known to be in a latent phase, our findings demonstrate that if appropriately developed xylitol has potential to use as an alternative antimicrobial for life threatening diseases.