RAPISARDA Viviana Andrea
congresos y reuniones científicas
INTRACELLULAR POLYPHOSPHATE INCLUSIONS PLAY A ROLE IN THE THERMOTOLERANCE OF THE IMMUNOBIOTIC Lactobacillus rhamnosus CRL 1505
CORREA DEZA, M. A.; GRILLO-PUERTAS, M.; SALVA, S.; MARTOS, G. I.; RAPISARDA, V. A.; GEREZ, C. L.; FONT DE VALDEZ, G.
Congreso; XII CONGRESO ARGENTINO DE MICROBIOLOGÍA GENERAL SAMIGE 2017; 2017
Sociedad Argentina de Microbiología General
The immunobiotic Lactobacillus rhamnosus CRL 1505 (CRL-1505) is produced as dehydrated powder by spray dried for subsequent addition into different raw matter to improve transportation and storage. The success of cell survival depends on the strain since this drying technique involves heat stress that causes loss of cell viability. Previous studies demonstrated that CRL-1505 is able to accumulate cytoplasmic inclusions of inorganic polyphosphate (polyP) when growing in a medium with inorganic phosphate. The accumulation of these inclusions, reported in Gram positive and negative organisms, depends on the concentration of inorganic phosphate in the culture medium and its presence could be related to stress response mechanisms. The aim of this work was to evaluate the effect of the presence of inorganic phosphate in culture medium on growth, polyP accumulation and thermotolerance of the strain CRL-1505. Fermentations were performed at 37°C under free pH in MCM medium with and without addition of inorganic phosphate. A DAPI-based fluorescence technique was used as a measuring of intracellular polyP accumulation. Cells from both culture media and stationary phase growth were harvested, suspended in phosphate buffer and exposed to heat shock (60°C, 5 min). The cell viability before and after heat shock was evaluated by plate count and flow citometry using the BD? Cell Viability Kit. No significant differences (p ≥ 0.05) in cell growth were observed, however, the polyP levels were lower (aprox. 40%) in cells grown without inorganic phosphate. The subsequent exposure to heat shock of these cells with low polyP content resulted in greater losses of cell viability (3.0 ± 0.5 Δlog CFU/mL) than the cells of CRL-1505 with high polyP content (2.0 ± 0.2 Δlog CFU/mL). These results were confirmed by flow cytometry. CRL-1505 with low polyP content and exposed to heat shock displayed 85.9% dead cells while 50.4% when cells were grown with high phosphate. From these results we conclude that the thermotolerance of CRL-1505 strain was dependent on the phosphate concentration in the culture media and, consequently, on the initial levels of polyP. To our knowledge, this is the first report that makes a relationship between en the presence of polyp with the lactic acid bacteria´s thermotolerance.