Impact of osmotic/matric stress and heat-shock on environmental tolerance induction of biocontrol agents against Fusarium verticillioides

SARTORI, MELINA; NESCI, ANDREA; ETCHEVERRY, MIRIAM

Tulln, Austria

Conferencia; ISM Conference 2009. Wordlwide Mycotoxin Reduction in Food and Feed Chains.; 2009

International Society for Mycotoxicology

Bacillus amyloliquefaciens and Microbacterium oleovorans reduced Fusarium verticillioides count and decreased significantly fumonisins B1 and B2 levels in maize grains from plants grown from treated seeds (Pereira et al. 2007). The aims of this study were to determine the effect of water stress tolerance and heat-shock survival in cells of the biocontrol agents B. amyloliquefaciens and M. oleovorans. Both biocontrol agents were grown in liquid and solid tryptic soy (TS) medium. The water activity (aw) of this basal medium was 0.99. The aw of solid and liquid media was modified by the addition of the ionic solute NaCl and with the non-ionic solutes such as glycerol and glucose to 0.98, 0.97 and 0.96. The non ionic solute polyethylene glycol (PEG 600) was used to modify matrically solid media. Bacteria grown in liquid and solid media unmodified and modified osmotically or matrically at 30ºC. After 24, 48 and 72 h samples from liquid media were spread-plate on nutrient agar medium and incubated 24 h to determine number of viable cells. The bacterial cells from different treatments were harvested by centrifugation, resuspended in phosphate-buffered solution and heat in a water bath at 45ºC during 30 min. After that, cells viability was determined. Significant improvements in water and heat stress tolerance were observed when both biocontrol agents grown in media modify with glycerol. No statistically significant differences were observed between different incubation time in liquid media and in the cells viability before and after heat-shock. The viability of cells from different incubation time (24, 48 and 72 h) in liquid media not showed statistically significant differences. Cells of B. amyloliquefaciens grown in liquid media amended with glycerol not only had better tolerance at low aw but also showed better survival under heat stress. These results could have important implications for optimizing and to improve formulations.