Effect of freezing and protectants on viability of the biocontrol bacterium Rahnella aquatilis

RODRIGUEZ FURLAN, LAURA TERESA; SANZ FERRAMOLA M. I.; BENUZZI, DELIA

Mendoza

Congreso; XXIII Reunión Científica Anual Sociedad de Biología de Cuyo. III Reunión Anual Sociedad Argentina de Microscopia; 2005

Biological control using microbial antagonists is an alternative to chemical methods of controlling pre- and post-harvest plant pathogens. To be of practical use, microbial agents must be formulated as products capable of being stored. Freezing is one of methods of preserving bacteria. In a previous work Calvo et al. showed the antagonistic activity of Rahnella aquatilis against the pathogens Penicillium expansum and Botrytis cinerea. The objective of this study was to compare the effect of freezing and the additions of range of additives in combinations with powdered skimmed milk as freezing protectants for preserving the viability of R. aquatilis. Bacterial cells were produced in YGM broth. Dilutions of this suspension were plated in duplicate onto the surface of YGM media in Petri plates before and after freezing. The number of colony forming units per milliliter were counted (CFU/ml) and percentages of survival were estimated. Statistical significance was set at p= 0,05. Freezing at ? 20 °C was a good method to preserve the viability of R. aquatilis using 10 % skim milk (1,2 % survival). Survival of was increased by using appropriate protective media containing combinations of skim milk and others such as 10 % galactose or glucose (4,0 % y 3,5 %) y 1 % de Ca (2,5 % survival).The effects of the freezing method with the use or not of protective agents on the viability of the biocontrol bacterium Rahnella aquatilis were studied.