Survival of Bacillus megaterium strains in water

Cultures of Bacillus megaterium strains, producers or not of poly-beta-hydroxy-butyrate (PHB+ and PHB-) were submitted to several shift-downs: nutritional (one hundred fold dilution in saline water S or artificial fresh water ADA) or nutritional and osmotic (one hundred fold dilution in water or W). In all conditions tested, the wild type strain survived, duplicated five times and sporulated. However, the PHB- mutant strain showed a drastic loss of viability in water (< 0.1%) not observed when the shift was only nutritional (S or ADA). Discussion was focused on the advantages of the potential use of Bacillus megaterium as host for delivering bio-insecticides in waters instead of natural hosts such as B. thuringiensis strains.