Stability analysis of a recombinant bacterium with larvicidal activity

Abstract

The recombinant DNA technology offers new alternatives in the production of improved microorganisms for large scale production. However, the stability of recombinant plas­mids during long culture periods is a serious problem for industrial use. The aim of this work was to introduce in the native aquatic bacterium Bacillus thuringiensis subsp. israeliensis CIB 30-0501b the plasmid pGSP11 that contains the genes coding the binary toxin of B. sphaericus and to analyze the expression and stability of this plasmid under laboratory conditions. This analysis showed that the bacterium grew best in the culture medium Lucia Bertani broth at 28°C with tetracicline (30 mg/mi). The presence of the pGSP11 plasmid was detected after eight hours of growth, coinciding with the moment that the expression of the plasmid-coded tox­ins started. An increase in the culture tempera­ture was always correlated with a decrease in toxin synthesis which was not accompanied by plasmid loss. The presence of the selec­tion antibiotic showed an important effect on plasmid conservation.