Genetic basis for alkaline activation of germination in Bacillus thuringiensis subsp. israelensis

Abstract

Differences in activation between spores from strains of Bacillus thuringiensis subsp. israelensis with and without the toxin-encoding plasmid pBtoxis are demonstrated. Following alkaline activation, the strain bearing pBtoxis shows a significantly greater germination rate. Expression of just three genes constituting a previously identified, putative ger operon from this plasmid is sufficient to produce the same phenotype and characterizes this operon as a genetic determinant of alkaline activation.

FIG. 1.

Germination responses of Bacillus thuringiensis subsp. israelensis (Bti) strains after heat activation with 10 mM l-alanine. Experiments were repeated three times. Error bars are shown as standard errors of the means after calculation of standard deviation.

FIG. 2.

Germination responses of B. thuringiensis subsp. israelensis strains after alkaline activation at pH 10. Shown are results for nutrient broth (A), 5 mM inosine (B), or 10 mM l-alanine (containing 13 mM d-cycloserine) (C). Experiments were repeated three times. Error bars represent the standard errors of the means after calculation of the standard deviation.

FIG. 3.

Time course of germination responses of B. thuringiensis subsp. israelensis (Bti) strains after alkaline activation. Germinants used were 5 mM inosine (A) and 10 mM l-alanine (containing 13 mM d-cycloserine) (B). Experiments were repeated three times. Error bars represent the standard errors of the means after calculation of the standard deviation.

FIG. 4.

Germination responses of B. thuringiensis subsp. israelensis (Bti) strains after alkaline activation at a range of pH with inosine germinant. Shown are the results for strains 4Q7 (A), 4Q5 (B), and 4Q7-ger (C). The experiments were repeated three times. Error bars represent the standard errors of the means after calculation of the standard deviation.