Volume 61, no. 4, p. 1624, column 2, lines 38-41: The sentence should read "For example, at position 21, the G nucleotide (Fig. 1) was present in all the ISR B. thuringiensis subspecies except for B. thuringiensis subsp. tenebrionis (Te4), which contained an A." Page 1624, column 2, line 45: "Position 62" should read "position 11." Page 1624, column 2, line 47: "Position 90" should read "position 39." Page 1624, column 2, line 49: "Position 83" should read "position 32." Page 1625, column 1, line 3: "Position 83" should read "position 32." Page 1626, column 1, line 1: "Positions 62, 90, and 165, and one deletion at position 83" should read "positions 11, 39, and 114, and one deletion at position 32." [This corrects the article on p. 1623 in vol. 61.].

Bacillus thuringiensis spacer regions between the 16S and 23S rRNAs were amplified with conserved primers, designated 19-mer and 23-mer primers. A spacer region of 144 bp was determined for all of 6 B. thuringiensis strains, 7 B. thuringiensis subspecies, and 11 B. thuringiensis field isolates, as well as for the closely related species Bacillus cereus and Bacillus anthracis. Computer analysis and alignment of nucleotide sequences identified three mutations and one deletion in the intergenic spacer region (ISR) of B. thuringiensis subsp. kurstaki HD-1 when compared with ISR sequences from other subspecies. The same differences were identified between the ISR of B. thuringiensis strains and the ISR of B. cereus and B. anthracis. These minor differences do not seem to be sufficient to allow the design of a species-specific oligonucleotide probe.

A rapid identification of Bacillus thuringiensis strains was established by using multiplex polymerase chain reaction (PCR). Primers of high homology specific to regions within genes encoding three major classes of B. thuringiensis crystal proteins were used to generate a PCR product profile characteristic of each strain of B. thuringiensis subsp. kurstaki. Differentiation among these strains was made on the basis of the electrophoretic pattern of the PCR products. Known B. thuringiensis subsp. kurstaki strains as well as unidentified strains isolated from insect cadavers were analyzed by PCR. Small amounts of crude sample lysates were assayed in a two-step PCR containing five primers capable of distinguishing between the strains giving products of 1,500, 858, and 653 bp for the CryIA(a) CryIA(b), and CryIA(c) genes, respectively. The method can be applied to rapidly detect the strains of B. thuringiensis subsp. kurstaki in commercial formulations and in the field.

The antimicrobial substance produced by strain HD-1 of Bacillus thuringiensis var. kurstaki has a large spectrum of activity inhibiting the growth of sixteen of the twenty bacterial strains and six of the seven fungal strains isolated from forest environments where B. thuringiensis is regularly applied. This inhibitory substance, of low molecular weight (between 1 and 8 kD), was sensitive to a proteolytic enzyme (proteinase K) and thermoresistant (30 min, 60-degrees-C). The activity of the crude supernatant culture was stable for 2 months. These results suggest that the application of B. thuringiensis preparations may influence the microbial ecology of the soil.