2 PUTATIVE INSERTION SEQUENCES FLANK A TRUNCATED GLYCOGEN BRANCHING ENZYME GENE IN THE THERMOPHILE BACILLUS-STEAROTHERMOPHILUS CU21

We have isolated a region from the Bacillus stearothermophilus CU21 ch romosome hybridizing strongly to a fragment of the B. caldolyticus gly cogen operon. Sequence analysis of this region revealed the presence o f a truncated glgB gene encoding the N-terminus of branching enzyme. A region highly similar to an internal fragment of B. caldolyticus glgC encoding ADP-glucose pyrophosphorylase was located approximately 1 kb downstream from the incomplete glgB gene. The two truncated genes app eared to flank a sequence with characteristics of bacterial Insertion Sequences, which was designated RSBst-alpha. The presence of RSBst-alp ha at this position indicates that integration of (an) IS-like element (s) may have been involved in deletion formation in the putative glyco gen operon. Upstream of glgB an additional incomplete ORF was found wi th significant similarity to putative transposases from bacterial Inse rtion Sequences. This region was designated RSBst-beta. Both RSBst-alp ha and RSBst-beta appeared to be present in multiple copies in the B. stearothermophilus CU21 chromosome.