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Late during sporulation, Bacillus subtilis produces glucose dehydrogenase (GlcDH; EC 1.1.1.47), which can react with D-glucose or 2-deoxy-D-glucose and can use nicotinamide adenine dinucleotide (NAD) or nicotinamide adenine dinucleotide phosphate (NADP) as a cofactor. This enzyme is found mainly in the forespore compartment and is present in spores; it is probably made exclusively in the forespore. The properties of GlcDH were determined both in crude cell extracts and after purification. The enzyme is stable at pH 6.5 but labile at pH 8 or higher; the pH optimum of enzyme activity is 8. After inactivation at pH 8, the activity can be recovered in crude extracts, but not in solutions of the purified enzyme, by incubation with 3 M KCl and 5 mM NAD or NADP. As determined by gel filtration, enzymatically active GlcDH has a molecular weight of about 115,000 (if the enzyme is assumed to be globular). GlcDH is distinct from a catabolite-repressible inositol dehydrogenase (EC 1.1.1.18), which can also react with D-glucose, requires specifically NAD as a cofactor, and has an electrophoretic mobility different from that of GlcDH.

A thermophilic (70 C), gram-negative bacterium has been isolated that resembles Thermus aquaticus but lacks the type-characteristic yellow carotenoid.

The DNA sequence of the structural gene for glucose dehydrogenase (EC 1.1.1.47) of Bacillus subtilis was determined and comprises 780 base pairs. The subunit molecular weight of glucose dehydrogenase as deduced from the nucleotide sequence is 28,196, which agrees well with the subunit molecular weight of 31,500 as determined from sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The sequence of the 49 amino acids at the NH2 terminus of glucose dehydrogenase purified from sporulating B. subtilis cells matched the amino acid sequence derived from the DNA sequence. Glucose dehydrogenase was purified from an Escherichia coli strain harboring pEF1, a plasmid that contains the B. subtilis gene encoding glucose dehydrogenase. This enzyme has the identical amino acid sequence at the NH2 terminus as the B. subtilis enzyme. A putative ribosome-binding site, 5'-AGGAGG-3', which is complementary to the 3' end of the 16S rRNA of B. subtilis, was found 6 base pairs preceding the translational start codon of the structural gene of glucose dehydrogenase. No known promoterlike DNA sequences that are recognized by B. subtilis RNA polymerases were present immediately preceding the translational start site of the glucose dehydrogenase structural gene. The glucose dehydrogenase gene was found to be under sporulation control at the trancriptional level. A transcript of 1.6 kilobases hybridized to a DNA fragment within the structural gene of glucose dehydrogenase. This transcript was synthesized 3 h after the cessation of vegetative growth concomitant to the appearance of glucose dehydrogenase.

Here we present the genome of strain Exiguobacterium sp. AT1b, a thermophilic member of the genus Exiguobacterium whose representatives were isolated from various environments along a thermal and physicochemical gradient. This genome was sequenced to be a comparative resource for the study of thermal adaptation with a psychroactive representative of the genus, Exiguobacterium sibiricum strain 255-15, that was previously sequenced by the U.S. Department of Energy's (DOE's) Joint Genome Institute (JGI) ( http://genome.ornl.gov/microbial/exig/ ).

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