The enzymes involved in gluconate utilization in Bacillus subtilis seemed to be gluconate permease and gluconate kinase. Several mutants unable to grow on gluconate were isolated. The mutations they harboured (gnt) were clustered between iol-6 and $2'~-74 on the B. subtilis chromosome (a tentative map order of gnt-f0, gnt-4, gnt-26, gnt-23 and gnt-9 was obtained). The gnt-f0 mutation seemed to be located within the structural gene of the kinase, and the gnt-23 and gnt-26 mutations seemed to be within that of the permease. An EcoRI fragment (4.5 MDal) containing an intact gluconate (gnt) operon consisting of these two structural genes was cloned in phage $105 by prophage transformation and was mapped physically. The physical location of the mutations coincided with their order on the genetic map. The HindIII-A fragment (2.4 MDal), which corrects all the gnt mutations, was subcloned in plasmid pC194. The fragment contained the structural genes for the gluconate permease and kinase, but not the regulatory region of the gluconate operon. I N T R O D U C T I O NAfter entering the Bacillus subtilis cell, gluconate is phosphorylated to gluconate 6-phosphate, which, because B. subtilis lacks the Entner-Doudoroff pathway, can only be metabolized through the pentose cycle. Therefore, only two enzymes may be needed for the utilization of gluconate as a carbon source; one is gluconate permease, which transports gluconate into the cell, and the other is gluconate kinase, which phosphorylates gluconate. Both enzymes are induced in response to gluconate and their induction is repressed in the presence of rapidly metabolizable carbohydrates such as glucose (Dowds et al., 1978;Nihashi & Fujita, 1984). We have tentatively reported the cloning of the genes for gluconate utilization in a temperate phage, pl1 (Fujita et d., 1983). In this paper, we communicate the genetic mapping and characterization of several gnt mutations that render the cell unable to grow on gluconate and we also report the recloning of an EcoRI fragment cloned in pl 1 in another temperate phage, $105. This fragment encodes an intact gluconate operon. To our knowledge, this work is the first example of the use of a B. suhtilis host -vector system to clone an intact catabolic operon of this species. M E T H O D SBactrriu, phugr und plu.smicis. Strain 6001 5 (trpC2 mrtC7) is our standard strain. Among Gnt-mutants, the isolation of strain 61656 (Aigj hisAl IruAB metB5 trpC2), YF127 (grit-4 trpC2 metC7) and YF029 (gnt-9purA16 IrttAX metB.5 hisA.3) has already been reported (Fujita & Freese, 1981 ;Fujita & Fujita, 1983). Strain YFI 58 (gnt-4 recE4 trpC2) was constructed from YF127 by congression using the DNA of strain lA423 (IrtiAB thr-5 urgAI5 recE4 r-m-), which was obtained from the Bacillus Genetic Stock Center, Ohio State University, Columbus, USA. Strain YF160 (pit-10 try<'? n~r C 7 )was isolated from strain 60015 that had been treated with t Present address:

The regulation of induction of inositol dehydrogenase (EC 1.1.1.18) and gluconate kinase (EC 2.7.1.12) was studied in Bacillus subtilis. Inositol dehydrogenase is induced by myo-inositol and gluconate kinase is induced by D-gluconate. Both inductions were strongly repressed by rapidly metabolizable carbohydrates such as D-glucose, D-mannose, D-fructose and glycerol (D-glucose had the strongest repressive effect) but they were weakly repressed by slowly metabolizable carbohydrates. Although each carbohydrate exerted a stronger effect on the induction of inositol dehydrogenase than that of gluconate kinase, it showed a similar tendency with respect to the degree of repression of each induction. This catabolite repression could not be diminished by addition of cyclic AMP to medium. In addition, non-metabolizable D-glucose analogues had no or weak repressive effects. On the assumption that rapidly metabolizable carbohydrates might be metabolized to repress both inductions, it was investigated whether several mutants blocked in the Embden-Meyerhof pathway could produce metabolite(s) (repressor) to repress them. A phosphoglycerate kinase (EC 2.7.2.3) deficient mutant could produce the repressor from D-glucose, D-mannose, D-fructose and glycerol but other mutants could not produce it from carbohydrates unable to be metabolized in each mutant. Thus, catabolite repression of both enzyme inductions seemed to be under similar regulation. The identification of the possible repressor of the induction of in of inositol dehydrogenase and gluconate kinase in vivo was discussed.

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