A clone which contains the complete chicken ovalbumin gene, including its leader coding sequences, has been isolated. From electron microscopic analysis of this DNA we conclude that the minimal size of the transcriptional unit for ovalbumin is 7.7 kilobases. The DNA sequence of the region surrounding the 5' end of the ovalbumin gene is presented. Comparison of this sequence with those of other eukaryotic genes reveals striking similarities, possibly related to a promoter region, approximately 30 base pairs upstream from the site coding for the 5' end of the mRNA.

Fig. 1. Bacteria were first grown in nutrient broth (17), and protoplasted in SMM, the sucrose-magnesium-maleate buffer of Wyrick and Rogers (13), to which 5 ,ug/ml of DNase I (Worthington Biochem. Corp.) had been added (SMMD). Protoplasts were made to revert to bacillary forms by plating on RDR, a rich regeneration agar medium of high tonicity (13), to which 5 /g/ml each of DNase I and rifamycin (Lepetit Labs, Milano) were added. Prototrophic clones within the film of growth that appeared on RDR plates after incubation were selected out by replica plating onto variously supplemented SDR medium. This is a nonhypertonic minimal medium (14), to which 20 ,M MnCl2, 5 gg/ml of DNase, 1 Ag/ml of rifamycin, and 15 g/liter of (Difco) agar have been added. It was used as a selection medium, both unsupplemented (SDR) and supplemented (see Table 2).Procedure Adopted for Fusion Experiments. Overnight precultures of both parental strains in nutrient broth at 300 were inoculated, before growth ceased, into 20 ml of broth, to give an initial optical density (OD570) = 0.05. These cultures were incubated with shaking at 370 until an OD of 0.4 was reached. From each culture, 15 ml were centrifuged, the pellets were taken up in 3 ml of SMMD (OD570 = 2, or about 4 X 108 colony forming units/ml), and lysozyme was added to a concentration of 200,ug/ml. Complete protoplast formation was usually seen after 10 min of gentle shaking at 420, but exposure to lysozyme was continued for 20 more minutes. Samples (0.1 ml) of each suspension were then plated on ordinary nutrient agar. The plates usually remained sterile, and indicated that the frequency of osmotic shock resistant forms was below 2.5 X 10-8.One milliliter samples from each of the two suspensions were mixed in a third tube, the three tubes were centrifuged, and each pellet was resuspended in 0.2 ml of SMMD. To one tube, 1.8 ml of a 40% (wt/vol) solution of polyethylene glycol (PEG)t in SMM was added and the suspension immediately homogenized by shaking. After a 1 min exposure to PEG, either at 200 or at 00, several 0.05 ml samples were spread on the surface of duplicate RDR plates and used to make 10-1 and 10-2 dilutions in SMMD, from which, in turn, further reversion plates and also tThe molecular weight is not critical; PEG 6000 from Merck was usually used.

Mutants of Bacillus subtilis with altered deoxyribonucleic-dependent ribonucleic acid polymerase activity have been isolated and characterized. These mutants, selected as strains resistant to rifampin or streptolydigin, demonstrate drug-resistant in vitro ribonucleic acid synthesis. Sporeforming ability and support of phage infection are altered in many of the mutants. Mutations to rifampin and streptolydigin resistance have been located on the B. subtilis chromosome and ordered relative to the markers cysA14 and str.

The Zymomonas mobilis gene (sacA) encoding a protein with sucrase activity has been cloned in Escherichia coli and its nucleotide sequence has been determined. Potential ribosome-binding site and promoter sequences were identified in the region upstream of the gene which were homologous to E. coli and Z. mobilis consensus sequences. Extracts from E. coli cells, containing the sacA gene, displayed a sucrose-hydrolyzing activity. However, no transfructosylation activity (exchange reaction or levan formation) could be detected. This sucrase activity was different from that observed with the purified extracellular protein B46 from Z. mobilis. These two proteins showed different electrophoretic mobilities and molecular masses and shared no immunological similarity. Thus, the product of sacA (a polypeptide of 58.4-kDa molecular mass) is a new sucrase from Z. mobiis. The amino acid sequence, deduced from the nucleotide sequence of sacA, showed strong homologies with the sucrases from Bacillus subtilis, Salmonella typhimurium, and Vibrio alginolyticus.The ethanologenic gram-negative bacterium Zymomonas mobilis can grow only on glucose, fructose, or sucrose and metabolizes these sugars with the production of ethanol and carbon dioxide as main fermentation products (1,22,41). Carbohydrate metabolism in Z. mobilis has been reviewed recently (43). The monosaccharides glucose and fructose are transported inside the cell by a facilitated diffusion system mediated by a carrier (12), phosphorylated by a specific kinase, and metabolized through the Entner-Doudoroff pathway. The disaccharide, sucrose, is first hydrolyzed to liberate glucose and fructose in the culture medium, and these sugars enter the cell by using the transport system described above. The number and nature of the enzymes involved in sucrose catabolism are not clearly known in Z. mobilis.Sucrose metabolism has been intensively studied in Bacillus subtilis (15). Three saccharolytic enzymes are present: an intracellular sucrase (sacA gene), an extracellular levansucrase (sacB gene), and a levanase (sacC gene). All enzymes act as 13-D-fructofuranosidases; in addition, levansucrase catalyzes the formation of levan, a high-molecular-weight polymer of fructose. The nucleotide sequences of sacA, sacB, and sacC genes have been determined (13,21,39). A strong homology of the N-terminal protein sequences of sucrase, levanase, and yeast invertase (SUC2 gene) was observed, while no similarity with levansucrase could be detected (21).Levan formation during growth of Z. mobilis on sucrose is well known and the presence of levansucrase is generally well accepted (22, 41). Furthermore, it has been demonstrated that levan formation is cell linked (25), while a high saccharolytic activity was detected in culture medium (28,33). These results raised the question of the existence, in addition to levansucrase, of a second enzyme, a sucrase, which may be liberated in culture medium during cell growth (41). More recently, two other polymers has been characterized: a cell-linked, high-...