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The effects on transformation and transduction of an ultraviolet sensitivity (uvr−) and two ultraviolet sensitivity-recombination deficiency (rec-1−and rec-2−) mutations in isogenic strains of Bacillus subtiliswere investigated. Transformation frequency in the rec-1−and rec-2−strains was reduced to approximately 5 and 25%, respectively, of the parental strains. Normal kinetics of deoxyribonucleic acid dose response in transformation were found for the rec-1+and rec-2−strains. Biphasic curves were obtained with the rec-1−strains. Transduction frequency with bacteriophage SP-10 decreased parallel to transformation frequency in the rec-1−and rec-2−strains. This result suggests that transformation and SP-10 transduction share a common mechanism for genetic recombination. It also indicates that the reduction in transformation frequency of these strains was not due to altered competence. Transduction frequency with bacteriophage PBS-1 or 3NT, on the contrary, was not diminished in rec-1−strains. This frequency was reduced in rec-2−strains but not as severely as that of transformation or SP-10 transduction. Several hypotheses to interpret these differences are presented. Recombination frequency between linked markers was reduced more than 50% in transformation by the presence of the rec-1−mutation. Linkage was unaffected in the rec-2−strains. Neither the rec-1−nor the rec-2−mutation had an effect on linkage in PBS-1 or 3NT transduction. The uvr−strains were transformed at a frequency equal to or greater than that of the parental strains. These strains were transduced by all bacteriophage systems at frequencies about twofold higher than those of parental strains.

Barat, M. (Centre National de la Recherche Scientifique, Gif-sur-Yvette, Seine et Oise, France), C. Anagnostopoulos, and A.-M. Schneider. Linkage relationships of genes controlling isoleucine, valine, and leucine biosynthesis in Bacillus subtilis. J. Bacteriol.90:357–369. 1965.—In Bacillus subtilis, the genetic loci controlling isoleucine and valine biosynthesis are not all clustered. Some of them were located on two distinct transforming deoxyribonucleic acid “molecules.” One of these molecules (the “ileilva2–4-metsegment”) carries the threonine deaminase and the dihydroxy acid dehydrase loci linked to methionine markers. The other (the “ilva1–3-leusegment”) bears the reductoisomerase locus and one or more loci involved in leucine synthesis. A phenylalanine marker was also shown to be weakly linked to this latter group. In transduction mediated by phage PBS-1, these groups are transferred jointly with other gene clusters. The phage appears to convey chromosome fragments considerably longer than the transforming “molecules.” The genetic maps of both the above segments were extended by transduction. Some groups previously studied by transformation can be placed in the following linear order: the ile-ilva2–4-metsegment, the cluster of loci involved in aromatic amino acid synthesis (trysegment), and a lysine locus. An arginine locus is cotransduced with the phe-ilva1–2-leusegment. Recombination frequencies between linked markers are much lower in transduction by this phage than in transformation.

Distribution of iron-containing oxidases in aging nodal roots of rice and wheat was studied. Activities of cytochrome c oxidase (1.9.3.1, cytochrome c : O2 oxidoreductase), catalase (1.11.1.6, H2O2: H2O2 oxidoreductase) and peroxidase (1.11.1.7, donor: H2O2 oxidoreductase) in wheat roots were comparatively higher than were those in rice roots at corresponding stages. Cytochrome c oxidase in roots remained active throughout the lives of the rice and wheat crops. In rice roots, catalase seemed to play a distinct role around the panicle formation stage. Decay of catalase activity took place earlier than did that of peroxidase and cytochrome c oxidase activities. In wheat roots similar enzyme activity changes were not observed. Data may suggest that the high activity of iron containing oxidases at the panicle formation stage (I) may be chiefly due to catalase activity in rice roots.

This experiment studies the comparative activities of terminal oxidases (Fe-containing oxidases, Cu-containing oxidases and CN-resistant oxidases) in roots of rice and wheat seedlings and the effect of root pruning on these terminal oxidases in the roots of those crops. Data indicate that (i) excepting a change in the activity of Cu-containing oxidases no appreciable difference in respiration or in Fe-containing and CN-resistant oxidases was noticed in the two types of seedling roots and (ii) root pruning did not produce any noticeable change in terminal oxidase activities in roots of wheat seedlings. A drastic change in terminal oxidase activities in roots of rice seedlings was observed, suggesting that a close relationship exists between CN-resistant oxidase and transplanting time.