Nalidixic acid, an antibiotic which affects DNA synthesis through interacting with DNA gyrase, the enzyme which catalyzes the supercoiling of DNA, was used to inhibit DNA synthesis in Escherichia coli B/r/1. Cultures of bacteria grown in a minimal salts and glucose medium were synchronized and at various cell ages were treated with nalidixic acid. After the antibiotic was removed the recovery cell division was examined. It was found that after a short period of treatment the pattern of recovery cell division was synchronous and contained a delay in division exactly proportional to the period of the treatment. In these cases, the growing points of the chromosome which existed prior to the treatment continued to their terminal after the recovery and cell division proceeded predictably and in a synchronous manner. With longer treatments recovery cell division was asynchronous and protracted. The ability of cells of various ages to divide synchronously during recovery from treatment appears to be unrelated to a specific cell age. Cells of all ages recovered synchronously from short periods of treatment and asychronously with longer inhibitions. These results suggest that the ability of E. coli B/r/1 to continue with an interrupted synchronous cell cycle brought about by a transient inhibition in DNA cycle depends on the duration of the treatment and not the cell age.
DNA polymerases I of several enteric bacteria were partially purified and their biochemical, antigenic properties and ability to replicate the DNA of colicine El plasmid (Col El) with the extracts of Escherichiacoil pol A were examined. The results suggested that all polymerases had almost the same molecular weight and pH optimum and showed resistance to araCTP and NEM. They also possessed both 3′-5′- and 5′-3′-exonucleases. The antigenicities and the ability to replicate Col El DNA, however, varied with each polymerise. Each polymerase seems to be composed of strongly conserved structure and of the structure which varies from genus to genus. The species-specificities observed in the polymerases seem to reflect the phylogenic relations of bacteria.
The conversion of single-stranded circular DNA of bacteriophage M13 or φX174 to the double-stranded form by cell-free extracts of Escherichiacoli requires Mg2+ as a cofactor. In this report, it was examined whether any other divalent cation could substitute for Mg2+ as a cofactor at the replication of these DNAs. The results showed that Mn2+, Co2+, Sr2+, and Ba2+ could replace Mg2+ The replacement, however, induced some abnormal synthesis of DNA. The DNA synthesized with Mn2+ or Sr2+ contained several interruptions in the synthesized strand. The synthesis of DNA seems to be initiated at several points on the identical template. The DNA synthesized with Mn2+, Co2+, or Sr2+ had plaque-forming ability, and the product synthesized with Mn2+, or Co2+ but not with Sr2+, showed high frequencies of mutation. Although the synthesis of φX174 DNA was not inhibited by rifampicin when Mg2+ was used as a cofactor, it was inhibited when Mn2+ or Sr2+ was used instead of Mg2+.
Two strains representative of an undescribed species of Debaryozyma, D. yamadae, have been recovered from samples of grassland soil and arboricolous lichen collected in South Africa. A description of the new species is given. The type strain of D. yamadae was found not to hybridize with two strains of the related species, D. melissophila.
By applying the co-mutation procedure, 258 mutants unable to reduce nitrate were isolated in Streptomyces coelicolor A3 (2) among hisA+ revertants induced by nitrosoguanidine (MNNG). Of these, 82 were isolated as temperature-sensitive mutants (ammtps) at the non-permissive temperature (39°). On the basis of their growth pattern, the amm co-mutants could be distinguished as falling into two main classes: 70 percent (ammA) were unable to utilize nitrite as a nitrogen source, while the remaining 30 percent (ammB) were able to reduce it. Finally, by using a functional allelism test based on heterokaryon formation in mixed cultures, the ammA and ammB classes of co-mutants were attributed to three and two different complementation groups (cistrons), respectively.
The addition of 2-deoxy-D-glucose and related glucose analogues to the cultures of Coprinus macrorhizus resulted in the induction of tyrosinase production and inhibition of fruiting body formation. The induction was inhibited by cycloheximide or high concentrations of glucose. Electrophoretic analyses revealed that tyrosinase, peroxidase, and tyrosinase inhibitors were present in crude mycelial extracts and that the production of an unusual tyrosinase isozyme was responsible for the enzyme induction.