Acta microbiologica Polonica. Series A: Microbiologia generalis最新文献

In the reduction process of sulphates by Desulfovibrio desulfuricans suitable concentration of mineral salts plays an important role. In particular, different K2HPO4, CaCl2 and Fe(NH4)2(SO4)2 content in the reaction medium has an observable effect on the reduction degree (x'), the induction time (t0) and the reduction rate constant (k). These data were recorded for 9 liquid media characterized by different content of mineral salts. The reaction rate constants were calculated for the reduction process in each medium. Optimal reduction conditions exists at the following element concentration ratios: P/S=0.068, K/S=0.086, Fe/S=0.08, N/S=0.33, C/S=1.80, Ca/S=0.03, Cl/S=0.80.

Commercial nisin was fractionated using a Bio-Gel P-10 column and ion-exchange chromatography on CM-sephadex C-25. Pure nisin having a titre of 40 X 10(6) units per gram was obtained. In polyacrylamide-gel electrophoresis the pure nisin gave three bands. It is suggested that heterogeneity of nisin is due to the presence of several biological polypeptides. The pure nisin is digested by chymotrypsin but it is not affected by TPCK-trypsin and pepsin.

The effect of dicumarol on growth of selected soil bacteria: Azotobacter chroococcum, Arthrobacter globiformis, A. citreus and Bacillus megaterium was studied. The following minimum concentrations were inhibitory in vitro: Arthrobacter citreus--20 mug/ml., Bacillus megaterium--40 mug/ml., Azotobacter chroococcum--40 mug/ml. Arthrobacter globiformis--70 mug/ml. Cells of all microorganisms studied grown in the presence of dicumarol developed aberrant morphological forms.

Rubella virus growth was tested in primary rabbit kidney cell cultures, maintained with or without calf serum. In fluid phase of the cultures maintained with 1.5% of heat-inactivated calf serum, the infectious virus titers were much higher than in the system without serum. The differences reached 1.5-2.0 log10 TCID50/ml. Virus multiplication curves also ran different courses. In serum-containing system virus titer increased up to the 9th day post infection, while without serum--only up to 4-5 days. The time of appearance and the type of cytopathic effect were not affected by the absence of serum or by its presence in a concentration of 1.5%.

Pectolytic activity of the Penicillum sp 7/4B/E11 mutant, which synthesized effectively PG and was not capable of producing PE, was studied on some by-products of food industries (apple pulp, beet pulp, and mixtures of apple pulp or beet pulp with wheat bran) supplemented in some experiments with mineral salts of the Czapek's medium. The strain showed good growth but a low PG activity when grown on by-products without mineral salts and an increase in PG activity after cultivation on these by-products (mainly on beet pulp) enriched with mineral salts. The highest PG activity was obtained after 6-8 days cultivation on beet pulp (3%) with mineral salts. Among the tested salts, NaNO3 influenced PG activity most effectively, K2HPO4 and MgSO4 to a smaller degree whereas others were ineffective. The mutant did not synthesize PE under these culture conditions.

The wild-type plasmid ColIb and its mutant drd7 derepressed in conjugation were transferred to Escherichia coli K12 P678-54 which produces minicells. Fertility functions of drd7 remained derepressed in the new host. P678-54drd7 transmitted the plasmid at a high frequency (28.6%) and it was effectively lysed by the phage If1. Significant amounts of 3H-DNA segregated from P67854Col+ into minicells dependent upon the presence of the plasmid. The depressed plasmid segregated more effectively into minicells than the wild-type plasmid. ColIb segregated into 2% whereas ColIbdrd7 into 8.4% of minicells. The difference in the frequency of segregation of the wild-type and the derepressed plasmid indicated different cell membrane attachment sites of each plasmid studied. Mini-drd7 were able to transfer the plasmid to E. coli Row at a low frequency (0.1%). Minicells carrying either of plasmid were capable to synthesize RNA and protein. RNA and protein synthesis were plasmid specific and the precursors were not incorporated into minicells without plasmids. Rifampin and chloramphenicol inhibited RNA and protein synthesis in minicells, respectively. The more effective incorporation of 3H-uridine or 14C-leucine into minicells harboring drd7 than ColIb resulted presumably from the high efficiency of the segregation of drd7 into minicells. Polyacrylamide gel electrophoresis of 3H-RNA has shown that plasmids in minicells were able to code low molecular RNA of 4s. No 16 or 23 ribosomal RNA was found in the profiles of de novo synthesized RNA in minicells.

Three r-determinants (Cb Cm Cf) out of eight present in R404 factor were transferred in transformation of Escherichia coli by the plasmid DNA isolated from minicells. The r-determinants acquired in this way formed the replicon tr404-1 and were untransferable by conjugation unless another self-transmissible plasmid was present in recipient. The evidences are presented in support of hypothesis that the transfer events consist in infection of transformant cells with sex factor, recombination between tr404-1 replicon and the sex factor and finally transfer of the new formed structure to the host cells of the sex factor.

Certain ts mutations in gene 43 of bacteriophage T4 are known to exhibit mutator or antimutator activities with respect to different rII mutations of this phage. The effect of these mutations on recombination frequencies of double mutant strains of phage T4 with genotype rII ts--homoallelic with respect to the ts trait--was examined. The results implicate the essential role of the genetic background in the investigated process.