NAD-dependent formate dehydrogenase from methylotrophic bacteria. Isolation and properties]

NAD-Dependent formate dehydrogenase (FDH) has been isolated from methylotrophyc strain Bacterium sp 1 by (NH4)2SO4 fractionation of cell extract, ion-exchange chromatography and preparative isotachophoresis. Preparation of FDH is homogeneous in analytical polyacrylamide gel electrophoresis and under ultracentrifugation. Sedimentation coefficient of FDH is 4.9S. Mikhaelis constants are 1.1-10(-4) M for NAD and 1.5-10(-2) M for formate. In the absence of sulfhydril compounds FDH is unstable, but it is stable in the presence of mercaptoethanol or ditiotreitol.     

Effect of exogenous DNAses on various stages of DNA replication in microorganisms

Effect of DNAase 1 on DNA synthesis and cell division was studied in microorganisms deficient in some stages of DNA replication initiation. The DNA synthesis induced by exogenous DNAase was found to be a replicative origin since it was registered from the "origin" of chromosomal replication under the conditions of initiation of proteins functioning. Stimulation of DNA synthesis in bacterial cells having mutations in DNA B and DNA G genes by DNAase 1 indicates that exogenous DNAases participate in replicative fork during the DNA synthesis.     

The role of bitoxibacillin components in the manifestation of its biological activity

New methods were developed and applied to quantitative determination of beta-exotoxin and antibiotic activity of delta-endotoxin with respect to Micrococcus spp. in bitoxibacillin (BTB) and the fermentation broths prepared under industrial conditions. The biosynthesis of beta-exotoxin in the period of its maximum accumulation during the fermentation was estimated. It was shown that the primary biological effect of BTB on insects consisted in the actions of beta-exotoxin and delta-endotoxin. Biological activity of each of the entomocidal components of the entomocidal components of BTB did not practically correlated with the number of viable spores. There was a correlation between the antibiotic activity of crystalline B. thuringiensis subsp. thuringiensis solutions and the insecticidal activity of the entomopathogenic preparations. Determination of beta-exotoxin and antibiotic activity of delta-endotoxin might be used as a complex procedure for testing the quality of BTB. The method for estimating antibiotic activity of the crystal solutions allowed one to assay the biological activity of other preparations based on Bacillus thuringiensis non-synthesizing beta-exotoxin.     

Isolation of nisin from native solution and its purification on cationites]

It was found possible to use organic sorbents and in particular carboxylic cationites for isolation of nisin from the fermentation broth filtrate and its purification. Nisin is known as a polypeptide antibiotic applied as a preservative. The sorbents were shown to have high exchange capacities by the isolated substance and mechanical strength and resistance. They also proved to be highly stable.     

The stability of the alkylating derivatives of oligodeoxyribonucleotides containing a cholesterol or phenazine radical added to the 3'-termination during their interaction with Acholeplasma laidlawii PG-8]

Stability of alkylating derivatives of decathymidylates protected on the 3'-terminal by cholesterol and phenazine residues has been studied in the process of their interaction with cells of Acholeplasma laidlawii PG-8. It is shown that the studied reagents are not split by nucleases of A. laidlawii PG-8 for the time necessary for alkylation of mycoplasma biopolymers.     

Antibiotic activity of marine gram-negative bacteria]

An antimicrobial substance was isolated from the culture fluid of Vibrio fischeri belonging to ++gram-negative sea bacteria. The substance was shown to be highly active against ++gram-positive cocci and less active against some other ++gram-positive bacteria and fungi. The active substance was defined as a low molecular weight compound which appeared to be thermostable and had positive ninhydrin reaction. The antibiotic formed when the culture was grown in the media containing sea water and protein hydrolysates or yeast extract during the exponential phase. The maximum antibiotic activity was observed during the stationary phase of culture development.     

Detection of new MHC mutations in mice by skin grafting, tumor transplantation and monoclonal antibodies: a comparison

Two mechanisms of major histocompatibility complex (MHC) mutations have been described in mice; gene conversion and homologous but unequal recombination. However, our knowledge of mutations in MHC is incomplete because studies have been limited almost exclusively to two haplotypes, H-2b and H-2d, while hundreds of haplotypes exist in nature; it has been biased by the use of only one procedure of screening for mutation, skin grafting. We used three procedures to screen for MHC mutations: (1) conventional techniques of skin grafting, (2) syngeneic tumor transplantation and (3) typing with monoclonal anti-MHC antibodies (mAbs) and complement. The faster technique of tumor transplantation detected mutants similar to those discovered by skin grafting technique. Screening with mAbs allowed us to detect both mutants that are capable of rejecting standard skin grafts and those that are silent in skin grafting tests, and which therefore resulted in a higher apparent mutation frequency. Two mutants of the H-2a haplotype were found that carry concomitant class I and class II antigenic alterations. Both MHC mutants silent in skin grafting tests and mutants carrying concomitant class I and class II alterations have never been studied before and are expected to reveal new mechanisms of generating MHC mutations. 1-Ethyl-1-nitrosourea (ENU) failed to induce de novo MHC mutations in male mice in our skin grafting series.     

Carbon dioxide fixation by the mycelium of the actinomycete Streptomyces chrysomallus var. macrotetrolidi

The mycelium of Streptomyces chryzomallus var. macrotetrolidi producing the macrotetrolide antibiotic nonactin was shown to be capable of carbon dioxide fixation. Carbon was found to be incorporated into nonactin and macromolecular compounds in the biomass. Carbon was incorporated within 20 to 40 min of the mycelium incubation with NaH14CO3. Pyruvic and propionic acids stimulated carbon incorporation.