[Adaptation of acrylamide producer Rhodococcus rhodochrous M8 to change in ammonium concentration in medium]. / Adaptatsiia produtsenta akrilamida Rhodococcus rhodochrous M8 k izmeneniiu kontsentratsii ammoniia v srede.

The mechanism of adaptation of the acrylamide producing strain Rhodococcus rhodochrous M8 to changes in ammonium concentrations in the medium was studied. An increase in the content of ammonium in the medium changed the activity of glutamine synthetase (GS) (EC 6.3.1.2) and glutamine dehydrogenase (GD) (EC 1.4.1.4), the enzymes of ammonium assimilation, as well as the activities of enzymes responsible for nitrile utilization: nitrile hydratase (EC 4.2.1.84) and amidase (EC 3.5.1.4). This also caused inhibition of activation of GS induced by phosphodiesterase (EC 3.1.4.1). Increases in the activities of nitrile hydratase and amidase and resistance of these enzymes to ammonium were observed in mutant of R. rhodichrous resistant to phosphotricine, an inhibitor of GS. An important role of GS in the mechanism of adaptation is suggested.

[The effect of small concentrations of antibiotics blocking the synthesis of bacterial cell wall on the permeability of Escherichia coli cell wall for plasmid DNA]. / Vliianie malykh kontsentratsii antibiotikov, narushaiushchikh sintez kletochnoi stenki bakterii, na pronitsaemost' kletochnoi stenki Escherichia coli dlia plazmidnykh DNK.

Short treatment of Escherichia coli cells with antibiotics disturbing synthesis of bacterial cell wall in small concentrations renders the cells capable of absorbing foreign plasmid DNA. A novel express-method for transformation of E. coli cells by plasmid DNA has been developed on the basis of the results obtained. The whole procedure can be performed at room temperature. Depending on cell strain and the plasmid size, the efficiency of transformation can vary from 1.10(4) to 5.10(5) transformants per 1 mkg of DNA. The method suggested improves significantly the every-day work aimed at constructing plasmids.

[Operations on the major duodenal papilla in nontumorous diseases]. / Operatsii na bol'shom duodenal'nom sosochke pri neopukholevykh zabolevaniiakh.

An experience with transduodenal operations on the major duodenal papilla in 123 patients is described, in 91% the operative interventions were performed on strict indications (stenosis of the papilla, incarceration of concrements in it). Complications of different degree without lethal outcomes were noted in 17.1% of the patients. Lethality was 3.2%. Long-term results from 6 months to 9 years were studied in 101 patients. Excellent and good results were observed in 80.2%, satisfactory--in 16.8%, bad--in 3% of the patients.

[Complex regulation of the activity of ilv genes in Escherichia coli K-12 cells]. / Kompleksnaia reguliatsiia aktivnosti ilv-genov v kletkakh Escherichia coli K-12.

The modern data on Escherichia coli K-12 ilv genes expression are reviewed. The problems of regulation of the ilv genes activity and of their possible role in the process of cell adaptation to changeable environment are discussed.

[Selection, analysis and mapping of mutations in the gene for resistance to kanamycin in plasmid RP4]. / Selektivnyi otbor, analiz i kartirovanie mutatsii v gene ustoichivosti k kanamitsinu plazmidy RP4.

We have tested possibilities of Escherichia coli strains dependent on drugs streptomycin and paromomycin for selection of spontaneous mutations in the RP4 kan gene specifying resistance to aminoglycosids--kanamycin, neomycin and paromycin. A set of kan gene mutations were obtained, classified ad mapped.

[Expression of the amino acid operons in Escherichia coli strains with an altered transcription and translation apparatus. III. The effect of mutations in the rpoB gene coding for the beta-subunit of RNA-poly-merase on ilv-operon expression]. / Funktsionirovanie aminokislotnykh operonov u shtammov Escherichia coli s izmenennym apparatom transkriptsii i transliatsii. Soobshchenie III. Vliianie mutatsii v gene rpoB, kodiruiushchem beta-sub"edinitsu RNK-polimerazy, na funktsionirovanie ilv-operona.

The influence of rifampicin resistance mutations on expression of the ilv operon of Escherichia coli was investigated. Some of these mutations, like those previously described in our works, occur in translation machinery of E. coli and inhibit derepression of the ilv operon. However, another group of mutations stimulated the expression of the operon when mutated cells were transferred from rich to minimal growth medium. The possible mechanisms of the effects of rifampicin resistance mutations on the action of coupled transcription--translation system are discussed.

[Expression of the amino acid operons in Escherichia coli strains with an altered transcription and translation apparatus. IV. The effect of mutations disturbing the coupling of the transcription and translation processes on ilv-operon expression in cells carrying the mutation in the spoT gene]. / Funktsionirovanie aminokislotnykh operonov u shtammov Escherichia coli s izmenennym apparatom transkriptsii i transliatsii. Soobshchenie IV. Vliianie mutatsii, narushaiushchikh sopriazhenie protsessov transkriptsii i transliatsii, na funktsionirovanie ilv-operona v kletkakh, nesushchikh mutatsiiu v gene spoT.

The rate of adaptation of Escherichia coli K-12 NF930 spoT1 cells with elevated intracellular level of ppGpp to various minimal media was studied. It has been found that the rate of adaptation of spoT cells, like that of parent and rel strains, depends mainly on the rate of derepression of the ilv operon. The maximal rate of the ilv operon derepression was observed when an optimal concentration of ppGpp was maintained in cells. Derepression of the ilv operon is sharply delayed when the level of ppGpp is elevated or reduced. Mutations altering the translation system do not change the rate of adaptation of spoT cells. Rifampicin resistance mutations which altered the structure of RNA polymerase change the rate of adaptation of spoT cells to minimal media, especially to those containing serine at high concentrations. The possible role of serine in the regulation of ppGpp degradation system is discussed.

[Functioning of amino acid operons in Escherichia coli strains with an altered transcription and translation apparatus. I. The effect of mutations in gene rpsL coding ribosomal protein S12 on the functioning of the ilv operon]. / Funktsionirovanie aminokislotnykh operonov u shtammov Escherichia coli s izmenennym apparatom transkriptsii i transliatsii. Soobshchenie I. Vliianie mutatsii v gene rpsL, kodiruiushchem ribosomnyi belok S12, na funktsionirovanie ilv-operona.

Derepression of the ilv operon in rel strains of Escherichia coli is delayed when cells are transferred from rich to minimal medium and is completely blocked when the mixture of amino acids--serine, methionine and glycine is present in the minimal medium. It is shown that alterations in translation machinery caused by streptomycine resistance mutation can also lead to the delay of the ilv operon derepression in rel+ strains or to its complete inhibition in rel strains of E. coli. The possible mechanisms of high sensitivity of the ilv operon to different alterations in E. coli are discussed.

[Functioning of amino acid operons in Escherichia coli strains with an altered transcription and translation apparatus. II. The effect of mutations in genes coding ribosomal protein S5 and translation elongation factor G on the functioning of the ilv operon]. / Funktsionirovanie aminokislotnykh operonov u shtammov Escherichia coli s izmenennym apparatom transkriptsii i transliatsii. Soobshchenie II. Vliianie mutatsii v genakh, kodiruiushchikh ribosomnyi belok S5 i faktor élongatsii transliatsii G, na funktsionirovanie ilv-operona.

It has been shown in our previous study that mutations in genes relA, relC and rpsL result in the delay in Escherichia coli ilv operon derepression; the complete inhibition of derepression of the ilv operon is observed in the double mutants having alterations in rpsL and relA or relC genes. At present, some mutations occurring in the fus gene and altering the structure of the translational elongation G factor have been also found to delay derepression of E. coli ilv operon and complete inhibition in fusr and rel double mutants. Phenotypical ile and val auxotrophy is also detected in the double E. coli mutants with spectinomycin resistance mutation in rpsE gene coding for the structure of ribosomal S5 protein and mutations in relA or relC genes. The suggestion of participation of the ilv operon in regulation of other E. coli amino acid operons expression is discussed.

[Method of selecting mutations for the plasmid genes of streptomycin resistance in Escherichia coli K-12 cells]. / Metod selektsii mutatsii po plazmidnym genam ustoichivosti k streptomitsinu v kletkakh Escherichia coli K-12.

Evidence is presented that streptomycin-dependent mutants of Escherichia coli K-12 are incompatible with the functional activity of streptomycin-resistance genes coding for aminoglycoside adenilyl transferase. On the basis of this phenomenon, a method for selection of streptomycin-sensitive mutations in these genes is proposed, and the possibility of the direct selection of hybrid DNA molecules carrying inserts inactivating streptomycin-resistance genes is discussed. The effectiveness of the method for isolation of streptomycin-sensitive R100.1 plasmid derivatives was demonstrated.

[Effect of mutations in Escherichia coli genes PolAm RecA, RecB and RecC on the frequency of genetic recombination in amber-mutants involving the early genes of bacteriophage T4]. / Izuchenie vliianiia mutatsii v genakh PolA, RecA, RecB i RecC Escherichia coli na chastotu geneticheskoi rekombinatsii u amber-mutantov po rannim genam bakteriofaga T4.

Effects of mutations in genes PolA, RecA, RecB and RecC of Escherichia coli on the recombination frequencies between rII markers of T4 have been studied in conditions of partial inhibition of some early functions. It was found that the presence of the mutations in genes PolA or RecA decreased significantly the recombination frequency of phage amber mutant in the gene 43 (DNA polymerase), increased it in the case of amber mutation in the gene 46 (exonuclease) and had no effect on the recombination of amber mutants in genes 30, 32, 33, 41, 42, 45, 44, 52. None of the amber mutants studied changed recombination frequencies in the presence of the mutations in genes RecB or RecC. Possible mechanisms of some of the effects observed are discussed.

[Effect of semipermissive conditions on recombination involving the early genes of bacteriophage T4 in amber-mutants. I. Effect of amber-mutation in gene 43]. / Rekombinatsiia u amber-mutantov po rannim genam bakteriofaga T4 v polupermissivnykh usloviiakh. Soobshchenie I. Effekt amber-mutatsii v gene 43.

Recombination frequencies between rII markers of bacteriophage T4 under conditions of partial inhibition of several early functions of the phage by amber mutations have been studied. Mutations in genes 33, 42 and 45 did not affect significantly recombination frequencies. Mutations in genes 32, 44 and 46 inhibited it. It has been found that effects of double mutations in pairs of genes: 43 and 30; 43 and 52; 43 and 33; 43 and 46; 43 and 32 were consistent with theoretically expected additive effects of corresponding single mutations. The presence of double mutations in pairs of genes: 43 and 41; 43 and 42, 43 and 44, 43 and 45 caused evident deviations from additivity. These deviations could reflect specific interactions of respective pairs of genes products under phage T4 recombination. Possible mechanisms of some of the effects observed are discussed.

[Characteristics of the intragenic recombination of T4B bacteriophage amber mutants under nonpermissive (su-) conditions]. / Osobennosti vnutrigennoi rekombinatsii amber-mutantov bakteriofaga T4B v nepermissivnykh (su-) usloviiakh.

Intragenic recombination of bacteriophage T4B amber mutants in early genes 30, 32, 42, 43, 44, 56 and in late gene 7 in su- cells of Escherichia coli B was studied. The frequency of recombination under such conditions was increased in genes 30, 43 and 7, but it was lowered in genes 46 and 44, and was completely inhibited in genes 32, 42 and 56. The level of stimulation or inhibition of recombination frequencies in early genes was gene-specific and did not depend either on the distances between amber mutations, or on progeny phage maturation delay. On the other hand, the level of recombination stimulation in the late gene 7 was greatly influenced by the distances between amber mutations tested. Wild type alleles arising in su- cells during recombination proved to be functionally active, and their activity caused the increase in progeny phage yield and in a partial removal of phage maturation delay.

[Mutation of bacteriophage T4 restoring phage supressor psul+ activity in bacterial strain Escherichia coli BN]. / Mutatsiia bakteriofaga T4, vosstanavlivaiushchaia aktivnost' fagovogo supressora psul+, v bakterial'nom shtamme Escherichia coli BN.

The mutant of bacteriophage T4psu1+XF2 carrying a mutational aleration in the central region of proline-serine tRNA precursor is isolated. The mutational alteration results in the recovery of amber suppressor activity of phage psu1+ serine tRNA in Escherichia coli BN in which the synthesis of this tRNA is normally blocked. Since the amber suppressor activity of mutant serine tRNA becomes sensitive to a restrictive action of strR mutations, its structure seems to be different from that of parental suppressor serine tRNA.