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S Z Mindlin

Publications and source records attributed to S Z Mindlin.

At least 37 records · Page 2Linked to original sources
PubMed1985

[Integration of the related prophages lambda, phi 80 and their hybrid lambda att80 into the secondary chromosomal att sites of wild-type Escherichia coli].

The family of lambdoid phages displays a varying specificity of integration into the host chromosome. The lambda phage DNA failed to get inserted at the secondary attachment site(s) of the gal operon (frequency less than 2.6 X 10(-8)) in the presence of the primary (normal) one. By contrast, phi 80 and the lambda att80 hybrid integrated into wild-type Escherichia coli at least, at two secondary att sites of the btuB locus, the latter phage being also capable of integration in the vicinity of purE and purC (frequency 2 X 10(-3) to 10(-4)). Integration of phi 80 and lambda att80 into btuB occurred with about the same frequency as in cells deleted for normal insertion site (0.7 divided by 4.0 X 10(-6)). An analysis of the secondary lysogens with the prophage in btuB showed them to be polylysogens; the additional prophage(s) was found in the primary att site. We also failed to observe integration of phi 80 and lambda att80 with formation of secondary monolysogens into other foci (frequency less than 0.0035, if multiplicity of infection was 10(-3) or 10). It is presumed that phi 80 and lambda att80 prophages get only integrated at secondary att sites in case the primary site is occupied.

Attachment Sites, Microbiological↗
PubMed1985

[Formation and genetic structure of polylysogens for lambda and phi 80 and their lambda att80 hybrid infecting wild-type Escherichia coli].

The frequency of polylysogeny and the genetic structure of polylysogens were studied for phages lambda, phi 80 and lambda att80. For none of these phages does frequency of polylysogeny vary by more than a factor of 2 within a wide range of multiplicities of infection (from 10(-3) up to 10) but the relative location of the prophages on the host chromosome is different. In the case of lambda, polylysogens are formed with a high frequency (0.20-0.41) and the prophages are inserted in tandem into the primary (normal) att site. In the case of phi 80 and lambda att80, polylysogens occur about 10 times less frequently and usually have one prophage inserted into the primary attachment site and another (sometimes, also a third) in one of the secondary ones. Wild-type Escherichia coli was shown to possess at least four secondary att80 sites, two of which (close to the his and tolC loci) are preferred. The frequency of secondary integration of phi 80 and lambda att80 does not differ significantly in the wild-type host and in cells deleted for the primary att site (0.041 and 0.045, respectively, among surviving cells at MOI 10). Certain properties of the phi 80 lysogens make it more difficult to decode their genetic structure.

Attachment Sites, Microbiological↗
PubMed1985

[Mechanism of non-tandem integration of prophage phi 80 into the chromosome of the wild-type Escherichia coli].

We studied the ability of lambda, phi 80 and their hybrid lambda att80 to lysogenize homoimmune monolysogens and examined the prophage locations on the chromosome of the resulting polylysogens. We observed an effective integration of phi 80 and lambda att80, in contrast to lambda, into the host chromosome, exclusively, at the attachment sites that were not occupied by the resident prophage (nontandem). Besides, the lambda att80 (int+) prophage was observed to ensure effective nontandem integration of a homoimmune int mutant DNA. Hence, we inferred that the expression of the int gene in the phi 80 prophage is constitutive, cI-independent and results in nontandem integration of the homoimmune prophage. The validity of this inference has been supported experimentally: (i) the only lysogen that was found to contain a phi 80 tandem was highly unstable (spontaneous segregation of monolysogens occurred 6-7 times more frequently than with the lambda tandem); (ii) an int inactivating mutation stabilized the phi 80 tandem; as a result, the int mutant has the frequency of tandem integration as high as that of lambda, while no nontandem integration was observed. A hypothesis is proposed which accounts for the instability of the phi 80 tandems and explains the relation between this phenomenon and the prophage ability to integrate into secondary attachment sites in the presence of the primary (normal) one.

Attachment Sites, Microbiological↗
PubMed1984

Integration of bacteriophages lambda and phi 80 in wild-type Escherichia coli at secondary attachment sites. I. Formation of secondary lysogens.

The family of lambdoid phages displays a varying specificity of integration into the host chromosome. The lambda phage DNA failed to get inserted at the secondary site(s) of the gal operon (frequency less than 2.6 X 10(-8) in the presence of the primary (normal) att site. By contrast, phi 80 and the lambda att80 hybrid (lambda X phi 80) became integrated into wild-type Escherichia coli at at least two secondary att sites of the btuB locus, and the latter near purE and purC as well (frequency 2 X 10(-3)-10(-4). The integration of phi 80 and lambda att80 into btuB occurred with about the same frequency as in cells in which the normal insertion site had been deleted (0.7-4.0 X 10(-6). An analysis of the secondary lysogens with the prophage in btuB showed them to be polylysogens; the additional prophage(s) was found at the primary att site. We also failed to observe the integration into other loci of phi 80 and lambda att80 with the formation of secondary monolysogens (frequency less than 0.0035 at MOI = 10(-3) or 10). It is presumed that these prophages become integrated at secondary att sites only if the primary site is occupied.

Bacteriophage lambda↗
PubMed1984

[Dominant mutations of rifampicin resistance in Escherichia coli K-12].

Significant portion (up to 20%) of dominant mutations (rifd mutations) was observed among spontaneous mutations of rifampicin resistance picked up in cells of haploid Escherichia coli strain. These mutations are similar to rifd mutations obtained earlier when selecting them in rif-s/rif-s merodiploids. On the basis of analysis of nucleotide substitutions taking place in formation of spontaneous and induced mutations, it is established that rifd mutations are caused by single nucleotide substitution. The majority of rifd mutations are localized in a small region of the central part of RNA polymerase beta-subunit gene covering less than 200 base pairs. A rifd mutant has been described which occurred as a result of micro-deletion in one of the "hot" spots of the central region of beta-subunit gene.

Amino Acid Sequence↗
PubMed1983

RNA polymerase rifampicin resistance mutations in Escherichia coli: sequence changes and dominance.

Five recombinant plasmids, pBK2646, pBK611, pRC3, pRC4 and pRC5, carrying rpoB rifampicin-resistant RNA-polymerase genes were obtained. The sequence analysis of these plasmids revealed certain structural changes in the rpoB gene which specify corresponding alterations in the beta-subunit of RNA polymerase. Some functional properties of the corresponding mutant strains and their RNA polymerases have been investigated.

Base Sequence↗
PubMed1981

Primary structure of Escherichia coli RNA polymerase nucleotide substitution in the beta subunit gene of the rifampicin resistant rpoB255 mutant.

The transducing phage lambda dsupM814 and the plasmid pIB1830 containing the wild-type rpoB gene have been constructed and the primary structure of the gene's central fragment has been established. In contrast with the wild-type, the gene of the rpoB255 mutant, whose primary structure has been published, was found to contain an A.T. leads to T.A. transversion entailing the substitution of a valine residue for the aspartic acid residue (516) of the wild-type beta subunit.

Base Sequence↗
PubMed1981

[Transducing lambda phages with Escherichia coli genes].

The paper presents data on transducing lambdoid phages containing Escherichia coli genes. The major genetic techniques for isolating transducing phages (in vivo) are outlined. A combined table of best-studied transducing phages obtained by the methods of molecular genetics and genetic engineering lists phages genotype & basic literature references for the phages and their derivatives. The chromosome fragments of E. coli inserted in phage DNA are separately specified. Another table presents information about phages carrying E. coli fused operons and genes. The paper also provides detailed physical maps of three regions of the E. coli chromosome. The bibliography contains 300 items.

Bacteriophage lambda↗
PubMed1980

[Effect of coumermycin A1 and nalidixic acid on lambda phage integration and transducing lambdoid phages containing RNA-polymerase genes].

A specific inhibitor of DNA gyrase, coumermycin A1, inhibits in vivo the interaction of bacteriophage lambda DNA and DNA of rifd transducing phages (lambda rifd47 and lambda att80 rifd35) carrying genes rpoB and rpoC of RNA polymerase. Besides, coumermycin A1 inhibits recA-dependent recombination between the bacterial region of rifd phages and a homologous region of Escherichia coli chromosome. The integration of transdusing phage DNA into the chromosome of recA host is significantly more sensitive to the inhibitory effect of coumermycin A1 than the two other processes (by one -- three orders or magnitude). Another inhibitor of DNA gyrase, nalidixic acid, does not depress the integration of both lambda and rifd phages DNA. The differential effect of coumermycin A1 on the integration of lambda and rifd phages correlates with our concept of the int-idependent mechanism of rifd phage DNA integration in recA bacteria. According to preliminary results, coumermycin A1, in contrast to its action on integration, does not inhibit the exclusion of lambda prophage from E. coli chromosome, while nalidixic acid produces a slight inhibitory effect.

Aminocoumarins↗
PubMed1979

[New transducing phage with RNA polymerase beta- and beta'-subunit genes derived from a hybrid phage lambda att80: isolation, genetic analysis and physical mapping].

A hybrid lambda att 80 phage with the genetic structure lambda (A-J) phi 80 (att-int-xis) imm lambda..cI857s7 is shown to be a convenient vector for creating transducing phages. On the one hand, the restriction analysis indicates that it has 3 restriction sites for EcoRI in comparison with 5 and 9 sites for parental phages lambda and phi 80 respectively. On the other hand, its buoyant density is less than that of phage lambda and under centrifugation it is easier separated from the phage transducing particles. When lambda att 80 prophage was excluded from the bfe locus of Escherichia coli, transducing phages with genes of two RNA polymerase beta-subunits (rpoB and rpoC) were isolated. To identify the latter, a convenient genetic test was worked out. A physical map of lambda att 80 drifd 35 transducing phage, carrying rpoB and rpoC genes has been constructed using endonucleases EcoRI and HindIII. A comparison of this map and the corresponding maps of transducing phages lambda drifd 18 and lambda drifd 47, studied earlier, led to the discovery of two integration sites of phage lambda within the locus bfe spaced apart by about 1800 nucleotide pairs. At all the sites both phages (lambda and lambda att 80) have integrated in the locus bfe in the counter clockwise order.

Bacteriophage lambda↗
PubMed1976

[Reversion of RNA-polymerase mutations affecting F'-factor stability].

Ts+ reversions of amber mutations tsR on the beta-subunit of Escherichia coli RNA polymerase (79 min on the genetic map) were investigated. TsR mutants are viable due to the partial suppression of amber mutations by su2 suppressor. Three types of reversions were isolated in the course of the selection for Ts+ character, namely, intragenic reversions and two types of extragenic reversions, located at different regions of the bacterial chromosome. The mutation N5, located between 0 and 15 min. on the map, increases practically to normal the amount of RNA polymerase beta-polypeptide, which is diminished as a result of ts22 amber mutation action, and increases the plating efficiency of several T4 phage amber mutants. The mutations designated as D are located on the chromosome near the spcA locus (64 min. on the E. coli map). These mutations are characterized by pleiotropic effect. They have properties of a weak suppressor increasing the efficiency of su2 action on amber mutations of E. coli and phage T4. At the same time D mutations are capable to decrease sharply the efficiency of the crosses with F' strains. Both these characters determined by D mutations do not segregate in transduction. It is suggested that the decrease of sexduction by D mutations depends on their influence on replication of episomes in the recipient cells.

Chromosome Mapping↗