Search PubMed⌕ Search

Biomedical subjects

N Datta

Publications and source records attributed to N Datta.

At least 73 records · Page 4Linked to original sources
PubMed1978

Copy numbers of coexisting plasmids in Escherichia coli K-12.

A strain of Escherichia coli K-12 carrying eight compatible and distinguishable plasmids was constructed. The amounts of plasmid DNA (measured as supercoiled molecules) per chromosome in this strain was about equal to the sum of the plasmid DNAs, extracted under controlled conditions, from strains each carrying one of the eight plasmids. Analysis of these DNA preparations showed that each plasmid in the multiplasmid strain was present in the same proportion per chromosome as in the single-plasmid strains. Also the level of phenotypic expression of each plasmid in the multiplasmid strain was the same as in the single-plasmid strains. Each plasmid, therefore, appears to control its own copy number irrespective of the presence of other compatible plasmids.

Conjugation, Genetic↗
PubMed1977

Two naturally occurring transposons indistinguishable from Tn7.

Two plasmids from different sources, determining trimethoprim and streptomycin resistances, harbour transposons which we designate Tn71 and Tn72. These transposons are indistinguishable from Tn7 in the resistances determined, in their molecular masses and in the number and relative positions of their sites susceptible to the restriction enzymes EcoRI, HindIII and BamHI. We conclude that Tn7 has been naturally spread among plasmids.

Base Sequence↗
PubMed1976

Plasmid-determined beta-lactamase indistinguishable from the chromosomal beta-lactamase of Escherichia coli.

A plasmid, derived from a naturally occurring strain of Proteus mirabilis, conferred resistance to cephalosporins, apparently mediated by a beta-lactamase indistinguishable from that determined by the chromosomal gene of Escherichia coli K-12. There was evidence for a recombination event between the wild-type plasmid and a defective F factor (Fsp) in the Escherichia coli K-12 culture in which it was stored.

Cephalosporins↗
PubMed1976

Compatibility properties of R483, a member of the I plasmid complex.

R483, an I pilus-determining plasmid previously reported as belonging to a distinct incompatibility group Ibeta, proved to be an atypical Ialpha plasmid; in a growing culture, the degree of inhibition of replication of one Ialpha plasmid by the presence of another was not uniform within the Ialpha group.

Colicins↗
PubMed1976

Transposition of a deoxyribonucleic acid sequence encoding trimethoprim and streptomycin resistances from R483 to other replicons.

R483, a plasmid of the Ialpha incompatibility group, contained a deoxyribonucleic acid (DNA) sequence encoding resistance to trimethoprim (TpR) and streptomycin (SmR) that could be transposed to other replicons, i.e., to the Escherichia coli chromosome and to related and unrelated plasmids. Each transposition resulted in the acquisition by the recipient replicon of a segment of DNA of about 9 X 10(6) daltons, both resistance genes, but never the colicin Ia or pilus genes of R483. Transposition took place at a single chromosomal site between dnaA and ilv and did not suppress the DnaA phenotype, in contrast to integration of the whole R483 plasmid. The chromosome, having received the transposition, could secondarily act as a transposition donor to another plasmid. Such a plasmid was indistinguishable from one having received a direct transposition from R483. TpR SmR transposition was very site specific and did not require a functional recA+ gene. We postulate that the TpR SmR segment of R483 is a transposon (TnC) with specific boundary sequences.

Base Sequence↗
PubMed1975

Properties of plasmids produced by recombination between R factors of groups J and FII.

Recombinant plasmids have been produced both by transduction of genetic material from FIIR factors into Proteus mirabilis strains carrying plasmids of group J and by insertion of a transposon conferring streptomycin and trimethoprim resistances into a J group R factor. The transposon-carrying derivative and one of the transductants were shown to be members of group J whereas another transductant was shown to be compatible with members of this group. This recombinant plasmid was able to eliminate but not to be eliminable by R factors of group FII. A model for the origin of this anomalous compatibility characteristic is presented based on the assumption that the recombinant plasmid carries part but not all of a complex of binding sites for the repressor of replication [Uhlin and Nordström (1975)].

Chromosome Mapping↗
PubMed1975

Infection caused by Proteus mirabilis strains with transferrable gentamicin-resistance factors.

During a period of 10 weeks, four patients in one hospital became infected with gentamicin-resistant Proteus mirabilis. In two of them septicaemia associated with indwelling catheters developed, one had urinary tract and wound infections, and in the fourth patient the organism was isolated from a superficial wound. The P. mirabilis strains showed multiple drug resistance. Strains form the first three patients were apparently identical and were sensitive to tobramycin. Their gentamicin resistance was not transferable to Escherichia coli K12, but could be transferred to another strain of P. mirablilis (PM13-3). The fourth strain was resistant to tobramycin; its gentamicin/tobramycin resistance was transferable to E. coli K12.

Anti-Bacterial Agents↗
PubMed1975

R factors from Serratia marcescens.

In recent years, Serratia marcescens has become established in certain localities as an agent of hospital infection and cross-infection (Clayton & von Graevenitz, 1966; Wilfert, Barrett & Kass, 1968; Davis, Foltz & Blakemore, 1970; Wilkowske, Washington, Martin & Ritts, 1970). In general, strains of S. marcescens isolated from infective lesions differ from those from other sources in being non-pigmented and antibiotic resistant (Ewing, Johnson & David, 1962; Clayton & von Graevenitz, 1966). Medeiros & O'Brien (1969) and Schaefler et al. (1971) described strains of S. marcescens, isolated from hospital patients, which were able to transfer R factors to Escherichia coli. Transfer of resistance to E. coli has also been reported from strains of S. marcescens isolated in France (Grimont & Dulong de Rosnay, 1972; Scavizzi, 1972; Lemosquet-Villemon, Morel & Freymuth, 1973)9 We have collected strains of S. marcescens, most, but not all, clinical isolates, from widely separate geographical areas; each strain was tested for antibiotic resistance and for R factors transmissible to E. coli K129 The R factors were classified by compatibility in K12 (Datta, 1974). Our purpose was to find out how much of the antibiotic resistance observed in S. marcescens is characteristic of that genus and to what extent it is shared with other bacterial genera (Coetzee, Datta & Hedges, 1972; Datta & Hedges, 1972a; Hedges, 1974). The R factors described by Medeiros & O'Brien (1969) and Lemosquet-Villemon et al. (1973) were included in this study.

Anti-Bacterial Agents↗