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D J Leblanc

Publications and source records attributed to D J Leblanc.

12 recordsLinked to original sources
PubMed2001

Nucleotide sequence and analysis of conjugative plasmid pVT745.

The complete nucleotide sequence and genetic map of pVT745 are presented. The 25-kb plasmid was isolated from Actinobacillus actinomycetemcomitans, a periodontal pathogen. Two-thirds of the plasmid encode functions related to conjugation, replication, and replicon stability. Among potential gene products with a high degree of similarity to known proteins are those associated with plasmid conjugation. It was shown that pVT745 derivatives not only mobilized a coresident nontransmissible plasmid, pMMB67, but also mediated their own conjugative transfer to different A. actinomycetemcomitans strains. However, transfer of pVT745 derivatives from A. actinomycetemcomitans to Escherichia coli JM109 by conjugation was successful only when an E. coli origin of replication was present on the pVT745 construct. Surprisingly, 16 open reading frames encode products of unknown function. The plasmid contains a conserved replication region which belongs to the HAP (Haemophilus-Actinobacillus-Pasteurella) theta replicon family. However, its host range appears to be rather narrow compared to other members of this family. Sequences homologous to pVT745 have previously been detected in the chromosomes of numerous A. actinomycetemcomitans strains. The nature and origin of these homologs are discussed based on information derived from the nucleotide sequence.

Aggregatibacter actinomycetemcomitans↗
PubMed1995

Transcriptional analysis of rolling circle replicating plasmid pVT736-1: evidence for replication control by antisense RNA.

Several plasmids have been described in Actinobacillus actinomycetemcomitans, a gram-negative coccobacillus. Recently, the nucleotide sequence of pVT736-1, a cryptic plasmid of A. actinomycetemcomitans VT736, was determined. This plasmid possesses all the features necessary for rolling circle replication. The present study involved a transcriptional analysis of pVT736-1. Results of Northern (RNA) blot analyses and primer extension studies indicated that the two open reading frames identified in pVT736-1 are each preceded by at least one promoter. Expression of these promoters varied with growth phase. In addition, an antisense RNA (Cop RNA) appeared to control the synthesis of the putative replication protein. To our knowledge, this is the first rolling circle replicating plasmid isolated from a gram-negative organism that has been subjected to such detailed analysis.

Aggregatibacter actinomycetemcomitans↗
PubMed1988

Transposon Tn916 mutagenesis in Bacillus anthracis.

Mutagenesis of Bacillus anthracis by the streptococcal tetracycline resistance transposon Tn916 is described. Tn916 was transferred from Streptococcus faecalis DS16C1 to B. anthracis VNR-1 by conjugation in a standard filter mating procedure. Tetracycline-resistant (Tcr) transconjugants were obtained at a frequency of 1.6 X 10(-8) per donor CFU. When donor and recipient cells were treated with nafcillin before conjugation, the frequency was increased nearly 10-fold. Nafcillin pretreatment of donor and recipient strains was used in all subsequent conjugation experiments. S.faecalis CG110, containing multiple chromosomal insertions of Tn916, transferred the transposon to B. anthracis VNR-1 at a frequency of 9.3 x 10(-5). A Tcr B. anthracis transconjugant, strain VNR-1-tet-1, transferred Tn916 to B. anthracis UM23-1 and Bacillus subtilis BST1 at frequencies of 2.1 x 10(-4) and 5.8 X 10(-6), respectively. The transfer of Tn916 occurred only on membrane filters, since no Tcr transconjugants were obtained when strains VNR-1-tet-1 and UM23-1 were mixed and incubated in broth culture. The presence of the Tn916-associated tetM gene in Tcr B. anthracis and B. subtilis transconjugants was confirmed in hybridization experiments by using a 5-kilobase-pair DNA fragment containing the tetM gene as a probe. Of 3,000 B. anthracis UM23-1 Tcr transconjugants tested, 21 were phenylalanine auxotrophs and 2 were auxotrophic for phenylalanine, tyrosine, and tryptophan.

Bacillus anthracis↗
PubMed1986

Related structures in the plasmid profiles of Bifidobacterium longum.

The plasmid profiles of 123 strains of B. longum were examined with the Southern blot-hybridization technique to reveal the existence of related structures. B. longum is the apparently unique species among those commonly found in man, which harbours extrachromosomal elements. Seven different structures were found and their frequency and distribution given. Twelve strains were used a source of probes in the hybridization experiments.

Bifidobacterium↗
PubMed1986

Related structures in the plasmid profiles of Bifidobacterium asteroides, B. indicum and B. globosum.

Seventy strains of B. asteroides isolated from the honey bees Apis mellifera and A. cerana raised in 15 different countries, 73 strains of B. indicum from Apis dorsata and A. cerana from The Philippines and 28 strains of B. globosum isolated from feces of various animals and sewage, were studied for the existence of related structures among their plasmid complements with the Southern blot-hybridization technique. Thirteen different structures were found in B. asteroides and three in B. indicum and B. globosum. A total of twenty five strains were used as source of probes in the hybridization experiments.

Animals↗
PubMed1984

Physical and genetic analyses of streptococcal plasmid pAM beta 1 and cloning of its replication region.

Plasmid pAM beta 1, originally isolated from Streptococcus faecalis DS5, mediates resistance to the MLS (macrolide, lincosamide, and streptogramin B alpha) group of antibiotics. A restriction endonuclease map of the 26.5-kilobase (kb) pAM beta 1 molecule was constructed by using the enzymes AvaI, HpaII, EcoRI, PvuII, Kpn1, BstEII, HpaI, HhaI, and HindIII. A comparison of this map to those of four independently isolated deletion derivatives of pAM beta 1 located the MLS resistance determinant within a 2-kb DNA segment and at least one conjugative function within an 8-kb region. The 5.0-kb EcoRI-B fragment from pAM beta 1 was ligated onto the 4.0-kb Escherichia coli plasmid vector, pACKC1, and used to transform E. coli HB101. The 9.0-kb chimeric plasmid was then used to transform Streptococcus sanguis Challis with concurrent expression of the E. coli kanamycin resistance determinant. The 5.0-kb EcoRI-B fragment from pAM beta 1 was subsequently used as a vector to clone a streptomycin resistance determinant from a strain of Streptococcus mutans containing no detectable plasmid DNA. Subcloning experiments, using a HindIII partial digest of pAM beta 1 DNA, narrowed the replication region of this plasmid to a 2.95-kb fragment.

Cloning, Molecular↗
PubMed1982

Plasmids in the genus Bifidobacterium.

A total of 1461 bacterial isolates, representing 24 different species of the genus Bifidobacterium, were examined for the presence of plasmid DNA. Approximately 20% of the isolates contained detectable plasmids, but only four species were presented: B. longum, the predominant bifid species in the human intestine; B. globosum, the most common in animals; and B. asteroides and B. indicum, species found exclusively in the intestines of western and asiatic honey bees, respectively. Multiple plasmids were common among isolates of B. longum and B. asteroides, while all plasmid-bearing isolates of B. globosum and 60% of B. indicum isolates contained only one plasmid each. Certain multiple plasma profiles were predominant among the B. longum and B. asteroides isolates.

Actinomycetaceae↗
PubMed1979

Rapid screening procedure for detection of plasmids in streptococci.

An enrichment procedure, yielding plasmid deoxyribonucleic acid preparations normally containing less than 5% chromosomal contamination, has been devised for the isolation of plasmids from virtually all species of streptococci. The procedure is rapid, reproducible, and inexpensive, requiring no radioisotopes or density gradient centrifugation. The procedure can be used for routine screening of several hundred isolates in a short period of time, and plasmids obtained from 10- to 20-ml cultures can readily be visualized in agarose gels.

DNA, Bacterial↗
PubMed1978

Transformation of group F streptococci by plasmid DNA.

When the Challis strain of Streptococcus sanguis was transformed by the 17 megadalton beta plasmid from Streptococcus faecalis strain DS5, the plasmid underwent a 1.5 megadalton deletion (LeBlanc & Hassell, 1976). Furthermore, the covalently closed circular (CCC) plasmid DNA isolated from Challis transformants was rapidly converted to a linear form which did not possess any detectable transforming activity. To obtain stable CCC plasmid DNA a competent culture of a Lancefield group F streptococcus, strain DL8 (ATCC 12393), was used as a recipient of beta plasmid DNA. The plasmid DNA isolated from group F transformants exhibited the same configuration and size characteristics as the DS5 beta plasmid, and the CCC configuration was stable upon storage. CCC plasmid DNA from a group F transformant was biologically active and, when added to competent cultures of strain DL8, transformed them at frequencies about 100-fold greater than did beta plasmid DNA from DS5. This suggests the existence of a restriction--modification system in strain DL8.

DNA, Circular↗
PubMedDate not supplied

Scope of practice for APNs (advanced practice nurses). Discussion.

A bill for Advanced Practice Nurse (APN) Prescriptive Authority was introduced into the Michigan state legislature in 1996, and again in 1997. The legislation would add registered professional nurses with specialty certification to the list of health practitioners granted independent prescribing rights. Currently, licensed dentists, medical doctors, osteopathic doctors, podiatrists, certified optometrists and veterinarians comprise the list of prescribers.

Drug Prescriptions↗