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Biomedical subjects

D Figurski

Publications and source records attributed to D Figurski.

10 recordsLinked to original sources
PubMed2001

Colonization and persistence of rough and smooth colony variants of Actinobacillus actinomycetemcomitans in the mouths of rats.

Fresh isolates of Actinobacillus actinomycetemcomitans (Aa) bind avidly to surfaces in vitro, but existing in vivo studies of the adherence of Aa are limited. This study had two goals: (1) to compare the oral colonization of two isogenic strains of Aa-CU1010, a clinical isolate that expresses the adherent phenotype, and CU1012, a minimally adherent laboratory variant-and (2) to check for phenotypic reversion of these strains in a clinical setting. Rifampicin-resistant strains, developed for tracking in Sprague-Dawley rats, were tested in vitro to determine their stability and binding. In study 1, after antibiotic suppression, six rats (group I) received CU1010 in their feed. The eight rats in group II received CU1012 in their feed and four were supplemented by oral swabbing and four by gastric gavage. Group III consisted of three sham-inoculated controls. All rats were inoculated for 4 days. Microbiological data were collected at 1, 4 and 8 weeks after inoculation. Supporting data were supplied by antibody titres and clinical measures of alveolar bone loss. Study 2 consisted of six rats in each of three groups as above, but tagged strains of Aa were delivered by food alone. At all time-points in both studies, Aa was absent before inoculation and controls had no Aa or antibody to Aa. In study 1, all six rats in group I yielded positive cultures for Aa at 8 weeks. In group II, five of eight had positive cultures for Aa at 1 week, two of eight at 4 weeks and none had Aa at 8 weeks (P < or =0.001). All six rats in group I had serum anti-Aa titres compared to group II, where titres were seen in four of eight rats (P < or =0.015). In vitro data paralleled those found in vivo. No phenotypic reversion of either strain was seen in vivo. In study 2, four of six rats in group I showed Aa and had titres to Aa, while no other animals showed Aa at any time. The model provides convincing evidence that, unlike laboratory variants, clinical isolates colonize, persist and integrate into an already established, albeit reduced, econiche.

Actinobacillus Infections↗
PubMed1986

Structure and regulation of the anthranilate synthase genes in Pseudomonas aeruginosa: II. Cloning and expression in Escherichia coli.

The genes for the large and small subunits of anthranilate synthase (trpE and trpG, respectively) have been cloned from Pseudomonas aeruginosa PAC174 into E. coli by R-prime formation with the broad-host-range plasmid R68.44. Sequential subcloning into plasmid vectors reduced the active Pseudomonas DNA fragment to a length of 3.1 kb. We obtained evidence that this region contains the promoter for its own expression and retains a vestigial regulatory response to tryptophan scarcity or excess.

Anthranilate Synthase↗
PubMed1977

Physical and genetic studies with restriction endonucleases on the broad host-range plasmid RK2.

The cleavage map of the plasmid RK2 was determined for the five restriction endonucleases EcoRI, HindIII, BamH-I, SalI and HpaI. DNA has been inserted into several of these sites and cloned in Escherichia coli. Efforts to obtain derivatives of RK2 reduced in size by restriction endonuclease digestion of the plasmid were not successful and indicated that genes required for the maintenance of this plasmid in E. coli are not tightly clustered. An RK2 derivative possessing an internal molecular rearrangement was obtained by transformation with restriction endonuclease digests of the plasmid.

DNA Replication↗
PubMed1977

Bidirection replication from a unique origin in a mini-F plasmid.

Replicating molecules of the mini F-kanamycin resistance plasmid, pML31, derived from F'lac, have been isolated from Escherichia coli as covalently-closed circular DNA molecules. These molecules were examined in the electron microscope after digestion with either EcoRI or BamHI restriction endonuclease. The structure of the majority of the molecules replicating was consistent with a bidirectional mode of replication starting at a unique origin on the F-fragment. This origin is located approximately 2.3 kilobases from one of the EcoRI sites. Orientation of the F-fragment relative to the physical map of F showed the position of the origin to be at 42.6 kilobases. A small proportion of molecules appeared to be replicating unidirectionally in either direction from this origin. Termination of replication of pML31 apparently occurs in the fragment containing the locus for kanamycin resistance in a unique region opposite the origin in the circular DNA molecule.

DNA Replication↗
PubMed1976

Generation in vitro of deletions in the broad host range plasmid RK2 using phage Mu insertions and a restriction endonuclease.

Several non-lethal deletions of the broad host range plasmid RK2 (molecular weight of 37.6 . 10(6) have been produced in vitro. The method employed relied on the single HindIII restriction nuclease site in RK2 and the ability of phage Mu to insert and thereby add new HindIII restriction sites at various positions in the plasmid. The deleted plasmids have in each case lost kanamycin (Km) resistance, and in two cases are defective in self-transmissibility. The method used to reduce the size of the RK2 plasmid also results in the cloning of each of the two ends of the Mu phage DNA on the plasmid derivatives.

Ampicillin↗
PubMed1976

Electron microscope study of a plasmid chimera containing the replication region of the Escherichia coli F plasmid.

pML31, a plasmid chimera constructed to contain the replication genes of an Flac plasmid, has been studied by electron microscope methods. Heteroduplex analysis shows that the only F sequence present in pML31 is that with corrdinates 40.3-49.3F. This region has previously been identified as essential for plasmid maintenance. The sequence of pML31, which was derived originally from R6-5, carries the km gene(s) and an inverted duplication of a 1.0-kilobase sequence. On the basis of length measurements, the repeated sequence is different from IS1, IS2, IS3, and an inverted repeat associated with the km gene(s) of plasmid JR67.

Base Sequence↗
PubMed1975

Molecular vehicle properties of the broad host range plasmid RK2.

The pladmid RK2 is stably maintained in a broad range of gram-negative bacteria. The RK2 DNA has a single Eco RI restriction site. The insertion of a DNA fragment into this site does not interfere with either plasmid maintenance or self-transmissibility. Because RK2 has a broad host range, it should be useful for the construction in vitro of hybrid plasmid molecules capable of being established by conjugal transfer or transformation into many genera of gram-negative organisms.

Conjugation, Genetic↗