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Biomedical subjects

R Curtiss

Publications and source records attributed to R Curtiss.

At least 127 records · Page 7Linked to original sources
PubMed1985

In vitro inhibition of adherence of Streptococcus mutans strains by nonadherent mutants of S. mutans 6715.

Four nonadherent mutants from Streptococcus mutans 6715 mutant UAB66 (serotype g) with similar phenotypes were shown to inhibit the adherence of adherence-proficient S. mutans serotypes c and g strains. One mutant, UAB108, was shown to inhibit adherence by wild-type strains representing serotypes a, d, and e as well. This inhibition of adherence was seen with pairs of strains grown in partially defined (PD) medium supplemented with 1% sucrose in both microtiter plates and glass tubes. The inhibiting factor was present in culture supernatant fluids of inhibiting strains grown in PD medium plus 1% sucrose and was heat stable. Ethanol precipitation of culture supernatant fluids of these strains yielded a water-soluble polymer which effectively inhibited the adherence of UAB66. This polymer, isolated from UAB108, was also shown to inhibit the adherence of UAB66 at lower concentrations than that needed to inhibit adherence with dextran T10. Partially purified glucosyltransferase, isolated from the culture supernatant fluids of glucose-grown UAB108, produced a water-soluble glucan which was shown to inhibit the adherence of UAB66 as well. The methods developed permit rapid screening for strains or mutants of strains or both that inhibit adherence or plaque formation or both by wild-type strains of S. mutans.

Adhesiveness↗
PubMed1985

Inhibition of plaque and caries formation by a glucan produced by Streptococcus mutans mutant UAB108.

A mutant (UAB108) derived from Streptococcus mutans UAB66, a spectinomycin-resistant (Spcr) isolate of strain 6715, inhibited plaque formation when grown with strain 6715 in a sucrose medium and also inhibited caries formation in gnotobiotic rats infected with both strain UAB108 and 6715. A substance obtained from UAB108 culture supernatant fluid after ethanol precipitation and DEAE-cellulose treatment, designated glucan 108, inhibited S. mutans 6715 virulence and was shown to be a water-soluble glucan. In the presence of sucrose and increasing concentrations of glucan 108, the activity of a glucosyltransferase (GTase) preparation from S. mutans 6715 to synthesize adhesive water-insoluble glucan (ad-WIG) was inhibited, and the activity to synthesize non-ad-WIG was stimulated. Glucan 108 similarly inhibited sucrose-dependent adherence of heat-treated cells, was a poor inducer of cell aggregation, and inhibited S. mutans 6715-induced dental caries in gnotobiotic rats. In the presence of GTase, glucan 108, and sucrose, the glucose moiety of sucrose was found to be incorporated into glucan 108, and most of this glucose-incorporated glucan 108 was found in the non-ad-WIG fraction. The mode of inhibition of plaque formation by S. mutans 6715 appears to involve a shift from ad-WIG to non-ad-WIG formation. The water-soluble glucan 108 was found to have an approximate molecular weight of 2 X 10(6) and was hydrolyzed by fungal dextranase to yield glucans with an average molecular weight of about 1.2 X 10(4). This glucan (designated glucan 12k) was further hydrolyzed by bacterial dextranase to yield smaller glucans and oligosaccharides, but was refractile to alpha (1----3) glucanase. These results suggest that glucan 108 is a branched alpha (1----6) glucan, and it is proposed that UAB108 is defective in its ability to polymerize glucan 12k with alpha (1----3)-linked glucosyl residues.

Adhesiveness↗
PubMed1985

Molecular analysis of DNA and construction of genomic libraries of Mycobacterium leprae.

Molecular analysis of DNA from Mycobacterium leprae, "Mycobacterium lufu," and Mycobacterium vaccae has demonstrated that the G + C (guanine plus cytosine) contents of the DNAs are 56, 61, and 65%, respectively, and that the genome sizes are 2.2 X 10(9), 3.1 X 10(9), and 3.1 X 10(9) daltons, respectively. Because of the significant differences in both G + C content and genome size among M. leprae, "M. lufu," and M. vaccae DNAs, these species are not related, although hybridization experiments under nonstringent conditions, with two separate cloned M. leprae DNA inserts as probes, indicate that there are some conserved sequences among the DNAs. The G + C content of Dasypus novemcinctus (armadillo, the animal of choice for cultivating M. leprae) DNA was determined to be 36%. Genomic libraries potentially representing more than 99.99% of each genome were prepared by cloning into the cosmid vector, pHC79, in Escherichia coli K-12. A genomic library representing approximately 95% of the genome of M. vaccae was prepared in pBR322. M. leprae DNA was subcloned from the pHC79::M. leprae library into an expression vector, pYA626. This vector is a 3.8-kilobase derivative of pBR322 in which the promoter region of the asd (aspartate semialdehyde dehydrogenase) gene from Streptococcus mutans has been inserted in place of the EcoRI-to-PstI fragment of pBR322. Several (44% of those tested) pYA626::M. leprae recombinants and one pBR322::M. vaccae recombinant synthesized new polypeptides in minicells of E. coli, indicating that mycobacterial DNA can be expressed in E. coli K-12, although expression is probably dependent upon use of nonmycobacterial promoters recognized by the E. coli transcription-translation apparatus.

Bacterial Proteins↗
PubMed1984

Temperature-dependent expression of virulence genes in Shigella species.

The pathogenicity of Shigella spp. involves the ability of the bacteria to penetrate and replicate within the epithelial cells of the large intestine. Model systems for examining the virulence of shigellae employ Henle intestinal epithelial cells in tissue culture and an in vivo assay for virulence in guinea pig eyes (Sereny test). Using these systems, we studied the genetic and physiological bases for the ability of shigellae to invade epithelial cells. We found that expression of virulence in Shigella spp. is dependent on the temperature at which the bacteria are grown. When grown at 37 degrees C, strains of Shigella flexneri 2a, Shigella sonnei, and Shigella dysenteriae 1 were fully virulent and invaded Henle cells. They also produced keratoconjunctivitis in guinea pigs. When grown at 30 degrees C, the bacteria neither penetrated Henle cells nor produced conjunctivitis in the Sereny test and were phenotypically avirulent. Strains grown at 33 degrees C were only partially invasive in the Henle assay, whereas strains grown at 35 degrees C were as invasive as strains grown at 37 degrees C. Using the Henle cell assay, we determined that the loss of ability to penetrate epithelial cells was completely reversed by shifting the growth temperature from 30 to 37 degrees C. The percentage of Henle cells invaded by bacteria increased with increasing time of growth at 37 degrees C. Restoration of invasiveness after growth at 30 degrees C required protein synthesis. When shigellae were grown at 30 degrees C and shifted to 37 degrees C for 2 h in the presence of chloramphenicol, the bacteria remained noninvasive. Similarly treated bacteria grown at 37 degrees C were still invasive. These results suggested that expression of one or more genes required for virulence of Shigella spp. are subject to regulation by growth temperature.

Animals↗
PubMed1984

Loss of pigmentation in Shigella flexneri 2a is correlated with loss of virulence and virulence-associated plasmid.

In this study, we examined the relationship between the virulence of Shigella flexneri 2a and the ability of strains of S. flexneri 2a to absorb Congo red. Spontaneous nonpigmented (i.e., unable to bind Congo red [Pcr-]) derivatives of a virulent, pigmented (Pcr+) strain of S. flexneri 2a were isolated and assayed for virulence as determined by their ability to invade epithelial cells. All Pcr- mutants examined lost the ability to invade epithelial cells and were thus avirulent. Agarose gel electrophoresis of plasmid DNA from these avirulent, Pcr- mutants showed that the majority of these strains had lost a plasmid band corresponding to a virulence-associated plasmid, pSf2a140. In many of the mutants, concomitant loss of pigmentation, virulence, and pSf2a140 was accompanied by the appearance of a new plasmid, smaller than pSf2a140. We believe these new plasmids to be deletion derivatives of pSf2a140 and that loss of pigmentation and loss of virulence are associated with deletions in pSf2a140. We transduced Pcr- mutants to Pcr+ and isolated transductants which suppressed the Pcr- phenotype. None of the Pcr+ transductants regained the ability to invade epithelial cells. Several suppressors of the Pcr- phenotype were identified as mutations in cell wall biosynthesis. These results support our belief that although pigmentation is usually associated with virulence, genetic determinants unrelated to virulence can also affect the ability of the cell to bind Congo red. Therefore, the ability of S. flexneri 2a to bind Congo red does not necessarily imply the ability to invade epithelial cells. However, loss of ability to bind Congo red is accompanied by loss of virulence.

Cell Line↗
PubMed1984

Bacteriophage Mu d1(Apr lac) generates vir-lac operon fusions in Shigella flexneri 2a.

Previous studies have demonstrated that expression of virulence in Shigella spp. is controlled by growth temperature. To study the regulation of virulence (vir) genes, we set out to develop a rapid, easily-assayed phenotype with which to measure expression of virulence. This report described a procedure for isolating vir-lac operon fusions in S. flexneri 2a by using the specialized transducing bacteriophage Mu d1(Apr lac) of Casadaban and Cohen (M. Casadaban and S. N. Cohen, Proc. Natl. Acad. Sci. U.S.A. 76:4530-4533, 1976). Mu d1(Apr lac) lysogens were isolated and screened for loss of virulence and for temperature-dependent expression of the lactose genes on Mu d1(Apr lac). A recombinant plasmid carrying the Mu immunity gene was also introduced into lysogens of interest to stabilize the Mu d1(Apr lac) insertion and prevent possible thermal induction at 37 degrees C. The mutant which we isolated failed to penetrate tissue culture cells in the assay for virulence and produced almost 15-fold more beta-galactosidase when grown at 37 degrees C than when grown at 30 degrees C. The site of insertion of Mu d1(Apr lac) in this strain was shown to be in the 140-megadalton plasmid pSf2a140, which is known to be associated with virulence. P1L4-mediated transduction of the insertion into a virulent recipient demonstrated genetic linkage of Mu d1(Apr lac) with loss of virulence and temperature-dependent expression of beta-galactosidase. All of these features fulfill the phenotype expected for a Mu d1(Apr lac)-induced vir-lac operon fusion. This mutant provides us with a means of measuring expression of a gene function required for virulence by assaying for beta-galactosidase. The insertion will also serve as a starting point for mapping of genes on pSf2a140 which are necessary for expression of virulence.

Bacteriophage mu↗
PubMed1983

Use of UV-irradiated bacteriophage T6 to kill extracellular bacteria in tissue culture infectivity assays.

We have utilized 'lysis from without' mediated by UV-inactivated bacteriophage T6 to eliminate extracellular bacteria in experiments measuring the internalization, intracellular survival and replication of Yersinia pestis within mouse peritoneal macrophages and of Shigella flexneri within a human intestinal epithelial cell line. The technique we describe has the following characteristics: (a) bacterial killing is complete within 15 min at 37 degrees C, with a greater than 10(3)-fold reduction in colony-forming units (CFU); (b) bacteria within cultured mammalian cells are protected from killing by UV-inactivated T6; (c) the mammalian cells are not observably affected by exposure to UV-inactivated T6. This technique has several advantages over the use of antibiotics to eliminate extracellular bacteria and is potentially widely applicable in studies of the interactions between pathogenic bacteria and host phagocytic cells as well as other target tissues.

Animals↗
PubMed1983

In vitro and in vivo complementation of Streptococcus mutans mutants defective in adherence.

Previous studies have shown that adherence-defective mutants of Streptococcus mutans PS14, serotype c, can be grouped into several different phenotypic groups. In this study a method was developed to test for complementation between pairs of nonadhering mutants which possess different genotypic defects. Mutant strains UAB95 and a spectinomycin-resistant derivative of UAB95 (UAB516) were found to exhibit increased levels of adherence when grown together with UAB230 in media containing sucrose as compared to the adherence of each strain grown separately. An increase in caries was also observed in gnotobiotic rats mixedly infected with the two mutants as compared to either strain alone. Tests revealed that UAB95 produced more water-insoluble glucan than its parent strain but had a defect in glucan binding. UAB230 was found to produce levels of a defective glucan that could not be bound by mutant or wild-type cells. Our results suggest that UAB95 produces a water-insoluble glucan which is bound by UAB230, thus allowing complementation for adherence and caries production.

Animals↗
PubMed1983

Expression of a Streptococcus mutans glucosyltransferase gene in Escherichia coli.

Chromosomal DNA from Streptococcus mutans strain UAB90 (serotype c) was cloned into Escherichia coli K-12. The clone bank was screened for any sucrose-hydrolyzing activity by selection for growth on raffinose in the presence of isopropyl-beta-D-thiogalactoside. A clone expressing an S. mutans glucosyltransferase was identified. The S. mutans DNA encoding this enzyme is a 1.73-kilobase fragment cloned into the HindIII site of plasmid pBR322. We designated the gene gtfA. The plasmid-encoded gtfA enzyme, a 55,000-molecular-weight protein, is synthesized at 40% the level of pBR322-encoded beta-lactamase in E. coli minicells. Using sucrose as substrate, the gtfA enzyme catalyzes the formation of fructose and a glucan with an apparent molecular weight of 1,500. We detected the gtfA protein in S. mutans cells with antibody raised against the cloned gtfA enzyme. Immunologically identical gtfA protein appears to be present in S. mutans cells of serotypes c, e, and f, and a cross-reacting protein was made by serotype b cells. Proteins from serotype a, g, and d S. mutans cells did not react with antibody to gtfA enzyme. The gtfA activity was present in the periplasmic space of E. coli clones, since 15% of the total gtfA activity was released by cold osmotic shock and the clones were able to grow on sucrose as sole carbon source.

Biological Transport↗
PubMed1982

Expression of Streptococcus mutans aspartate-semialdehyde dehydrogenase gene cloned into plasmid pBR322.

Streptococcus mutans chromosomal DNA cloned into the vector plasmid pBR322 in Escherichia coli is able to complement the metabolic defect of an aspartate-semialdehyde dehydrogenase (EC 1.2.1.11) gene (asd) deletion in the host strain. We constructed two Asd+ recombinant plasmids, pYA570 and pYA571, containing 4.7 and 4.5 kilobases, respectively, of S. mutans chromosomal DNA inserted into the HindIII restriction endonuclease site of pBR322 in the same orientation. The S. mutans UAB62 Asd+ DNA did not hybridize with E. coli DNA which contained an intact asd gene, but did not hybridize with S. mutans UAB62 chromosomal DNA. Derivative Asd+ plasmids were then constructed from pYA570. One, pYA574, had a 4.5 kilobase S. mutans insert DNA in the opposite direction from pYA570. In another pYA575, the S. mutans insert DNA was reduced in size to 1.3 kilobases. It was seen that the orientation of the S. mutans DNA fragment inserted into the promotor region of the pBR322 tetracycline resistance (Tcr) gene affected expression of Tcr. Orientation of the S. mutans insert also affected the stability of the plasmid in certain E. coli strains. Restriction maps for pYA570, pYA571, pYA574 and pYA575 using the endonucleases EcoRI, BamHI, HindIII, PstI and SalI were determined, Asd+ plasmid-directed protein synthesis was studied in E. coli minicells. The plasmids pYA570, pYA574 and pYA575 each produced large amounts of a protein with a monomeric molecular weight of about 45000, that was distinct from both pBR322 and E.coli specified proteins: this protein is the S. mutans asd gene product. Smaller derivatives of recombinant plasmid pYA575 that were Asd- allowed the location of the S. mutans asd gene promotor and the direction of transcription to be determined.

Aspartate-Semialdehyde Dehydrogenase↗
PubMed1982

Streptococcus mutans genes that code for extracellular proteins in Escherichia coli K-12.

Chromosomal DNA from Streptococcus mutans 6715 (serotype g) was cloned into Escherichia coli K-12 by using the cosmid pJC74 cloning vector and a bacteriophage lambda in vitro packaging system. Rabbit antiserum against S. mutans extracellular proteins was used for immunological screening of the clone bank. Twenty-one clones produced weak to strong precipitin bands around the colonies, but only after the lambda c1857 prophage was induced by being heated to lyse the E. coli cells. None of the clones expressed enzyme activity for several known S. mutans extracellular enzymes. One of these clones contained a 45-kilobase recombinant plasmid designated pYA721. An 8.5-kilobase fragment of S. mutans DNA from pYA721 was isolated and recloned into the BamHI restriction site of the plasmid vector pACYC184 to construct pYA726. pYA726 contained all, or nearly all, of the gene for a surface protein antigen (the spaA protein) of S. mutans 6715. This was deduced from immunological studies in which extracts of cells harboring pYA726 reacted with antisera against both purified 6715 spaA protein (about 210,000 daltons) and the immunologically similar antigen I/II of serotype c strains of S. mutans. In addition, the S. mutans spaA protein was found to possess at least one antigenic determinant not present on the protein specified by pYA726. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of E. coli clone extracts revealed that pYA726 produced a polypeptide with a molecular mass of about 180,000 daltons which was predominantly found in the periplasmic space of E. coli cells. Antisera to the spaA protein of S. mutans reacted with extracellular protein from representative strains of S. mutans serotypes a, c, d, e, f, and g, but not b.

Antigens, Bacterial↗