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B B Magee

Publications and source records attributed to B B Magee.

33 records · Page 2Linked to original sources
PubMed1989

Genetic differences between type I and type II Candida stellatoidea.

Genetic similarities and differences between type I and type II Candida stellatoidea were studied. The electrophoretic karyotype, mitochondrial DNA (mtDNA) restriction patterns, and midrepeat sequence of nuclear DNA in type I C. stellatoidea were clearly distinguishable from those of a reference culture of Candida albicans. The karyotype and the major bands of the midrepeat sequence of type II C. stellatoidea were indistinguishable from those of the reference C. albicans. The mtDNA restriction patterns of four type I isolates were homogeneous regardless of the endonucleases and probes used. The mtDNA restriction patterns of type II C. stellatoidea varied from strain to strain. Some of them were identical to that of C. albicans, while others were the same as that of type I C. stellatoidea. Immunofluorescence with C. albicans serotype A-specific monoclonal antibody indicated that the four isolates of type I C. stellatoidea were serotype B (non-A), whereas all three type II isolates studied were serotype A. Taken together, these results support the hypothesis that the isolates of C. stellatoidea type II studied are sucrose-negative mutants of serotype A C. albicans. Since C. stellatoidea type I differs from C. albicans in several major genetic characteristics, it cannot be viewed as a simple mutant derived from C. albicans. Hybrids produced by protoplast fusion of type I and type II cells were capable of assimilating sucrose, indicating that the sucrose-negative phenotypes of the parents are due to different mutations.

Candida↗
PubMed1989

Separation of chromosomes of Cryptococcus neoformans by pulsed field gel electrophoresis.

Chromosomes from Cryptococcus neoformans, an encapsulated yeast pathogen, were separated by contour-clamped homogeneous field gel electrophoresis. Seven strains representing all four serotypes were studied. It was found that each strain had a unique, reproducible pattern of chromosome bands which could potentially be used for strain polymorphism studies. There were between 10 and 12 chromosomes in the strains studied, with an approximate genomic size of 15,000 to 17,000 kilobases. Chromosome separation also could be used to assign locations for cloned genes, and the ribosomal DNA genes were found on one of the larger C. neoformans chromosomes. The technique of electrophoretic karyotyping should be helpful for genetic and molecular investigations into the biology of C. neoformans.

Candida albicans↗
PubMed1988

Opaque-white phenotype transition: a programmed morphological transition in Candida albicans.

This paper reports that the opaque and white phenotypes of Candida albicans constitute a true high-frequency reversible transition system. The rDNA restriction fragment and orthogonal field alternating gel electrophoresis profiles of opaque and white phenotypes are indistinguishable, and a genetic marker introduced into a white strain is present in all opaque derivatives of this strain. Opaque and white derivatives appear markedly different on a bismuth indicator medium and differ in a number of other respects. We have used bismuth medium to examine the spontaneous and temperature-induced frequencies of transition from opaque to white. The temperature-induced transition from opaque to white does not occur when opaque cells are held in water.

Candida albicans↗
PubMed1988

Assignment of cloned genes to the seven electrophoretically separated Candida albicans chromosomes.

By using orthogonal-field alternating gel electrophoresis (OFAGE), field-inversion gel electrophoresis (FIGE), and contour-clamped homogeneous field gel electrophoresis (CHEF), we have clearly resolved 11 chromosomal bands from various Candida albicans strains. OFAGE resolves the smaller chromosomes better, while FIGE, which under our conditions causes the chromosomes to run in the reverse order of OFAGE, is more effective in separating the larger chromosomes. CHEF separates all chromosomes under some conditions, but these conditions do not often resolve homologs. The strains examined are highly polymorphic for chromosome size. Fourteen cloned Candida genes, isolated on the basis of conferral of new properties to or complementation of auxotrophic deficiencies in Saccharomyces cerevisiae, and three sequences of unknown function have been hybridized to Southern transfers of CHEF, FIGE, and OFAGE gels. Four sets of resolvable bands have been shown to be homologous chromosomes. On the basis of these data, we suggest that C. albicans has seven chromosomes. Genes have been assigned to the seven chromosomes. Two chromosomes identified genetically have been located on the electrophoretic karyotype.

Candida albicans↗
PubMed1987

Electrophoretic karyotypes and chromosome numbers in Candida species.

The electrophoretic karyotypes of five Candida albicans isolates and of five other Candida species have been determined, using orthogonal field alternating gel electrophoresis (OFAGE). None of the C. albicans isolates had the same electrophoretic karyotype. By comparing all five strains, we arrived at a chromosome number of nine to ten, but since the organism is diploid, we cannot distinguish genetically different chromosomes from homologues which resolve. We determined minimal chromosome numbers of 9 for Candida stellatoidea, 10 for C. glabrata and 6 for C. guilliermondii.

Candida↗
PubMed1987

Strain and species identification by restriction fragment length polymorphisms in the ribosomal DNA repeat of Candida species.

Restriction fragment length polymorphisms in the ribosomal DNA (rDNA) have been shown to be a useful criterion for distinguishing among various isolates of Candida albicans. In a sample of 12 clinical isolates, we found six different classes based on variations in the fragments produced from genomic DNA by EcoRI and visualized after Southern transfer by being probed with a plasmid containing Saccharomyces cerevisiae rDNA. Some of the classes appeared to be heterozygous at the rDNA locus. Similar digestion of other Candida species showed that each could be identified on the basis of its restriction patterns. Since these are highly reiterated genes, the differences were apparent on ethidium bromide-stained gels; Southern transfers were not necessary. EcoRI restriction maps of the rDNA of C. albicans, C. stellatoidea, C. tropicalis, and C. guilliermondii were determined.

Candida↗
PubMed1983

Construction of a new yeast cloning vector containing autonomous replication sequences from Candida utilis.

DNA sequences from the Candida utilis genome which, when cloned into a yeast integration plasmid (YIp5), confer on YIp5 the ability to replicate autonomously in Saccharomyces cerevisiae are described. Several recombinant plasmids which transform S. cerevisiae YNN27 to Ura3+ with an efficiency of 2 X 10(3) transformants per microgram of DNA were obtained. One of the recombinant plasmids, pHMR22 (6.6 kilobases) contains ars (autonomous replication sequence), which is homologous with two different DNA fragments of the C. utilis genome but has no detectable homology to total DNA from Candida albicans, Pachysolen tannophilus, or S. cerevisiae. Restriction and subcloning analyses of pHMR22 showed that Sau3A destroys the functions of cloned ars whereas there are no BamHI, PstI, SalI, HindIII, EcoRI, or PvuII sites in the region of ars which is required for its functional integrity. Thus, pHMR22 appears to be a useful vector for cloning desired genes in S. cerevisiae.

Base Sequence↗
PubMed1977

The structure of chromatin: interaction of ethidium bromide with native and denatured chromatin.

The binding of ethidium bromide, as monitored by fluorescence enhancement, to chromatin prepared by nuclease digestion has been compared with the binding of the dye to sheared chromatin. The nuclease preparation (native chromatin) is characterized by a high affinity region of the Scatchard plot (r = 0-0.025, K1 = 1 X 10(6) M-1), a transition (r = 0.025-0.05), and a low affinity region (r = 0.05-0.12, K2 = 3 X 10(5) M-1). The final amount of ethidium bromide bound per base is 0.12 as compared with 0.20 for free DNA. Sheared chromatin has the two regions of high and low affinity (K1 = 2 X 10(6) M-1, K2 = 5 X 10(5) M-1) as originally shown by Angerer and Moudrianakis (1972), but the transition is much reduced or absent. Binding of the dye to native chromatin is independent of salt at concentrations ranging from 0.2 mM EDTA to 10 mM Tris-Cl, 10 mM NaCl, 0.2 mM EDTA, while sheared chromatin and DNA both bind ethidium bromide electrostatically as well as by intercalation at the low salt concentration, leading to extensive energy transfer. Thus the phosphate groups in native chromatin are unavailable to external cations even at very low salt. Polarization of fluorescence of ethidium bromide intercalated into native chromatin at low r is very high, indicating a highly rigid structure. As r approaches 0.02, there is a very rapid depolarization; at r = 0.03, the polarization is no greater than that of the dye intercalated into DNA. Depolarization is not due to energy transfer. The Scatchard plot derived for the bulk preparation of native chromatin is very similar to the one derived for the monomer nu body. These results indicate that the DNA in native chromatin is in a very rigid form, with its phosphate anions neutralized by structural components, not by free salt. Ethidium bromide intercalation appears partially to disrupt this structure, perhaps by unwinding, leading to slight changes in its properties.

Binding Sites↗
PubMed1975

Separation of lymphocyte chromatin into template-active fractions with specificity for eukaryotic RNA polymerase II or prokaryotic RNA polymerase.

When chromatin prepared from WI-L2 lymphocytes by low salt extraction and shearing is centrifuged on a glycerol gradient, one area of the gradient yields chromatin enriched in template activity for Escherichia coli DNA-dependent RNA polymerase (EC 2.7.7.6; nucleosidetriphosphate:RNA nucleotidyltransferase) as compared to Saccharomyces cerevisiae RNA polymerase II (or B). Another area yields chromatin preferred by the eukaryotic enzyme. Kinetic studies indicate that the differences in activity cannot be explained by differences in affinity of the enzymes for the various templates. The DNA isolated from either fraction has a molecular weight of 8.5 X 106. The "yeast active" fraction seems enriched in proteins. Mixing experiments indicate that the yeast enzyme does not alter the template in such a way as to improve it for the bacterial enzyme.

Cell Line↗
PubMed1974

Isolation and partial characterization of a temperature-sensitive Escherichia coli mutant with altered glutaminyl-transfer ribonucleic acid synthetase.

A temperature-sensitive mutant of Escherichia coli has been found in which the conditional growth is a result of a thermosensitive glutaminyl-transfer ribonucleic acid synthetase. The corresponding genetic locus glnS is cotransduced with lip. In a strain containing the mutationally altered glutaminyl-transfer ribonucleic acid synthetase, no derepression of the enzyme itself nor of glutamine synthetase was observed.

Acylation↗
PubMedDate not supplied

Use of rDNA restriction fragment length polymorphisms to differentiate strains of Candida albicans in women with vulvovaginal candidiasis.

Epidemiologic studies in women with recurrent Candida vaginitis have been hampered in the past by the lack of a reproducible typing system. Several molecular probes have now been developed that have the ability to differentiate strains of Candida albicans and give reproducible results. In this investigation, 24 women with Candida vaginitis were studied in a longitudinal fashion for 30 days following short-course antifungal therapy. Seven women with either recurrent vaginitis or with multiple culture-positive sites with C. albicans were included in an epidemiological study. A total of 18 isolates of C. albicans (12 vaginal and six rectal) were typed utilizing restriction fragment length polymorphisms of rDNA. This technique was able to differentiate five different strains of C. albicans. Our epidemiologic study revealed that vaginal and rectal strains recovered from the same women were usually different. None of our patients had a similar vaginal and rectal strain prior to treatment, and only one patient had the same strain isolated from both the rectum and the vagina at the time of recurrence. On the other hand, we found that the same strain of C. albicans was initially and later recovered from the vagina in four of five women who failed treatment or developed recurrent vaginitis. These results suggest that recurrent episodes of C. albicans vaginitis, following short-course antifungal therapy, are often due to relapse of the original infecting strain and not due to autoinoculation from the rectum.(ABSTRACT TRUNCATED AT 250 WORDS)

Candida albicans↗
PubMedDate not supplied

Person-to-person transfer of Candida albicans in the spacecraft environment.

We assessed the exchange of Candida albicans among crew members during 10 Space Shuttle missions. Throat, nasal, urine and faecal specimens were collected from 61 crew members twice before and once after space flights ranging from 7 to 10 days in duration; crews consisted of groups of five, six or seven men and women. Candida albicans was isolated at least once from 20 of the 61 subjects (33%). Candida strains were identified by restriction-fragment length polymorphism (RFLP) after digestion by the endonucleases EcoRI and HinfI; further discrimination was gained by Southern blot hybridization with the C. albicans repeat fragment 27A. Eighteen of the 20 Candida-positive crew members carried different strains of C. albicans in the specimens collected. Possible transfer of C. albicans between members of the same crew was demonstrated only once in the 10 missions studied. We conclude that the transfer of C. albicans among crew members during Space Shuttle flights is less frequent than had been predicted from earlier reports.

Candida albicans↗
PubMedDate not supplied

Chromosome reorganization in Candida albicans 1001 strain.

The karotype of Candida albicans 1001, a pathogenic isolate, presents two additional chromosome bands when compared with C. albicans 1006 strain. These two bands were a 2600 kb chromosome located between chromosome group 1-R and chromosome 2 (named chromosome 2*) and a 710 kb small chromosome, called snc due to its similarity in size to the supernumerary chromosome in strain WO-1. A comparison of karyotypes of strains 1001, 1006 and WO-1 has enabled us to conclude that chromosomes 2 and 7 are involved in such a reorganization giving rise to the new chromosome bands of strain 1001. We describe a tentative physical map of C. albicans 1001 based on the previously outlined map of C. albicans strain 1006.

Candida albicans↗