Cooperative effects of bacterial mutations affecting lambda N gene expression. I. Isolation and characterization of a nusB mutant.
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Chromosome Mapping↗
Biomedical subjects
L S Baron
Publications and source records attributed to L S Baron.
Plasmid-determined ability of a Salmonella tennessee strain to ferment lactose and sucrose.
The ability of a Salmonella tennessee strain to ferment both lactose and sucrose was attributed to a conjugally transmissible plasmid, deoxyribonucleic acid molecular weight 164 x 10(6), bearing the genetic determinants of both fermentation characters.
Conjugation, Genetic↗
Extensive segments of the Escherichia coli K12 chromosome in Proteus mirabilis diploids.
Various Escherichia coli K12 Hfr donors transfer at low frequency portions of the E. coli genome to Proteus mirabilis. By remating such Proteus hybrids with the same or a different E. coli Hfr strain, other genetic characters could be added to yield diploid Proteus hybrids which contained more than 30 percent of the E. coli genome. The extent of the E. coli genetic material in these unstable Proteus diploid hybrids included segments with the following selected markers: gal, lac, ara, mel, mtl, and malA. Unselected markers known to map throughout this region of the chromosome were also detected in these hybrids. Among the markers expressed in Proteus hybrids with the E. coli malA region was the receptor site for coliphage lambda. Although plaques were not seen, lambda was adsorbed by the Proteus hybrids. Examination of DNA from the various Proteus hybrids by CsCl density gradient centrifugation showed a satellite component of E. coli DNA with a size that corresponded to the extent of the E. coli genome present as determined by genetic analysis.
Centrifugation, Density Gradient↗
Ineffectiveness of Vi and chemically treated endotoxins as typhoid vaccines in mice challenged with a Salmonella typhosa-Salmonella typhimurium hybrid.
Purified Vi antigen, acetic anthydride-treated Salmonella typhosa endotoxin, and potassium methylate-treated S. typhosa endotoxin employed as vaccines in Swiss white mice failed to protect these animals against challenge with a virulent S. typhimurium hybrid expressing S. typhosa antigens.
Animals↗
Characterization of transmissible genetic elements from sucrose-fermenting Salmonella strains.
Two of seven sucrose-fermenting Salmonella strains obtained from clinical sources were found capable of conjugal transfer of the sucrose fermentation (Scr+) property to the Escherichia coli K-12 strain WR3026. The genetic elements conferring this Scr+ property, designated scr-53 and scr-94, were then conjugally transmissible from Escherichia coli WR3026 Scr+ exconjugants to other strains of Escherichia coli at frequences of 5 times 10- minus 6 to 5 times 10- minus 3 for the scr-53 element and 10- minus 6 to 10- minus 5 for the scr-94 element. In Escherichia coli hosts, both of these elements were compatible with F-lac and with each of six previously characterized transmissible lac elements. No antibiotic resistance characteristics or colicin production were discovered to be associated with either scr-53 or scr-94. Neither scr element generated a male host response to the female-specific phage phiII, but the scr-53 element rendered its Escherichia coli host sensitive to the male-specific phage R-17. Escherichia coli hosts containing scr-53 were susceptible to lysis by P1vir, and transduction of the scr-53 element was accomplished with this phage. The scr-53 element was isolated from Escherichia coli WR3026, Scr+ transductants, and Escherichia coli WR2036 Scr+ exconjugants as a covalently closed circular deoxyribonucleic acid molecule with a molecular weight (determined by electron microscopy) of approximately 52 times 10-6. Receipt of the scr-94 element rendered Escherichia coli hosts of this element unsusceptible to lysis by P1vir, although adsorption of the phage by an Escherichia coli WR3026 exconjugant containing scr-94 occurred as efficiently as it did on WR3026 itself. Repeated examination of Escherichia coli strains harboring scr-94, as well as of the Salmonella strain which initially contained it, did not reveal the presence of circular deoxyribonucleic acid. The synthesis of the sucrose cleaving enzyme was inducible in Escherichia coli exconjugants containing either scr-53 or scr-94.
Centrifugation, Density Gradient↗
Homology between the deoxyribonucleic acid of fertility factor P and Vibrio cholerae chromosomal deoxyribonucleic acid.
The deoxyribonucleic acid (DNA) of the Vibrio cholerae fertility factor P was isolated by the dye-buoyant density method and hybridized to V. cholerae chromosomal DNA. The DNA of this fertility plasmid had between 35 to 40% homology with the V. cholerae chromosomal DNA. Little or no homology was detected between the P factor DNA and DNA of the Escherichia coli sex factor F.
Centrifugation, Density Gradient↗
Conservation of Salmonella typhimurium deoxyribonucleic acid by chromosomal insertion in a partially diploid Escherichia coli hybrid.
A partially diploid Escherichia coli hybrid recovered from mating with a Salmonella typhimurium donor was converted to an Hfr strain, designated WR2080, as a means to examine the manner in which the added Salmonella genetic material was conserved in it. The Salmonella argH-+, metB-+, and RHA-+ alleles contained as supernumerary genes in WR2080 were transferred together to E. coli recipients in interrupted mating experiments approximately 25 min after initial parental contact; transfer of the allelic E. coli genes by a haploid Hfr of the same transfer orientation occurred between 23.5 min (argH-+) and 25 min (rha-+) after initial contact. Entry of the E. coli ilv-+ marker of WR2080 in these experiments occurred at 29.5 min, 1.5 min later than the entry time of this marker from the haploid E. coli Hfr. When unselected inheritance of the recessive E. coli argH-minus and rha-minus alleles of WR2080 was examined among ilv-+ selected E. coli recipients in which unselected inheritance of the Salmonella donor genes was shown to be low (8%), inheritance of argH-minus was only 7%, whereas 51% inherited the neighboring rha-minus gene. In a comparative cross employing a haploid E. coli Hfr, in which rha inheritance was similar at 56%, argH inheritance was 41%. It was concluded that the Salmonella genes contained in WR2080 were conserved on a genetic segment about 1.5 min in length chromosomally inserted near the allelic E. coli genes, thus creating a duplication on that region within the hybrid chromosome.
Alleles↗
Genetic characterization of a bacterial locus involved in the activity of the N function of phage lambda.
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Chromosome Mapping↗
Intraperitoneal mouse virulence of Salmonella typhimurium hybrids expressing somatic antigen 9.
Salmonella typhimurium hybrids expressing somatic antigen 9 after mating with either S. typhosa or S. enteritidis Hfr donors did not differ from their S. typhimurium parent with respect to the number of organisms required to produce death in mice inoculated intraperitoneally.
Animals↗
Role of typhoid antigens in protection and pathogenicity for mice.
Swiss white mice immunized with acetone-killed vaccines prepared from strains of Salmonella typhosa, S. typhimurium, and mouse-virulent S. typhimurium hybrids which had acquired, by conjugal genetic transfer, the S. typhosa antigens 9, Vi, and d were challenged with the S. typhimurium hybrids and with the S. typhimurium parent strain. The results of these experiments suggested that the Salmonella somatic antigens were important in conferring protection against death in this system. The S. typhosa Vi antigen did not appear to play any significant role in this protection. The S. typhimurium hybrids employed in these studies did not show any loss of mouse virulence as the consequence of acquisition of various combinations of the S. typhosa somatic, flagella, or Vi antigens, nor did S. typhosa hybrids which had acquired the somatic antigen of S. typhimurium show any increase in mouse virulence.
Animals↗
Assay of typhoid vaccines with Salmonella typhosa-Salmonella typhimurium hybrids.
Salmonella typhimurium hybrids expressing the S. typhosa antigens 9, d, and Vi were constructed by genetic crosses with an S. typhosa Hfr donor. The hybrids retained the same degree of mouse virulence as their S. typhimurium parent strain, the minimum lethal dose being less than 50 organisms when tested either in C(57) black mice or Swiss white mice. Vaccination of the Swiss white mice with S. typhosa Ty2 vaccines prepared by acetone treatment, alcohol treatment, or heat-killing conferred significant protection against challenge by the hybrid strains but not against their S. typhimurium parent. Both the acetone-treated and alcohol-treated typhoid vaccines were markedly more protective than the heat-killed, phenol-preserved vaccine.
Animals↗
Isolation and characterization of the fertility factor P of Vibrio cholerae.
Vibrio cholerae strains with the transmissible fertility factor P contained a supercoiled circular deoxyribonucleic acid (DNA) component amounting to between 2 and 6% of the total DNA obtained from the cells. Such a component was not observed in V. cholerae strains lacking the fertility factor. This supercoiled circular DNA was isolated from P(+) cells, and the molecular weight was determined by sedimentation velocity experiments and electron microscopy to be approximately 80 million daltons. These supercoiled circular DNA molecules, which have a guanine plus cytosine (G + C) composition of 42%, were concluded to be the extrachromosomal P factor. It was calculated that there is approximately one copy of the P factor per chromosome. A small amount of supercoiled circular DNA was occasionally isolated from the P(-) strains of V. cholerae. The function of this component, which has a molecular weight of 40 million daltons, is not known. The molecules found in the P(-) strains were readily distinguished from the P(+) circular molecules by their smaller molecular weight and different G + C composition.
Centrifugation, Density Gradient↗
Conservation of Salmonella typhimurium deoxyribonucleic acid in partially diploid hybrids of Escherichia coli.
Partially diploid Escherichia coli K-12 hybrids recovered from mating with a Salmonella typhimurium Hfr strain were found to differ with respect to the manner in which they conserved the added Salmonella deoxyribonucleic acid (DNA). Five of the diploid hybrids examined appeared to maintain the Salmonella DNA as part of a functional F-merogenote; these hybrids were sensitive to the male-specific phage, R-17, responded as males to the female-specific phage, phiII, and transferred their inherited Salmonella genetic markers at high frequency in conjugation experiments. Six diploid hybrids were observed which were not sensitive to R-17, and from which the added Salmonella DNA was not transmissible in conjugation tests; nevertheless, these hybrids responded as males to phiII, and the Salmonella chromosomal fragments were conserved in them as parts of supercoiled, circular DNA elements. It was concluded that these circular DNA elements were defective F-merogenotes, unable to direct the synthesis of F-pili. Three diploid hybrids were found which were not sensitive to R-17, and which responded as females to phiII; no circular DNA was found in them, and it was concluded that their conservation of the Salmonella genetic fragments was accomplished in some manner which did not involve association with F or assumption of the supercoiled circular configuration. Other partially diploid hybrids were observed which appeared similar to these latter three hybrids with regard to their conservation of the Salmonella DNA, but which also contained an infecting F-factor; in these hybrids, both genetic and molecular experiments indicated that the unstably conserved Salmonella DNA was not associated physically with the F-factor.
Carbon Isotopes↗
Isolation and characterization of circular deoxyribonucleic acid obtained from lactose-fermenting Salmonella strains.
Six lac elements originally contained in Salmonella strains were transferred to Escherichia coli WR3026. All of the six E. coli strains that received one of the lac elements were observed to contain supercoiled, circular deoxyribonucleic acid (DNA) when examined by the dye-buoyant density method. Segregants of each of these E. coli WR3026 strains that had lost the ability to utilize lactose, when examined in the same manner as the lactose-fermenting strains, were not observed to contain these supercoiled, circular DNA molecules. Thus the DNA of the lac elements is maintained in E. coli WR3026 in the supercoiled, circular form. Molecular weights of the supercoiled, circular molecules isolated from strains carrying the lac elements were determined by sucrose density gradient centrifugation to be 30 million to 56 million. The calculated number of copies per chromosome of the lac elements varied from 1.4 to 3.7, depending upon the particular lac element examined. Each of the elements was determined to have a guanine plus cytosine composition of 50%. All six of the E. coli WR3026 strains containing a transmissible lac element were tested with the E. coli male-specific phage, R-17, and the E. coli female-specific phage, phiII, and did not respond to either of these phages as do F-containing derivatives of E. coli K-12.
Carbon Radioisotopes↗
Formation of hybrids between coliphage lambda and Salmonella phage P22 with a Salmonella typhimurium hybrid sensitive to these phages.
An unusual Salmonella typhimurium hybrid with sensitivity to coliphage lambda and salmonella phage P22 has been recovered from matings between an Escherichia coli K-12 Hfr donor and an S. typhimurium recipient. The hybrid is an excellent host for achieving genetic recombination between lambda and P22. Two broad classes of hybrid phages were isolated. The lambda-P22 hybrid class, which has the protein coat of lambda, contains at least the c region of P22. The P22-lambda hybrid class has the protein coat of P22 and has inherited at least the c marker of lambda.
Animals↗
Recombination of Escherichia coli chromosomal segments in Salmonella typhosa.
Approximately half of Salmonella typhosa hybrids resulting from mating with Escherichia coli Hfr donors inherit the selected donor marker by recombination, and the length of the E. coli chromosomal segment most frequently incorporated in these recombinants is between 1 and 2 min.
Chromosome Mapping↗
Chromosomal localization of the structural genes of the polypeptide chain elongation factors.
A survey of the polypeptide chain elongation factors in potentially sexually compatible genera was carried out. Factors from Escherichia coli and Proteus mirabilis were found to be clearly distinguishable by immunochemical and electrophoretic techniques. Mapping of the structural genes of these factors was undertaken by a study of the gene products in genetically defined E. coli-P. mirabilis hybrid diploid strains. It was found that the EF G factor mapped within 5 min of the streptomycin resistance locus, but the EF Ts factor did not map in this region.
Bacterial Proteins↗
Lytic replication of coliphage lambda in Salmonella typhosa hybrids.
Hybrids between Escherichia coli K-12 and Salmonella typhosa which conserved a continuous K-12 chromosomal diploid segment extending from pro through ara to the strA locus were sensitive to plaque formation by wild-type lambda. These partially diploid S. typhosa hybrids could be lysogenized with lambda and subsequently induced to produce infectious phage particles. When the K-12 genes were segregated from a lysogenic S. typhosa hybrid, phage-productive ability was no longer detectable due to loss of a genetic region necessary for vegetative replication of lambda. However, lambda prophage was shown to persist in a quiescent state in the S. typhosa hybrid segregant with phage-productive ability being reactivated after replacement of the essential K-12 lambda replication region. Low-frequency transduction and high-frequency transduction lysates containing the gal(+) genes of S. typhosa were prepared by induction of lambda-lysogenic S. typhosa hybrids indicating that the attlambda site is chromosomally located in S. typhosa in close proximity to the gal locus as in E. coli K-12. After propagation in S. typhosa hybrids, lambda was subject to restriction by E. coli K-12 recipients, thus establishing that S. typhosa does not perform the K-12 modification of lambda deoxyribonucleic acid. Hybrids of S. typhosa, however, did not restrict lambda grown previously on E. coli K-12. The K-12 genetic region required for lambda phage production in S. typhosa was located within min 66 to min 72 on the genetic map of the E. coli chromosome. Transfer of an F-merogenote encompassing the 66 to 72 min E. coli chromosomal region to lambda-insensitive S. typhosa hybrids enabled them to replicate wild-type lambda. The lambda-insensitive S. typhosa hybrid, WR4255, which blocks lambda replication, can be mutagenized to yield mutant strains sensitive to lambdavir and lambdaimm434. These WR4255 mutants remained insensitive to plaque formation by wild-type lambda.
Chromosome Mapping↗