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B A Stocker

Publications and source records attributed to B A Stocker.

12 recordsLinked to original sources
PubMed1979

Segregation of the mutator property of plasmid R46 from its ultraviolet-protecting property.

Plasmid R46 (an R factor conferring resistance to ampicillin, sulfonamides, streptomycin and tetracycline) reduces the bactericidal effect of UV irradiation but increases its mutagenic effect (reversion of hisG46), and raises the frequency of spontaneous reversion (mutator effect). Putative deletion mutants of R46 were obtained by transduction of the plasmid, then two successive conjugal transfers. Plasmids of five of six deletion classes, each with a different combination of drug resistance traits, retained conjugative ability and the UV-protecting, mutagenesis-enhancing and mutator effects of R46. (pKM101, used in the Ames system to enhance responsiveness to chemical mutagens, is one such mutant of R46.) Plasmids of a sixth class, represented by pKM115, conferred resistance only to streptomycin and were non-conjugative. All of several such plasmids (of independent origin) had a much stronger mutator effect than did R46, but lacked UV-protecting ability and did not enhance the mutagenic effect of UV irradiation. We infer that R46 possesses: (i) a gene, uvp, which increases capacity for error-prone repair of UV-damaged DNA, and thus causes both UV protection and enhancement of UV mutagenesis; (ii) gene(s) whose action in the absence of gene uvp greatly increases the frequency of spontaneous reversion of hisG46. A plasmid of another incompatibility group, pLS51, has UV-protecting and mutagenesis-enhancing effect but lacks the mutator property; introduction of pLS51 into a clone of hisG46 carrying a pKM115-type plasmid greatly reduced its spontaneous reversion rate, as expected if pLS51 also has a uvp gene able to modulate the mutator effect of R46-derived gene(s) in the pKM115-type plasmid.

DNA Repair↗
PubMed1979

Evaluation of the immune response directed against the Salmonella antigenic factors O4,5 and O9.

A pair of O4,5,12 and O9,12 his(+) sister transductants derived from a virulent Salmonella typhimurium parent were used as intraperitoneal and oral challenge strains to determine whether immunity directed against the O9 and O4,5 antigenic components could be detected after immunization with heat-killed vaccines containing one or the other of these antigenic components. Challenge with a mixture (ca. 1:1) of the two strains and culturing of livers and spleens at intervals indicated that the O4,5,12 strain multiplied to a greater extent than the O9,12 strain after both oral and intraperitoneal challenge of CF1 and C57BL/6J control mice. Immunization with O4,5,12 or O9,12 vaccine resulted in diminished bacterial counts from the livers and spleens for the homologous strain but had little effect on the heterologous strain. The diminution of the homologous strain was more evident after intraperitoneal challenge but was clearly demonstrable after oral challenge, particularly in the C57BL/6J mice. Of several live vaccines tested, an FOR S. typhimurium (O4,5,12) strain phenotypically smooth but avirulent seemed the most promising, suppressing the multiplication of both members of the challenge pair. After oral challenge suppression of the O4,5,12 strain was greater. These results indicate that the specific immune response directed against either the O4,5 (O-acetyl abequose) or the O9 (tyvelose) antigen is a measurable component of the overall response after both intraperitoneal and oral challenge.

Animals↗
PubMed1979

Effect of host lex, recA, recF, and uvrD genotypes on the ultraviolet light-protecting and related properties of plasmid R46 in Escherichia coli.

The ability of plasmid R46 to reduce the lethal but enhance the mutagenic effect of ultraviolet (UV) irradiation was tested in sets of Escherichia coli K-12 derivatives, wild type or with different mutations affecting DNA repair capacity, but otherwise isogenic. UV protection and enhancement of UV mutagenic effect were obtained in uvrA6, uvrB5, uvrD3, and recF143 hosts, but not in a recA56 strain. The plasmid gave some UV protection in two lexA1 and two lexA101 strains and in one lexA102 host, but produced no such effect in another lexA102 host. The plasmid restored UV mutagenic effect in a lexB30 strain, the yield of induced mutants per survivor of irradiation (10 J/m2) being about the same for the lexB30(R46) and lex+(R46) strains; by contrast the plasmid, though it reduced the UV sensitivity of the lexB30 strain, did not make it as UV-resistant as the lex+ R-strain.

DNA Repair↗
PubMed1979

Mutants defective in the 33K outer membrane protein of Salmonella typhimurium.

Salmonella typhimurium LT2 lines, if phenotypically rough, are fully sensitive to bacteriocin 4-59, produced by Salmonella canastel strain SL1712. Bacteriocin-resistant mutants fell into three classes. Those resistant to phage ES18 and to albomycin proved to be mutants of class chr (equivalent to tonB of Escherichia coli); these mutants still adsorb the bacteriocin and so are classified as tolerant. Another class of (incompletely) tolerant mutants was resistant to phage PH51; their envelope fractions lacked the band corresponding to outer membrane protein 34K, known to serve for adsorption of phage PH51. A third class of mutants, which did not adsorb the bacteriocin, was unaltered in sensitivity to phages. Their envelopes lacked the 33K band, indicating absence of the outer membrane protein 33K, considered to correspond to outer membrane protein II* of E. coli, which in that species is determined at locus ompA (formerly tolG or con). Phage P22 HT105/1 cotransduced the 33K S. typhimurium gene (to be called ompA, to accord with E. coli usage) with pyrD+ at about 30% frequency when the donor allele was ompA+ or one ompA, but at only 3 to 11% when the donor allele was another ompA. When the donor carried either of two long deletions of the put (proline utilization) operon, phage P22 HT105/1 cotransduced put (and ompA+) with pyrD+ at low frequency. The cotransduction data indicate that ompA of S. typhimurium is located between pyrD and put, nearer the former. This corresponds to the map position of ompA in E. coli K-12.

Bacterial Proteins↗
PubMed1978

Lipopolysaccharide core defects in Salmonella typhimurium mutants which are resistant to Felix O phage but retain smooth character.

FOR mutants of Salmonella typhimurium are resistant to Felix O phage, whose receptor includes the N-acetylglucosamine branch of the lipopolysaccharide (LPS) core, but smooth in cultural properties, antigenic character and phage sensitivity pattern (MacPhee et al., 1975). The rfa(FOR) genes determining the FOR character of nine mutants were transduced into a smooth cysE pyrE recipient: the nine FOR transductants (and a tenth FOR mutant) were then made rfb (i.e. unable to make O chains) by transduction or Hfr crosses. The rfb FOR strains were sensitive to FO phage but nearly all of them showed a somewhat reduced efficiency of plating and diminished rate of adsorption of the phage. This observation and the Ra (complete core) serological activity of their LPS (tested by haemagglutination inhibition) indicate the presence of some, but less than the normal number of, completed core chains in FOR rfb LPS. On the basis of the sensitivities of the FOR transductants and their rfb derivatives to various 'rough-specific' phages, their increased sensitivities to some antibiotics and to deoxycholate and the serological activity of the rfb FOR LPS in various incomplete core systems, the mutants were divided into three groups: (i) five mutants with probable defects in previously undetected rfa gene(s) concerned with formation of both the galactose I and the galactose II units of the LPS core; (ii) two mutants with defects inferred to affect the structure of the inner part of the core and also interfere with addition of the N-acetylglucosamine branch; (iii) three mutants in which no type of incomplete core could be detected, probably affected in formation of the inner part of the core chain. The mutation of one mutant of the last class, unlike those of the other nine mutants tested, lay outside the cysE-pyrE segment, in the 90 to 116 min region of the linkage map.

Anti-Bacterial Agents↗
PubMed1977

Comparison of the virulence of O:9,12 and O:4,5,12 Salmonella typhimurium his+ transductants for mice.

The purpose of these experiments was to determine whether qualitative differences in the O repeat unit of the lipopolysaccharide of pathogenic Salmonella species affected virulence for mice. O:4,5,12 and O:9,12 sister his+ transductants were derived from a virulent Salmonella typhimurium. Fermentation markers were introduced by transduction to differentiate these strains, and the strains were used as mixed challenge to CF1 and C57B1/6J mice. Liver and spleen cultures of the mice of various intervals after challenge indicated that the O:4,5,12 member of the nearly isogenic pair regularly multiplied to a greater extent than the O:9,12 after intraperitoneal challenge for both strains of mice. After oral challenge, there was little difference in the amount of multiplication of the O:4,5,12 and O:9,12 strains in CF1 mice, but the O:4,5,12 was the predominant strain recovered in 8 of 10 instances in the C57B1/6J mice.

Animals↗
PubMed1977

Genetics of sensitivity of Salmonella species to colicin M and bacteriophages T5, T1, and ES18.

Nearly all of 62 strains of Salmonella paratyphi B were sensitive to colicin M and phage T5 but resistant to phages T1 and ES18 and to colicin B. All tested S. typhimurium strains were resistant to colicin M and phage T5, and many were sensitive to phage ES18. A rough S. typhimurium LT2 strain given the tonA region of Escherichia coli or S. paratyphi B became sensitive to colicin M and phage T5. We infer that the tonA allele of S. paratyphi B, like that of E. coli, determines an outer membrane protein that adsorbs T5 and colicin M but not phage ES18, whereas the S. typhimurium allele determines a protein able to adsorb only ES18. The partial T1 sensitivity of a rough LT2 strain with a tonA allele from E. coli or S. paratyphi B and also the tonB(+) phentotype of an E. coli B trp-tonB Delta mutant carrying an F' trp of LT2 origin showed that S. typhimurium LT2 has a tonB allele like that of E. coli with respect to determination of sensitivity to colicins and phage T1. Rough S. paratyphi B, although T5 sensitive, remained resistant to T1 even when given F' tonB(+) of E. coli origin. Classes of Salmonella mutants selected as resistant to colicin M included: T5-resistant mutants, probably tonA(-); mutants unchanged except for M resistance, perhaps tolerant; and Exb(+) mutants, producing a colicin inhibitor (presumably enterochelin). Some Exb(+) mutants were resistant to a bacteriocin inactive on E. coli but active on all tested S. paratyphi B and S. typhimurium strains (and on nearly all other tested Salmonella). A survey showed sensitivity to colicin M in several other species of Salmonella.

Bacteriophages↗
PubMed1976

Ultraviolet light protection, enhancement of ultraviolet light mutagenesis, and mutator effect of plasmid R46 in Salmonella typhimurium.

Plasmid R46 partially protected Salmonella typhimurium, wild type or uvrB or polA, against the lethal effect of ultraviolet (UV) irradiation, but did not protect recA mutants. The plasmid also increased frequency of UV-induced reversion to His+ in all tested his point mutants (wild type for UV sensitivity), including amber, ochre, UGA, missense, and frame-shift mutants. Plasmid R46 also increased UV-induced reversion to His+ in uvrB and polA strains, but no UV mutagenic effect was detected in R- or R46-carrying recA derivatives of a his (amber) mutant. The spontaneous reversion frequency of his nonsense mutants of all classes, and of some his missense mutants, was increased about 10-fold when the strains carried R46, but the plasmid had no effect on the spontaneous reversion frequency of some other his missense mutations or of reversion rate of his frame-shift mutants (except for two uvrB derivatives of one single-base insertion mutant). The plasmid increased the ability of wild-type, polA, and uvrB hosts to support plaque production by UV-irradiated phage, and made strain LT2 hisG46 less sensitive to methyl methane sulfonate and to X rays and more responsive to the mutagenic effect of visible-light irradiation. R46 increased spontaneous reversion frequency of a his (amber) rec+ strain, but had no such effect in its recA sublines. Since the plasmid in the absence of host recA function fails to produce its mutator effect, or to confer UV protection or to enhance UV mutagenesis, these three effects may be produced via some mechanism involved in recA-dependent deoxyribonucleic acid repair, perhaps by an increase in activity of the "error prone" component of the inducible repair pathway.

Drug Resistance, Microbial↗
PubMed1976

Salmonella typhimurium mutants generally defective in chemotaxis.

The mutations of eight chemotaxis-deficient strains of Salmonella typhimurium, including five new mutants in strain LT2, were mapped by P22 transduction in relation to various fla mot deletions in S. abortus-equi. Seven recessive che mutations mapped between motB and flaC: three, all nontumbling, the che region I, adjacent to motB, and four, including one ever-tumbling, in che region II, adjacent to flaC. Mutant che-107, never-tumbling and dominant to wild type, mapped at flaAII, other mutations of which cause either absence of flagella or lack of locomotor function. We surmise that gene flaAII specifies a protein that polymerizes to form an essential component of the basal apparatus (so that absence of gene product prevents formation of flagela); that a component built up from certain mutationally altered proteins cannot transmit (or generate) active rotation of the hook and flagellum, and so causes the Mot (paralysis) phenyotype; and that a component built up from protein with the che-107 alteration permits only counterclockwise rotation, so that the tumble, normally produced by transient clockwise rotation, cannot be effected.

Chemotaxis↗
PubMed1975

Integration, at hag or elsewhere, of H2 (phase-2 flagellin) genes transduced from Salmonella to Escherichia coli.

A fla mutant of E. coli K12 was given fla+ and H1-i by phage P1kc cotransduction from S. typhimurium, then made Fla- by transduction of ah1 from S. typhimurium. Motile clones expressing a Salmonella phase-2 antigen, e,n,x or 1,2, were obtained from the K12 i ah1 (therefore Fla-) line by P1kc transduction of flagellin-specifying genes, H2-e,n,x or H2-1,2, from Salmonella donors. Of eighteen such transductants sixteen failed to show phase variation, and on transduction back to Salmonella each structural gene for a phase-2 flagellin (or at least for its antigenically determinant part) now behaved as an allele of H1, presumably in consequence of incorporation in the hag region of the K12 recipient, in place of H1-i ah1. The e,n,x- and 1,2-specifying genes were shown to have been integrated in the K12 chromosome without the linked H1-repressor gene or the adjacent vh2 gene (controlling rate of phase-variation) and they responded to the repressing activity of an H2 allele elsewhere in the cell, in this respect resembling H1 alleles of Salmonella or hag alleles of E. coli. Two K12 e,n,x transductants had flagellin-specifying genes which when transduced back to Salmonella were integrated at H2; they are inferred to have resulted from integration of H2-e,n,x in the K12 chromosome elsewhere than the hag region. These two clones showed phase variation, between a Fla+ phase, with antigen e,n,x, and a Fla- phase (with e,n,x determinant in the nonactive state and the determinant of antigen i inactivated by ah1). The two integrated e,n,x genes when in the "active" state retained the ability to repress expression of exogenote H1 alleles, which indicates that the closely linked H1-repressor gene also was integrated. One of the two exceptional transductants derived its e,n,x gene from a Salmonella donor with the linked vh2- gene, which in Salmonella almost entirely prevents change of phase, and transduction of this e,n,x gene back to Salmonella recipients proved that vh2- had been incorporated into the E. coli chromosome along with the e,n,x determinant and the H1-repressor gene. The high frequency of change of phase (Fla+ in equilibrium Fla-) in the K12 e,n,x vh2- transductant concerned suggests that vh2- fails to prevent frequent change of state of the phase-determined part of H2 when vh2- and H2 are incorporated in the E. coli chromosome.

Bacterial Proteins↗
PubMed1975

Mutations in Salmonella typhimurium conferring resistance to Felix O phage without loss of smooth character.

Several mutants obtained from smooth Salmonella typhimurium strains by selection for resistance to Felix O (FO) phage [whose receptor site includes the N-acetylglucosamine branch of the lipopolysaccharide (LPS) core] were smooth in cultural properties, antigenic character and phage sensitivity pattern (except for their FO resistance). However, the affected genes of several such 'FOR' (FO-resistant) mutants were shown by transduction of map in the short cysE-pyrE segment, which includes nearly all known rfa genes responsible for synthesis of LPS core. All of seven FOR mutants differed from their parents, and resembled rfa mutants with defects in the deeper part of the LPS core, by increased sensitivity to various antibiotics. One FOR mutant was non-virulent (LD50 greater than 10-7, compared with smaller than 100 for its parent); LT7 derivatives given this FOR gene by co-transduction with cysE+ were likewise non-virulent. It is inferred that FOR mutations affect the assembly of the inner part of the LPS core, perhaps causing incomplete blocks in glycosyl transferase reactions.

Acetylglucosamine↗