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H E Hemphill

Publications and source records attributed to H E Hemphill.

At least 19 recordsLinked to original sources
PubMed1987

Genome homology and divergence in the SP beta-related bacteriophages of Bacillus subtilis.

Chromosomal organization in related temperate Bacillus subtilis bacteriophages SP beta, phi 3T, rho 11, Z, and E was compared. DNA-DNA hybridization studies done in conjunction with available restriction fragment maps of SP beta, phi 3T, and rho 11 demonstrated that DNA homology between these three phages extended over most of their respective genomes, although each contained unique chromosomal segments, phi 3T, rho 11, Z, and E, but not SP beta, possessed apparently homologous structural genes (thyP) for thymidylate synthetase. DNA from all thyP-containing phages transformed thymine auxotrophs of B. subtilis SP beta lysogens to prototrophy. This transformation commonly involved incorporation of the thyP gene into SP beta prophage within a region corresponding to the middle of the viral chromosome. Chimeric plasmids containing the thyP gene from phi 3T or cloned fragments of SP beta DNA were used in DNA-DNA hybridization studies to locate the thymidylate synthetase gene near the center of the phi 3T chromosome, and to demonstrate that the organization of this region resembled the analogous portion of the SP beta genome. Profiles of virion structural proteins from the five phages were also very similar, further suggesting functional homology between these viruses. However, despite these evidences of relatedness, populations of fragments generated by digesting SP beta, phi 3T, rho 11, Z, and E DNA with restriction enzymes were quite dissimilar.

Bacillus subtilis↗
PubMed1985

Deletion mutants of Bacillus subtilis bacteriophage SP beta.

The central portion of the chromosome of temperate Bacillus subtilis bacteriophage SPB was found to contain a region in which large deletions occurred, sometimes at high frequency. Most of the deletions could be placed into one of three groups, del1, del3, and del4, which were missing 11.8, 14.2, and 14 kilobase pairs of DNA, respectively. The chromosomal positions of the three types of deletions overlapped and together defined a continuous region of 27 kilobase pairs surrounding the prophage attachment site attPSPB. The 27-kilobase-pair segment contained no functions required for lytic growth of the phage, but DNA within this region was used as a template for RNA synthesis at several stages in the life cycle of SPB. In addition the transcription of DNA during lytic infection was found to be initiated over a large portion of one-half of the viral chromosome (the arbitrary left half). Subsequently, the synthesis of early RNA was terminated as late transcription continued on the opposite side of the chromosome.

Bacillus subtilis↗
PubMed1984

Genome organization of Sp beta c2 bacteriophage carrying the thyP3 gene.

Thymine auxotrophs of Bacillus subtilis strains lysogenic for temperate bacteriophage SP beta c2 were transformed to prototrophy by DNA from related phage phi 3T. During transformation, the phi 3T-encoded thymidylate synthetase gene, thyP3, became integrated into the extreme right end of the SP beta c2 prophage near the bacterial citK gene. Upon heat induction, the transformed B. subtilis cells released SP beta c2T phages that could lysogenize thymine auxotrophs and convert them to prototrophy. Comparison of restriction endonuclease fragments of DNAs from SP beta c2 and SP beta c2T phages revealed that the latter contained a large region of deletion and substitution near the center of the chromosome. This region included the phage attachment site on the SP beta c2 genome.

Bacillus subtilis↗
PubMed1980

Prophage-mediated production of a bacteriocinlike substance by SP beta lysogens of Bacillus subtilis.

Cultures of Bacillus subtilis lysogenic for the temperature bacteriophage SP beta release "betacin", a bacteriocinlike substance that inhibits B. subtilis strains which do not carry this phage. Production of betacin is blocked by mutations in the bet gene on the prophage and a second phage gene, tol, is apparently involved in making the lysogen itself tolerant to betacin. Mutations in a bacterial gene betR, located on the B. subtilis chromosome between metC and pyrD, render nonlysogens tolerant to betacin.

Antigens, Bacterial↗
PubMed1979

The role of temperate bacteriophage SP beta in prophage-mediated interference in Bacillus subtilis.

Virulent bacteriophage phi 1 grows on a variety of Bacillus subtilis strains, mutants of this virus which abortively infect the transformable bacillus. B. subtilis 168, while retaining the ability to productively infect related bacteria have been found. In the present study, we demonstrate that the inability of one such variant, phi 1m, to develop normally in strain 168 is mediated by cryptic prophage SP beta. The latter is a temperate bacteriophage which is carried by B. subtilis 168 and most strains derived from this bacterium. Phi 1 m infection of SP beta lysogens begins with apparently normal adsorption, penetration, and inititaion of virus-directed syntheses. At about the 20th min of the latent period, however, there is an abrupt cessation of nucleic acid synthesis and cellular respiration, accompanied by a change in cell permeability. This course of events can be altered to a permissive infection by mutation in the mpi gene of SP beta, by mutation in the spoOA gene of the host, or by growing SP beta lysogens at high temperature. In addition, we found a second class of phi 1 mutants which abortively infect B. subtilis 168 derivatives even in the absence of the SP beta prophage.

Bacillus subtilis↗
PubMed1976

Genetic and physiological studies of abortive infections of hydroxymethyluracil-containing bacteriophages in lysogens of temperate Bacillus subtilis bacteriophage SPO2.

Wild-type bacteriophage phie and IS (interference-sensitive) mutants of the related phage SP82G did not productively infect strains of Bacillus subtilis that were lysogenic for temperate phage SPO2. In these abortive infections, the sensitive phages adsorbed to and penetrated the nonpermissive host, phage-directed macromolecular syntheses were initiated, but both viral and bacterial nucleic acid production abruptly stopped about 15 min after addition of the phages. The cessation of RNA and DNA synthesis was preceded or coincident with a reduction in oxygen utilization by the infected cultures. Genetic studies of both phie and SP82G suggest sensitivity to SPO2-mediated abortive infection was controlled by a single gene. A mutant of SPO2, SPO2ehp4-, lysogens of which no longer interfere with the development of SP82GIs, was also isolated. The discovery of this ehp- variant suggests the normal SPO2 prophage synthesized a substance that alters cell physiology in some manner detrimental to SP82GIs development. Since SPO2ehp4- grew on and lysogenized bacteria sensitive to wild-type SPO2, the product of the eph gene was apparently not an essential function of this temperate phage.Overall, these observations exhibit remarkable similarities to the inhibition of T4rII mutants by the product of the rex gene of phage lambda.

Adsorption↗
PubMed1975

Viral mutation affecting bacteriophage phi 1 development in Bacillus subtilis 168.

Bacillus subtilis bacteriophage phi 1m, a host-range variant, was isolated after mutagenesis of virulent bacteriophage phi 1. Unlike its wild-type antecedent, phi 1m could not form plaques on lawns of B subtilis 168 at 37 C, although it adsorbed to, penetrated, and killed this bacterium. Experiments conducted in liquid medium at 37 C showed that B. subtilis 168 cells allowed reduced levels of phi 1m development at low multiplicities of infection, whereas high multiplicity infections of this strain by the phage were abortive. Certain mutants, derived originally from B. subtilis 168, were observed to be permissive for phi 1m at 37 C; moreover, their permissive phenotype could be duplicated by growing wild-type B. subtilis 168 cells at temperatures above 47 C. Studies on phi 1m and host nucleic acid synthesis under nonpermissive conditions demonstrated that transciption and DNA synthesis proceeded up to 20 min after infection, after which time there was a cessation of all nucleic acid production. These observations are discussed with respect to other abortive bacteriophage infections in B. subtilis.

Bacillus subtilis↗
PubMed1974

Abortive infection of lysogenic Bacillus subtilis 168(SPO2) by bacteriophage phi 1.

Virulent bacteriophage phi1 was not able to productively infect strains of Bacillus subtilis which were lysogenic for the temperate bacteriophage SPO2, although it adsorbed to, penetrated, and killed these bacteria. Studies of phage and host nucleic acid production in the nonpermissive host demonstrated that normal phi1 transcription was initiated early in the latent period, but this was followed by a general failure of host and phage nucleic acid synthesis about 10 to 15 min after infection. Mixed infections of phi1 and SPO2c(1), a clear-plaque mutant of SPO2, indicated that a similar inhibition of phi1 development occurred when this phage infected nonlysogenic B. subtilis cells committed to the SPO2c(1) lytic cycle. It is proposed that the SPO2- and SPO2c(1)-mediated interference did not act directly on the phi1 genome, but rather these phages altered the host physiology in such a manner that some normal step in phi1 development triggered a collapse of vital metabolic activities.

Bacillus subtilis↗
PubMed1974

Mixed infections of Bacillus subtilis involving bacteriophages SP82 and beta 22.

Progeny yields and the synthesis of nucleic acids have been investigated in two strains of Bacillus subtilis mixedly infected with two unrelated phages, SP82 and beta22. When B. subtilis strain 168 was the host, the first phage added dominated the infection; when B. subtilis strain SB11 was the host, beta22 produced progeny even when added to cells 5 min after infection with SP82. Dominance in these mixed infections could be correlated with qualitative and quantitative differences in the synthesis of phage-specific RNAs.

Adenosine↗
PubMed1973

Mixed infections of Bacillus subtilis involving bacteriophage SPO2c 1 .

The synthesis of ribonucleic acid (RNA) and deoxyribonucleic acid (DNA) was studied in Bacillus subtilis cells mixedly infected with phages SPO2c(1) and either SP82 or beta22. It was found that cells preinfected 5 min with either beta22 or SP82 could not support significant amounts of RNA or DNA synthesis from the genome of superinfecting SPO2c(1). Conversely, cells preinfected with SPO2c(1) remained susceptible to superinfection even at the midpoint of the latent period. When SP82 was added to cells preinfected 5 min with SPO2c(1), the former greatly inhibited the replication and transcription of the SPO2c(1), DNA, but if superinfection with SP82 was delayed until the 15th min of the SPO2c(1) latent period, RNA and DNA specific for both phages were synthesized. Both viral genomes were transcribed throughout the remainder of the lytic cycle when beta22 was added to cells preinfected either 5 or 15 min with SPO2c(1). In both the SPO2c(1)-SP82 and the SPO2c(1)-beta22 mixed infections, the types of phage-specific RNAs synthesized at a given time in the latent period were similar to those synthesized in single infections with each phage. The association of SPO2c(1) DNA with the host cell membrane in certain of the doubly infected cells was different from that observed in singly infected cells. In the SPO2c(1)-SP82 infection, SPO2c(1) DNA was not released from the membrane; in the SPO2c(1)-beta22 mixed infections, significantly less SPO2c(1) DNA was membrane-bound when beta22 was added before SPO2c(1). However, binding and release of SPO2c(1) DNA was normal in cells infected first with SPO2c(1) and then with beta22. The synthesis of phage-specific nucleic acids and the binding of phage DNA to the membrane are discussed with respect to dominance relationships among these phages.

Bacillus subtilis↗
PubMed1973

Prophage-mediated interference affecting the development of Bacillus subtilis bacteriophage phi e.

Bacteriophage phie shows a reduced efficiency of plating on strains of Bacillus subtilis which are lysogenic for the temperate bacteriophage SP02. Although this phenomenon resembles prophage-mediated restriction observed in other bacteria, host-controlled modification of phie was not observed. Mutants of phie which plated with high efficiency on the lysogenic host were isolated.

Adsorption↗
PubMed1972

Dominance relationships in mixedly infected Bacillus subtilis.

The progeny released from Bacillus subtilis cells mixedly infected with bacteriophages beta22, SP82, and SP02(c1) have been studied at varying multiplicities of infection and orders of addition and with different host strains of the bacterium. In B. subtilis 168, SP02(c1) was subordinate to both SP82 and beta22 and did not yield significant numbers of progeny even when added 5 min before the superior phage. Dominance in mixed infections of beta22 and SP82 was host-dependent. In B. subtilis 168, SP82 was dominant and greatly reduced the yield of beta22 if added simultaneously or before the subordinate partner. However, in the same mixed infection in B. subtilis SB11, beta22 was the dominant phage and totally suppressed the production of SP82 even when added 5 min after the latter.

Adsorption↗
PubMed1972

Nucleic acid synthesis in bacteriophage SPO2c 1 -infected Bacillus subtilis.

The synthesis of host macromolecules was shut off very slowly and incompletely by bacteriophage SPO2c(1). No change in the rate of incorporation of radioactive precursors into protein and ribonucleic acid (RNA) could be detected after infection, and the rate of incorporation of thymidine was increased only slightly. The relative proportions of phage and host species of nucleic acids at various intervals in the latent period were determined by means of nucleic acid hybridization. Phage-specific RNA populations synthesized early were different from those synthesized late in the latent period. Host deoxyribonucleic acid (DNA) replication continued until 8 to 10 min after SPO2c(1) infection and then decreased markedly as phage-specific DNA synthesis was initiated. Host DNA was not degraded to trichloroacetic acid-soluble fragments, and its nucleotides were not found in either newly synthesized intracellular phage DNA or in progeny phage particles. The average burst size of SPO2c(1) was approximately 200 plaque-forming units per cell.

Bacillus subtilis↗
PubMed1970

Nucleic acid synthesis in Bacillus subtilis infected with bacteriophage beta-22.

Changes in the synthesis of host and phage nucleic acid after infection of Bacillus subtilis with virulent bacteriophage beta22 were analyzed by deoxyribonucleic acid (DNA)-DNA and ribonucleic acid (RNA)-DNA hybridization. Host DNA replication continued during the first third of the 55-min latent period and then ceased at approximately the time replication of the phage genome was initiated. Host-specific RNA was synthesized concurrently with phage RNA during the first half of the latent period but was repressed late in the infection. For much of the latent period, the population of phage-specific RNA changed continually as new species were transcribed and earlier species were repressed; detectable changes ceased coincidentally with the appearance of intracellular phage. Control over transcription of phage DNA was to some degree an intrinsic property of the interaction of B. subtilis DNA-dependent RNA polymerase and the phage genome, since only the early species of phage RNA were synthesized in vitro by B. subtilis polymerase and pure beta22 DNA. In vitro transcription of late functions was demonstrated by using the endogenous RNA polymerase activity of the nucleoprotein complex (nuclear fraction) from infected cells.

Bacillus subtilis↗