Fate of transforming DNA following uptake by competent Bacillus subtilis. IV. The endwise attachment and uptake of transforming DNA

Fate of transforming deoxyribonucleic acid after uptake by competent Bacillus subtilis: phenotypic characterization of radiation-sensitive recombination-deficient mutants

A collection of 16 isogenic recombination-deficient strains of Bacillus subtilis isolated on the basis of sensitivity to methyl methane sulfonate (MMS) or mitomycin C (MC) were characterized phenotypically. All were found to be somewhat sensitive to ultraviolet irradiation, MC, and MMS. The mutants were all blocked in "late" steps in the transformation process and were provisionally grouped into four categories on the basis of the various properties examined. Class I mutants were deficient in transformation and heterologous transduction with phage PBS1 but were transducible with homologous donors at nearly the wild-type frequency. They were blocked in donor-recipient complex (DRC) formation but formed essentially normal amounts of double-strand fragments (DSF) and single-strand fragments (SSF). The class IIa strain was deficient in transformation and PBS1 transduction, and formed DRC which was normal by all available physical and biological criteria. Class IIb mutants were deficient in transformation and PBS1 transduction, and failed to form DRC. They did produce DSF and SSF. Class III mutants were deficient in transformation, were normal in PBS1 transduction, and formed DRC which was physically indistinguishable from that of the Rec(+) parent although with slightly lowered donor-type transforming activity. Class IV strains were deficient in PBS1 transduction but were transformed at nearly the wild-type efficiency. None of the mutant strains was deficient in the adenosine triphosphate-dependent deoxyribonuclease.

Fate of transforming deoxyribonucleic acid after uptake by competent Bacillus subtilis: nonrequirement of deoxyribonucleic acid replication for uptake and integration of transforming deoxyribonucleic acid

Studies on transformation of Bacillus subtilis using the inhibitor 6-(p-hydroxyphenylazo)-uracil show that deoxyribonucleic acid (DNA) replication is not required for the uptake and integration of donor DNA and genetic markers.

Chromatographically fractionated complementary strands of Bacillus subtilis deoxyribonucleic acid: transformation of hybrids

The annealing properties as measured by the restoration of transforming activity and hypochromicity of methylated albumin-kieselguhr (MAK)-fractionated complementary strands of Bacillus subtilis deoxyribonucleic acid (DNA) are presented. Temperature-absorbance measurements performed on annealed mixtures of various L and H strand fractions indicated the existence of a complementarity gradient between the two MAK peaks. The markers purA16, leu-8, metB(5), thr-5, and the linked marker hisB(2)-try-2 exhibited different bimodal distributions on MAK columns. The transforming efficiency of heteroduplex mixtures, prepared by cross-annealing resolved complementary strands of wild-type and recipient DNA, was compared. The transforming efficiency of the wild-type L and H strands was equal in one preparation and unequal in a second preparation. It was found that in the second strand preparation the heteroduplex DNA containing the H strand from wild type was more efficient for all of the markers tested. The variations in transforming efficiencies of the complementary strands in heteroduplex molecules reported here and by others are due in part to strands of unequal length and probably to the self-annealing property of the H strands. At present, no conclusion could be made regarding the existence of strand selection bias during integration of donor DNA in competent B. subtilis cells.

Fate of transforming deoxyribonucleic acid after uptake by competent Bacillus subtilis: size and distribution of the integrated donor segments

A series of sheared donor-recipient complex samples were prepared from a competent Bacillus subtilis culture which had been transformed by using (3)H, (2)H-labeled deoxyribonucleic acid. Measurement of the molecular weights and buoyant densities of these samples led to the following conclusions. (i) The average size of the single-stranded donor segment which is integrated is 2.8 x 10(6). (ii) These donor segments are not randomly distributed in the recipient genome, but are clustered in groups, each group containing several discrete donor segments.

Early extracellular events in infection of competent Bacillus subtilis by DNA of bacteriophage SP82G

Analysis, by the recovery of specific genetic "markers," of the effects of DNase I, physical shear, and temperature shock on DNA-cell complexes demonstrates that sequential attachment of both ends of bacteriophage SP82G DNA to Bacillus subtilis precedes entry of the DNA molecule into the cell, and that each attachment is end-and time-specific. The first attachment involves an initial reversible phase, followed by irreversible binding. After a latent period, the second end then attaches to the cell. Entry of the molecule begins immediately after binding of the second end has occurred, and entry is complete within 3 min. The polarity of entry, as judged by attainment of resistance to DNase I, is the reverse of that observed in normal phage injection.