Plasmid deoxyribonucleic acid in Bacillus subtilis and Bacillus pumilus

The Large pBS32/pLS32 Plasmid of Ancestral Bacillus subtilis

The ancestral strain of Bacillus subtilis NCIB3610 (3610) bears a large, low-copy-number plasmid, called pBS32, that was lost during the domestication of laboratory strain derivatives. Selection against pBS32 may have been because it encodes a potent inhibitor of natural genetic competence (ComI), as laboratory strains were selected for high-frequency transformation. Previous studies have shown that pBS32 and its sibling, pLS32 in Bacillus subtilis subsp. natto, encode a replication initiation protein (RepN), a plasmid partitioning system (AlfAB), a biofilm inhibitor (RapP), and an alternative sigma factor (SigN) that can induce plasmid-mediated cell death in response to DNA damage. Here, we review the literature on pBS32/pLS32, the genes found on it, and their associated phenotypes.

Identification, sequencing and comparative analysis of pBp15.S plasmid from the newly described entomopathogen Bacillus pumilus 15.1

The Bacillus pumilus 15.1 strain, a recently described entomopathogenic strain active against Ceratitis capitata, contains at least two extrachromosomal elements, pBp15.1S and pBp15.1B. Given that B. pumilus is not a typical entomopathogenic bacterium, the acquisition of this extrachromosomal DNA may explain why B. pumilus 15.1 is toxic to an insect. One of the plasmids present in the strain, the pBp15.1S plasmid, was sub-cloned, sequenced and analyzed using bioinformatics to identify any potential virulence factor. The pBp15.1S plasmid was found to be 7785 bp in size with a GC content of 35.7% and 11 putative ORFs. A replication module typical of a small rolling circle plasmid and a sensing and regulatory system specific for plasmids was found in pBp15.1S. Additionally, we demonstrated the existence of ssDNA in plasmid preparations suggesting that pBp15.1S replicates by the small rolling circle mechanism. A gene cluster present in plasmid pPZZ84 from a distantly isolated B. pumilus strain was also present in pBp15.1S. The plasmid copy number of pBp15.1S in exponentially growing B. pumilus cells was determined to be 33 copies per chromosome. After an extensive plasmid characterization, no known virulence factor was found so a search in the other extrachromosomal elements of the bacteria is needed.

Small rolling circle plasmids in Bacillus subtilis and related species: Organization, distribution, and their possible role in host physiology

Bacillus subtilis and related species (Bacillus licheniformis, Bacillus pumilus, Bacillus amyloliquefaciens, and Bacillus mojavensis) represent a group of bacteria largely studied and widely employed by industry. Small rolling circle replicating plasmids of this group of bacteria have been intensively studied as they represent a convenient model for genetic research and for the construction of molecular tools for the genetic modification of their hosts. Through the computational analysis of the available plasmid sequences to date, the first part of this review focuses on the main stages that the present model for rolling circle replication involves, citing the research data which helped to elucidate the mechanism by which these molecules replicate. Analysis of the distribution and phylogeny of the small RC plasmids inside the Bacillus genus is then considered, emphasizing the low level of diversity observed among these plasmids through the in silico analysis of their organization and the sequence divergence of their replication module. Finally, the parasitic vs. mutualistic nature of small rolling circle plasmids is briefly discussed.

A novel Bacillus natto plasmid pLS32 capable of replication in Bacillus subtilis

Plasmid pLS32 is a relatively large (approximately 70 kbp), cryptic, low copy-number plasmid present in Bacillus natto. We isolated and analyzed the replication region of the plasmid in B. subtilis, and the following results were obtained: the replication region contained an open reading frame encoding a 287-amino acid protein (RepN), whose amino acid sequence was partially homologous with those of the Rep proteins encoded on plasmids pAD1 and pLJ1 isolated from Enterococcus faecalis and Lactobacillus helveticus, respectively; the replication origin (oriN) was located in the repN-coding region; the copy number of a pLS32 derivative, pBET131, was 2 to 3 per chromosome; replication of pBET131 required poll. These features show that pLS32 is a novel plasmid capable of replication in B. subtilis.

Homology among nearly all plasmids infecting three Bacillus species

We have surveyed naturally occurring plasmids in strains of Bacillus subtilis and the closely related species B. mojavensis and B. licheniformis. Previous studies have failed to find host-benefitting functions for plasmids of these species, suggesting that these plasmids are nonmutualistic. Only one type of plasmid was found in each plasmid-bearing strain, suggesting that most of the plasmids infecting these Bacillus species are in the same incompatibility group. A sample of 18 plasmids from these species ranged in size from 6.9 to 16 kb, with all but 6 plasmids falling into three size groups. These groups differed in the sizes of their host ranges and geographical ranges. All but 1 of the 18 plasmids from these three host species are homologous with one another. The cryptic plasmids from these three species are far less diverse than are plasmids (from other species) that are known to benefit their bacterial hosts. The low-level diversity among these cryptic plasmids is consistent with the hypothesis that host-benefitting adaptations play an important role in fostering the coexistence of plasmid populations, but other explanations for the low-level plasmid diversity are possible. Comparison of the phylogenies of the plasmids with those of their hosts suggests that Bacillus plasmids are horizontally transferred in nature at a low rate similar to that found for the colicin plasmids of Escherichia coli.

The Bacillus subtilis spo0J gene: evidence for involvement in catabolite repression of sporulation

Previous observations concerning the ability of the Bacillus subtilis bacteriophages SP10 and PMB12 to suppress mutations in spo0J and to make wild-type sporulation catabolite resistant suggested that spo0J had a role in catabolite repression of sporulation. This suggestion was supported in the present report by the ability of the catabolite-resistant sporulation mutation crsF4 to suppress a Tn917 insertion mutation of the B. subtilis spo0J locus (spo0J::Tn917 omega HU261) in medium without glucose. Although crsF4 and SP10 made wild-type B. subtilis sporulation catabolite resistant, neither crsF4 nor SP10 caused a mutant with spo0J::Tn917 omega HU261 to sporulate in medium with glucose. Sequencing the spo0J locus revealed an open reading frame that was 179 codons in length. Disruption of the open reading frame resulted in a sporulation-negative (Spo-) phenotype that was similar to those of other spo0J mutations. Analysis of the deduced amino acid sequence of the spo0J locus indicated that the spo0J gene product contains an alpha-helix-turn-alpha-helix unit similar to the motif found in lambda Cro-like DNA-binding proteins.

Bacteriophage-enhanced sporulation: comparison of spore-converting bacteriophages PMB12 and SP10

The previously characterized bacteriophage SP10 enhanced the frequency of wild-type sporulation by Bacillus subtilis W23 and 3-13. Comparison of SP10 with the spore-converting bacteriophage PMB12 indicated that both bacteriophages significantly increased the sporulation frequency of an oligosporogenic mutant that contained spo0J::Tn917 omega HU261. SP10 and PMB12 caused wild-type bacteria to sporulate in a liquid medium that initially contained enough glucose to inhibit the sporulation and expression of alpha-amylase by uninfected bacteria. SP10 also induced the expression of alpha-amylase in the presence of glucose, whereas PMB12 had no detectable effect. These observations were consistent with the conclusion that SP10 is a spore-converting bacteriophage and that SP10 and PMB12 relieve glucose-mediated catabolite repression of sporulation by different mechanisms.

Corrected Version Distribution of Heterogeneous and Homologous Plasmids in Bacillus spp

A total of 75 strains (including 5 reference strains) of Bacillus amyloliquefaciens, B. cereus, B. circulans, B. licheniformis, B. megaterium, B. pumilus, B. sphaericus, B. subtilis , and B. thuringiensis and 36 species-unidentified Bacillus strains were surveyed for plasmids by cesium chloride-ethidium bromide equilibrium centrifugation of cell lysates in a study of antibiotic resistance in host cells. Of the 111 strains, 13 (including 3 reference strains) were found to harbor plasmids, and 5 of the 13 showed antibiotic resistance. This antibiotic resistance appeared not to be due to the plasmids, however, because the trait was not cured by cultivation of cells in nutrient medium containing ethidium bromide (1 μg/ml), sodium dodecyl sulfate (0.2 μg/ml), or novobiocin (1 μg/ml), except in one strain, in which kanamycin and streptomycin resistances were cured by novobiocin. One strain of B. amyloliquefaciens , S294, was found to harbor a plasmid, pFTB14, which differed from the plasmid species of classes 1 to 6 in B. subtilis and B. amyloliquefaciens , as determined by restriction analysis and DNA contour length determination. However, in DNA-DNA hybridization on a filter after Southern blotting from an agarose gel, the pFTB14 DNA hybridized with plasmids of classes 1 to 5. Three strains of B. thuringiensis each carried at least 4 to 11 plasmid species, whereas no plasmids were detected in four strains of B. cereus , which, in relation to B. thuringiensis , is closely related taxonomically and has highly homologous DNA sequences. The plasmid DNAs prepared from species other than B. subtilis and B. amyloliquefaciens did not hybridize with that of pFTB14.

Isolation of a tetracycline-resistance plasmid excised from a chromosomal DNA sequence in Bacillus subtilis

When Bacillus subtilis GSY908 (recE4-) (H. C. Spatz and T. A. Trautner, 1971, Mol. Gen. Genet. 113, 174-190) protoplasts were infected with Staphylococcus aureus plasmid pNS1 specifying tetracycline resistance (Tcr) (N. Noguchi et al., 1983, Gene 21, 105-112), which was modified such that it either could not replicate or did not carry a functional Tcr gene, a plasmid with a molecular weight of 3.1 X 10(6) (4.9 kb) was generated in Tcr phenotypes. This plasmid, named Tcr pNS1981, exhibited completely different restriction endonuclease cleavage patterns to pNS1 and showed only negligible sequence homology in hybridization experiments. Southern hybridization experiments revealed that pNS1981 arises by excision of a B. subtilis chromosomal DNA sequence. No sequence corresponding to pNS1 was detectable on the chromosome of pNS1981-maintaining B. subtilis. The production of pNS1981 was also observed in B. subtilis RM125 (r-Mm-Mrec+) (T. Uozumi et al., 1977, Mol. Gen. Genet. 152, 65-69.) with almost the same frequency as B. subtilis GSY908. Since the recipient B. subtilis Marburg 168 derivatives stated above are sensitive to Tc, the results indicate that information essential for Tcr is under negative regulatory control in the integrated state on the chromosome. Restriction endonuclease analysis suggested that pNS1981 is essentially the same as pBC16, formerly found in B. cereus (K. Bernhard, H. Schrempf, and W. Goebel, 1978, J. Bacteriol. 133, 897-903).

Megacinogenic plasmids of Bacillus megaterium

Megacins A-216 and A-19213 in Bacillus megaterium are plasmid encoded, as shown by analysis of cured, non-megacinogenic (Meg-) derivatives of strains 216 and ATCC 19213 and by polyethylene glycol-mediated protoplast transformation of Meg- bacteria with plasmid DNA. The results of both techniques implicated a 31-megadalton plasmid, pBM309, in megacin A-216 production and a 29-megadalton plasmid, pBM113, in megacin A-19213 production.

Distribution of heterogeneous and homologous plasmids in Bacillus spp

A total of 75 strains (including 5 reference strains) of Bacillus amyloliquefaciens, B. cereus, B. circulans, B. licheniformis, B. megaterium, B. pumilus, B. sphaericus, B. subtilis, and B. thuringiensis and 36 species-unidentified Bacillus strains were surveyed for plasmids by cesium chloride-ethidium bromide equilibrium centrifugation of cell lysates in a study of antibiotic resistance in host cells. Of the 111 strains, 13 (including 3 reference strains) were found to harbor plasmids, and 5 of the 13 showed antibiotic resistance. This antibiotic resistance appeared not to be due to the plasmids, however, because the trait was not cured by cultivation of cells in nutrient medium containing ethidium bromide (1 microgram/ml), sodium dodecyl sulfate (0.2 micrograms/ml), or novobiocin (1 microgram/ml), except in one strain, in which kanamycin and streptomycin resistances were cured by novobiocin. One strain of B. amyloliquefaciens, S294, was found to harbor a plasmid, pFTB14, which differed from the plasmid species of classes 1 to 6 in B. subtilis and B. amyloliquefaciens, as determined by restriction analysis and DNA contour length determination. However, in DNA-DNA hybridization on a filter after Southern blotting from an agarose gel, the pFTB14 DNA hybridized with plasmids of classes 1 to 5. Three strains of B. thuringiensis each carried at least 4 to 11 plasmid species, whereas no plasmids were detected in four strains of B. cereus, which, in relation to B. thuringiensis, is closely related taxonomically and has highly homologous DNA sequences. The plasmid DNAs prepared from species other than B. subtilis and B. amyloliquefaciens did not hybridize with that of pFTB14.

Elimination of plasmid-linked polyglutamate production by Bacillus subtilis (natto) with acridine orange

Treatment of Bacillus subtilis (natto) strains Asahikawa, F, and M with acridine orange resulted in the conversion of approximately 64.2% of the Asahikawa population, 22.4% of the F population, and 9.2% of the M population to polyglutamate-nonproducing colonies. Such curing is suggestive of the involvement of plasmid DNA. Samples of cleared lysates of both parental and their cured strains were subjected to agarose gel electrophoresis to determine the plasmid composition. Parental strains were found to possess a plasmid, but polyglutamate-nonproducing derivatives were missing the plasmid. The plasmid-linked polyglutamate production, which was originally isolated from B. subtilis (natto), could be transformed in B. subtilis.

Transformation of Bacillus thuringiensis subsp. galleria protoplasts by plasmid pBC16

Protoplasts of the entomopathogenic bacterium Bacillus thuringiensis subsp. galleria were transformed by plasmid pBC16. The frequency of transformation was much lower than that of Bacillus subtilis. All isolated B. thuringiensis transformants were characterized by increased sensitivity to lysozyme as compared with the original strain.

New cryptic plasmid of Bacillus subtilis and restriction analysis of other plasmids found by general screening

A new cryptic plasmid, pTA1030 (4.5 megadaltons, copy number 16), was characterized by restriction analysis, together with some other plasmids of Bacillus subtilis.

Insertional inactivation of trpC in cloned Bacillus trp segments: evidence for a polar effect on trpF

Plasmid pUB110 was previously used as a vector to clone fragments of deoxyribonucleic acid that complement the trpC2 mutation in Bacillus subtilis from endonuclease EcoRI digested B. licheniformis, B. pumilus, and B. subtilis cellular deoxyribonucleic acid. Each of several such trp plasmids was subsequently shown to contain a segment of the trp gene cluster on the basis of genetic complementing activity. In the present study, analysis of the Trp enzyme levels in B. subtilis harboring the constructed trp plasmids confirms the genetic constitution of the plasmids. Thus, plasmids that complement mutations in specific trp genes specify the corresponding enzyme activities. The levels of the plasmid-specified Trp enzymes in B. subtilis were generally above the repressed level of the chromosomally specified Trp enzymes and equal to or below the derepressed levels of the chromosomally specified Trp enzymes. Certain cloned trp segments contain a single HindIII-sensitive site. Insertion of HindIII-generated deoxyribonucleic acid fragments into these trp plasmids resulted in inactivation of trpC complementing activity, loss of the trpC-specified enzyme activity, and a 10-fold reduction in the specific activity of the plasmid-specified trpF product. The HindIII insertions had no detectable effect on the level of the trpD product, nor did the insertions detectably alter plasmid-specified complementing activity other than to abolish trpC complementation. Removal of the HindIII insertions was accompanied by recovery of trpC complementing activity and restoration of the trpC-and trpF-determined enzymes to the levels specified by the parent plasmids.

High frequency transformation of Bacillus subtilis protoplasts by plasmid DNA

A highly efficient method for transformation of Bacillus subtilis by plasmid DNA is reported. The procedure, which involves polyethylene glycol-induced DNA uptake by protoplasts and subsequent regeneration of the bacterial cell wall, yields up to 80% transformants with an efficiency of 4 x 10(7) transformants per microgram of supercoiled DNA. Plasmids constructed by in vitro ligation or endonuclease-generated fragments of linear plasmid DNA can also transform PEG-treated protoplasts, but at a lower frequency.

Isolation and characterization of plasmid from the Bacillus brevis var. G.-B. cells

The plasmid designated pAD1 was isolated from the cells of four variants of Bacillus brevis var. G.-B. The plasmid DNA has a molecular weight of about 47.1 x 10(6) daltons and contains 43.4 mole % G+C. The bulk of pAD1 DNA (96--98%) is associated with the fraction of chromosome DNA and membranes. Restriction endonucleases Sma I, Sal I and Bam HI cleaved the plasmid DNA into two, two and six fragments, respectively. The cleavage map of the pAD1 genome has been constructed for these three endonucleases. Restriction enzymes Eco RI, Hind III, Kpn I and Pst I hydrolized the plasmid DNA into 16, 21, 10 and 9 fragments, respectively. The presence of repeated sequences in the plasmid genome was shown based on pAD1 DNA cleavage by these endonucleases.

Recombination between compatible plasmids containing homologous segments requires the Bacillus subtilis recE gene product

Plasmid pSL103 was previously constructed by cloning a Trp fragment (approximately 2.3 X 10(6) daltons) from restriction endonuclease EcoRI-digested chromosome DNA of Bacillus pumilus using the neomycin-resistance plasmid pUB110 (approximately 2.8 X 10(6) daltons) as vector and B. subtilis as transformation recipient. In the present study the EcoRI Trp fragment from pSL103 was transferred in vitro to EcoRI fragments of the Bacillus plasmid pPL576 to determine the ability of the plasmid fragments to replicate in B. subtilis. Endonuclease EcoRI digestion of pPL576 (approximately 28 X 10(6) daltons) generated three fragments having molecular weights of about 13 X 13(6) (the A fragment), 9.5 X 10(6) (B fragment, and 6.5 X 10(6) (C fragment). Trp derivatives of pPL576 fragments capable of autonomous replication in B. subtilis contained the B fragment (e.g., pSL107) or both the B and C fragments (e.g., pSL108). Accordingly, the B fragment of pPL576 contains information essential for autonomous replication. pSL107 and pSL108 are compatible with pUB110. Constructed derivatives of the compatible plasmids pPL576 and pUB110, harboring genetically distinguishable EcoRI-generated Trp fragments cloned from the DNA of a B. pumilus strain, exhibited relatively high frequency recombination for a trpC marker when the plasmid pairs were present in a recombination-proficient strain of B. subtilis. No recombination was detected when the host carried the chromosome mutation recE4. Therefore, the recE4 mutation suppresses recombination between compatible plasmids that contain homologous segments.

Molecular cloning of genetically active fragments of Bacillus DNA in Bacillus subtilis and properties of the vector plasmid pUB110

Plasmid pUB110 (approximately 2.8 x 10(6) daltons), originally detected in Staphylococcus aureus, specifies resistance to neomycin and has been transformed into Bacillus subtilis 168, In B. subtilis, pUB110 is stably maintained at about 50 copies per chromosome and renders the host resistant to neomycin sulfate at 5 microgram/ml. pUB110 isolated from B. subtilis transforms Rec+ and recE4-containing strains of B. subtilis at frequencies greater than or equal to 10(3) transformants per microgram of plasmid. pUB110 was transferred by PBS1 or SP10 transduction from B. subtilis to strains of B. pumilus and B. licheniformis. pUB110 is compatible with each of four previously described Bacillus plasmids, including pPL576, pPL10, pPL7065, and pPL2. pUB110 contains a single EcoR1-sensitive site and was used as vector to clone DNA fragments that complement the trpC2 mutation in B. subtilis 168 from EcoR1 digests of the chromosome DNA isolated from B. pumilus strains NRRL B-3275 and NRS576, B. licheniformis strains 9945A and 749C, and B. subtilis 168. Genetic and physical properties of each of the constructed Trp derivatives of pUB110 are described.

Bacteriocin and antibiotic resistance plasmids in Bacillus cereus and Bacillus subtilis

A number of plasmids have been isolated as covalently closed circular DNAs from strains of Bacillus cereus and B. subtilis. From 12 out of 15 strains of B. cereus, plasmids could be isolated. Most of the B. cereus strains contained two or more plasmids. Their molecular weights ranged from 1.6 X 10(6) to 105 X 10(6). Bacteriocin production could be attributed to a 45 X 10(6)-dalton plasmid (pBC7) from B. cereus DSM 336, and tetracycline resistance to a 2.8 X 10(6) plasmid (pBC16) from B. cereus GP7. Two streptomycin-resistant strains of B. subtilis harbored plasmids of 5.2 X 10(6) and 9 X 10(6), respectively, which were, however, not correlated with the antibiotic resistance. The plasmid carrying resistance to tetracycline, pBC16, which was originally isolated from B. cereus, could be subsequently transformed in B. subtilis, where it is stably maintained.

Molecular cloning and in vitro transcription of Bacillus subtilis plasmid in Escherichia coli

A composite plasmid (pAT2010) has been constructed in vitro from RSF2124 and Bacillus subtilis IFO3022 plasmid (pAT1060) by covalent joining of the two DNA molecules by means of Escherichia coli DNA ligase through the cohesive ends generated by restriction endonuclease RI (EcoRI) cleavage. The composite plasmid was selected by transformation of E. coliC600r-m- with the ligated mixture after enrichment for composite plasmid by preparative agarose gel electrophoresis, and plating of the transformants on a medium containing ampicillin and colicin E1. Treatment of the composite plasmid with EcoRI yielded two fragments corresponding to the linear forms of the parental plasmids. The composite plasmids replicated as biologically functionally units in E. coli, and expressed genetic information carried by RSF2124. In the presence of chloramphenicol, the composite plasmids continued to replicate and the copy number gradually increased. Such nature of replication in the presence of chloramphenicol is characteristic to RSF2124 derived from colicin E1 factor, and so it is suggested that the replicator of RSF2124 is functional in the composite plasmid. The composite plasmid was found to synthesize mRNA of B. subtilis plasmid in cell-free extracts of E. Coli, by hybridization of the mRNA to the original plasmid DNA of pAT1060.

Host function specified by Bacillus pumilus plasmid pPL7065

Plasmid pPL7065 ( approximately 4.7 x 10(6) daltons; approximately 20 copies per chromosome) determines the production of, and immunity or resistance to, a killing activity in strains of Bacillus pumilus. Plasmid pPL7065 is compatible with plasmid pPL576 ( approximately 28 x 10(6) daltons; approximately 2 copies per chromosome).

Isolation and characterization of four types of plasmids from Bacillus subtilis (natto)

Covalently closed circular deoxyribonucleic acids were found in 10 strains of Bacillus natto. The plasmids could be classified into four types on the basis of the molecular weights as well as the patterns in agarose gel electrophoresis after digestion with restriction endonucleases: (i) plasmids (seven were detected) with a molecular weight of 3.6 X 10(6); (ii) plasmids (two were detected) with a molecular weight of 4.0 X 10(6); (iii) plasmids (eight were detected) with a molecular weight of about 34 X 10(6); and (iv), a plasmid with an approximate molecular weight of 46 X 10(6). Out of the 10 plasmid-carrying strains, 6 (IFO3009, IFO3013, IFO3335, IFO13169, IAM1143, and IAM1207) harbored both type 1 and 3 plasmids; 2 (IAM1114 and IAM1168) harbored both type 2 and 3 plasmids, and IFO3936 and IAM1163 carried type 1 and 4 plasmids, respectively.

Temperature range variants of Bacillus megaterium

Facultatively and obligately thermophilic variants were isolated from 3 out of 12 tested mesophilic Bacillus megaterium strains. The variants occurred at a frequency of 10(-8)-10(-9). The ability to grow at elevated temperatures was cured by means of treatment with acridine orange. Stable revertants were isolated from facultatively and obligately thermophilic variants. An unknown type of megacin was produced by the facultative thermophiles. This megacin attacked mesophilic and obligately thermophilic strains. The thermophiles displayed a few divergent taxonomic characteristics but a close relationship between the strains was indicated by the megacin spectrum and sensitivity to phage. Arrhenius plots revealed that the strains could be considered as temperature range variants and that the temperature characteristic increased with growth at a higher temperature range. The case for a plasmid involvement in the phenomenon is discussed.

Effect of site-specific endonuclease digestion on the thyP3 gene of bacteriophage phi 3T and the thyP11 gene of bacteriophage rho11

phi 3T and rho11 are closely related bacteriophages of Bacillus subtilis which can "convent" thymine auxotrophs to thymine prototrophs upon infection or transfection. The effect of endonuclease digestion on the ability of both bacteriophage and prophage DNA from phi eT and rho11 to transform for thymine prototrophy was determined. All of the endonucleases tested: BamHI, Bg/II, BsuRI, EcoRI, HindII+ III, and HpaII reduced the efficiency of thyP transformation to an equal extent in prophage and bacteriophage DNA. Only HpaII completely abolished thyP transformation. The reduction in transformation with BamHI, Bg/II, BsuRI, EcoRI, and HpaII fragments is size related. The thyP transforming fragments generated by these endonucleases are potentially clonable.

Isolation and characterization of four plasmids from Bacillus subtilis

Nineteen Bacillus subtilis isolates obtained from type culture collections were examined for the presence of covalently closed circular duplex deoxyribonucleic acid molecules by the technique of cesium chloride-ethidium bromide density gradient centrifugation. Four of the 19 strains tested carried covalently closed circular molecules. Two of these strains (IFO3022, IFO3215) harbored a similar plasmid with a molecular weight of 5.4 X 10(6). The other two strains (IAM1232, IAM1261) carried 4.9 C 10(6)-and 5.3 X 10(6)-dalton plasmids, respectively. These plasmid-harboring strains did not show phenotypic traits such as antibiotic resistance orbacteriocin production. The plasmid deoxyribonucleic acids were digested by three restriction endonucleases, EcoRI, HindIII, and BamNI, and were classified into three different types from their electrophoretic patterns in agarose gels.

Transformation of Bacillus subtilis and Escherichia coli by a hybrid plasmid pCD1

The gene thyP3 from Bacillus subtilis bacteriophage phi 3T was cloned in the plasmid pMB9. The resulting chimeric plasmid, pCD1, is effective in transforming both Escherichia coli and Bacillus subtilis to thymine prototrophy. The activity of the thyP3 gene product, thymidylate synthetase, was assayed and found to be 9 times greater in a transformed strain of Escherichia coli than in a phi 3T lysogen of Bacillus subtilis. The physical location of restriction sites has been determined for two related plasmids pCD1 and pCD2. Hybridization studies clearly indicate that the plasmid gene responsible for Thy+ transformation is the gene from the bacteriophage phi 3T. The lack of restriction in this transformation process is consistent with our previous studies using bacterial DNA in heterospecific exchanges indicating that the nucleotide sequence surrounding the gene is the dominant factor in determining interspecific transformation.

Two-dimensional restriction analysis of the Bacillus subtilis genome: gene purification and ribosomal ribonucleic acid gene organization

With two-dimensional restriction enzyme analysis we have been able to cleave the Bacillus subtilis genome and resolve the resulting deoxyribonucleic acid (DNA) segments into discrete bands on agarose gels. A general procedure for gene purification has been developed by coupling multidimensional restriction analysis with a biological assay for gene detection. The organization of ribosomal ribonucleic acid (rRNA) genes was studied by hybridizing 16S and 23S rRNA probes to the two-dimensional DNA banding patterns.

Genetic aspects of bacterial endospore formation

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Bacillus pumilus plasmid pPL10: properties and insertion into Bacillus subtilis 168 by transformation

Bacillus pumilus ATCC 12140 harbors 10 or more copies per chromosome of each two small plasmids. Variants of this strain were isolated which were sensitive to a killing activity produced by the plasmid-containing parent. Each of 24 such sensitive (S) variants tested lacked detectable levels of supercoiled deoxyribonucleic acid. Transduction of S variants to the Kill+ phenotype was performed using phage PBP1 propagated on a mutant of ATCC 12140, designated strain L10, that remained Kill+ but retained only a single plasmid species (plasmid pPL10; molecular weight, approximately 4.4 X 10(6), approximately 20 copies per chromosome; RHO = 1.698). Resulting Kill+ transductants of S variants contained a single plasmid species having a size and copy number comparable to that of pPL10. Transfer of pPL10 from strain L10 TO B. pumilus strain NRS 576 was accomplished by transduction with selection for the Kill+ phenotype. Strain NRS 576 naturally harbors about two copies per chromosome of a 28-million-dalton plasmid, pPL576. In Kill + transductants of NRS 576, plasmids pPL10 and pPL576 stably coexisted at a ratio of about 11 molecules of pPL10 to 1 molecule of pPL576. Therefore, pPL576 and pPL10 are compatible plasmids. B. subtilis 168 is naturally resistant to pPl10- determined killing activity. Plasmid pPl10 was therefore inserted into B-subtilis 168 by transformation, using an indirect selection procedure and a spoB mutant as recipient. The plasmid is stably maintained at an estimated 10 copies per chromosome in the spore- recipient and in spore+ transformants. pPL10 is sensitive to cleavage by the endonucleases Hind III and EcoR1.

Low-frequency, pbsi-mediated plasmid transduction in Bacillus pumilus

Three bacteriophages were tested for ability to transduce the plasmid of pPL10 between W mutant derivatives of Bacillus pumilus NRS 576. Phage PBP1- and PMB1-generated plasmid transductants occurred at about 10% the frequency of transductants for a chromosome marker. Phage PBS1-generated plasmid transductants occurred at less than 0.1% the frequency of transductants for a chromosome marker. Possible reasons for the extremely reduced capacity of PBS1 to generate plasmid transductants are discussed.