Spontaneous auxotrophic and pigmented mutants occurring at high frequency in Bacillus pumilus NRRL B-3275

Harnessing Native Bacillus spp. for Sustainable Wheat Production

The genus Bacillus has been widely applied in contemporary agriculture as an environmentally-friendly biological agent. However, the real effect of commercial Bacillus-based fertilizers and pesticides varies immensely in the field. To harness Bacillus for efficient wheat production, we reviewed the diversity, functionality, and applicability of wheat-associated native Bacillus for the first time. Our main findings are: (i) Bacillus spp. inhabit the rhizosphere, root, stem, leaf, and kernel of wheat; (ii) B. subtilis and B. velezensis are the most widely endophytic species that can be isolated from both below and aboveground tissues; (iii) major functions of these representative strains are promotion of plant growth and alleviation of both abiotic and biotic stresses in wheat; (iv) stability and effectiveness are 2 major challenges during field application; (v) a STVAE pipeline that includes 5 processes, namely, Screen, Test, Validation, Application, and Evaluation, has been proposed for the capture and refinement of wheat-associated Bacillus spp. In particular, this review comprehensively addresses possible solutions, concerns, and criteria during the development of native Bacillus-based inoculants for sustainable wheat production.

Physiological role and potential clinical interest of mycobacterial pigments

The production of pigments by bacterial colonies has sparked interest among bacteriologists since the 19th century, whether for taxonomy or, in the case of carotenoids for their association with antibiotics resistance. Mycobacteria have gained a very special place in the bacterial world due to their clinical importance. Alone, Mycobacterium tuberculosis is responsible for about two million deaths annually worldwide making tuberculosis one of the most influential diseases in the history of mankind. Almost half of the Nontuberculous Mycobacteria species identified are associated with opportunistic infections in animals and humans. Mycobacterial pigmentary characteristics started to be documented about 80 years ago; but to date, their main use has been only for limited taxonomic and identification purposes. While mycobacterial pigments, especially carotenoids have been clearly associated with cellular photoprotection and survival, the regulation of their production and their physiological role have been largely unstudied. Recent advances in deciphering mycobacterial genomes and characterization of carotenoid synthesis genes, combined with an urgent need for innovative approaches to understand Mycobacterium tuberculosis pathogenic properties open new avenues for exciting research opportunities that might lead to new therapeutic strategies against a devastating secular disease.

Genetic effects of dimethyl sulfate, diethyl sulfate, and related compounds

DMS and DES are monofunctional alkylating agents that have been shown to induce mutations, chromosomal aberrations, and other genetic alterations in a diversity of organisms. They have also been shown to be carcinogenic in animals. As an alkylating agent, DMS is a typical SN2 agent, attacking predominantly nitrogen sites in nucleic acids. DES is capable of SN1 alkylations as well as SN2 and thereby causes some alkylation on oxygen sites including the O6-position of guanine which is thought to be significant in mutagenesis by direct mispairing. The mutagenicity of DMS is better explained in terms of indirect, repair-dependent processes. With respect to both alkylating activity and genetic effects, striking similarities are found between DMS and MMS and between DES and EMS. In most systems where they have been tested, both DMS and DES are mutagenic. Results of many of the mutagenesis studies involving these compounds and other alkylating sulfuric acid esters are summarized in Tables 6, 7, 8, 9 and 10 of this review. Most data are consistent with these agents acting primarily as base-pair substitution mutagens. In the case of DES, strong specificity for G.C to A.T transitions has been reported in some systems but has not been clearly supported in some others. Low levels of frameshift mutations of the deletion type are also likely. In addition to the induction of mutations, recombinogenic and clastogenic effects have been described.

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.

Temperate bacteriophage infectious for asporogenic variants of Bacillus pumilus

Bacillus pumilus strain NRRL B-3275 is lysogenic for an inducible, nondefective temperate bacteriophage phi75. phi75 infects and lysogenizes several asporogenic mutants of B. pumilus strain NRS 576 but does not productively infect the spore(+) parent. phi75 DNA is a linear duplex with a mol wt of about 29 x 10(6) and a buoyant density of 1.701 g/cm(3). The location of the phi75 prophage attachment site on the chromosome of both host strains is adjacent to a lysine marker. The apparent order is phi75 att lys trp.

Some properties of the PBP1 transduction system in Bacillus pumilus

Bacteriophage PBP1 is a flagella-specific virus that performs generalized transduction in strains of Bacillus pumilus. PBP1 is morphologically and serologically distinct from two other flagella-specific phages, PBS1 and SP-15, which perform generalized transduction in certain Bacillus species. The DNA extracted from PBP1 particles has a buoyant density of 1.690 g/cm(3) in cesium chloride gradients, a melting temperature of 86.1 C, and a sedimentation velocity of 47S in neutral sucrose gradients. Assuming the molecule is a linear duplex, PBP1 DNA has a molecular weight of approximately 76 x 10(6). In two strains of B. pumilus which are sensitive to both PBP1 and PBS1, co-transducible genetic markers are more tightly linked by PBS1 transduction than by PBP1 transduction. The size of the fragment of bacterial DNA carried by PBP1-transducing particles, inferred from transduction studies and sedimentation analysis of viral DNA, suggests that PBP1 may be useful for genetic studies of extrachromosomal DNA elements present in two strains of B. pumilus. Genetic exchange of chromosomally located genes between the plasmid(+) and plasmid(-)B. pumilus strains NRS 576 and NRRL B-3275 has been demonstrated by PBP1 transduction.

Enzymatic defects in three genetic classes of serine-requiring mutants of Bacillus pumilus

Serine-requiring mutants of Bacillus pumilus NRRL B-3275 have been divided into three groups based on the position of the mutant loci on the linkage map of this organism. Representatives of each group were found deficient in enzymatic activities that constitute the phosphorylated pathway for serine biosynthesis. The evidence suggests that the genes coding for the enzymes of the phosphorylated pathway of serine biosynthesis are not clustered in B. pumilus.

Plasmid in Bacillus pumilus and the enhanced sporulation of plasmid-negative variants

Approximately 3% of the deoxyribonucleic acid (DNA) of Bacillus pumilus NRS576 can be isolated as covalently closed, circular duplex molecules of homogeneous size. The mol wt of the 576 plasmid is approximately 30 million. NRS576 (plasmid(+)) is oligosporogenic; less than 1% of the cells form spores during incubation in liquid AK sporulation medium. Variants that form spores at a high frequency (greater than 50% spores in 24 h) occur spontaneously at a frequency of approximately 10(-5). More than 25 such variants have been examined and all lack detectable plasmid DNA. A relationship appears to exist between the oligosporogenic properties of NRS576 and the presence of the 576 plasmid.