Transduction in Bacillus megaterium

Bacillus megaterium—from simple soil bacterium to industrial protein production host

Bacillus megaterium has been industrially employed for more than 50 years, as it possesses some very useful and unusual enzymes and a high capacity for the production of exoenzymes. It is also a desirable cloning host for the production of intact proteins, as it does not possess external alkaline proteases and can stably maintain a variety of plasmid vectors. Genetic tools for this species include transducing phages and several hundred mutants covering the processes of biosynthesis, catabolism, division, sporulation, germination, antibiotic resistance, and recombination. The seven plasmids of B. megaterium strain QM B1551 contain several unusual metabolic genes that may be useful in bioremediation. Recently, several recombinant shuttle vectors carrying different strong inducible promoters and various combinations of affinity tags for simple protein purification have been constructed. Leader sequences-mediated export of affinity-tagged proteins into the growth medium was made possible. These plasmids are commercially available. For a broader application of B. megaterium in industry, sporulation and protease-deficient as well as UV-sensitive mutants were constructed. The genome sequence of two different strains, plasmidless DSM319 and QM B1551 carrying seven natural plasmids, is now available. These sequences allow for a systems biotechnology optimization of the production host B. megaterium. Altogether, a "toolbox" of hundreds of genetically characterized strains, genetic methods, vectors, hosts, and genomic sequences make B. megaterium an ideal organism for industrial, environmental, and experimental applications.

Inactivation of the major extracellular protease from Bacillus megaterium DSM319 by gene replacement

An efficient method for gene replacement in Bacillus megaterium was developed and used to inactivate the chromosomal neutral protease gene (nprM) from strain DSM319. A temperature-dependant suicide vector was constructed to allow replacement of the normal chromosomal copy with an altered version of the nprM gene. One mutant B. megaterium MS941 was selected for further characterization. Measurement of extracellular protease activity from strain MS941 indicated the existence of an additional minor extracellular protease in B. megaterium. Inhibitor studies revealed that this minor protease, comprising only 1.4% of the wild-type total extracellular protease activities, is a serine-type enzyme.

Transposition of Tn917 in Bacillus megaterium

Transposon Tn917, carried on plasmid pTV1, was introduced into Bacillus megaterium and transposed efficiently and apparently randomly. Insertional mutations included at least eight different auxotrophic loci, two carbon source loci, and sporulation loci. One trp::Tn917 mutation was further verified as an insertion by both reversion and transduction.

Genetics of leucine biosynthesis in Bacillus megaterium QM B1551

Genes involved in the biosynthesis of leucine have been mapped in Bacillus megaterium QM B1551, using transducing phage MP13. Mutations were designated leuA, leuB, or leuC on the basis of enzyme assays. Two mutant strains were deficient in the enzyme activities of leuA (alpha-isopropylmalate synthase) and leuC (beta-isopropylmalate dehydrogenase) and so may contain polar mutations. Fine-structure transduction mapping established the gene order leuC-leuB-leuA-ilv-hem-phe. The orientation of the leu genes to the ilv gene is the same as in Bacillus subtilis, but the relationship in respect to two other linked markers, hem and phe, differs.

Cotransductional mapping of the trp-his region of Bacillus megaterium

Eight trp mutations (four trpE, two trpB, one trpC, and one trpD) have been mapped in Bacillus megaterium QM B1551 and were found to be linked to two hisH mutations and unlinked to several other his mutations.

Characterization of a new Bacillus megaterium bacteriophage, MJ-1, from tropical soil

A new Bacillus megaterium bacteriophage is characterized. It is a tailed phage with regular polyhedral head belonging to Bradley's group B. Head and tail dimensions are 56.4 and 300 nm, respectively. Lysis was restricted to strains of B. megaterium. No antigenic relationship with pumilus phage FP-1 or subtilis phage FS-1 was observed. The phage is sensitive to 60 degrees C and moderately sensitive to chloroform. The nucleic acid is double-stranded linear DNA with a G-C mole% of 38.8 and a mol wt of (53 +/- 3) X 10(6).

MP13, a generalized transducing bacteriophage for Bacillus megaterium

The first generalized transducing bacteriophage reported for Bacillus megaterium has been characterized. Optimum conditions for lysate production and transduction procedures were established so that transducing frequencies of 8 x 10(-6) and higher are now possible. The phage, MP13, has a head diameter of 97 nm and a contractile tail (202 by 17 nm) and adsorbs to the periphery of the cell. MP13 was inactivated rapidly at 60 degrees C, but not at 55 degrees C, and was sensitive to toluene, ether, and chloroform. When centrifuged in a neutral CsCl gradient, two bands were observed, a major band of 1.490 g cm-3 and a minor band of 1.482 g cm-3 buoyant density. The major band contained only infective particles, whereas the minor band contained both infective and transducing particles. Phage DNA was resistant to several restriction endonucleases, but yielded 9 fragments with MboI, more than 34 with HindIII, and 7 with BstEII. The molecular weights for the fragments from MboI-BstEII double digests total 97 x 10(9).