APPENDIX A 
3 
B. Current and potential vectors for recombinant molecule experiments 
Lovett and coworkers have recently described cryptic plasmids in B_. 
pumil us (17) and B_. subtil is (18). Of these organisms, B_. subtil is ATCC 
7003 appears to be the most useful since it carries one to two copies of 
a plasmid with a molecular weight of 46 x 10®. This strain is also closely 
related to B_. subtil is 168. Another strain of B_. subti 1 is (ATCC 15841) 
contains 16 copies of a plasmid with a molecular weight of 4.6 x 10®. 
Currently it is not known whether genetic markers can be readily introduced 
into these plasmids. To date it has not been possible to readily stabilize 
plasmids derived from B_. pumil us in B_. subtil is even with heavy selective 
pressure (P. Lovett, personal communication). 
Two temperate bacteriophages are under development as vectors in B_. 
subtil is , <|>3T and SP02. Lysogeny of thymine auxotrophs (strains carrying 
thy A thyB ) by bacteriophage <f>3T results in "conversion" to a Thy + phenotype. 
The attachment site for this bacteriophage and the bacteriophage gene for 
thymidylate synthetase ( thyP ) map between the bacterial thy A and thyB 
loci in the terminal region of the chromosome of B_. subti 1 is (19). The 
viral genome is readily cleaved by the site-specific endonuclease, Bam 1 
(20), to produce 5 fragments (one of which carries the thyP gene). The 
thyP carrying gene can be integrated into the bacterial genome in the 
absence of the intact viral genome. Because deletions are available that 
include the thyP region, it is theoretical ly possible to introduce thyP 
at many sites on the chromosome. The thyP gene can be readily purified 
[ 123 ] 
