| molecular characterization of a phage-inducible middle promoter and its transcriptional activator from the lactococcal bacteriophage phi31. | an inducible middle promoter from the lactococcal bacteriophage phi31 was isolated previously by shotgun cloning an 888-bp fragment (p15a10) upstream of the beta-galactosidase (beta-gal) gene (lacz.st) from streptococcus thermophilus (d. j. o'sullivan, s. a. walker, s. g. west, and t. r. klaenhammer, bio/technology 14:82-87, 1996). the promoter showed low levels of constitutive beta-gal activity which could be induced two- to threefold over baseline levels after phage infection. during this stud ... | 1998 | 9473048 |
| leaky lactococcus cultures that externalize enzymes and antigens independently of culture lysis and secretion and export pathways. | a novel system that leaks beta-galactosidase (beta-gal) without a requirement for secretion or export signals was developed in lactococcus lactis by controlled expression of integrated phage holin and lysin cassettes. the late promoter of the lytic lactococcal bacteriophage phi31 is an 888-bp fragment (p(15a10)) encoding the transcriptional activator. when a high-copy-number p(15a10)::lacz.st fusion was introduced into l. lactis strains c10, ml8, nck203, and r1/r1t, high levels of the resultant ... | 2001 | 11133453 |
| overexpression of peptidases in lactococcus and evaluation of their release from leaky cells. | walker and klaenhammer (2001) developed a novel expression system in lactococcus lactis that facilitated the release of beta-galactosidase (117 kda monomer) without the need for secretion or export signals. the system is based on the controlled expression of integrated prophage holin and lysin cassettes via a lactococcal bacteriophage phi31 transcriptional activator (tac31a) that resides on a high-copy plasmid. approximately 85% of beta-galactosidase activity was detected in the supernatant of l ... | 2002 | 12416795 |
| analysis of the genetic switch and replication region of a p335-type bacteriophage with an obligate lytic lifestyle on lactococcus lactis. | the dna sequence of the replication module, part of the lysis module, and remnants of a lysogenic module from the lytic p335 species lactococcal bacteriophage phi31 was determined, and its regulatory elements were investigated. the identification of a characteristic genetic switch including two divergent promoters and two cognate repressor genes strongly indicates that phi31 was derived from a temperate bacteriophage. regulation of the two early promoters was analyzed by primer extension and tra ... | 2001 | 11229902 |
| an explosive antisense rna strategy for inhibition of a lactococcal bacteriophage. | the coding regions of six putative open reading frames (orfs) identified near the phage phi31 late promoter and the right cohesive end (cos) of lactococcal bacteriophage phi31 were used to develop antisense constructs to inhibit the proliferation of phage phi31. two middle-expressed orfs (orf 1 and orf 2) and four late-expressed orfs (orf 3 through orf 6) were cloned individually between the strong lactobacillus p6 promoter and the t7 terminator (t(t7)) to yield a series of antisense rna transcr ... | 2000 | 10618241 |