@article{romero_klaenhammer_1992, title={IS946-mediated integration of heterologous DNA into the genome of Lactococcus lactis subsp. lactis}, volume={58}, number={2}, journal={Applied and Environmental Microbiology}, author={Romero, D. A. and Klaenhammer, T. R.}, year={1992}, pages={699} }
 @article{romero_klaenhammer_1991, title={CONSTRUCTION OF AN IS946-BASED COMPOSITE TRANSPOSON IN LACTOCOCCUS-LACTIS SUBSP LACTIS}, volume={173}, ISSN={["0021-9193"]}, DOI={10.1128/jb.173.23.7599-7606.1991}, abstractNote={An artificial composite transposon was constructed based on the lactococcal insertion sequence IS946. A 3.0-kb element composed of the pC194 cat gene (Cmr) flanked by inversely repeated copies of IS946 was assembled on pBluescript KS+. When subcloned into the shuttle vector pSA3 (Emr), two putative transposons were created on the recombinant plasmid pTRK128: the 3.0-kb Cmr element (Tn-CmA) and an inverse 11.5-kb Emr element (Tn-EmA). pTRK128 was electroporated into the recombination-deficient strain Lactococcus lactis MMS362, which contains the self-transmissible plasmid pRS01. An MMS362 Cmr Emr transformant was used to assay for transposition events via conjugal mobilization of pTRK128-encoded Cmr or Emr to L. lactis LM2345. Transfer of either marker alone occurred at frequencies of ca. 2 x 10(-4) per input donor. Approximately 19% of the Emr transconjugants were Cms, indicating loss of the cat gene marker. No Cmr Ems transconjugants were recovered (n = 550). Plasmid analysis showed that the Cms Emr isolates contained a single large plasmid that was determined to be a cointegrate between pRS01 and the Tn-EmA element. A 32P-labeled pSA3 probe hybridized specifically to pTRK128 sequences and revealed different junction fragments within each of the cointegrate plasmids. DNA sequence analysis of the Tn-EmA::pRS01 junctions from a representative cointegrate verified transposition by Tn-EmA. This represents the first example of a functional composite transposon in the genus Lactococcus and serves as an experimental tool and model for the genetic analyses of transposons in these organisms.}, number={23}, journal={JOURNAL OF BACTERIOLOGY}, author={ROMERO, DA and KLAENHAMMER, TR}, year={1991}, month={Dec}, pages={7599–7606} }
 @article{romero_klaenhammer_1990, title={ABORTIVE PHAGE INFECTION AND RESTRICTION MODIFICATION ACTIVITIES DIRECTED BY PTR2030 DETERMINANTS ARE ENHANCED BY RECOMBINATION WITH CONJUGAL ELEMENTS IN LACTOCOCCI}, volume={136}, ISSN={["0022-1287"]}, DOI={10.1099/00221287-136-9-1817}, abstractNote={Summary: The recombinant plasmid pTK6 is composed of a 13·6 kb fragment from pTR2030 encoding phage resistance determinants for restriction/modification (R+/M+) and abortive phage infection (Hsp+) cloned into shuttle vector pSA3 (erythromycin resistance, Emr). Conjugal matings were performed to mobilize pTK6-encoded markers from Lactococcus lactis subsp. lactis MMS362 and MG1363. Emr transconjugants were recovered at 10−6 per input donor and harboured pTK6 or recombinant plasmids not found in either parental strain. The recombinant plasmids (pTRK78 and pTRK79) encoded Emr, Hsp+ and R+/M+, and transferred at high frequency in second-round matings. Mobilization of pTK6 from the otherwise plasmid-free donor, L. lactis MG1363, confirmed the presence of a conjugal element in this strain. Phage resistance in transconjugants containing pTRK78 and pTRK79 was markedly enhanced over pTK6-directed Hsp+ and R+/M+. In L. lactis LM2345 transconjugants, a reduction in plaque size was accompanied by a significant decrease in the efficiency of plaquing for phages c2 (10−2 to 10−6) and p2 (< 10−9). L. lactis NCK203 transconjugants containing pTRK78 or pTRK79 exhibited an additional 100-1000-fold reduction in the plaquing efficiency of o48 (10−4 to 10−5) over pTK6 imposed restriction (10−2). Increased resistance to phage was a consequence of the physical interaction of pTR2030-derived sequences on pTK6 with a conjugal element resident in the donor strains.}, journal={JOURNAL OF GENERAL MICROBIOLOGY}, author={ROMERO, DA and KLAENHAMMER, TR}, year={1990}, month={Sep}, pages={1817–1824} }