Aims: This paper describes optimization of electrotransformation of Mu transposition complexes into Lactococcus lactis cells and identification of genes affecting nisin production.
Methods and Results: The highest transformation efficiency, 1·1 × 102 transformants μg−1 of input transposon DNA, was achieved when cells were grown to an OD600 of 0·5 in the presence of 1·5% of glycine and treated with 20 μg ml−1 ampicillin for 60 min. Three insertions affecting nisin production, which were identified at nisB, fhuR, and rpiA genes, were screened from a library of ∼2000 erythromycin‐resistant transformants using a nisin bioassay method. NisB is part of the nisin biosynthetic machinery, explaining the loss of nisin production in nisB mutant. FhuR is a transcription regulator involved in sulphur acquisition. Inactivation of fhuR presumably results in a low cellular cystein level, which affects nisin biosynthesis that involves utilization of cystein. RpiA is involved in pentose phosphate pathway and carbon fixation. The rpiA mutant showed reduction in nisin production and slow growth rate.
Conclusions: The results showed that Mu transposition complex mutagenesis can be used to identify genes in L. lactis. Three genes involved in nisin production were identified.
Significance and Impact of the Study: Expanding the Mu transposition‐based mutagenesis to Lactococci adds a new tool for studies of industrially important bacteria.
We wished to investigate the outcome of surgery combined with external-beam radiotherapy (EBRT) or brachytherapy (125 I seeds) for the treatment of primary adenoid cystic carcinoma (ACC) of the oral and maxillofacial region. Data of patients with primary ACC were reviewed retrospectively. Patients were divided into EBRT and brachytherapy groups. Wide tumor excision was done to achieve negative margins. Standard radiotherapy in the EBRT group was 60 Gy. A treatment-planning system was used to create implantation plans with a prescribed dose of 60e 120 Gy and 125 I seeds were implanted postoperatively. KaplaneMeier method and log-rank tests were used to analyze local control and survival. The median duration of followup was 66.1 and 46.8 months for the EBRT group and brachytherapy group, respectively. There was no significant difference in local control, control of metastasis to regional lymph nodes, or control of distant metastasis between the two groups. There was no significant difference in overall survival, disease-specific survival, or disease-free survival in the two groups at 3 years and 5 years. The prevalence of complications in the brachytherapy group was lower than that in the EBRT group. Both methods elicited good treatment effects, but the prevalence of adverse events was lower in the brachytherapy group.
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