Genetic stability of bacterium as a starter culture is vital for product quality in fermentation industry. The commercial strain Lactobacillus plantarum NCU116 widely used in fruit and vegetable fermentation was induced with various stressors to investigate the stability of potential prophages. PHAge Search Tool (PHAST) identified three potential prophages in bacterial genome. By spectrophotometric analysis, mitomycin C (MMC), lactic acid, and bile salt were found to inhibit the growth of L. plantarum NCU116 while ethanol and hydrogen peroxide had no notable impacts. Transcriptions of four phage-synthesizing genes (phaR, phacap, phaada, phatail) and four phage-resistant genes (cas116, helR, hsd1, hsd2) under stressors were investigated by quantitative reverse transcription PCR. MMC was found to most significantly upregulated transcriptions of phage-synthesizing genes, followed by lactic acid and bile salt. By transmission electron microscopy, no virus particles from the lysates of strain NCU116 treated by MMC were observed, corresponding to the result that no phage nucleic acids could be extracted from the supernatants of strain NCU116 treated by MMC. This study suggested that no prophages could be induced from L. plantarum NCU116 by strong inducer MMC, indicating its genetic stability, which supports the comprehensive application of strain NCU116 in industry without causing fermentation failure.

中文翻译：

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商业菌株植物乳杆菌 NCU116 在各种应激源下潜在原噬菌体的稳定性

细菌作为发酵剂的遗传稳定性对于发酵工业中的产品质量至关重要。用各种压力源诱导广泛用于水果和蔬菜发酵的商业菌株植物乳杆菌 NCU116，以研究潜在原噬菌体的稳定性。PHAge 搜索工具 (PHAST) 在细菌基因组中鉴定了三种潜在的原噬菌体。通过分光光度法分析，发现丝裂霉素 C (MMC)、乳酸和胆汁盐抑制植物乳杆菌 NCU116 的生长，而乙醇和过氧化氢没有显着影响。通过定量逆转录 PCR 研究了压力源下四种噬菌体合成基因（phaR、phacap、phaada、phatail）和四种噬菌体抗性基因（cas116、helR、hsd1、hsd2）的转录。发现 MMC 最显着地上调噬菌体合成基因的转录，其次是乳酸和胆汁盐。透射电镜显示，MMC处理的NCU116菌株裂解液中未观察到病毒颗粒，对应于MMC处理的NCU116菌株上清液中未提取到噬菌体核酸。本研究表明，强诱导剂MMC不能从植物乳杆菌NCU116中诱导出原噬菌体，表明其遗传稳定性好，支持菌株NCU116在工业上的综合应用，且不会导致发酵失败。与MMC处理的菌株NCU116的上清液中没有提取出噬菌体核酸的结果相对应。本研究表明，强诱导剂MMC不能从植物乳杆菌NCU116中诱导出原噬菌体，表明其遗传稳定性好，支持菌株NCU116在工业上的综合应用，且不会导致发酵失败。与MMC处理的菌株NCU116的上清液中没有提取出噬菌体核酸的结果相对应。本研究表明，强诱导剂MMC不能从植物乳杆菌NCU116中诱导出原噬菌体，表明其遗传稳定性好，支持菌株NCU116在工业上的综合应用，且不会导致发酵失败。