Abstract：
In this study, the transcriptome analysis was practiced to identify potential genes of probiotic Bacillus subtilis BSN313 involved in selenium (Se) enrichment metabolism. The transcriptomic variation of the strain was deliberated in presence of three different sodium selenite concentrations (0, 3, and 20 μg/mL). The samples were taken at 1 and 13 h subsequent to inoculation of selenite and gene expression profiles in Se metabolism were analyzed through RNA sequencing. The gene expression levels of the pre log phase were lower than the stationary phase. It is because, the bacteria has maximum grown with high concentration of Se (enriched with organic Se), at stationary phase. Bacterial culture containing 3 μg/mL concentration of inorganic Se (sodium selenite) has shown highest gene expression as compared to no or high concentration of Se. This concentration (3 μg/mL) of sodium selenite (as Se) in the medium promoted the upregulation of thioredoxin reductase expression, whereas its higher Se concentration inhibited the formation of selenomethionine (SeMet). The result of 5 L bioreactor fermentation showed that SeMet was also detected in the fermentation supernatant as the growth entered in the late stationary phase and reached up to 857.3 ng/mL. The overall intracellular SeMet enriched content in BSN313 was extended up to 23.4 μg/g dry cell weight. The other two selenoamino acids (Se-AAs), methyl-selenocysteine, and selenocysteine were hardly detected in medium supernatant. From this study, it was concluded that SeMet was the highest content of organic Se byproduct biosynthesized by B. subtilis BSN313 strain in Se-enriched medium during stationary phase. Thus, B. subtilis BSN313 can be considered a commercial probiotic strain that can be used in the food and pharmaceutical industries. This is because it can meet the commercial demand for Se-AAs (SeMet) in both industries.
摘要：
在这项研究中,进行转录组分析以鉴定参与硒（Se）富集代谢的益生菌枯草芽孢杆菌BSN313的潜在基因。在存在三种不同的亚硒酸钠浓度（0、3和20μg/mL）的情况下，研究了菌株的转录组变异。在亚硒酸盐接种后1和13小时采集样品，并通过RNA测序分析Se代谢中的基因表达谱。预对数期的基因表达水平低于稳定期。这是因为,细菌在高浓度硒（富含有机硒）的情况下最大限度地生长，在固定阶段。与不含或高浓度的Se相比，含有3μg/mL浓度的无机Se（亚硒酸钠）的细菌培养物显示出最高的基因表达。培养基中亚硒酸钠（以Se计）的浓度（3μg/mL）促进了硫氧还蛋白还原酶表达的上调，而较高的Se浓度抑制了硒代蛋氨酸（SeMet）的形成。5L生物反应器发酵结果表明，随着生长进入稳定期后期，发酵上清液中也检测到SeMet，最高可达857.3ng/mL。BSN313中的总细胞内SeMet富集含量延长至23.4μg/g干细胞重量。其他两种硒代氨基酸（Se-AAs），甲基硒代半胱氨酸，在培养基上清液中几乎检测不到硒代半胱氨酸。从这项研究中,结论是，SeMet是枯草芽孢杆菌BSN313菌株在固定阶段在富硒培养基中生物合成的有机硒副产物含量最高的。因此，枯草芽孢杆菌BSN313可被认为是可用于食品和制药工业的商业益生菌菌株。这是因为它可以满足两个行业中对Se-AAs(SeMet)的商业需求。
