Yang Leyun, Zheng Cheng, Chen Yong, Ying Hanjie
State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, Nanjing, China.
National Engineering Research Center for Biotechnology, College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, Nanjing, China.
Front Microbiol. 2018 Aug 23;9:1860. doi: 10.3389/fmicb.2018.01860. eCollection 2018.
immobilization is commonly used for efficient ethanol fuel production in industry due to the relatively higher ethanol stress resistance of in biofilms relative to planktonic cells. The mechanisms of biofilm formation and stress resistance, however, remain ambiguous. By analyzing biofilm and planktonic cell transcriptomes, this study observed that (encoding a transcription factor) expression in cells increases during the biofilm formation process. To identify the role of in yeast biofilm formation and the ethanol resistance of these cells, was deleted and complemented in 1308. Results showed the deletion mutant strain demonstrated weaker biofilm formation ability both on fibers and plastic than the wild-type and these could be restored by expressing in deletion mutant. To verify the ability of to regulate the expression of genes, which encode adhesions responsible for yeast biofilm formation, gene transcription levels were measured via qRT-PCR. Relative to wild-type , the adhesion genes , and which also demonstrate increased expression in the transcriptome of yeast cells during biofilm formation, but not , were down-regulated in the mutant strain. Additionally, the mutant lost a majority of its flocculation ability, which depended on cell-cell adhesions and its slightly invasive growth ability, dependent on cell-substrate adhesion. Deleting , and decreased biofilm formation on plastics, suggesting these genes contribute to the biofilm formation process alongside . Moreover, the ethanol tolerance of yeast decreased in the deletion mutant as well as the deletion mutant, resulting in reduced biofilm formation during fermentation. It remains possible that in the later period of fermentation, when ethanol has accumulated, an over-expression of the , and genes regulated by would enhanced cell-cell adhesions and thus protect cells in the outer layer of biofilms from ethanol, a function primarily dependent on cell-cell adhesions. This work offers a possible explanation for how biofilm formation is regulated during the immobilized fermentation process, and can enhance environmental tolerance in industrial production.
由于生物膜中的细胞相对于浮游细胞对乙醇胁迫具有较高的抗性，固定化在工业上常用于高效生产乙醇燃料。然而，生物膜形成和抗胁迫的机制仍不明确。通过分析生物膜和浮游细胞的转录组，本研究观察到细胞中（编码一种转录因子）的表达在生物膜形成过程中增加。为了确定在酵母生物膜形成和这些细胞的乙醇抗性中的作用，在1308中删除并互补了。结果表明，缺失突变株在纤维和塑料上的生物膜形成能力均比野生型弱，通过在缺失突变体中表达可以恢复。为了验证调节编码负责酵母生物膜形成的粘附蛋白的基因表达的能力，通过qRT-PCR测量基因转录水平。相对于野生型，在生物膜形成过程中酵母细胞转录组中表达也增加的粘附基因、和，但不是，在突变株中下调。此外，突变体失去了大部分絮凝能力，这取决于细胞间粘附，其轻微的侵袭性生长能力取决于细胞与底物的粘附。删除、和会减少在塑料上的生物膜形成，表明这些基因与一起有助于生物膜形成过程。此外，缺失突变体和缺失突变体中酵母的乙醇耐受性降低，导致发酵过程中生物膜形成减少。仍然有可能在发酵后期，当乙醇积累时，由调节的、和基因的过表达会增强细胞间粘附，从而保护生物膜外层的细胞免受乙醇影响，这一功能主要取决于细胞间粘附。这项工作为固定化发酵过程中生物膜形成如何被调节提供了一种可能的解释，并可以提高工业生产中的环境耐受性。
