Liu Li, Yu Bin, Sun Wenjun, Liang Caice, Ying Hanjie, Zhou Shengmin, Niu Huanqing, Wang Yibing, Liu Dong, Chen Yong
1National Engineering Research Center for Biotechnology, College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, Nanjing, China.
2State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, Nanjing, 211816 People's Republic of China.
Biotechnol Biofuels. 2020 Mar 16;13:54. doi: 10.1186/s13068-020-01692-1. eCollection 2020.
Biofilms, as a kind of fixed-cell community, can greatly improve industrial fermentation efficiency in immobilized fermentation, but the regulation process is still unclear, which restricts their application. Ca was reported to be a key factor affecting biofilm formation. However, the effect of Ca on biofilm structure and microbiology was yet only studied in bacteria. How Ca-mediated calcineurin signaling pathway (CSP) alters biofilm formation in bacteria and fungi has rarely been reported. On this basis, we investigated the regulation of CSP on the formation of biofilm in .
Deletion of the key genes , , or in the CSP lowered the Ca concentration in the mycelium to a different extent, inhibited the formation of biofilm, reduced the hydrophobicity and adhesion of spores, destroyed the cell wall integrity of hyphae, and reduced the flocculation ability of hyphae. qRT-PCR results showed that the expression of spore hydrophobic protein , galactosaminogalactan (GAG) biosynthesis genes (, , , ), and α-1,3-glucan biosynthesis genes (, ) in the ∆, ∆, ∆, ∆ strains were significantly down-regulated compared with those of the wild type (WT). In addition, the transcription levels of the chitin synthesis gene (, ) and β-1,3-glucan synthesis gene () were consistent with the change in chitin and β-1,3-glucan contents in mutant strains.
These results indicated that CSP affected the hydrophobicity and adhesion of spores, the integrity of mycelial cell walls and flocculation by affecting Ca levels in mycelium, which in turn affected biofilm formation. This work provides a possible explanation for how CSP changes the formation of biofilm, and reveals a pathway for controlling biofilm formation in industrial immobilized fermentation.
生物膜作为一种固定细胞群落，在固定化发酵中可极大提高工业发酵效率，但调控过程仍不明确，这限制了它们的应用。据报道，钙是影响生物膜形成的关键因素。然而，钙对生物膜结构和微生物学的影响仅在细菌中得到研究。钙介导的钙调神经磷酸酶信号通路（CSP）如何改变细菌和真菌中的生物膜形成鲜有报道。在此基础上，我们研究了CSP对[具体生物名称]生物膜形成的调控作用。
CSP中关键基因[基因名称1]、[基因名称2]、[基因名称3]或[基因名称4]的缺失使菌丝体中的钙浓度不同程度降低，抑制了[生物名称]生物膜的形成，降低了孢子的疏水性和黏附性，破坏了菌丝的细胞壁完整性，并降低了菌丝的絮凝能力。qRT-PCR结果表明，与野生型（WT）相比，Δ[基因名称1]、Δ[基因名称2]、Δ[基因名称3]、Δ[基因名称4]菌株中孢子疏水蛋白[蛋白名称]、半乳糖氨基半乳聚糖（GAG）生物合成基因（[基因名称5]、[基因名称6]、[基因名称7]、[基因名称8]）和α-1,3-葡聚糖生物合成基因（[基因名称9]、[基因名称10]）的表达显著下调。此外，几丁质合成基因（[基因名称11]、[基因名称12]）和β-1,3-葡聚糖合成基因（[基因名称13]）的转录水平与突变菌株中几丁质和β-1,3-葡聚糖含量的变化一致。
这些结果表明，CSP通过影响菌丝体中的钙水平来影响孢子的疏水性和黏附性、菌丝细胞壁的完整性以及絮凝作用，进而影响生物膜的形成。这项工作为CSP如何改变[生物名称]生物膜的形成提供了一种可能的解释，并揭示了一条控制工业固定化发酵中生物膜形成的途径。
