Cellulose degradation by cellulase is brought about by complex communities of interacting microorganisms, which significantly contribute to the cycling of carbon on a global scale. β-Glucosidase (BGL) is the rate-limiting enzyme in the cellulose degradation process. Thus, analyzing the expression of genes involved in cellulose degradation and regulation of BGL gene expression during composting will improve the understanding of the cellulose degradation mechanism. Based on our previous research, we hypothesized that BGL-producing microbial communities differentially regulate the expression of glucose-tolerant BGL and non-glucose-tolerant BGL to adapt to the changes in cellulose degradation conditions. To confirm this hypothesis, the structure and function of functional microbial communities involved in cellulose degradation were investigated by metatranscriptomics and a DNA library search of the GH1 family of BGLs involved in natural and inoculated composting. Under normal conditions, the group of non-glucose-tolerant BGL genes exhibited higher sensitivity to regulation than the glucose-tolerant BGL genes, which was suppressed during the composting process. Compared with the expression of endoglucanase and exoglucanase, the functional microbial communities exhibited a different transcriptional regulation of BGL genes during the cooling phase of natural composting. BGL-producing microbial communities upregulated the expression of glucose-tolerant BGL under carbon catabolite repression due to the increased glucose concentration, whereas the expression of non-glucose-tolerant BGL was suppressed. Our results support the hypothesis that the functional microbial communities use multiple strategies of varying effectiveness to regulate the expression of BGL genes to facilitate adaptation to environmental changes.

中文翻译：

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堆肥过程中β-葡萄糖苷酶基因差异表达

纤维素酶对纤维素的降解是由相互作用的微生物的复杂群落引起的，这对全球范围内的碳循环有重大贡献。β-葡萄糖苷酶（BGL）是纤维素降解过程中的限速酶。因此，分析堆肥过程中参与纤维素降解的基因表达和BGL基因表达的调控，将提高对纤维素降解机制的理解。基于我们之前的研究，我们假设产生 BGL 的微生物群落差异调节葡萄糖耐受性 BGL 和非葡萄糖耐受性 BGL 的表达以适应纤维素降解条件的变化。为了证实这个假设，通过宏转录组学和参与天然和接种堆肥的 BGL GH1 家族的 DNA 文库搜索，研究了参与纤维素降解的功能性微生物群落的结构和功能。在正常条件下，非葡萄糖耐受性BGL基因组对调节的敏感性高于葡萄糖耐受性BGL基因，后者在堆肥过程中受到抑制。与内切葡聚糖酶和外切葡聚糖酶的表达相比，功能微生物群落在自然堆肥冷却阶段表现出不同的BGL基因转录调控。由于葡萄糖浓度增加，产生 BGL 的微生物群落在碳分解代谢物抑制下上调了耐葡萄糖 BGL 的表达，而非葡萄糖耐受性BGL的表达被抑制。我们的结果支持这样的假设，即功能性微生物群落使用多种不同有效性的策略来调节 BGL 基因的表达以促进适应环境变化。