Biological Resources and Post-Harvest Division, Japan International Research Center for Agricultural Sciences (JIRCAS), 1-1 Ohwashi, Tsukuba, Ibaraki, 305-8686, Japan.
Excellent Center of Enzyme Technology and Microbial Utilization, Pilot Plant Development and Training Institute (PDTI), King Mongkut's University of Technology Thonburi (KMUTT), Bangkok, 10150, Thailand.
Appl Microbiol Biotechnol. 2024 Oct 1;108(1):477. doi: 10.1007/s00253-024-13310-3.
Herbivorax saccincola A7 is an anaerobic alkali-thermophilic lignocellulolytic bacterium that possesses a cellulosome and high xylan degradation ability. To understand the expression profile of extracellular enzymes by carbon sources, quantitative real-time PCR was performed on all cellulosomal and non-cellulosomal enzyme genes of H. saccincola A7 using cellulose and xylan as carbon sources. The results confirmed that the scaffolding proteins of H. saccincola A7 were expressed. In general, the cellulosomal genes belonging to the glycoside hydrolase families 9, 10, 11, and 48 were repressed when xylan was the sole carbon source, but these genes were significantly induced in the presence of cellulose. These results indicate that cellulose, not xylan, is a key inducer of cellulosomal genes in H. saccincola A7. The RsgI-like proteins, which regulate a carbohydrate-sensing mechanism in Clostridium thermocellum, were also found to be encoded in the H. saccincola A7 genome. To confirm the regulation by RsgI-like proteins, the relative expression of σI1-σI4 factors was analyzed on both carbon sources. The expression of alternative σI1 and σI2 factors was enhanced by the presence of cellulose. By contrast, the expression of σI3 and σI4 factors was activated by both cellulose and xylan. Taken together, the results reveal that the cellulosomal and non-cellulosomal genes of H. saccincola A7 are regulated through a carbohydrate-sensing mechanism involving anti-σ regulator RsgI-like proteins. KEY POINTS: • qRT-PCR performed on cellulosomal and non-cellulosomal genes of H. saccincola A7 • Cellulose is a key inducer of the cellulosome of H. saccincola A7 • H. saccincola A7 possesses a similar system of anti-σ regulator RsgI-like proteins.
粪产碱杆菌 A7 是一种厌氧嗜碱木质纤维素分解菌，具有细胞外酶和高木聚糖降解能力。为了了解碳源对细胞外酶表达谱的影响，我们使用纤维素和木聚糖作为碳源，对粪产碱杆菌 A7 的所有纤维素酶和非纤维素酶基因进行了定量实时 PCR。结果证实了粪产碱杆菌 A7 的支架蛋白得到了表达。一般来说，当木聚糖是唯一的碳源时，属于糖苷水解酶家族 9、10、11 和 48 的纤维素酶基因受到抑制，但在存在纤维素时，这些基因显著诱导。这些结果表明，纤维素而不是木聚糖是粪产碱杆菌 A7 中纤维素酶基因的关键诱导物。在热纤维梭菌中，调节碳水化合物感知机制的 RsgI 样蛋白也被发现编码在粪产碱杆菌 A7 基因组中。为了证实 RsgI 样蛋白的调节作用，我们分析了在这两种碳源上 σI1-σI4 因子的相对表达。在纤维素的存在下，替代 σI1 和 σI2 因子的表达增强。相比之下，σI3 和 σI4 因子的表达被纤维素和木聚糖激活。总之，结果表明，粪产碱杆菌 A7 的细胞外酶和非细胞外酶基因受到涉及抗 σ 调节蛋白 RsgI 样蛋白的碳水化合物感知机制的调节。关键点：• 在粪产碱杆菌 A7 的细胞外酶和非细胞外酶基因上进行 qRT-PCR• 纤维素是粪产碱杆菌 A7 纤维素酶的关键诱导物• 粪产碱杆菌 A7 具有类似的抗 σ 调节蛋白 RsgI 样蛋白系统。
