Génétique Moléculaire, Génomique, Microbiologie, UMR 7156 Université de Strasbourg/CNRS, Strasbourg, France.
Microb Cell Fact. 2012 Feb 3;11:16. doi: 10.1186/1475-2859-11-16.
The recycling of the organic matter is a crucial function in any environment, especially in oligotrophic environments such as Acid Mine Drainages (AMDs). Polymer-degrading bacteria might play an important role in such ecosystem, at least by releasing by-products useful for the rest of the community. In this study, physiological, molecular and biochemical experiments were performed to decipher the role of a Paenibacillus strain isolated from the sediment of Carnoulès AMD.
Even though Paenibacillus sp. strain Q8 was isolated from an oligotrophic AMD showing an acidic pH, it developed under both acidic and alkaline conditions and showed a heterotrophic metabolism based on the utilization of a broad range of organic compounds. It resisted to numerous metallic stresses, particularly high arsenite (As(III)) concentrations (> 1,800 mg/L). Q8 was also able to efficiently degrade polymers such as cellulose, xylan and starch. Function-based screening of a Q8 DNA-library allowed the detection of 15 clones with starch-degrading activity and 3 clones with xylan-degrading activity. One clone positive for starch degradation carried a single gene encoding a "protein of unknown function". Amylolytic and xylanolytic activities were measured both in growing cells and with acellular extracts of Q8. The results showed the ability of Q8 to degrade both polymers under a broad pH range and high As(III) and As(V) concentrations. Activity measurements allowed to point out the constitutive expression of the amylase genes and the mainly inducible expression of the xylanase genes. PACE demonstrated the endo-acting activity of the amylases and the exo-acting activity of the xylanases.
AMDs have been studied for years especially with regard to interactions between bacteria and the inorganic compartment hosting them. To date, no study reported the role of microorganisms in the recycling of the organic matter. The present work suggests that the strain Q8 might play an important role in the community by recycling the scarce organic matter (cellulose, hemicellulose, starch...), especially when the conditions change. Furthermore, function-based screening of a Q8 DNA library allowed to assign an amylolytic function to a gene previously unknown. AMDs could be considered as a reservoir of genes with potential biotechnological properties.
有机物的循环是任何环境中的关键功能，特别是在贫营养环境如酸性矿山排水（AMD）中。聚合物降解细菌在这样的生态系统中可能发挥重要作用，至少通过释放对群落其他成员有用的副产品。在这项研究中，进行了生理、分子和生化实验，以破译从 Carnoulès AMD 沉积物中分离的一株粘芽孢杆菌的作用。
尽管粘芽孢杆菌 Q8 是从贫营养 AMD 中分离出来的，其表现出酸性 pH 值，但它在酸性和碱性条件下都能生长，并表现出基于广泛利用有机化合物的异养代谢。它能抵抗多种金属压力，特别是高亚砷酸盐（As(III)）浓度（>1800mg/L）。Q8 还能有效地降解纤维素、木聚糖和淀粉等聚合物。对 Q8 DNA 文库的功能筛选检测到 15 个具有淀粉降解活性的克隆和 3 个具有木聚糖降解活性的克隆。一个对淀粉降解呈阳性的克隆携带一个编码“未知功能蛋白”的单一基因。在生长细胞和 Q8 的无细胞提取物中均测量了淀粉酶和木聚糖酶的活性。结果表明，Q8 能够在广泛的 pH 范围和高 As(III)和 As(V)浓度下降解这两种聚合物。活性测量表明，淀粉酶基因的组成型表达和木聚糖酶基因的主要诱导型表达。PACE 证明了淀粉酶的内切活性和木聚糖酶的外切活性。
多年来，AMD 一直受到研究，特别是关于细菌与容纳它们的无机部分之间的相互作用。迄今为止，尚无研究报道微生物在有机物循环中的作用。本研究表明，Q8 菌株通过回收稀缺的有机物（纤维素、半纤维素、淀粉等）在群落中可能发挥重要作用，尤其是在条件发生变化时。此外，对 Q8 DNA 文库的功能筛选将一个以前未知的基因赋予了淀粉酶功能。AMD 可以被认为是具有潜在生物技术特性的基因的储库。
