Estación Experimental del Zaidín, Department of Environmental Protection, Consejo Superior de Investigaciones Científicas, Calle Profesor Albareda, 1, Granada, 18008, Spain.
Materials + Technologies Research Group (GMT), Department of Chemical and Environmental Engineering, Faculty of Engineering of Gipuzkoa, University of the Basque Country, Pza Europa 1, Donostia-San Sebastian, 20018, Spain.
Microb Biotechnol. 2019 Jul;12(4):662-676. doi: 10.1111/1751-7915.13399. Epub 2019 May 14.
Polycyclic aromatic compounds (PAHs) are toxic compounds that are released in the environment as a consequence of industrial activities. The restoration of PAH-polluted sites considers the use of bacteria capable of degrading aromatic compounds to carbon dioxide and water. Here we characterize a new Xanthobacteraceae strain, Starkeya sp. strain N1B, previously isolated during enrichment under microaerophilic conditions, which is capable of using naphthalene crystals as the sole carbon source. The strain produced a structured biofilm when grown on naphthalene crystals, which had the shape of a half-sphere organized over the crystal. Scanning electron microscopy (SEM) and GC-MS analysis indicated that the biofilm was essentially made of cellulose, composed of several micron-long nanofibrils of 60 nm diameter. A cellulosic biofilm was also formed when the cells grew with glucose as the carbon source. Fourier transformed infrared spectroscopy (FTIR) confirmed that the polymer was type I cellulose in both cases, although the crystallinity of the material greatly depended on the carbon source used for growth. Using genome mining and mutant analysis, we identified the genetic complements required for the transformation of naphthalene into cellulose, which seemed to have been successively acquired through horizontal gene transfer. The capacity to develop the biofilm around the crystal was found to be dispensable for growth when naphthalene was used as the carbon source, suggesting that the function of this structure is more intricate than initially thought. This is the first example of the use of toxic aromatic hydrocarbons as the carbon source for bacterial cellulose production. Application of this capacity would allow the remediation of a PAH into such a value-added polymer with multiple biotechnological usages.
多环芳烃（PAHs）是有毒化合物，它们作为工业活动的结果而释放到环境中。受 PAH 污染的场地的修复考虑使用能够将芳香族化合物降解为二氧化碳和水的细菌。在这里，我们描述了一种新的黄杆菌科菌株，Starkeya sp. 菌株 N1B，该菌株先前在微需氧条件下的富集过程中被分离出来，能够利用萘晶体作为唯一的碳源。当在萘晶体上生长时，该菌株会产生结构生物膜，其形状为在晶体上组织的半球体。扫描电子显微镜（SEM）和 GC-MS 分析表明，生物膜主要由纤维素组成，由几个微米长的 60nm 直径的纳米原纤维组成。当细胞以葡萄糖作为碳源生长时，也会形成纤维素生物膜。傅里叶变换红外光谱（FTIR）证实，在这两种情况下，聚合物均为 I 型纤维素，尽管材料的结晶度极大地取决于用于生长的碳源。通过基因组挖掘和突变体分析，我们确定了将萘转化为纤维素所需的遗传补充物，这些补充物似乎是通过水平基因转移逐渐获得的。当萘作为碳源时，围绕晶体形成生物膜的能力对于生长是可有可无的，这表明该结构的功能比最初想象的要复杂。这是首次将有毒芳烃用作细菌纤维素生产的碳源的例子。这种能力的应用将允许将 PAH 修复成具有多种生物技术用途的附加值聚合物。
