Pereira Sara B, Mota Rita, Vieira Cristina P, Vieira Jorge, Tamagnini Paula
i3S-Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Rua Júlio Amaral de Carvalho 245, 4200-135 Porto, Portugal.
IBMC-Instituto de Biologia Molecular e Celular, Universidade do Porto, Rua do Campo Alegre 823, 4150-180 Porto, Portugal.
Sci Rep. 2015 Oct 6;5:14835. doi: 10.1038/srep14835.
Many cyanobacteria produce extracellular polymeric substances (EPS) with particular characteristics (e.g. anionic nature and presence of sulfate) that make them suitable for industrial processes such as bioremediation of heavy metals or thickening, suspending or emulsifying agents. Nevertheless, their biosynthetic pathway(s) are still largely unknown, limiting their utilization. In this work, a phylum-wide analysis of genes/proteins putatively involved in the assembly and export of EPS in cyanobacteria was performed. Our results demonstrated that most strains harbor genes encoding proteins related to the three main pathways: Wzy-, ABC transporter-, and Synthase-dependent, but often not the complete set defining one pathway. Multiple gene copies are mainly correlated to larger genomes, and the strains with reduced genomes (e.g. the clade of marine unicellular Synechococcus and Prochlorococcus), seem to have lost most of the EPS-related genes. Overall, the distribution of the different genes/proteins within the cyanobacteria phylum raises the hypothesis that cyanobacterial EPS production may not strictly follow one of the pathways previously characterized. Moreover, for the proteins involved in EPS polymerization, amino acid patterns were defined and validated constituting a novel and robust tool to identify proteins with similar functions and giving a first insight to which polymer biosynthesis they are related to.
许多蓝细菌会产生具有特定特性（如阴离子性质和硫酸盐的存在）的胞外聚合物（EPS），这使得它们适用于诸如重金属生物修复或增稠、悬浮或乳化剂等工业过程。然而，它们的生物合成途径在很大程度上仍然未知，这限制了它们的利用。在这项工作中，对蓝细菌中可能参与EPS组装和输出的基因/蛋白质进行了全门类分析。我们的结果表明，大多数菌株含有与三种主要途径相关的蛋白质编码基因：Wzy依赖性、ABC转运蛋白依赖性和合成酶依赖性，但通常没有定义一种途径的完整基因集。多个基因拷贝主要与较大的基因组相关，而基因组减小的菌株（如海洋单细胞聚球藻属和原绿球藻属的进化枝）似乎已经丢失了大部分与EPS相关的基因。总体而言，不同基因/蛋白质在蓝细菌门内的分布提出了这样一种假设，即蓝细菌EPS的产生可能并不严格遵循先前表征的途径之一。此外，对于参与EPS聚合的蛋白质，定义并验证了氨基酸模式，构成了一种新颖且强大的工具，用于识别具有相似功能的蛋白质，并初步了解它们与哪种聚合物生物合成相关。
