Department of Microbiology, Oregon State University, 226 Nash Hall, Corvallis, OR, 97331, USA.
Department of Earth & Environmental Sciences, University of Michigan, Ann Arbor, MI 48109-1005, USA; Cooperative Institute for Great Lakes Research (CIGLR), University of Michigan, Ann Arbor, MI 48109-1005, USA.
Harmful Algae. 2018 Jul;77:93-107. doi: 10.1016/j.hal.2018.05.009. Epub 2018 Jun 29.
In order to better understand the relationships among current Nostocales cyanobacterial blooms, eight genomes were sequenced from cultured isolates or from environmental metagenomes of recent planktonic Nostocales blooms. Phylogenomic analysis of publicly available sequences placed the new genomes among a group of 15 genomes from four continents in a distinct ADA clade (Anabaena/Dolichospermum/Aphanizomenon) within the Nostocales. This clade contains four species-level groups, two of which include members with both Anabaena-like and Aphanizomenon flos-aquae-like morphology. The genomes contain many repetitive genetic elements and a sizable pangenome, in which ABC-type transporters are highly represented. Alongside common core genes for photosynthesis, the differentiation of N-fixing heterocysts, and the uptake and incorporation of the major nutrients P, N and S, we identified several gene pathways in the pangenome that may contribute to niche partitioning. Genes for problematic secondary metabolites-cyanotoxins and taste-and-odor compounds-were sporadically present, as were other polyketide synthase (PKS) and nonribosomal peptide synthetase (NRPS) gene clusters. By contrast, genes predicted to encode the ribosomally generated bacteriocin peptides were found in all genomes.
为了更好地了解当前念珠藻目蓝细菌水华的关系，我们从培养的分离物或最近浮游性念珠藻目的水华的环境宏基因组中测序了 8 个基因组。基于公开可用序列的系统基因组分析将新基因组置于一个包含来自四大洲的 15 个基因组的组中，这些基因组在念珠藻目中属于一个独特的 ADA 进化枝（鱼腥藻属/多列螺旋藻属/节旋藻属）。该进化枝包含四个种级别的组，其中两个组包括具有类似鱼腥藻属和类似水华鱼腥藻属形态的成员。这些基因组包含许多重复的遗传元件和一个相当大的泛基因组，其中 ABC 型转运蛋白高度表达。除了光合作用、固氮异形胞分化以及主要营养物质 P、N 和 S 的摄取和整合的常见核心基因外，我们在泛基因组中还鉴定出了几个可能有助于生态位分化的基因途径。有问题的次生代谢物——蓝藻毒素和气味和味道化合物的基因是零星存在的，还有其他聚酮合酶 (PKS) 和非核糖体肽合成酶 (NRPS) 基因簇也是如此。相比之下，预测编码核糖体产生的细菌素肽的基因存在于所有基因组中。
