Department of Biology and Environmental Science, Centre for Ecology and Evolution in Microbial Model Systems (EEMiS), Linnaeus University, Kalmar, Sweden.
Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, Uppsala, Sweden.
Environ Microbiol Rep. 2024 Oct;16(5):e70005. doi: 10.1111/1758-2229.70005.
In nature, the number of genome or chromosome copies within cells (ploidy) can vary between species and environmental conditions, potentially influencing how organisms adapt to changing environments. Although ploidy levels cannot be easily determined by standard genome sequencing, understanding ploidy is crucial for the quantitative interpretation of molecular data. Cyanobacteria are known to contain haploid, oligoploid, and polyploid species. The smallest cyanobacteria, picocyanobacteria (less than 2 μm in diameter), have a widespread distribution ranging from marine to freshwater environments, contributing significantly to global primary production. In this study, we determined the ploidy level of genetically and physiologically diverse brackish picocyanobacteria isolated from the Baltic Sea using a qPCR assay targeting the rbcL gene. The strains contained one to four genome copies per cell. The ploidy level was not linked with phylogeny based on the identity of the 16S rRNA gene. The variation of ploidy among the brackish strains was lower compared to what has been reported for freshwater strains and was more similar to what has been reported for marine strains. The potential ecological advantage of polyploidy among picocyanobacteria has yet to be described. Our study highlights the importance of considering ploidy to interpret the abundance and adaptation of brackish picocyanobacteria.
在自然界中，细胞内的基因组或染色体拷贝数（倍性）在不同物种和环境条件下可能会有所不同，这可能会影响生物如何适应不断变化的环境。尽管倍性水平不能通过标准的基因组测序轻易确定，但了解倍性对于分子数据的定量解释至关重要。蓝细菌已知包含单倍体、寡倍体和多倍体物种。最小的蓝细菌，即微微型蓝细菌（直径小于 2μm），在从海洋到淡水的环境中广泛分布，对全球初级生产力有重要贡献。在这项研究中，我们使用针对 rbcL 基因的 qPCR 检测法，测定了从波罗的海分离的遗传和生理上具有多样性的咸水微微型蓝细菌的倍性水平。这些菌株每个细胞含有一个到四个基因组拷贝。倍性水平与基于 16S rRNA 基因身份的系统发育无关。与淡水菌株相比，咸水菌株的倍性变异较低，与海洋菌株的报道更为相似。多倍体在微微型蓝细菌中的潜在生态优势尚未被描述。我们的研究强调了考虑倍性对于解释咸水微微型蓝细菌的丰度和适应性的重要性。
