Abstract：
Dolichospermum is a cyanobacterial genus commonly associated with toxic blooms in lakes and brackish water bodies worldwide, and is a long-term resident of Lake Stechlin, northeastern Germany. In recent decades, shifts in the phosphorus loading and phytoplankton species composition have seen increased biomass of Dolichospermum during summer blooms from 1998, peaking around 2005, and declining after 2020. Cyanobacteria are known to rapidly adapt to new environments, facilitated by genome adaptation. To investigate the changes in genomic features that may have occurred in Lake Stechlin Dolichospermum during this time of increased phosphorus loading and higher biomass, whole genome sequence analysis was performed on samples of ten akinetes isolated from ten, 1 cm segments of a sediment core, representing a ∼45-year period from 1970 to 2017. Comparison of these genomes with genomes of extant isolates revealed a clade of Dolichospermum that clustered with the ADA-6 genus complex, with remarkable genome stability, without gene gain or loss events in response to recent environmental changes. The genome characteristics indicate that this species is suited to a deep-chlorophyll maximum, including additional light-harvesting and phosphorus scavenging genes. Population SNP analysis revealed two sub-populations that shifted in dominance as the lake transitioned between oligotrophic and eutrophic conditions. Overall, the results show little change within the population, despite diversity between extant populations from different geographic locations and the in-lake changes in phosphorus concentrations.
摘要：
Dolichospermum是一种蓝细菌属，通常与全球湖泊和微咸水体中的有毒水华有关，他是Stchlin湖的长期居民,德国东北部。近几十年来,从1998年开始，夏季开花期间，磷负荷和浮游植物物种组成的变化使Dolichospermum的生物量增加，在2005年左右达到峰值，并在2020年之后下降。蓝细菌可以快速适应新环境,通过基因组适应促进。为了研究在磷负荷增加和生物量增加的这段时间内StechlinDolichospermum湖可能发生的基因组特征变化，全基因组序列分析是对从10个样本中分离出的10个样本进行的，沉积物核心的1厘米部分，代表1970年至2017年的45年时间。将这些基因组与现有分离株的基因组进行比较，发现了与ADA-6属复合体成簇的Dolichospermum进化枝，具有显著的基因组稳定性，没有响应于最近的环境变化的基因增益或丢失事件。基因组特征表明该物种适合于深层叶绿素最大值，包括额外的光收集和磷清除基因。种群SNP分析显示，随着湖泊在贫营养和富营养化条件之间过渡，两个亚群的优势发生了变化。总的来说,结果显示人口内部几乎没有变化，尽管来自不同地理位置的现存种群之间存在差异，并且湖中磷浓度变化。
