Identification of Specific Variations in a Non-Motile Strain of Cyanobacterium Synechocystis sp. PCC 6803 Originated from ATCC 27184 by Whole Genome Resequencing

Cyanobacterium Synechocystis sp. PCC 6803 is a widely used model organism in basic research and biofuel biotechnology application. Here, we report the genomic sequence of chromosome and seven plasmids of a glucose-tolerant, non-motile strain originated from ATCC 27184, GT-G, in use at Guangzhou. Through high-throughput genome re-sequencing and verification by Sanger sequencing, eight novel variants were identified in its chromosome and plasmids. The eight novel variants, especially the five non-silent mutations might have interesting effects on the phenotype of GT-G strains, for example the truncated Sll1895 and Slr0322 protein. These resequencing data provide background information for further research and application based on the GT-G strain and also provide evidence to study the evolution and divergence of Synechocystis 6803 globally.     

Untargeted Lipidomics Analysis of the Cyanobacterium Synechocystis sp. PCC 6803: Lipid Composition Variation in Response to Alternative Cultivation Setups and to Gene Deletion

Cyanobacteria play an important role in several ecological environments, and they are widely accepted to be the ancestors of chloroplasts in modern plants and green algae. Cyanobacteria have become attractive models for metabolic engineering, with the goal of exploring them as microbial cell factories. However, the study of cyanobacterial lipids’ composition and variation, and the assessment of the lipids’ functional and structural roles have been largely overlooked. Here, we aimed at expanding the cyanobacterial lipidomic analytical pipeline by using an untargeted lipidomics approach. Thus, the lipid composition variation of the model cyanobacterium Synechocystis sp. PCC 6803 was investigated in response to both alternative cultivation setups and gene deletion. This approach allowed for detecting differences in total lipid content, alterations in fatty-acid unsaturation level, and adjustments of specific lipid species among the identified lipid classes. The employed method also revealed that the cultivation setup tested in this work induced a deeper alteration of the cyanobacterial cell lipidome than the deletion of a gene that results in a dramatic increase in the release of lipid-rich outer membrane vesicles. This study further highlights how growth conditions must be carefully selected when cyanobacteria are to be engineered and/or scaled-up for lipid or fatty acids production.     

转基因聚球藻7942培养中光传递及其对细胞生长的影响

对转人源胸腺素a1基因聚球藻7942光生物反应器分批培养过程中光的分布、平均光强变化及其对藻细胞生长的影响进行了分析. 结果表明，Hyperbolic光衰减模型较之Lambert-Beer光衰减模型能更好地描述转基因聚球藻7942培养液中的光衰减；随着藻细胞密度的增加，光生物反应器内平均光强不断减小，藻细胞的光能比吸收速率也不断降低，反应器中“暗区”体积不断加大；培养时间0~1.5 d，藻细胞能获得充足光能，因而呈指数生长；1.5 d后藻细胞处于光限制，比生长速率不断下降，但体积光能吸收速率达到最大并保持恒定，藻细胞进入线性生长期；5 d后光生物反应器“暗区”体积超过了反应器总体积的50%，藻细胞吸收的光能用于维持的比例不断增加，从而导致生长速率下降；培养8 d，转基因聚球藻7942中人源胸腺素a1表达量为4.53 mg/L.