Cyanobacteria are model organisms for photosynthesis and are attractive for biotechnology applications. To aid investigation of genotype-phenotype relationships in cyanobacteria, we develop an inducible CRISPRi gene repression library in Synechocystis sp. PCC 6803, where we aim to target all genes for repression. We track the growth of all library members in multiple conditions and estimate gene fitness. The library reveals several clones with increased growth rates, and these have a common upregulation of genes related to cyclic electron flow. We challenge the library with 0.1 M L-lactate and find that repression of peroxiredoxin bcp2 increases growth rate by 49%. Transforming the library into an L-lactate-secreting Synechocystis strain and sorting top lactate producers enriches clones with sgRNAs targeting nutrient assimilation, central carbon metabolism, and cyclic electron flow. In many examples, productivity can be enhanced by repression of essential genes, which are difficult to access by transposon insertion.

蓝细菌是光合作用的模式生物，在生物技术应用中具有吸引力。在蓝藻基因型-表型关系的援助调查，我们开发的诱导CRISPRi基因抑制库蓝藻藻。PCC 6803，我们的目标是针对所有基因进行抑制。我们跟踪在多种条件下所有图书馆成员的成长，并估算基因适合度。该文库揭示了几个克隆，它们的生长速率增加，并且这些克隆具有与循环电子流相关的基因的共同上调。我们用0.1 M L-乳酸挑战文库，发现过氧化物酶bcp2的抑制可将生长速率提高49％。将文库转化为分泌L-乳酸盐的集囊藻菌株和分选的顶级乳酸生产者通过针对营养同化，中心碳代谢和循环电子流的sgRNA富集克隆。在许多示例中，可以通过抑制必需基因来提高生产力，而必需基因很难通过转座子插入来获得。