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Fatty acids are synthesized solely from the sequential condensation of acetyl-CoA subunits in the photosynthetic cyanobacteria Synechococcus sp. PCC 7002. Feeding acetyl-CoA precursors, such as acetate, can increase acetyl-CoA availability and enhance photosynthetic fatty acid production in the eukaryotic algae Chlamydomonas reinhardtii. However, we found that the same strategy failed to increase fatty acid production in a strain of the cyanobacteria PCC 7002 engineered to produce the free fatty acid (FFA) octanoic acid. We supplemented PCC 7002 cultures with ¹³C acetyl-CoA precursors acetate and pyruvate simultaneously to determine if these were utilized for fatty acid synthesis and to reveal potential bottlenecks limiting fatty acid synthesis from acetyl-CoA precursors. ¹³C labeling data showed that the supplements, taken together, incorporated into the acetyl-CoA pool at a rate of roughly 40 – 50%, but failed to increase fatty acid production. Additionally, acetyl-CoA labeling from acetate saturated at the lowest supplement concentration, while acetyl-CoA labeling from pyruvate did not. These data appear to suggest that precursors can increase acetyl-CoA availability without increasing fatty acid synthesis and point to bottlenecks in acetate uptake or acetate conversion to acetyl-CoA.