Nagao Misato, Ozaki Takato, Fukuda Hirofumi, Kanesaki Yu, Asayama Munehiko
College of Agriculture, Ibaraki University, Ibaraki, Japan.
United Graduate School of Agricultural Science, Tokyo University of Agriculture and Technology, Tokyo, Japan.
FEBS Open Bio. 2025 Jun;15(6):949-962. doi: 10.1002/2211-5463.70009. Epub 2025 Mar 6.
Microalgae such as cyanobacteria convert CO to compatible drop-in fuels, such as alkanes. However, the production yield is approximately 0.05-1.0% of the dry weight of natural algae. Here, we aimed to study the role of transcriptional expression, mRNA molecular structure and culture-dependent accumulation of alkanes from two cyanobacteria species. The transcription start sites of the alkane biosynthesis genes ado and aar were identified in the representative cyanobacteria strains Synechocystis sp. PCC 6803 and Limnothrix sp. SK1-2-1, which produce heptadecane and pentadecane, respectively. This characterisation revealed the potential promoters and unique mRNA structures of the ado and aar genes in these species. Transcripts from these genes were induced more in the nitrogen-depleted BG11 (BG11-N) culture than in the BG11 culture, although the biomass was reduced, and as such the amount of alkanes obtained per unit medium was greater for BG11 than for BG11-N. PCC 6803 transconjugants carrying alkane biosynthesis genes from PCC 6803 or SK1-2-1 showed an approximately 1.8- to 2.3-fold increase in heptadecane production compared to the control strain when grown on BG11 cultures without any nitrogen depletion. These results suggest that not only the enzymes ADO/AAR but also the intracellular production of fatty acyl-ACP substrates may be important for the mass production of target alkanes.
诸如蓝细菌之类的微藻能将一氧化碳转化为可替代的现成燃料，例如烷烃。然而，产量约为天然藻类干重的0.05%-1.0%。在此，我们旨在研究转录表达、mRNA分子结构以及两种蓝细菌物种中烷烃的培养依赖性积累的作用。在代表性蓝细菌菌株集胞藻属PCC 6803和泥生颤藻属SK1-2-1中鉴定出了烷烃生物合成基因ado和aar的转录起始位点，这两种菌株分别产生十七烷和十五烷。这一表征揭示了这些物种中ado和aar基因的潜在启动子和独特的mRNA结构。尽管生物量减少，但这些基因的转录本在缺氮的BG11（BG11-N）培养基中的诱导程度高于在BG11培养基中的诱导程度，因此，BG11培养基中每单位培养基获得的烷烃量比BG11-N培养基中的更多。携带来自PCC 6803或SK1-2-1的烷烃生物合成基因的PCC 6803转接合子在不含任何氮消耗的BG11培养基上生长时，与对照菌株相比，十七烷产量增加了约1.8至2.3倍。这些结果表明，不仅酶ADO/AAR，而且脂肪酰-ACP底物的细胞内产生对于目标烷烃的大规模生产可能也很重要。
