School of Minerals Processing and Bioengineering, Central South University, Changsha 410083, China.
J Microbiol Biotechnol. 2010 Jan;20(1):71-7.
The time, yield and related genes expression of PHB accumulation of Acidiphilium cryptum DX1-1 were investigated under four different initial C/N ratios 1.2, 2.4, 7.5, and 24. The results of time and yield of PHB accumulation show that the initial C/N ratio 2.4 was optimum for strain DX1-1 to accumulate PHB, both higher and lower initial C/N ratios did not favor that process. Based on the genome of Acidiphilium cryptum JF-5, 13 PHB accumulation related genes in strain JF-5 were chosen and successfully cloned from strain DX1-1. The differential expression of the 13 functional genes, in different C/N ratios as cited above, was then studied by Real-time PCR. The results show that all the 13 genes were most upregulated when initial C/N ratio was 2.4, and among which the gene Acry_3030 encoding poly-beta-hydroxybutyrate polymerase and Acry_0626 encoding acetyl-CoA synthetase were much more upregulated than the other genes, which prove that they play the most important role for PHB accumulation and acetate is the main initial substance for PHB accumulation for strain DX1-1. Potential regulatory motifs analysis shows that the genes related to PHB accumulation are regulated by different promoters and that the motif had weak similarity to the model promoters, suggesting that PHB- metabolism in Acidiphilium cryptum may be mediated by a different mechanism.
研究了在四种不同初始 C/N 比（1.2、2.4、7.5 和 24）下，嗜酸极端嗜热菌 DX1-1 积累 PHB 的时间、产量和相关基因表达。PHB 积累的时间和产量结果表明，初始 C/N 比 2.4 最有利于菌株 DX1-1 积累 PHB，较高和较低的初始 C/N 比均不利于该过程。基于嗜酸极端嗜热菌 JF-5 的基因组，从菌株 DX1-1 中成功克隆了 13 个与 PHB 积累相关的基因。然后通过 Real-time PCR 研究了在上述不同 C/N 比下 13 个功能基因的差异表达。结果表明，当初始 C/N 比为 2.4 时，所有 13 个基因的表达均上调最为显著，其中编码聚-β-羟基丁酸聚合酶的基因 Acry_3030 和编码乙酰辅酶 A 合成酶的基因 Acry_0626 的表达上调程度远高于其他基因，证明它们在 PHB 积累中起最重要的作用，而乙酸是菌株 DX1-1 积累 PHB 的主要初始物质。潜在调控基序分析表明，与 PHB 积累相关的基因受不同启动子调控，该基序与模型启动子具有较弱的相似性，表明嗜酸极端嗜热菌中的 PHB 代谢可能通过不同的机制进行调节。
