Demidenko Aleksandr, Akberdin Ilya R, Allemann Marco, Allen Eric E, Kalyuzhnaya Marina G
Department of Biology, San Diego State University, Campanile DriveSan Diego, CA, USA; Scripps Institution of Oceanography, University of California San Diego, Gilman DriveLa Jolla, CA, USA.
Department of Biology, San Diego State University, Campanile Drive San Diego, CA, USA.
Front Microbiol. 2017 Jan 10;7:2167. doi: 10.3389/fmicb.2016.02167. eCollection 2016.
Methane utilization by methanotrophic bacteria is an attractive application for biotechnological conversion of natural or biogas into high-added-value products. Haloalcaliphilic methanotrophic bacteria belonging to the genus are among the most promising strains for methane-based biotechnology, providing easy and inexpensive cultivation, rapid growth, and the availability of established genetic tools. A number of methane bioconversions using these microbial cultures have been discussed, including the derivation of biodiesel, alkanes, and OMEGA-3 supplements. These compounds are derived from bacterial fatty acid pools. Here, we investigate fatty acid biosynthesis in . Most of the genes homologous to typical Type II fatty acid biosynthesis pathways could be annotated by bioinformatics analyses, with the exception of fatty acid transport and regulatory elements. Different approaches for improving fatty acid accumulation were investigated. These studies indicated that both fatty acid degradation and acetyl- and malonyl-CoA levels are bottlenecks for higher level fatty acid production. The best strain generated in this study synthesizes 111 ± 2 mg/gDCW of extractable fatty acids, which is ~20% more than the original strain. A candidate gene for fatty acid biosynthesis regulation, , was identified and studied. Its deletion resulted in drastic changes to the fatty acid profile, leading to an increased pool of C18-fatty acid methyl ester. The FarE-regulon was further investigated by RNA-seq analysis of gene expression in -knockout mutants and -overexpressing strains. These gene profiles highlighted a novel set of enzymes and regulators involved in fatty acid biosynthesis. The gene expression and fatty acid profiles of the different -strains support the hypothesis that metabolic fluxes upstream of fatty acid biosynthesis restrict fatty acid production in the methanotroph.
甲烷营养型细菌对甲烷的利用是将天然气或沼气生物技术转化为高附加值产品的一个有吸引力的应用。属于 属的嗜盐嗜碱甲烷营养型细菌是基于甲烷的生物技术中最有前景的菌株之一，具有易于培养且成本低廉、生长迅速以及拥有成熟的遗传工具等优点。已经讨论了许多使用这些微生物培养物进行的甲烷生物转化，包括生物柴油、烷烃和欧米伽-3补充剂的衍生。这些化合物源自细菌脂肪酸库。在这里，我们研究了 中的脂肪酸生物合成。除了脂肪酸转运和调控元件外，大多数与典型II型脂肪酸生物合成途径同源的基因都可以通过生物信息学分析进行注释。研究了提高脂肪酸积累的不同方法。这些研究表明，脂肪酸降解以及乙酰辅酶A和丙二酰辅酶A水平都是更高水平脂肪酸生产的瓶颈。本研究中产生的最佳菌株合成了111±2毫克/克干细胞重量的可提取脂肪酸，比原始菌株多约20%。鉴定并研究了一个脂肪酸生物合成调控的候选基因 。其缺失导致脂肪酸谱发生剧烈变化，导致C18-脂肪酸甲酯库增加。通过对 -基因敲除突变体和 -过表达菌株中的基因表达进行RNA测序分析，进一步研究了FarE-调控子。这些基因谱突出了一组参与脂肪酸生物合成的新酶和调控因子。不同 -菌株的基因表达和脂肪酸谱支持了这样的假设，即脂肪酸生物合成上游的代谢通量限制了甲烷营养菌中的脂肪酸生产。
