Biswas Ranjita, Wilson Charlotte M, Giannone Richard J, Klingeman Dawn M, Rydzak Thomas, Shah Manesh B, Hettich Robert L, Brown Steven D, Guss Adam M
Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37830 USA ; BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN 37830 USA ; Centre for Rural Development and Technology, Indian Institute of Technology Delhi, Hauz Khas, New Delhi, 110016 India.
Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37830 USA ; BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN 37830 USA.
Biotechnol Biofuels. 2017 Jan 3;10:6. doi: 10.1186/s13068-016-0684-x. eCollection 2017.
Metabolic engineering is a commonly used approach to develop organisms for an industrial function, but engineering aimed at improving one phenotype can negatively impact other phenotypes. This lack of robustness can prove problematic. Cellulolytic bacterium is able to rapidly ferment cellulose to ethanol and other products. Recently, genes involved in H production, including the hydrogenase maturase and NiFe hydrogenase , were deleted from the chromosome of . While ethanol yield increased, the growth rate of Δ decreased substantially compared to wild type.
Addition of 5 mM acetate to the growth medium improved the growth rate in , whereas wild type remained unaffected. Transcriptomic analysis of the wild type showed essentially no response to the addition of acetate. However, in , 204 and 56 genes were significantly differentially regulated relative to wild type in the absence and presence of acetate, respectively. Genes, Clo1313_0108-0125, which are predicted to encode a sulfate transport system and sulfate assimilatory pathway, were drastically upregulated in in the presence of added acetate. A similar pattern was seen with proteomics. Further physiological characterization demonstrated an increase in sulfide synthesis and elimination of cysteine consumption in . had a higher growth rate than in the absence of added acetate, and a similar but less pronounced transcriptional and physiological effect was seen in this strain upon addition of acetate.
Sulfur metabolism is perturbed in strains, likely to increase flux through sulfate reduction to act either as an electron sink to balance redox reactions or to offset an unknown deficiency in sulfur assimilation.
代谢工程是一种常用于改造生物以实现工业功能的方法，但旨在改善一种表型的工程改造可能会对其他表型产生负面影响。这种缺乏稳健性可能会带来问题。纤维素分解菌能够快速将纤维素发酵为乙醇和其他产物。最近，参与氢气产生的基因，包括氢化酶成熟酶和镍铁氢化酶，已从该菌的染色体中删除。虽然乙醇产量增加了，但与野生型相比，Δ菌的生长速率大幅下降。
在生长培养基中添加5 mM乙酸盐可提高该菌的生长速率，而野生型不受影响。对野生型进行转录组分析表明，添加乙酸盐后基本没有反应。然而，在该菌中，分别在不存在和存在乙酸盐的情况下，相对于野生型，有204个和56个基因受到显著差异调节。预测编码硫酸盐转运系统和硫酸盐同化途径的基因Clo1313_0108 - 0125在添加乙酸盐的情况下在该菌中大幅上调。蛋白质组学也观察到类似模式。进一步的生理特征表明，该菌中硫化物合成增加且半胱氨酸消耗消除。在不添加乙酸盐的情况下，该菌的生长速率高于Δ菌，并且在添加乙酸盐后，该菌株也观察到类似但不太明显的转录和生理效应。
该菌菌株的硫代谢受到干扰，可能是为了增加通过硫酸盐还原的通量，要么作为电子汇来平衡氧化还原反应，要么抵消硫同化中未知的缺陷。
