Rajaraman Eashwar, Agrawal Ankit, Crigler Jacob, Seipelt-Thiemann Rebecca, Altman Elliot, Eiteman Mark A
BioChemical Engineering, College of Engineering, University of Georgia, Athens, GA, 30602, USA.
Department of Biology, Middle Tennessee State University, Murfreesboro, TN, 37132, USA.
Appl Microbiol Biotechnol. 2016 Sep;100(17):7777-85. doi: 10.1007/s00253-016-7724-0. Epub 2016 Jul 22.
Eighteen strains of Escherichia coli were compared for maximum specific growth rate (μ MAX) on 85 mM acetate as the sole carbon source. The C strain ATCC8739 had the greatest growth rate (0.41 h(-1)) while SCS-1 had the slowest growth rate (0.15 h(-1)). Transcriptional analysis of three of the strains (ATCC8739, BL21, SMS-3-5) was conducted to elucidate why ATCC8739 had the greatest maximum growth rate. Seventy-one genes were upregulated 2-fold or greater in ATCC8739, while 128 genes were downregulated 2-fold or greater in ATCC8739 compared to BL21 and SMS-3-5. To generate a strain that could grow more quickly on acetate, ATCC8739 was cultured in a chemostat using a progressively increasing dilution rate. When the dilution rate reached 0.50 h(-1), three isolated colonies each grew faster than ATCC8739 on 85 mM acetate, with MEC136 growing the fastest with a growth rate of 0.51 h(-1), about 25 % greater than ATCC8739. Transcriptional analysis of MEC136 showed that eight genes were downregulated 2-fold or greater and one gene was upregulated 2-fold or greater compared to ATCC8739. Genomic sequencing revealed that MEC136 contained a single mutation, causing a serine to proline change in amino acid 266 of RpoA, the α subunit of the RNA polymerase core enzyme. The 260-270 amino acid region of RpoA has been shown to be a key region of the protein that affects the interaction of the α subunit of the RNA polymerase core enzyme with several global transcriptional activators, such as CRP and FNR.
对18株大肠杆菌在以85 mM乙酸盐作为唯一碳源的条件下的最大比生长速率（μ MAX）进行了比较。C菌株ATCC8739的生长速率最大（0.41 h⁻¹），而SCS - 1的生长速率最慢（0.15 h⁻¹）。对其中三株菌株（ATCC8739、BL21、SMS - 3 - 5）进行转录分析，以阐明ATCC8739具有最大生长速率的原因。与BL21和SMS - 3 - 5相比，ATCC8739中有71个基因上调了2倍或更多，而有128个基因下调了2倍或更多。为了获得在乙酸盐上能更快生长的菌株，将ATCC8739在恒化器中培养，采用逐渐增加的稀释率。当稀释率达到0.50 h⁻¹时，三个分离的菌落各自在85 mM乙酸盐上的生长速度都比ATCC8739快，其中MEC136生长最快，生长速率为0.51 h⁻¹，比ATCC8739快约25%。对MEC136的转录分析表明，与ATCC8739相比，有8个基因下调了2倍或更多，1个基因上调了2倍或更多。基因组测序显示，MEC136包含一个单一突变，导致RNA聚合酶核心酶的α亚基RpoA的第266位氨基酸由丝氨酸变为脯氨酸。RpoA的260 - 270氨基酸区域已被证明是该蛋白质的一个关键区域，它影响RNA聚合酶核心酶的α亚基与几种全局转录激活因子（如CRP和FNR）的相互作用。
