Department of Microbiology Immunology and Molecular Genetics, University of California, Los Angeles, 405 Hilgard Avenue, Los Angeles, CA 90095, USA.
BMC Microbiol. 2010 Feb 23;10:62. doi: 10.1186/1471-2180-10-62.
The archaeon, Methanosarcina acetivorans strain C2A forms methane, a potent greenhouse gas, from a variety of one-carbon substrates and acetate. Whereas the biochemical pathways leading to methane formation are well understood, little is known about the expression of the many of the genes that encode proteins needed for carbon flow, electron transfer and/or energy conservation. Quantitative transcript analysis was performed on twenty gene clusters encompassing over one hundred genes in M. acetivorans that encode enzymes/proteins with known or potential roles in substrate conversion to methane.
The expression of many seemingly "redundant" genes/gene clusters establish substrate dependent control of approximately seventy genes for methane production by the pathways for methanol and acetate utilization. These include genes for soluble-type and membrane-type heterodisulfide reductases (hdr), hydrogenases including genes for a vht-type F420 non-reducing hydrogenase, molybdenum-type (fmd) as well as tungsten-type (fwd) formylmethanofuran dehydrogenases, genes for rnf and mrp-type electron transfer complexes, for acetate uptake, plus multiple genes for aha- and atp-type ATP synthesis complexes. Analysis of promoters for seven gene clusters reveal UTR leaders of 51-137 nucleotides in length, raising the possibility of both transcriptional and translational levels of control.
The above findings establish the differential and coordinated expression of two major gene families in M. acetivorans in response to carbon/energy supply. Furthermore, the quantitative mRNA measurements demonstrate the dynamic range for modulating transcript abundance. Since many of these gene clusters in M. acetivorans are also present in other Methanosarcina species including M. mazei, and in M. barkeri, these findings provide a basis for predicting related control in these environmentally significant methanogens.
古菌 Methanosarcina acetivorans 菌株 C2A 能够利用多种一碳底物和乙酸生成甲烷，甲烷是一种强效温室气体。虽然生成甲烷的生化途径已经得到充分研究，但对于编码用于碳流、电子传递和/或能量守恒的蛋白质的许多基因的表达知之甚少。对 Methanosarcina acetivorans 中的二十个基因簇进行了定量转录分析，这些基因簇涵盖了 100 多个基因，这些基因编码已知或潜在参与底物转化为甲烷的酶/蛋白质。
许多看似“冗余”的基因/基因簇的表达确立了对甲醇和乙酸利用途径中约 70 个基因的底物依赖性控制，以生成甲烷。这些基因包括可溶性和膜结合型异型二硫化物还原酶（hdr）、包括 vht 型 F420 非还原型氢化酶在内的氢化酶、钼型（fmd）和钨型（fwd）甲酰甲硫氨酸脱氢酶、rnf 和 mrp 型电子传递复合物、乙酸摄取以及多个 aha-和 atp 型 ATP 合成复合物的基因。对七个基因簇的启动子分析表明，UTR 长度为 51-137 个核苷酸，这增加了转录和翻译水平控制的可能性。
上述发现确立了 Methanosarcina acetivorans 中两种主要基因家族对碳/能量供应的差异和协调表达。此外，定量 mRNA 测量证明了调节转录物丰度的动态范围。由于 Methanosarcina acetivorans 中的许多这些基因簇也存在于其他 Methanosarcina 物种（包括 M. mazei 和 M. barkeri）中，这些发现为预测这些具有重要环境意义的产甲烷菌的相关控制提供了依据。
