Liu Binbin, Zhang Xiaojun, Bakken Lars R, Snipen Lars, Frostegård Åsa
Faculty of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, Ås, Norway.
State Key Laboratory of Microbial Metabolism and School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, China.
Front Microbiol. 2019 Jan 8;9:3208. doi: 10.3389/fmicb.2018.03208. eCollection 2018.
Denitrification allows sustained respiratory metabolism during periods of anoxia, an advantage in soils with frequent anoxic spells. However, the gains may be more than evened out by the energy cost of producing the denitrification machinery, particularly if the anoxic spell is short. This dilemma could explain the evolution of different regulatory phenotypes observed in model strains, such as sequential expression of the four denitrification genes needed for a complete reduction of nitrate to N, or a "bet hedging" strategy where all four genes are expressed only in a fraction of the cells. In complex environments such strategies would translate into progressive onset of transcription by the members of the denitrifying community. We exposed soil microcosms to anoxia, sampled for amplicon sequencing of , and genes and transcripts after 1, 2 and 4 h, and monitored the kinetics of NO, NO, and N. The cDNA libraries revealed a succession of transcribed genes from active denitrifier populations, which probably reflects various regulatory phenotypes in combination with cross-talks via intermediates ( , NO) produced by the "early onset" denitrifying populations. This suggests that the regulatory strategies observed in individual isolates are also displayed in complex communities, and pinpoint the importance for successive sampling when identifying active key player organisms.
反硝化作用使得在缺氧时期能够维持呼吸代谢,这对于频繁出现缺氧时段的土壤来说是一个优势。然而,生产反硝化机制的能量成本可能会抵消甚至超过这种优势,特别是当缺氧时段较短时。这种困境可以解释在模式菌株中观察到的不同调控表型的进化,例如将硝酸盐完全还原为氮气所需的四个反硝化基因的顺序表达,或者一种“风险对冲”策略,即所有四个基因仅在一部分细胞中表达。在复杂环境中,这种策略会转化为反硝化群落成员转录的逐步开始。我们将土壤微观生态系统暴露于缺氧环境中,在1小时、2小时和4小时后对 、 和 基因及转录本进行扩增子测序采样,并监测一氧化氮、一氧化二氮和氮气的动力学。cDNA文库揭示了活跃反硝化菌群体中转录基因的相继出现,这可能反映了各种调控表型以及与“早期开始”反硝化群体产生的中间体( 、一氧化氮)的相互作用。这表明在单个分离物中观察到的调控策略也在复杂群落中表现出来,并指出了在识别活跃关键生物体时连续采样的重要性。
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