Boyer Grayson M, Schubotz Florence, Summons Roger E, Woods Jade, Shock Everett L
School of Earth and Space Exploration, Arizona State University, Tempe, AZ, United States.
MARUM and Department of Geosciences, University of Bremen, Bremen, Germany.
Front Microbiol. 2020 Feb 20;11:229. doi: 10.3389/fmicb.2020.00229. eCollection 2020.
The influence of oxidation-reduction (redox) potential on the expression of biomolecules is a topic of ongoing exploration in geobiology. In this study, we investigate the novel possibility that structures and compositions of lipids produced by microbial communities are sensitive to environmental redox conditions. We extracted lipids from microbial biomass collected along the thermal and redox gradients of four alkaline hot springs in Yellowstone National Park (YNP) and investigated patterns in the average oxidation state of carbon (Z), a metric calculated from the chemical formulae of lipid structures. Carbon in intact polar lipids (IPLs) and their alkyl chains becomes more oxidized (higher Z) with increasing distance from each of the four hot spring sources. This coincides with decreased water temperature and increased concentrations of oxidized inorganic solutes, such as dissolved oxygen, sulfate, and nitrate. Carbon in IPLs is most reduced (lowest Z) in the hot, reduced conditions upstream, with abundance-weighted Z values between -1.68 and -1.56. These values increase gradually downstream to around -1.36 to -1.33 in microbial communities living between 29.0 and 38.1°C. This near-linear increase in Z can be attributed to a shift from ether-linked to ester-linked alkyl chains, a decrease in average aliphatic carbons per chain (nC), an increase in average degree of unsaturation per chain (nUnsat), and increased cyclization in tetraether lipids. The Z of lipid headgroups and backbones did not change significantly downstream. Expression of lipids with relatively reduced carbon under reduced conditions and oxidized lipids under oxidized conditions may indicate microbial adaptation across environmental gradients in temperature and electron donor/acceptor supply.
氧化还原电位对生物分子表达的影响是地球生物学中一个正在进行探索的课题。在本研究中，我们探究了一种新的可能性，即微生物群落产生的脂质的结构和组成对环境氧化还原条件敏感。我们从黄石国家公园（YNP）四个碱性温泉的热梯度和氧化还原梯度沿线采集的微生物生物质中提取脂质，并研究了碳的平均氧化态（Z）的模式，Z是根据脂质结构的化学式计算得出的一个指标。随着与四个温泉源头中每一个的距离增加，完整极性脂质（IPL）及其烷基链中的碳变得更加氧化（Z值更高）。这与水温降低以及氧化无机溶质（如溶解氧、硫酸盐和硝酸盐）浓度增加相吻合。在热的、上游还原条件下，IPL中的碳还原程度最高（Z值最低），丰度加权Z值在-1.68至-1.56之间。在温度为29.0至38.1°C的微生物群落中，这些值向下游逐渐增加至约-1.36至-1.33。Z值的这种近乎线性的增加可归因于从醚键连接的烷基链向酯键连接的烷基链的转变、每条链平均脂肪族碳数（nC）的减少、每条链平均不饱和度（nUnsat）的增加以及四醚脂质中环化程度的增加。脂质头部基团和主链的Z值在下游没有显著变化。在还原条件下具有相对还原碳的脂质以及在氧化条件下具有氧化脂质的表达可能表明微生物在温度和电子供体/受体供应的环境梯度中的适应性。
