氮是维持生命活动最重要的营养元素之一,环境微生物在氮的生物地球化学循环中起着重要作用,但由于大部分微生物不可培养,对其认识非常有限。本文结合表面增强拉曼光谱(Surface-Enhanced Raman Spectroscopy,SERS)与15N稳定同位素标记,证明15N可引起细菌SERS谱峰明显偏移。偏移谱峰可作为细菌同化氮的良好指示。另外15N比例与SERS谱峰呈现良好的线性关系,说明SERS可以用于研究氮相关的功能和活性微生物,并根据偏移程度判断活性。我们也比较了15N、13C、氘代葡糖糖和氘水引起的SERS谱峰偏移,结果显示位于腺嘌呤环上的C和N引起的偏移要大于氘重同位素引起的偏移。以上研究有助于选择合适的拉曼-稳定同位素标记方法,针对不同元素进行研究。

Nitrogen is an essential nutrient element sustaining all life forms.Environmental microorganisms play an important role in biogeochemical cycle of nitrogen.However,because a large majority of environmental microorganisms are uncultured,our knowledge on them is very limited.Here,by combining surface-enhanced Raman spectroscopy (SERS) with 15N stable isotope probing,obvious 15N-induced band shifts in SERS spectra of bacteria were identified.Bands shifted linearly with 15N percentage in media,providing a way to study extent of nitrogen assimilation or activity of bacteria.The selective enhancement of SERS on N-related biomolecules accounted for the presence of indicator bands.Finally,SERS band shift induced by 15N,13C and deuterium were compared and the results indicated that 15N induced a larger shift than deuterium.The reason is related to the position of N and H in the ring structure of adenine.