Chaudhary Srishti, Singh Ramandeep, Yadav Sukrampal, Patil Sunil A
Department of Earth and Environmental Sciences, Indian Institute of Science Education and Research Mohali (IISER Mohali), Sector 81, SAS Nagar, Knowledge City, Punjab 140306, India.
iScience. 2021 Jun 5;24(6):102682. doi: 10.1016/j.isci.2021.102682. eCollection 2021 Jun 25.
Electrotrophic microorganisms have not been well studied in extreme environments. Here, we report on the nitrate-reducing cathodic microbial biofilm from a haloalkaline environment. The biofilm enriched electrochemical approach under 9.5 pH and 20 g NaCl/L salinity conditions achieved current density and nitrate reduction efficiency via partial and complete denitrification. Voltammetric characterization of the biocathodes revealed a redox center with ( Ag/AgCl) formal potential putatively involved in the electron uptake process. The lack of soluble redox mediators and hydrogen-driven nitrate reduction suggests direct-contact cathodic electron uptake by the nitrate-reducing microorganisms in the enriched biofilm. 16S-rRNA amplicon sequencing of the cathodic biofilm revealed the presence of unreported and spp. at , and relative sequence abundances, respectively. The enriched nitrate-reducing microorganisms also reduced nitrate efficiently using soluble electron donors found in the lake sediments, thereby suggesting their role in N-cycling in such environments.
在极端环境中，对电营养微生物的研究还不够充分。在此，我们报告了来自卤碱性环境的硝酸盐还原阴极微生物生物膜。在pH 9.5和盐度20 g NaCl/L的条件下，通过富集电化学方法获得的生物膜通过部分和完全反硝化作用实现了电流密度和硝酸盐还原效率。对生物阴极的伏安特性表征揭示了一个具有(Ag/AgCl)形式电位的氧化还原中心，推测其参与了电子摄取过程。缺乏可溶性氧化还原介质以及氢驱动的硝酸盐还原表明，富集生物膜中硝酸盐还原微生物通过直接接触阴极摄取电子。对阴极生物膜的16S - rRNA扩增子测序显示，分别存在相对序列丰度为 、 和 的未报道的 和 属物种。富集的硝酸盐还原微生物还利用湖泊沉积物中发现的可溶性电子供体有效地还原了硝酸盐，从而表明它们在此类环境中的氮循环中发挥的作用。
