Zhuang Zheng, Xia Xue, Yang Guiqin, Zhuang Li
Guangdong Key Laboratory of Environmental Pollution and Health, School of Environment, Jinan University, Guangzhou, China.
Front Microbiol. 2022 Jun 16;13:927246. doi: 10.3389/fmicb.2022.927246. eCollection 2022.
Direct interspecies electron transfer (DIET) is an effective mechanism for microbial species to exchange electrons cooperatively during syntrophic metabolism. It is generally accepted that DIET is mainly mediated by electrically conductive pili and outer surface -type cytochromes (-Cyts). However, as an extracellular matrix is ubiquitous and abundant on the surface of microorganisms, the effect and mechanism of exopolysaccharides on DIET are still unclear. This study constructed a co-culture of exopolysaccharides-deficient with to explore the role of exopolysaccharides in DIET. Results revealed that the deficiency of exopolysaccharides extended the metabolic period of the co-culture by 44.4% and changed the proportions of each species in the co-culture. The exopolysaccharides-deficient co-culture failed to form large, tight spherical aggregates and the expression of -Cyts and pili was decreased. The addition of magnetite and granular activated carbon (GAC), respectively, might compensate for the functions of -Cyts and pili in the first generation of co-culture, but the stimulatory effect on the metabolic stable period co-culture was fairly limited. These findings demonstrate that non-conductive exopolysaccharides are an important component of DIET aggregates and an extracellular matrix for DIET-required -Cyts.
种间直接电子转移（DIET）是微生物在互营代谢过程中协同交换电子的一种有效机制。人们普遍认为，DIET主要由导电菌毛和外表面型细胞色素（-Cyts）介导。然而，由于细胞外基质在微生物表面普遍存在且含量丰富，胞外多糖对DIET的作用和机制仍不清楚。本研究构建了胞外多糖缺陷型与[具体微生物名称缺失]的共培养体系，以探究胞外多糖在DIET中的作用。结果表明，胞外多糖的缺乏使共培养的代谢周期延长了44.4%，并改变了共培养体系中各物种的比例。缺乏胞外多糖的共培养体系未能形成大而紧密的球形聚集体，且-Cyts和菌毛的表达降低。分别添加磁铁矿和颗粒活性炭（GAC）可能会在第一代共培养中补偿-Cyts和菌毛的功能，但对代谢稳定期共培养的刺激作用相当有限。这些发现表明，非导电胞外多糖是DIET聚集体的重要组成部分，也是DIET所需-Cyts的细胞外基质。
