In Situ Probing of the Intrinsic Adhesion Strength of Single Anaerobic Microbial Cells.

Probing the single-cell mechanobiology in situ is imperative for microbial processes in the medical, industrial, and agricultural realms, but it remains a challenge. Herein, we present a single-cell force microscopy method that can be used to measure microbial adhesion strength under anaerobic conditions in situ. This method integrates atomic force microscopy with an anaerobic liquid cell and inverted fluorescence microscopy. We obtained the nanomechanical measurements of the single anaerobic bacterium Ethanoligenens harbinense YUAN-3 and the methanogenic archaeon Methanosarcina acetivorans C2A and their nanoscale adhesion forces in the presence of sulfoxaflor, a successor of neonicotinoid pesticides. This study presents a new tool for in situ single-cell force measurements of various anoxic and anaerobic species and provides new perspectives for evaluating the potential environmental risk of neonicotinoid applications in ecosystems.

Single bubble probe atomic force microscope and impinging-jet technique unravel the interfacial interactions controlled by long chain fatty acid in anaerobic digestion.

Anaerobic digestion of lipid-rich wastewater generally suffers from foaming induced by long chain fatty acid (LCFA). However, a systematic understanding of LCFA inhibition, especially the physical inhibition on interfacial interaction still remains unclear. Here, we combined bubble probe atomic force microscope and impinging-jet technique to unravel the interfacial interactions controlled by long chain fatty acids in anaerobic digestion. We showed that LCFA had a significant inhibition on methane production in anaerobic reactors for the inhibition of the conversion of VFAs to methane. By measuring the LCFA influence on methanogenic archaea Methanosarcina acetivorans C2A, the results demonstrated that methanogenesis was limited for substrates utilization but not metabolic pathways. The impinging-jet technique results indicated that LCFA enhanced bubble separation from anaerobic granules and reduced the bubble-bubble coalescence probability. In addition, the bubble probe atomic force microscope (AFM) revealed that LCFA enhanced the adhesion force between bubbles by enhancing electrical double layer (EDL) repulsion and decreasing hydrophobic interactions. Overall, these results complement framework of LCFA inhibition in anerobic digestion and provide a nanomechanical insight into the fundamental interfacial interactions related to bubbles in anaerobic reactors.