Growth Coordination Between Butyrate-Oxidizing Syntrophs and Hydrogenotrophic Methanogens

Abstract

Syntrophy is a thermodynamically required mutualistic cooperation between fatty acid-oxidizing bacteria and methanogens that plays the important role in organic decomposition and methanogenesis in anoxic environments. In this study, three experiments were conducted to evaluate the cell-to-cell interaction in a thermophilic coculture consisting of Syntrophothermus lipocalidus and Methanocella conradii and a mesophilic coculture consisting of Syntrophomonas wolfei and Methanococcus maripaludis. First, syntrophs and methanogens were inoculated at different initial cell ratios to evaluate the growth synchronization. The quantitative PCR analysis revealed that the organism with a lower relative abundance at the beginning always grew faster, and the cell ratio converged over time to relative constant values in both the thermophilic and mesophilic cocultures. Next, intermittent ultrasound and constant shaking treatments were used to evaluate the influence of physical disturbance on microbial aggregation in the mesophilic coculture. The fluorescence in situ hybridization and scanning electron microscopy revealed that the tendency of syntrophic aggregation was not affected by the physical disturbances, although the activity was slightly depressed. Syntrophomonas dominated in the initial microbial aggregates, which, however, did not grow until Methanococcus was attached and increased to a significant extent, indicating the local growth synchronization during the formation and maturation of syntrophic aggregates. Last, microfluidic experiments revealed that whether or not Syntrophomonas or Methanococcus was loaded first, the second organism preferred moving to the place where the first organism was located, suggesting the cell-to-cell attraction between Syntrophomonas and Methanococcus. Collectively, our study demonstrated the growth synchronization and cell-to-cell attraction between the butyrate-oxidizing bacteria and methanogens for optimizing the syntrophic cooperation.

Quantitative and Qualitative Changes in the Genetic Diversity of Bacterial Communities in Anaerobic Bioreactors with the Diatomaceous Earth/Peat Cell Carrier

“…variant, as compared to WF-control ( Figure 4 and Figure 7 ). Additionally, the study carried out by other authors shows that acetogenic bacteria of the genus of Syntrophomonas , which play an important role in the syntrophic oxidation of LCFA (long chain fatty acids), are one of the dominant genera in the anaerobic digestion of organic waste [ 61 ].…”

Wet Anaerobic Codigestion of Sewage Sludge and OFMSW in Pilot-Scale Continuously Stirred Tank Reactors: Focus on the Reactor Microbial Communities

“…Nevertheless, only acetoclastic Archaea are inhibited by a high total VFA content and low pH [73] and high ammonia content [74]. In these cases, however, a shift in methanogens can occur, leading to hydrogenoclastic methanogens overcoming acetoclastic bacteria and a cooperation with syntrophic propionate-oxidizing bacteria (SPOB) [75] and Butyrateoxidizing syntrophs [76].…”