Rumen Synergistota: new insights into their role in mimosine and fluoroacetate toxicity of ruminant livestock

Abstract

ABSTRACT This paper examines several rumen bacteria in the Synergistota phylum, specifically focusing on their potential to detoxify harmful compounds found in plants grazed by ruminants. Synergistota bacteria ferment amino acids for energy, while rumen Synergistes jonesii from which the phylum was named, can also metabolize toxins found in the forage plant Leucaena leucocephala (leucaena). Specifically, S. jonesii is able to detoxify mimosine, a non-protein amino acid in leucaena, by converting it into less harmful metabolites. Historically, S. jonesii was introduced to ruminants in Australia to mitigate leucaena toxicity based on the notion that the bacterium was absent on this continent. Recent studies indicate geographic variations in S. jonesii’s presence and effectiveness, suggesting that strain variability may impact its detoxification efficacy. PCR-based assays have improved the detection of S. jonesii , revealing its widespread distribution in Australia and globally, but often low abundance in ruminant microbiomes. Additionally, other rumen Synergistota species ( Cloacibacillus porcorum and Pyramidobacter piscolens ) have recently been isolated and identified as agents for metabolizing fluoroacetate, another toxin present in Australian flora. These bacteria degrade fluoroacetate through a novel molecular mechanism of reductive dehalogenation, thus producing fluoride ions and acetate as byproducts. This mechanism has been detected in soil and contaminated groundwater but not the rumen. These findings underscore the ecological importance of Synergistota bacteria in reducing plant toxicity in ruminants. Ongoing research is recommended to isolate new strains, optimize rumen populations of these bacteria, and further understand the molecular pathways involved in toxin degradation to enhance detoxification capabilities in ruminant populations.

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