In the complex milieu of the human gut microbiome, understanding the intricate interactions within microbial communities is essential to unravel the dynamics that govern health and disease. This study focuses on the symbiotic relationship between Escherichia coli and Enterococcus faecalis and investigates their adaptive responses to acid stress^1,2 and polyamine cross-feeding³ under physiological conditions. Ornithine, a polyamine crucial for this interplay⁴, is produced by the enzyme SpeF, marking its significance in the context of microbiome interactions. By analyzing various pathogenic and non-pathogenic E. coli strains, we were able to show that the presence of regulatory elements essential for speF expression appears to correlate with their efficacy in defense against Salmonella typhimurium. To understand the role of ornithine production by SpeF in this cross-protection, we are using high-performance liquid chromatography (HPLC) to analyze polyamine secretion and uptake in selected E. coli strains, including the human uropathogenic UTI89 and the pathogenic Mt1B1 strain, under conditions of E. faecalis coexistence and acid stress. This study sheds light on the role of acid stress and polyamine cross-feeding in shaping bacterial interactions of the human gut microbiome.

References

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