Direct visualization of yeast mannan metabolism in bovine-adapted Bacteroides thetaiotaomicron strains at the single cell level using fluoresceinamine - yeast mannan conjugates

Abstract

The rumen of beef cattle houses a diverse community of microorganisms that impact feed digestion, nutrient accessibility, host health, and waste production. Fibrolytic enzymes, probiotics, and prebiotics are promising candidates for next-generation feed additives, with the goal of inducing beneficial changes to the rumen microbiome. Current methods to investigate the mechanistic interactions between bacteria and feed glycans are “indirect” and lack the required sensitivity to validate probiotic-prebiotic application. To address these limitations, I have extended fluorescent glycan conjugates (FGCs) to visualize polysaccharide uptake in bacterial isolates and complex ecosystems at the single-cell level. Yeast α-mannan (YM) was conjugated to 6-aminofluorescein and fed to pure cultures of Bacteroides thetaiotaomicron VPI-5482, a well-studied intestinal symbiont that metabolizes YM, and closely related bovine-adapted bacterial isolates. Uptake of FGCs, coupled to complementary genomic and transcriptomic analysis, provided direct evidence of individual genotypes endowed with YM metabolic potential in pure and complex culture.