ИСТИНА

An important subfield of microbial ecology focuses on the chemical dialogue within the host organism—microbiota consortium that presumably involves neurochemicals (biogenic amines, amino acids, etc.). Human microbial inhabitants, e.g., Escherichia coli, produce biogenic amines. The symbiotic microbiota includes lactobacteria, and some of them represent probiotics. Are neuromediators released by lactobacteria contained in fermented dairy items and starter cultures? Materials and Methods: The contents of biogenic amines (BAs) and regulatory amino acids (RAAs) in dairy products and pure Lactobacillus cultures were measured using high performance liquid chromatography (HPLC) on a reversed-phase column.The BAs were determined amperometrically with a glass-carbon electrode (+0.85 V), and the RAAs were complexated with ortho-phthalic aldehyde and determined fluorometrically (the excitatory and emission wavelengths were 230 and 392 nm, respectively). Results: A comparison of milk and yogurt samples revealed that the yogurts are enriched in noradrenaline, dopamine, DOPA, their precursor, and RAAs such as glycine, taurine, and GABA (contained in the fruit filler-lacking yogurt only). The pure cultures of Lactobacillus helveticus 100ash, L. helveticus NK-1, L. casei K3III24, and L. delbrueckii subsp. bulgaricus release into the milk- or pancreatic hydrolysate of milkcontaining medium (sub)micromolar amounts of DOPA, dopamine, noradrenaline, serotonin (produced by L. helveticus 100ash only), GABA (at concentrations that are close to those in the human blood and spinal fluid), glutamate, glycine, and taurine. Conclusions: The data obtained suggest that the bacteria that interact with the human organism, exemplified by several Lactobacillus species/strains, form neuromediators such as BAs and RAAs. They can exert a local effect and, with the gut-blood and blood-brain barrier-passing DOPA and GABA, a systemic influence, particularly on the functioning of the brain. These compounds presumably function as signal agents in the microbiotagut- brain axis.