LAUSR

Vitamins are indispensable micronutrients that are needed for a myriad of metabolic and regulatory processes critical for all living organisms [1–3]. Because humans do not have the capacity to synthesize most of these essential nutrients themselves, they need to be obtained externally. Even though vitamins can be found in various foods, deficiencies still occur in developing and industrialized countries [4]. A rather unexpected source of vitamins is the microbiota present in the gastrointestinal (GI) tract. Most of these microbes can synthesize vitamins de novo and even produce them in excess, notably vitamin K and vitamins in the B group such as riboflavin, niacin, and cobalamin [5,6]. It has been estimated that they produce up to 30% of the recommended daily intake for the host; however, this depends on the microbiome composition and the host’s diet [7]. Moreover, microbes can work together to produce vitamins that can modulate the metabolic activity and composition of the human gut microbiome [8,9]. Interestingly, recent research has highlighted the importance of vitamins in the pathology of opportunistic pathogens that live as commensals in the human GI tract [10,11].