Define Importance of Intestinal Bacterial Synthesis as a Source of Vitamin K?

Intestinal microflora synthesizes large amounts of menaquinones, which are potentially available as a source of vitamin K. Quantitative measurements at different sites of the human intestine has demonstrated that most of these menaquinones are present in the distal colon. Major forms produced are MK-10 and MK-11 by Bacteroides, MK-8 by Enterobacter, MK-7 by veillonella, and MK-6 by Eubacterium  lentum etc.

However, the balance of evidence suggests that the bioavailability of bacterial menaquinones is poor because they are for the most part tightly bound to the bacterial cytoplasmic membrane and also because the largest pool is present in the colon, which lacks bile salts for their solubilisation.