Neglected Niches

Abstract

Every day we excrete 100–200 g of feces. Given that 75% of the wet weight is composed of bacteria (Stephen and Cummings, 1980) and that each gram contains 1 × 1011 organisms belonging to up to 400 different species (Moore and Holdeman, 1974), it is clear that we are the outer casing of possibly one of the most highly evolved and complex microbial ecosystems of them all. Freter et al (1983a) have commented on the apparent paradox that 100 years of intensive research has not brought us close to an understanding of what controls the indigenous microbiota* of the gastrointestinal tract. This lack of progress does not seem so surprising if we consider the intestine as a continuous culture vessel containing at the one time hundreds of organisms in steady state conditions. The study of even two or three organisms in steady state in a culture vessel is difficult enough. And yet, here the culture vessel of the gut compounds the problem by being composed of living animal cells.