Role of gut bacterial flora in nutrition and health: a review of recent advances in bacteriological techniques, metabolism, and factors affecting flora composition.

Abstract

In the past decade, there has been a resurgence of scientific interest in man's intestinal microbiota and its role in determining the normal physiology and health status of the host. The vast majority of fecal and intestinal microbes are strict anaerobes, many extremely sensitive to molecular oxygen. Intestinal anaerobes may outnumber aerobes and facultative anaerobes by a factor of 103 or greater. As a result of newer and more rigorous anaerobic bacteriological procedures for the isolation of gut flora components, viable recoveries of significant fractions (1/3 to 2/3) of the numerous microbes observed by direct microscopic examination of fecal specimens have been achieved. Data from several recent studies put the viable count in normal human feces at 2 to 4 × 1011/g dry weight. Extensive studies of human fecal flora components employing both selective media and nonselective random isolation procedures have revealed an unexpected order of complexity both within and between individuals. It is estimated th...