Paneth cells, antimicrobial peptides and the regulation of the intestinal microbiota

Published on September 27, 2011 Updated on February 27, 2017   45 min

Other Talks in the Series: Microbiota

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My name is Dr. Nita Salzman. I am a Professor of Pediatrics in the Division of Gastroenterology at The Medical College of Wisconsin. The title of my presentation today is "Paneth Cells, Antimicrobial Peptides, and the Regulation of the Intestinal Microbiota".
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Humans and other mammals are colonized by a vast number of diverse microorganisms collectively known as the microbiome. The human microbiome is defined as, "The totality of microorganisms and their collective genetic material present in or on the human body." The human microbiome, while predominantly bacterial, is also comprised of viruses, archaea, and eukaryotic microbes. Each body site harbors a distinct microbiome. The GI tract is the largest mammalian mucosal surface and contains the majority of the total human microbiome. The majority of the bacteria comprising the microbiota resist culturing by conventional techniques.
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The GI tract is the largest mammalian mucosal surface. And this mucosal surface is highly colonized by a diverse microbial ecosystem. If you consider the GI tract as a tube that starts at the mouth and ends at the rectum, the red dots depicted in this cartoon represent bacterial colonization. Mammals including humans are colonized by vast numbers of microbes, predominantly bacteria. And the majority of these colonizers are in the GI tract. At current estimates between 500 and 1,000 different bacterial species can be found in the GI tract. Anaerobic bacteria outnumber aerobic bacteria by 10-100 fold. Bacteria in the GI tract are comprised of transient organisms and indigenous organisms. And currently, there is no accepted way of distinguishing these groups. The overall dominant phyla in the small and large bowel include the Bacteroides which are Gram-negative, and the Firmicutes, which are Gram-positive. The most abundant members of the Firmicutes phylum are clostridial species. The density of colonization as well as the specific composition and diversity of colonization is dependant on site and specific intestinal microenvironment, including pH, oxygen environment, nutrient environment, and likely several factors that are yet undetermined. The mouth, which is generally at a neutral pH, is highly colonized. The esophagus has a low level of resident microbiota. While the stomach has somewhat increased bacterial abundance. The proximal small intestine reflects the bacterial burden of the stomach, at about 10 to the 4th cfu/ml. But the bacterial burden increases, as you move distally, ultimately reaching 10 to the 8th cfu/ml in the terminal ileum. At the junction, between the terminal ileum and the large intestine, there is an abrupt change in bacterial abundance, with the highest abundance of bacteria in the large colon at approximately 10 to the 12th cfu/ml. Although the bacterial composition are similar at the phylum level, there are significant differences between the small and large intestine, with respect to both bacterial diversity and relative abundance of specific bacterial taxa.
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Paneth cells, antimicrobial peptides and the regulation of the intestinal microbiota

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