2623
This microbiota is considered to play a number of key roles in the maintenance of host health , including aiding digestion of otherwise indigestible dietary compounds , synthesis of vitamins and other beneficial metabolites , immune system regulation and enhanced resistance against colonisation by pathogenic microorganisms .
 None
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 None