The order 'Bacteroidales' comprises five families of environmental bacteria. One of the orders assigned to the Phylum that includes Cytophaga Flavobacterium and Bacteroides, sole order in the class Bacteroidetes. A study done in Norway in 2014, found significant correlations between bacteria in stool samples and depression, with elevated levels of the order Bacteroidales and a reduced abundance of the family Lachnospiraceae.
Microbial Abundance Data: Bacteroidales (Percent of total population with standard deviation [PMID: 22698087])