Why related bacterial species bloom simultaneously in the gut: principles underlying the 'Like will to like' concept

Abstract

The large intestine is host to a complex ecological community composed predominantly of obligate anaerobic bacteria belonging to the classes Bacteroidia and Clostridia. This community confers benefits through its metabolic activities and host interactions. However, a microbial imbalance (dysbiosis) characterized by a decreased abundance of Clostridia and a bloom of facultative anaerobic Proteobacteria is commonly observed during inflammation in the large bowel. Here we review recent insights into the principles that favour simultaneous increases in the abundance of closely related species belonging to the Proteobacteria during inflammation, which provides important clues for the rational design of strategies to treat dysbiosis.

Figure 1

Changes in gut-associated microbial communities commonly associated with inflammation of the lower GI tract. Pie charts provide a schematic illustration of the balanced microbial community structure of the healthy lower GI tract (top) and the imbalanced microbial community structure (dysbiosis) associated with inflammation of the large bowel (bottom). Black arrows point to recent studies suggesting that this association between the inflammatory host response and dysbiosis is a conserved ecological pattern observed in the lower GI tract.

Figure 2

The host inflammatory response provides a growth advantage for Proteobacteria. Pie charts provide a schematic illustration of the balanced microbial community structure of the healthy lower GI tract (left) and the dysbiosis associated with inflammation (right). In the absence of inflammation, complex carbohydrates and amino acids support growth of obligate anaerobic bacteria by fermentation (left). The inflammatory host response enables facultative anaerobic bacteria to consume fermentation end products, thereby increasing their prevalence within the community (right).