PMC

A stratified approach was used to identify transient changes in OTUs. Each of the OTUs depicted differed significantly between the HC and the LC treatment, as well as between the HCR10 and the HC groups, or between the HCR10 and the LC groups.

Note the significantly (p<0.001; 7–8 measurements, average length 1180 µm vs. 393 µm) elongated crypts in HC compared LC. The surface area increase secondary to this morhological change was calculated to be 20% in HC compared to LC (magnification ×40).

Principle coordinates analysis (PCoA) shows separation of the colonic mucosal microbiome on high cellulose diet (high cellulose [12.5%]; n = 5). This separation decreased by 10 days of reversal (10 days reversal from high cellulose diet [HCR10]; n = 5) compared to controls (▪control [2.5% cellulose] diet; n = 10). Individual animals did not show separation depending on cage origin.

A. High cellulose (12.5%, HC) diet stimulated a significantly increased number of detectable families compared to low cellulose (2.5%, LC). This separation persisted 10 days following reversal (HCR10). B. The OTU counts of species were slightly increased in the HC group compared to LC, but not in the reversal group (HCR10). p values represent two tailed non-paired T test.

Upon 3% DSS challenge (, n = 8–10), the animals on the LC diet lost significantly more weight than on regular chow. On the seventh day, the experiment had to be terminated for severe weight loss in the LC group. In independent experiments where the mice did not receive DSS (, n = 14–40), colonic lengths of mice fed the synthetic diet were significantly shorter than in animals fed regular (12.5% fiber) chow.

Altered relative abundance of bacterial families was presented upon high cellulose (HC) diet compared to control (Low cellulose, LC). This alteration diminished following 10 day reversal (HCR10). B. Relative abundance of the five most common (and the unclassified) families within the colonic mucosal samples. The HC group is more different from the LC than the 10 day reversal dietary group (HCR10). C. Abundance variation in the 10 most abundant bacterial families between the dietary groups. A trend for reversal in abundance can be seen in most of the taxa by 10 days of reversal (HCR10) from the high cellulose diet (HC) in relationship to the low cellulose (LC) group.

A. Colons were significantly longer in animals receiving 12.5% cellulose supplemented diet (HC). This trophic effect persisted after 10 days of reversal (HCR10) from the 12.5% cellulose to 2.5% cellulose diet (LC P90) [n = 40-10-15]. B. Other mice were exposed to 2% DSS (as opposed to 3% in , due to the increased sensitivity of mice to DSS on the low cellulose diet) in their drinking water at P90 for 5 days then received regular water. Mice reversed for 10 days (HCR10) from the high cellulose (12.5%) diet were protected (less weight loss) against DSS compared to controls (LC P90) [n = 7–10 per group]. The histological score confirmed our results: high cellulose supplemented group had decreased severity of colitis upon DSS challenge (See ). C. The cellulose supplementation induced trophic effect was lost after 40 days of reversal (HCR40) from the 12.5% cellulose to 2.5% cellulose diet (LC P120) [n = 8-8]. D. Colitis susceptibility was also similar between the 40 day reversal (HCR40) and control groups (LC P120) [n = 7–10 per group].