Host selection of caecal acetogens with growth

Reductive acetogens performing acetyl coenzyme A (acetyl-CoA) pathway are good candidates to remove hydrogen produced in the gut of herbivores as it accumulates additional energy for host from fermentation through acetate production,they also has been considered to be used in biofuel industry for converting waste gases into important industrial chemicals and biofuels. But little information about if there is a host selection on the gut acetogen population exists. In this study, we selected rabbits at four different age stage (30, 60, 120 and 180 days) as model and fed them with the same diet to avoid feed effect, to study if the acetogen community would change with growth stage under host selection. Many novel potential acetogen populations were observed in the caecum of rabbits across all the age groups. The young and adult rabbit had their own distinct acetogen community even though they received same diet which suggested that from young to adultthe acetogens in the ceacum undergoes developmental changes because of host selection that are independent of diet, and perhaps the different acetogen community resulted in their different hydrogenotrophic character. The within-group similarity increased with age indicating the acetogen community converge to a more homogeneous and mature arrangement with age development because its mutualistic relationship with host.The abundance of potential acetogens was always high and not changed significantly withgrowth, which may suggested the important role of acetogens in caecal hydrogenotrophyof rabbits.