Investigating Gastrointestinal Tract Functional Zonation in the Gut Microbiome and Enzyme Activity of Oncorhynchus mykiss (Rainbow Trout) with Temperature and Ion-poor Water Salinity Challenge

The regional distribution of digestion, metabolic, osmoregulatory and detoxification function along the GIT of fish are poorly understood. Several studies have shown evidence for zonation in the enzyme activity and zonation in the microbiome of the fish GIT; however, few studies have provided a more comprehensive survey of the interplay between the microbiome and enzyme activity with respect to zonation. The objective of this study was to explore functional zonation by manipulating two external environmental factors, specifically temperature and salinity, to observe zonation patterns in the bacterial communities, and corresponding digestive, metabolic, osmoregulatory and detoxification enzyme alterations along the GIT. It was found that zonation was more indicative of bacterial species communities and enzyme activity than temperature and salinity. The findings in this research will contribute to our understanding of the functionality of each region and the complexity of fish GIT physiology.