Culture-Based Study of the Digestive Abilities Possessed by Anaerobic Bacteria Isolated From the Hindgut of the Marine Herbivorous Fish Kyphosus sydneyanus

Abstract

This project investigated novel growth factors for fish gut bacteria present in brown algae. This is an in vitro study of strictly anaerobic bacteria isolated from the gut of Kyphosus sydneyanus (Silver Drummer), a fish common to the Northeastern New Zealand coast. The strictly anaerobic gut bacteria require specialised culture methods and media. Fish gut bacteria have the potential to be used in industry for large scale fermentation, producing high value natural products.

There are two major findings of this study, which improved further analysis of the functional digestive abilities possessed by these bacteria. The first is a novel methodology for high throughput in vitro culture-based investigation of fastidious and strictly anaerobic bacteria. Allowing direct comparison of bacterial growth across conditions. The second is novel media for optimal in vitro growth of K. sydneyanus gut bacteria. Three different nutrients from brown algae Undaria pinnatifida were found to produce significantly faster bacterial growth than the standard of fish gut fluid.

Using these method developments, it was found that the growth rate of the K. sydneyanus gut microbiome was significantly increased in a mixed isolate culture, in a demonstration of community digestive action. Also, a significant variation in digestive ability at the family level was found, showing functional diversity in substrate preference. These findings help industry to improve fermentation conditions for K. sydneyanus gut bacteria.