Gut bacteria of rainbow trout fed live yeast in warm water

Aims: The objective of the present study was to determine the effects of feeding high inclusions of live Saccharomyces cerevisiae yeast and increasing water temperature on gut microbiota of rainbow trout.Methods and Results: Fish were fed fishmeal or yeast and reared in water temperatures of 11°C (cold) or 18°C (warm) for six weeks. Content and mucosa were collected from the distal gut. For gut bacteria, sequencing of 16S rRNA gene amplicons using Illumina MiSeq showed lower bacterial diversity and abundance of lactic acid bacteria, especially Lactobacillus, in fish reared in warm rather than cold water. Fish fed yeast had similar diversity, despite lower abundance of Leuconostocaceae and Photobacterium than fish fed fishmeal.Conclusions: Increased water temperature significantly altered the gut microbiota of rainbow trout in terms of bacterial diversity and abundance, while feeding live yeast had minor effects.