Fish are continuously exposed to a wide range of microorganisms present in the environment,
and the microbiota of fish have been the subject of several reviews. This review evaluates lactic
acid bacteria in fish, and focuses on the several investigations that have demonstrated that
Streptococcus, Leuconostoc, Lactobacillus, and Carnobacterium belong to the normal microbiota
of the gastrointestinal tract in healthy fish.