The Gut Microbiota of Fish - Aquaculture Nutrition: Gut Health, Probiotics and Prebiotics - page 82

Bacterial genus

Desulfovibrio spp.

Faecalibacterium sp.

Enterovibrio sp.

Peptostreptococcus spp. Marine water

Freshwater

Eubacterium spp.

Fusobacterium spp.

Bacteroides spp.

Clostridium spp.

0 2 4

Number of fishes

6 8 10

Fig. 4.4 Anaerobic bacteria reported in the GI tract of marine and freshwater fish. (Source: Data from
Izvekova 2007.)

Phylum

Fusobacteria

Firmicutes

Actinobacteria

Marine water
Freshwater

Bacteroidetes

Proteobacteria

0 10 20 30

Number of fishes

40 50 60

Fig. 4.5 The bacteria phyla reported in the GI tract of marine and freshwater fish. (Source: Data from
Izvekova 2007.)

observed may contribute with different activities to the host inner environment. Bacteria
belonging to the Proteobacteria phylum, which were present in a high percentage in all
families, are known to induce important responses in the host (Rawls et al. 2004; 2007; Bates
et al. 2006). Also, members of this phylum can exploit environmental reservoirs outside their
hosts to proliferate and persist in aqueous environments, which helps to explain the relative
high prevalence of these bacteria in the GI tract of fish (Rawls et al. 2006).