Probiotic Modulation of the Gut Microbiota of Fish - Aquaculture Nutrition: Gut Health, Probiotics and Prebiotics - page 206

C3

I1

C2

C1

C4

I4

I3

P2

P1

Probiotic Group

P4

P3

I2

40 60 80 100

Fig. 8.3 DGGE profiles and dendrogram of red Nile tilapia allochthonous gut microbiota showing
resemblance and similarity of the initial (I1-I4; day 0), control (C1-C4; day 32) and P. acidilactici
(P1-P4; day 32) fed fish. The probiotic is indicated by the box. (Source: Adapted from Ferguson et al .
2010. Reproduced with permission of John Wiley & Sons.)

direct antagonism between P . acidilactici and an indigenous unidentified bacterial clone (most
similar to an unidentified uncultured bacterium from the gut of Atlantic salmon: Liu etal . 2008)
(Figure 8.4). Low levels of this bacterium were present whilst high levels of the probiotic were
present in the intestines, but as the abundance of the probiotic slowly declined with time a
clear inverse relationship was observed as the abundance of this phylotype increased. Addi-
tionally, an unidentified bacterium from the Actinomycetales order showed a general decline
in abundance concomitantly as the probiotic declined and the salmon gut phylotype increased.

8.4 OTHER PROBIONTS

A number of other bacterial genera have been investigated for use as potential probionts in in-
fish: for example Pseudomonas (Gram et al . 1999; 2001; Spanggaard et al. 2001; Korkea-aho
et al . 2011; 2012), Shewanella (Sáenz de Rodrigáñez et al . 2009; de La Banda et al . 2010),
Phaeobacter (Hjelm etal . 2004; Planas etal . 2006) and Psychrobacter (Sun etal . 2011b; Yang
et al . 2011). In addition, some early studies investigated members of the Aeromonas (Irianto
and Austin 2002) and Vibrio (Austin et al. 1995; Gatesoupe 1997; Ringø and Vadstein 1998;
Ringø et al . 1996; Irianto and Austin 2002) genera as probiotic candidates; using such strains
may not be wise and, even if efficacy is shown to be high, is questionable in terms of safety
and regulatory authorization (see Chapter 13 ).
Some of the aforementioned studies have investigated potential GI colonization or the
impact on the endogenous microbiota (refer to Table 8.3). These studies, mostly focused on