Probiotic Applications in Crustaceans - Aquaculture Nutrition: Gut Health, Probiotics and Prebiotics - page 294

conditions (in air, water, dust, soil and sediment). It is reported that Bacillus species are
ubiquitous and even dominate the marine microbiota (Priest 1993). Present in the water column
as well as the sediment, Bacillus spp., especially Bacillus subtilis , Bacillus licheniformis and
Bacillus coagulans , are considered autochthonous members of the crustacean's environment
and a component of the intestinal microbiota entering the gut via the food or water. However, it
is interesting to highlight that the most recent studies, which used molecular techniques to char-
acterize the gut microbiota of crustaceans, rarely report the presence of Bacillus species within
the gastrointestinal (GI) tract (Li P. et al. 2007; Liu H. et al. 2011a), suggesting either a minor
component of the microbiota belongs to this genus or it constitutes a transient population.
Moriarty (1998) emphasized several reasons for the use of Bacillus , rather than antibiotics,
to improve shrimp culture success: Bacillus strains naturally produce many different antibi-
otic compounds, secrete many enzymes, compete for nutrients and surface adhesion sites, and
hence are able to inhibit other bacteria. Furthermore, the robustness of these spore forming
bacteria is often viewed as a great advantage as it may enable passage across the gastric bar-
rier and offer better stability during feed processing and shelf life/storage. The large interest
in the Bacillus genus in shrimp aquaculture can indeed be explained by these characteristics,
but it is also for historical reasons as the first successful studies of probiotic in shrimps were
conducted with Bacillus species (Rengpipat et al. 1998; Moriarty 1998).
Among Bacillus spp., B. subtilis is the most recurrent species being tested and used in crus-
taceans either alone (Rengpipat et al. 1998; 2000; 2003; Moriarty 1998; Dalmin et al. 2001;
Meunpol et al. 2003; Vaseeharan and Ramasamy 2003; Marques et al. 2006a; Balcázar et al.
2007; Yu et al. 2008; Liu et al. 2009; Tseng et al. 2009; Liu K.-F. et al. 2011b; Shen et al.
2010) or in combination with other Bacillus spp. (Decamp et al. 2008; Boonthai et al. 2011),
other probiotic species (Wang et al. 2005; Wang 2007) or prebiotic supplements (Li et al.
2009; Daniels et al. 2010; Zhang et al. 2011). The other Bacillus species documented so far
as probiotics for crustacean are B. licheniformis (Li K. et al. 2007), B. coagulans (Zhou et al.
2009) and B. pumilus (Hill et al. 2009).
Interestingly B.subtilis is also widely used in terrestrial animals and in humans, with claims
of bacteriotherapy and bacterioprophylaxis of GI disorders (Cutting 2011). In shrimp, Vasee-
haran and Ramasamy (2003) reported the beneficial effect of B. subtilis , isolated from shrimp
culture ponds, on the survival of black tiger shrimp ( Penaeus monodon ) juveniles challenged
with Vibrio harveyi , when the probiotic was delivered in the culture water at a density of
10 6 -10 8 CFU ml -1 . Furthermore, these authors demonstrated under invitro and invivo condi-
tions that the probiotic was able to control the growth of V. harveyi . Balcázar and Rojas-Lunas
(2007) also evaluated the dietary supplementation of a B. subtilis strain (UTM 126) on the
survival of juvenile Pacific white shrimp Litopenaeus vannamei following an immersion chal-
lenge with Vibrioparahaemolyticus . The strain was initially isolated from the digestive tract of
adult L. vannamei according to its antimicrobial activity against V. harveyi , Vibrio vulnificus, ,
and Vibrio fluvialis (Balcázar et al. 2007). The results indicated that the probiotic strain exhib-
ited in vitro antagonism toward V. parahaemolyticus and could induce a significant increase
in the survival rate and performance of the host (weight gain and feed conversion ratio, FCR)
when fed for 28 days to juveniles at 10 5 CFU g -1 of diet. Rengpipat et al. (1998) also isolated
a Bacillus strain (strain S11) from the gut of healthy Penaeus monodon with antimicrobial
properties against V. harveyi and V . parahaemolyticus. In several P. monodon studies, and
under various experimental conditions (Rengpipat et al . 1998; 2000; 2003; 2008), it has been
reported that this probiotic strain, when administered as fresh cells at a concentration of 10 9