Agriculture Reference
In-Depth Information
the intestine and these LAB were able to inhibit the growth of several pathogens
in vitro
and
improved the immune status
in vivo
(Jatoba
et al
. 2011). Merrifield
et al
. (2010b) evaluated
Chlorogloeopis
as a dietary supplement for red Nile tilapia (
Oreochromis niloticus
), and
reported an uncultured
Lactobacillus
sp. in the posterior intestinal communities of the fish.
Weissella
spp. have also been identified by DGGE and sequence analyses as an indigenous
member of the autochthonous and allochthonous gut microbiota of red Nile tilapia (Merrifield
et al
. 2011b; Ferguson and Merrifield unpublished data).
Vijayabaskar and Somasundaram (2008) isolated LAB from the digestive tract of Mozam-
bique tilapia (
Oreochromis mossambicus
), but no further information was presented with
regards to whether these bacteria were allochthonous, autochthonous or a mixture of both.
6.16 SERRANIDAE
It has been demonstrated that LAB species are members of the
normal
microbiota of grouper
(Sun
etal
. 2009; Zhou
etal
. 2009; Yang
etal
. 2012). Sun
etal
. (2009) observed that three LAB
species,
Lc. lactis
MM1,
Lb. casei
MM2 and
E. faecium
MM4, accounted for 0.1-0.7% of the
total culturable bacterial community of the whole intestine of healthy juvenile orange-spotted
grouper (
Epinephelus coioides
). The
Lc. lactis
MM1 and
E. faecium
MM4 strains exhibited
antagonism against bacterial pathogens and showed good resistance to artificial gastric and
intestinal fluids under
in vitro
conditions (Sun
et al
. 2010; Yang
et al
. 2010). A subsequent
in vivo
study showed that individual dietary administration of the two candidate probiotics at
a dose of 10
8
CFU g
−1
for 60 days could significantly improve the feed utilization of juve-
nile orange-spotted grouper (Sun
et al
. 2012a). Interestingly, enhanced specific activities of
digestive enzymes were observed in the probiotic groups, while the two probiotic strains did
not secrete any digestive enzymes (protease, amylase and lipase) under
in vitro
conditions.
Therefore, the authors speculated that the probiotics may induce the secretion of digestive
enzymes and this might have led to improved digestive processes, enhancing the digestibility
of feed and thereby the nutritive utilization of feed (Sun
et al
. 2012a). Also, dietary admin-
istration of
Lc. lactis
and
E. faecium
individually improved the general immune responses
(Sun
et al
. 2012a), and elevated the autochthonous intestinal microbial diversity of juvenile
E. coioides
by stimulating some potentially beneficial and unidentified bacteria (Sun
et al
.
2012b; 2012c).
Using DGGE, a
Lc. lactis
subsp.
lactis
LMG-like bacterium was detected in the stomach
and pyloric caeca of adult yellow grouper (
Epinephelus awoara
) (Zhou
et al
. 2009), while an
Enterococcus
sp.-like bacterium was detected in the MG and DI of orange-spotted grouper fed
the probiotic
Bacillus clausii
for 60 days (Yang
et al
. 2012).
6.17 RACHYCENTRIDAE
Xing (2010) characterized a
P. pentosaceus
strain (#4012) isolated from the intestine of cobia
(
Rachycentron canadum
), and the strain demonstrated
in vitro
inhibitory effects on pathogenic
Photobacterium damselae
subsp.
piscicida
, the causative agent of fish photobacteriosis (Liu
et al
. 2003). Dietary administration of
P. pentosaceus
4012 for 2 weeks improved the growth
rate of cobia, and significantly elevated the respiratory burst activity of peripheral blood
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