Agriculture Reference
In-Depth Information
6.9 MORONIDAE
Significant changes in the gut microbiota have been reported during larval growth of European
sea bass (
Dicentrarchus labrax
). Analysis performed at 11 days post hatching (dph) revealed
low levels of culturable anaerobic and aerobic bacteria, enterobacteria (10
5
CFU g
−1
) and LAB
(10
4
CFU g
−1
) (Silvi
etal
. 2008). The total culturable microbiota levels increased significantly
at 22 days dph: higher numbers of anaerobic (10
9
CFU g
−1
), aerobic (10
9
CFU g
−1
) and enter-
obacteria (10
8
CFU g
−1
) were observed, and concomitantly LAB levels (10
3
CFU g
−1
)were
reduced. Among the LAB the following species were identified:
Lb. curvatus
(17.4% and
16.7% of the total LAB community at 11 and 22 dph, respectively),
Lb. delbrueckii
subsp
.
delbrueckii
(8.5% and 7.4% at 11 and 22 dph, respectively),
Lb. brevis
(29.3% and 31.3%, at
11 and 22 dph, respectively),
Lb. fructivorans
(7.1% and 8.3% at 11 and 22 dph, respectively),
Lactobacillus
spp. (19.0% and 18.5% at 11 and 22 dph, respectively) and
Lc. lactis
subsp
. lac-
tis
(18.7% and 17.8% at 11 and 22 dph, respectively) (Silvi
et al
. 2008). Counts at 30, 50 and
70 dph evidenced a decrease in the levels of anaerobes and aerobes as well as a decrease in total
LAB, particularly at 30 dph, where the LAB were identified as
Lb. fructivorans
,
Lb. brevis
,
Lb. curvatus
,
Lb. acidophilus
,
Lb. viridescens
,
Lb. delbrueckii
subsp.
delbrueckii
,
Lb. lindneri
,
Lactobacillus
spp.,
Aerococcusviridans
,
Lc.lactis
subsp.
lactis
and
Leu.mesenteroides
subsp.
mesenteroides
. The diversity of LAB species decreased marginally at 50 dph and at 70 dph,
where only five different LAB species remained:
Lb. acidophilus
(27.0%),
Lb. delbrueckii
subsp.
delbrueckii
(10%),
Lb. fructivorans
(14.0%),
Lb. lindneri
(46%) and
Lactobacillus
spp.
(4.0%) (Silvi
et al
. 2008).
Carnevali
et al
. (2006) isolated an indigenous
Lb. delbrueckii
subsp.
delbrueckii
(AS13B)
strain from the intestine of adult sea bass. The strain showed good capability to colonize
the gut of sea bass larvae, thereby modifying the gut microbiota, and exerting positive
effects on the survival of the treated sea bass (Silvi
et al
. 2008). In addition, the probiotic
strain elevated the levels of intestinal T cells, in keeping with increased total body TcR-β
transcripts, and increased acidophilic granulocytes concomitantly with lower transcription of
pro-inflammatory genes (IL-1-β,TGF-β, IL-10, Cox-2) (Picchietti
et al
. 2009; Abelli
et al
.
2009), indicating that it might be an important component of the indigenous microbiota.
Recently, Bourouni
et al
. (2012) isolated 47 LAB strains from the intestinal tract of farmed
sea bass and examined the strains phenotypically and phylogenetically. Most of the strains
belonged to
Enterococcus
and were identified as
E. faecium
(59% of the isolates),
E. faecalis
(21%),
E. sanguinicola
(8%),
E. mundtii
(2%) and
E. pseudoavium
(2%). In addition
Lc
.
lactis
(2%) and
Ae
.
viridans
(2%) were isolated. The LAB strains were further tested for antimicro-
bial activities
in vitro
against pathogenic and spoilage bacteria and 32 strains inhibited the
growth of the test bacteria.
6.10 SPARIDAE
The microbial community reported in the early developmental stages (35 dph) of gilthead sea
bream (
Sparus aurata
), from the same farm as the sea bass described by Silvi
et al
. (2008),
was quite different - indicating therefore a host selective pressure rather than reflecting the fish
farm of origin (Carnevali
et al
. 2004). The anaerobe/aerobe ratio was 0.43 and
Lactobacillus
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