Indigenous Lactic Acid Bacteria in Fish and Crustaceans - Aquaculture Nutrition: Gut Health, Probiotics and Prebiotics - page 141

6.3.9 Bifidobacterium
Bifidobacterium constitute a significant portion of the human and mammalian intestinal micro-
biota and have beneficial effects on their host (Vaughan et al . 2000). These obligate anaerobes
compete with other species of intestinal flora and transient organisms for nutrients and attach-
ment sites in the gut. Recent studies have also reported the presence of bifidobacteria in the
GI tract of honey bees, bumblebees and cockroaches (Vlková et al. 2012).
Using a nested PCR approach, based on initial PCR using Bifidobacterium 16S rRNA
specific primers, and secondary PCR targeting the 16S rRNA V3 region, Kopecny et al .
(2010) reported the presence of bifidobacteria in the GI tract of brown trout. Unfortunately
no sequence analyses were presented for the presumed bifidobacterial DGGE bands obtained
from trout samples, but sequence alignments for bands obtained from other host organ-
isms (i.e. wasps and cockroaches) were low, with the highest reported similarity of bands
being 91-94% similar to (Bifidobacterium adolescentis . Given that the highest sequences
obtained from this study were below 95% similarity, the general level for acceptance of
genus classification, we suggest that these bacteria are Bifidobacterium -like strains. The
authors used qPCR to provide quantitative data which indicated that the Bifidobacterium -like
populations accounted for 1.1% of the bacterial community relative to the 'total' bacterial
community. However, the total community was estimated based on qPCR of Bacteroides
uniformis and, given that Bacteroides are often a minor component of the gut microbiota
of fish, including trout, this value could be an overestimation and an accurate quantification
cannot be concluded from this study. This study is however the first study, to the authors'
knowledge, to report the presence of bifidobacteria-like species from the GI tract of fish. A
second study published in 2010 also provided evidence of a minor presence of bifidobacteria
in the gut of rainbow trout (Mansfield et al . 2010). The construction of clone libraries of
bacterial communities from the distal intestine of rainbow trout revealed one bifidobacterial
clone ( (Bifidobacterium adolescentis ) present in one group of fish, accounting for 0.1% of
the clones generated (Mansfield et al . 2010). More recently, Vlková et al. (2012) identified
presumptive bifidobacteria in the distal intestine of one of 15 rainbow trout examined. The
levels recovered were log 3.5 CFU g −1 compared to total bacterial levels of log 8.85 bacteria
g −1 (determined from FISH) and thus bifidobacterial levels represented

0.0005% of the
total bacterial community. A representative isolate of this population was identified by 16S
rRNA sequence analysis as B. longum (98% similarity). Using pyrosequencing of the distal
gut contents of rainbow trout, Desai et al . (2012) recovered a very small number of sequences
identified as Bifidobacterium sp. 12_1_47BFAA from one sample.

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6.4 GADIDAE

Several papers have reported LAB in the GI tract of Atlantic cod (Daczkowska-Kozon 1988;
Strøm 1988; Strøm and Olafsen 1990; Strøm and Ringø 1993; Ringø et al . 2006c; Seppola
et al . 2006; Lauzon et al . 2010; Løvmo Martinsen et al . 2011; Askarian et al . 2013; Zhou
et al . 2013).
Daczkowska-Kozon (1988) reported low population levels of LAB in the gut of cod from
the Baltic Sea; the level varied between

200 and 380 LAB g −1 intestine. Strøm (1988) iso-
lated C . divergens -like strains and C . maltaromaticum -like strains from the intestine of wild
juveniles and adults and farmed Atlantic cod and reported that their population level was

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