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International Journal of Aquaculture, 2014, Vol.4, No.01
http://ija.sophiapublisher.com
1
Research Article Open Access
Gut Associated Lactic Acid Bacteria Isolated from the Estuarine Fish
Mugil
cephalus
: Molecular Diversity and Antibacterial Activities against Pathogens
Shubhankar Ghosh
1
, Einar RingØ
2
, A. Deborah Gnana Selvam
1
, Mujeeb Rahiman K. M.
1
, Naveen Sathyan
1
, Nifty John
1
,
Hatha A. A. M
1,
1. Dept. of Marine Biology, Microbiology and Biochemistry, School of Marine Sciences, Cochin University of Science and Technology, Fine arts Avenue,
Cochin, India - 682016
2. Norwegian College of Fishery Science, Faculty of Biosciences, Fisheries and Economics, University of Tromsø, N-9037, Brevikia, Norway
Corresponding author email:
mohamedhatha@gmail.com
,
mohamedhatha@cusat.ac.in
International Journal of Aquaculture, 2014, Vol.4, No.01 doi: 10.5376/ija.2014.04.0001
Received: 11 Nov., 2013
Accepted: 18 Dec., 2013
Published: 22 Jan., 2014
Copyright © 2014
Ghosh et al., This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted
use, distribution, and reproduction in any medium, provided the original work is properly cited.
Preferred citation for this article
:
Ghosh et al., 2014, Gut Associated Lactic Acid Bacteria Isolated from the Estuarine Fish
Mugil cephalus
: Molecular Diversity and Antibacterial Activities
against Pathogens, International Journal of Aquaculture, Vol.4, No.01: 1-11 (doi: 10.5376/ija.2014.04.0001)
Abstract
In the present study we address the issue on gut associated lactic acid bacteria (LAB) isolated from the intestine of
estuarine fish
Mugil cephalus
using de Man Rogossa and Sharpe (MRS) agar. LAB isolates were identified biochemically and
screened for their ability to inhibit
in
vitro
growth of various fish, shrimp and human pathogens. Most of the LAB isolates displayed
an improved antagonism against fish pathogens compared to shrimp and human pathogens. Selected representative strains displaying
high antibacterial activity were identified using 16S rRNA gene sequence analysis. Of the selected strains
Lactobacillus brevis
was
the most predominant. Four other species of
Lactobacillus
,
Enterobacter hormaechei
and
Enterobacter ludwigii
were also identified.
It was also observed that even among same species, considerable diversity with respect to substrate utilization persisted. Considering
the euryhaline nature of grey mullet (
Mugil cephalus)
, the LAB isolated from the gut possessed good tolerance to varying salt
concentrations. This finding merits further investigation to evaluate whether the isolated LAB could be used as probiotics in various
fresh and sea water aquaculture
.
Keywords
Probiotics; Antibiotic resistance; Lactobacilli; Molecular diversity
Introduction
During the last decade commercial aquaculture has
extensively increased and the usage of antibiotics has
also increased manifold (Saleh, 2006). At high
bacterial population densities, as is reported in
aquaculture ponds – genetic exchange leading to the
rise of resistant organism can occur through plasmids
(Molina-Aja et al., 2002) or by viral transduction or
even by direct transformation through DNA absorbed
onto sediment particles (Moriarty, 1997).
Lactobacilli and other bacterial genera have been
suggested to be used as probiotics as they have shown
potential to inhibit pathogen colonization in the gut
through a number of ways such as competitive
exclusion (Gomez-Gill et al., 2000; RingØ et al., 2005;
Balcazar et al., 2006; Gomez & Balcázar, 2008),
production of organic acids (Atrih et al., 2001) and
low molecular weight compounds such as reuterin
(Vandenbergh, 1993). These organisms are environment
friendly and are thus sustainable in the long run. The
use of probiotics in aquaculture started in the 90’s and
numerous studies have been reported since then
(Austin et al., 1995; Gildberg & Mikkelsen, 1998;
RingØ & Vadstein, 1998; Gatesoupe, 1994;
Nikoskelainen et al., 2001; Panigrahi et al., 2004;
RingØ et al., 2005). It is well known that lactic acid
bacteria (LAB) produce acids and di acetyl (Messens
& De Vuyst, 2002), antifungal compounds (Corsetti et
al., 1998), phenyl lactic acid (Lavermicocca et al.,
2000)
and bacteriocins to inhibit the
in vitro
colonization of pathogens (De Vugst & Vandamme,
1994; Gatesoupe, 1999; RingØ et al., 2005; Gatesoupe,
2007; Wang et al., 2008). Several studies on the gut
microbiota of fish from different habitats (Cahill, 1990;
RingØ et al., 1995; Hansen & Olafsen, 1999; RingØ
& Birkbeck, 1999; Saha et al., 2006; RingØ et al.,
2010) have revealed establishment of LAB in the gut
though they are not dominant forms among the gut
microflora (RingØ & Gatesoupe, 1998; RingØ et al.,
2004; Lauzon & RingØ, 2011).
To our knowledge there is limited available
information about the presence of LAB in the