Profiling of
bacterial species associated with haddock larviculture by PCR amplification
of 16S rDNA and denaturing gradient gel electrophoresis
S.
Griffiths, K. Melville, M. Cook, S. Vincent, M. St-Pierre, C. Lanteigne-2001
Journal of Aquatic Animal Health, 13(4): 355-363
(from Current Contents)
Abstract :
A major limitation to marine finfish culture is the
sudden and substantial increase in mortality frequently referred to as a
"larval crash." Contamination of the production system with
opportunistic pathogenic bacteria has frequently been implicated as a cause
of this mortality. In studies designed to test this hypothesis, 15 larval
haddock from 16 tanks were sampled weekly between hatching and weaning in
spring 2000 for their bacterial 16S rDNA profiles by polymerase chain
reaction amplification combined with denaturing gradient gel electrophoresis
(PCR-DGGE). The profiles obtained were generally dominated by fewer than
five bands. A well-defined trend in bacterial succession was observed during
the growth of the haddock larvae, the diversity of bacterial species being
greater at the onset but invariably ending with a singular predominance by a
species with 16S rDNA homology to various alpha -Proteobacteria such as
Roseobacter. Sequence analysis of a larger fragment of 16S rDNA (1,437
nucleotides) of these species revealed closest similarity (96%) to two
species of Sulfitobacter. During the monitoring period, a single event of
acute mortality occurred. The affected tank was the only one of the 16
examined in which the progression to Sulfitobacter did not occur; rather, a
species of Pseudoalteromonas was identified as dominant in the PCR-DGGE
profile of larvae sampled 1 d before the "crash."
(Res & Productivity Council, 921 Coll Hill Rd,
Fredericton, NB E3B 6Z9, Canada, e-mail: sgriffit@rpc.unb.ca)