Abstract
Streptococcus iniae is known as a most common pathogen in rainbow trout farms,
which its pathogenicity depends strongly on temperature. This study was performed
to identify the metabolic responses of the Streptococcus iniae at different temperatures
(22, 18, 14, 10°C). For this purpose, the samples of the bacteria were cultured
at experimental temperatures in three replicates. After metabolite extraction, the
metabolites were identified and quantified. The results of PLS-DA
analysis showed
the main metabolites responsible for the separation of the temperature treatments,
including acetone, betaine, inserin, N-acetyl-
ornithine,
N-acetylglutamine
and pyruvate.
In addition, the results of analysis of variance showed a significant difference
in the content of metabolome between temperature treatments. Bacteria exposed
to higher temperatures showed higher concentrations of acetone and betaine than
those grown at 10°C. Higher levels of N-acetyl
glutamine were observed in bacteria
inoculated at temperatures less than 14°C compared to those grown at 18 and
22°C. Anserin concentration increased as the temperature increased, however, a significant
decrease occurred at 22°C. The rise of temperature from 10 to 22°C significantly
decreased the levels concentrations of N-acetylcysteine,
N-acetyl
tyrosine,
5-hydroxy-
indole-
3-
acetate.
In conclusion, the results of the present study revealed
that temperature alters the metabolome content Streptococcus iniae, which may be
linked to its pathogenicity. Temperature may affect fermentation, homeostasis, energy
status and amino acid metabolism in the Streptococcus iniae.