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  • Characterization of operons for sucrose metabolism in marine bacteria of the Vibrio genus
    Publication . Eslami, Saeideh; Power, Deborah; Cardoso, João
    Some species of the Vibrio genus are within the most frightening pathogenic bacteria to aquaculture and human health and the frequent emergence of novel bacteria strains represents an additional risk. The bacterium Vibrio ichthyoenteri is an important fish pathogen causing high mortality in aquaculture. Recently our group characterized two V. ichthyoenteri isolates (V. ichthyoenteri 1 and 2) and biochemical studies revealed that they have different phenotypes in relation to sucrose metabolism. The aim of this study was to understand the basis of their genetic and phenotypic differences and how this potentially relates with virulence using bioinformatics, microbiology, and molecular approaches. Bioinformatic annotation revealed that V. ichthyoenteri 1 has 4711 genes while V. ichthyoenteri 2 contains 4643 genes and the main differences reside in genes involved in functional/metabolic processes. Characterization of the sucrose operon revealed that two clusters (1A and 1B) exist in V. ichthyoenteri 1 (non-sucrose fermenter strain) while only one operon is present in V. ichthyoenteri 2 (sucrose fermenter strain). Like other bacteria the V. ichthyoenteri sucrose operon is composed of four genes, but sequence comparisons and phylogenetic analysis revealed that V. ichthyoenteri 1A is more like other Vibrios while V. ichthyoenteri 1B and 2 are identical. Gene linkage analysis revealed that V. ichthyoenteri 1A was likely to have acquired extra gene copies by horizontal gene transfer. The presence of sucrose did not modify bacteria growth kinetics but decreased the activity of enzymes that are potentially related with virulence. This was also true for the pathogenic V. harveyi. Gene expression studies targeting the sucrose hydrolysis gene (scrB) revealed that in both strains this gene is expressed in the presence or absence of sucrose and expression increases with culture time suggesting it was probably involved in other metabolic processes. The mechanism responsible for the difference in sucrose utilization between the two strains remains to be further explored.
    2024-02-29Dissertação de mestrado Acesso aberto Ver mais