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A major secreted elastase is essential for pathogenicity of Aeromonas hydrophila.

ABSTRACT: Aeromonas hydrophila is an opportunistic pathogen and the leading cause of fatal hemorrhagic septicemia in rainbow trout. A gene encoding an elastolytic activity, ahyB, was cloned from Aeromonas hydrophila AG2 into pUC18 and expressed in Escherichia coli and in the nonproteolytic species Aeromonas salmonicida subsp. masoucida. Nucleotide sequence analysis of the ahyB gene revealed an open reading frame of 1,764 nucleotides with coding capacity for a 588-amino-acid protein with a molecular weight of 62,728. The first 13 N-terminal amino acids of the purified protease completely match those deduced from DNA sequence starting at AAG (Lys-184). This finding indicated that AhyB is synthesized as a preproprotein with a 19-amino-acid signal peptide, a 164-amino-acid N-terminal propeptide, and a 405-amino-acid intermediate which is further processed into a mature protease and a C-terminal propeptide. The protease hydrolyzed casein and elastin and showed a high sequence similarity to other metalloproteases, especially with the mature form of the Pseudomonas aeruginosa elastase (52% identity), Helicobacter pylori zinc metalloprotease (61% identity), or proteases from several species of Vibrio (52 to 53% identity). The gene ahyB was insertionally inactivated, and the construct was used to create an isogenic ahyB mutant of A. hydrophila. These first reports of a defined mutation in an extracellular protease of A. hydrophila demonstrate an important role in pathogenesis.

SUBMITTER: Cascon A

PROVIDER: S-EPMC97569 | biostudies-literature | 2000 Jun

REPOSITORIES: biostudies-literature

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A major secreted elastase is essential for pathogenicity of Aeromonas hydrophila.

Cascón A A Yugueros J J Temprano A A Sánchez M M Hernanz C C Luengo J M JM Naharro G G

Infection and immunity 20000601 6

Aeromonas hydrophila is an opportunistic pathogen and the leading cause of fatal hemorrhagic septicemia in rainbow trout. A gene encoding an elastolytic activity, ahyB, was cloned from Aeromonas hydrophila AG2 into pUC18 and expressed in Escherichia coli and in the nonproteolytic species Aeromonas salmonicida subsp. masoucida. Nucleotide sequence analysis of the ahyB gene revealed an open reading frame of 1,764 nucleotides with coding capacity for a 588-amino-acid protein with a molecular weight ...[more]

PMID: 10816468

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Project description:Aeromonas hydrophila is the most common Aeromonas species causing infections in human and other animals such as amphibians, reptiles, fish and crustaceans. Pathogenesis of Aeromonas species have been reported to be associated with virulence factors such as lipopolysaccharides (LPS), bacterial toxins, bacterial secretion systems, flagella, and other surface molecules. Several mutant strains of A. hydrophila AH-3 were initially used to study their virulence in two animal species, Pacifastacus leniusculus (crayfish) and Tenebrio molitor larvae (mealworm). The AH-3 strains used in this study have mutations in genes involving the synthesis of flagella, LPS structures, secretion systems, and some other factors, which have been reported to be involved in A. hydrophila pathogenicity. Our study shows that the LPS (O-antigen and external core) is the most determinant A. hydrophila AH-3 virulence factor in both animals. Furthermore, we studied the immune responses of these hosts to infection of virulent or non-virulent strains of A. hydrophila AH-3. The AH-3 wild type (WT) containing the complete LPS core is highly virulent and this bacterium strongly stimulated the prophenoloxidase activating system resulting in melanization in both crayfish and mealworm. In contrast, the ?waaE mutant which has LPS without O-antigen and external core was non-virulent and lost ability to stimulate this system and melanization in these two animals. The high phenoloxidase activity found in WT infected crayfish appears to result from a low expression of pacifastin, a prophenoloxidase activating enzyme inhibitor, and this gene expression was not changed in the ?waaE mutant infected animal and consequently phenoloxidase activity was not altered as compared to non-infected animals. Therefore we show that the virulence factors of A. hydrophila are the same regardless whether an insect or a crustacean is infected and the O-antigen and external core is essential for activation of the proPO system and as virulence factors for this bacterium.

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A major secreted elastase is essential for pathogenicity of Aeromonas hydrophila.

Publications

A major secreted elastase is essential for pathogenicity of Aeromonas hydrophila.

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