Interaction between fish spoilage bacteria Pseudomonas sp. and Shewanella putrefaciens in fish extracts and on fish tissue |
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Authors: | L Gram J Melchiorsen |
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Institution: | Danish Institute for Fisheries Research, Department of Seafood Research, Lyngby, Denmark |
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Abstract: | The interaction between fish spoilage bacteria, Pseudomonas sp. and Shewanella putrefaciens , was investigated using fish extract and fish tissue as model systems. Isolates of Pseudomonas that produced iron chelators, siderophores, inhibited growth of S. putrefaciens in a fish-extract-agar diffusion assay but no, or only weak, antagonistic activity was seen when the medium was supplemented with iron. Sterile-filtered supernatant fluid from a siderophore-producing Pseudomonas grown in fish extract was inhibitory to S. putrefaciens if the number of Pseudomonas was above 108 cfu ml?1. In contrast, supernatant fluids from siderophore-negative Pseudomonas isolates did not inhibit growth of S. putrefaciens. The inhibitory effect was, except for one strain of Pseudomonas , not seen in supernatant fluids from iron-enriched cultures of Pseudomonas sp. Finally, siderophore-producing Pseudomonas sp. lowered the maximum cell level of S. putrefaciens 1–2 log units from 109 to 1010 cfu g?1 when the strains were grown on fish muscle blocks at 0°C but the growth rate of S. putrefaciens was not affected. |
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