Isolation of a psychrotrophic bacterium from the organic residue of a water tank keeping rainbow trout and antibacterial effect of violet pigment produced from the strain

The identification of a psychrotrophic bacterium, which produced a violet pigment, isolated from the organic residue of a water tank keeping rainbow trout and the antibacterial effect of the violet pigment were investigated experimentally. The psychrotrophic bacterium was found to be a new species very closely related to Janthinobacterium lividum. H-1 NMR, C-13 NMR, and Fr-MS spectra analyses results showed that the chemical structure of the violet pigment was a mixture of violacein and deoxyviolacein. The antibacterial effect of the violet pigment was confirmed for putrefactive bacteria such as Bacillus subtilis, Bacillus megaterium, Staphylococcus aureus, and Pseudomonas aeruginosa. The growth-inhibitory and lethal effects of the violet pigment on the putrefactive bacteria were evaluated by increasing the concentration of the violet pigment, ranging from 5 to 20 mg dm(-3). It was found that higher concentrations of the violet pigment caused not only growth inhibition but also the death of the putrefactive bacteria. (C) 2002 Elsevier Science B.V. All rights reserved.