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The biological activities of lipopolysaccharide-like substance (LLS)

A new species, Vibrio trachuri sp. nov., was isolated from the cultured Japanese horse mackerel (Trachurus japonicus). These Vibrio were Gram negative, motile rods and formed yellow colonies on BTB teepol and TCBS plate, turned TSI medium to yellow and was sensitive to 150 μM O/129 (2,4‐diamino‐6,7‐diisopropyl pteridine phosphate) like Listonella anguillarum which has been described as Vibrio anguillarum. However, the results of VP test and decarboxylation of lysine or dihydrolation of arginine suggested that these Vibrio are rather closely related to V. parahaemolyticus. DNA similarity determined by the microplate hybridization technique revealed that these Vibrio are genetically quite distant from Listonella anguillarum or V. parahaemolyticus and rather close to V. harveyi, although there was no Vibrio species which had more than 70% similarity value. From these results we propose to nominate Vibrio trachuri sp. nov. for this new Vibrio species.

Induction of single strand breaks in DNA was assessed by the conversion of supercoiled closed circular plasmid DNA into the open circular form. Euflavine produced single-strand breaks following irradiation but not in the control maintained in the dark. The single strand breaking activity of photoactivated euflavine was found to be dose-dependent. The effective dose conversion 50% (ED50) of the closed circular DNA to the open circular form was 0.53 microM. A comparison of 8 acridine compounds revealed that the ED50 of diaminoacridines such as euflavine, proflavine and acridine yellow or the 3,6-dimethylamino-derivative (acridine orange) was less than 1 microM while the ED50 values of the other acridines were greater than 80 microM. Euflavine was markedly inhibited by singlet oxygen scavengers such as NaN3, histidine, alpha-tocopherol or beta-carotene and partly inhibited by superoxide dismutase, mannitol or catalase. These results suggest that enflavine induces single strand breaks in DNA mainly by a type II photodynamic mechanism. Photodynamic single strand breaking activities appeared related to their mutagenic activities on yeast. This experimental system described here is useful for the quantitative assessment of the single strand breaking activities of various photosensitizers in vitro and for the determination of active oxygen species involved in those processes.

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