Formation of indigoidine derived-pigments contributes to the adaptation of Vogesella sp. strain EB to cold aquatic iron-oxidizing environments

We investigated previously under explored cold aquatic environments of Andean Patagonia, Argentina. Oily sheens similar to an oil spill are frequently observed at the surface of water in creeks and small ponds in these places. Chemical analysis of a water sample revealed the occurrence of high concentrations of iron and the presence of a free insoluble indigoidine-derived pigment. A blue pigment-producing bacterium (strain EB) was isolated from the water sample and identified as Vogesella sp. by molecular analysis. The isolate was able to produce indigoidine and another derived-pigment (here called cryoindigoidine) with strong antifreeze properties. The production of the pigments depended on the cell growth at cold temperatures (below 15 °C), as well as on the attachment of cells to solid surfaces, and iron limitation in the media. The pigments produced by strain EB showed an inhibitory effect on the growth of diverse microorganisms such as Candida albicans, Escherichia coli and Staphylococcus aureus. In addition, pigmented cells were more tolerant to freezing than non-pigmented cells, suggesting a role of cryoindigoidine/indigoidine as a cold-protectant molecule. The possible roles of the pigments in strain EB physiology and its interactions with the iron-rich environment from which the isolate was obtained are discussed. Results of this study suggested an active role of strain EB in the investigated iron-oxidizing ecosystem.