Identification of free indigoidine pigment in aquatic environments of Andean Patagonia

HERRERO M; VILLALBA MS; ALVAREZ, H. M.

Tucumán

Congreso; VII Congreso Argentino de Microbiologia General (SAMIGE),; 2011

SAIB

Reddish-deposits of iron hydroxides can be frequently observed in superficial bodies of water in Andean Patagonia (El Bolsón- Lago Puelo). The abundance of bacteria able to metabolize iron leaching from the ground; which is rich in pyrite in that place, is responsible for these deposits. An oily sheen on the water surface that reflects a rainbow of colors (principally blue) like an oil spill frequently occurs. It is unknown the exact origin of this oily sheen, although it is presumed that this sheen probably contains iron and manganese compounds produced by bacteria of the genus Leptothrix. We collected water samples from natural aquifers in El Bolsón for chemical and microbiological analyses. We identified Leptothrix- like bacteria from neutral-water samples containing high amounts of iron (3.8 mg/ml). In addition, we were able to identify heterotrophic associated bacteria, belonging to the genera Microbacterium, Arthrobacter, Janthinobacterium, Pseudomonas, Exiguobacterium, Micrococcus, and Flavobacterium, as revealed the 16S rDNA sequencing. In one of the samples of the oil-like film collected from the surface of water, we isolated a bacterial strain belonging to Vogesella genus (strain EB), which produced blue colonies and was able to excrete extracellularly a blue pigment. The free pigment in the culture medium showed a similar appearance than the oil-like film observed in the natural water samples. The pigment was purified and identified as indigoidine by visible spectral and IR analyses. Indigoidine is a blue pigment produced by different Gram-negative bacteria, which may be involved in neutralization of free radicals during oxidative stress. We were no more able to isolate indigoidine-producing strains from successive oil-like film samples. However, we identified free indigoidine in the oily sheen samples collected from water surfaces as revealed the comparison between IR spectra of the blue pigment purified from Vogesella cells (strain EB) and the pigments directly extracted from natural water samples. All these results suggest that the oil-like blue film usually associated with iron-oxidizing bacteria in aquatic environments, can contain free indigoidine and probably other pigments produced by heterotrophic bacteria. Indigoidine may be excreted by heterotrophic bacteria occurring in iron-oxidizing ecosystems as response against oxidative stress in water environments of the Andean Patagonia.