GLIDING FILAMENTS FROM PHORMIDIUM SP. DOMINATED MAT IN QUENN'S LAUNDRY POOL, YELLOWSTONE NATIONAL PARK, US, AND EL TATIO GEOTHERMAL AREA, CHILE

The mobile forms of bacteria include cyanobacteria are swimming and gliding. The cyanobacteria, a large group of phototropic prokaryotes of various morphologies, are the most widespread gliding bacteria. Filamentous cyanobacteria, such as Oscillatoria sp., possess permanent gliding mobility, whereas others produce specialized gliding filaments which represent a brief stage of life cycle. The gliding mobility mechanism is relatively few know. However, during the gliding an active translocation of cells of filamentous bacteria require contact with a solid or semisolid substrate. In most cases, forward movement is accompanied by revolution of the filaments about its long axis, the direction of revolution being species specific. Here we present a detailed study of ring-shaped filamentous structures produced by gliding cyanobacteria in a microbial mat dominated by Phormidium sp. At Queen’s Laundry Pool, Yellowstone National Park, US, and El Tatio geothermal area, Chile. Samples were collected during the summer of 2009. The thermotolerant species thrives in mid-temperature (40-45°C silica-depositing pools with near neutral pH. Living (fresh and silicified) Phormidium spp. dominated mat was stored in gluteraldehyde diluted with filtered natural hot spring water. Si-mineralized analogues of Phormidium sp. dominated mat was collected from an inactive area. Living layered mats were careful sectioned and fixed via histological techniques. Thin sections were prepared of mineralized mat. Detailed Scanning Electron Microscope and Focused Ion D-Beam analyses were performed to characterize different layers of the mat. Analyses of living and mineralized mat show the presence of ring-shaped (average diameter: 25 µm) structures generated by gliding segmented filaments. FIB sectioning and analysis revealed the presence (absorption) of colloidal silica around filament walls, which indicates that the filaments glide during the early stage of mineralization. The locomotion gliding mechanism is interpreted as a protective behavior that allows the organism to delay silica absorption on their walls.

Acknowledgements We kindly thank Wendy Smythe (OGI, OR), Armando Azua-Bustos (Pontificia Universidad del Chile), Rick Hugo and Justine Stone (PSU, OR), Mary N. Parenteau (NASA Ames Research Center), Jessica Goin (S.S. Papadapolous).