Narlikar, J. V.Lloyd, DavidWickramasinghe, N. C.et al.2012-03-262012-03-262002-03-30http://hdl.handle.net/11007/1630Direct evidence for living cells in the air samples collected aseptically over Hyderabad (India) at various altitudes is presented. In the preliminary experiment, samples collected from altitudes of 10 to 36 Km yielded six identical bacterial colonies with phenotypic characteristics distinct from hitherto described Pseu-domonas stutzeri, a terrestrial bacterium. Since in this earlier experiment the air-samples were collected over a long range of altitude (including the ones at low altitudes), it was not possible to completely rule out terrestrial contamination. On the other hand in the current experiment, the samples were collected at altitudes ranging from 20 to 41 Km, well above tho Tropopause over Hyderabad. Voltage-sensitive dyes that could detect the presence of viable cells were used on these air-samples. Clumps of viable cells were present in samples collected at all the altitudes. The images obtained from electron microscopy are consistent with the above picture. Arguments are advanced against the detected cells (in the samples collected in the present experiment above the local tropopause at 16 Kin) being due to terrestrial contamination.enLiving cellsElectron microscopyArticle