the microbiology of the atmosphere 



Early Studies of the Upper Air 



Measurements of microbial concentrations at heights above ground- 

 level were first attempted from towers and tall buildings by Miquel 

 (1883), Carnelley et al. (1887), and, more recently, by Kelly and others 

 (cf, p. 143). Miquel found that the bacterial content of the air at the level 

 of the Lanterne of the Pantheon in Paris was only i/20th of that in the 

 street below. 



Probing upwards into the atmosphere for microscopic life started 

 dramatically when the Manchester physician Blackley (1873) used two 

 kites in series to lift sticky microscope slides to a height of 300 metres 

 and caught from 15 to 20 times as much pollen as on slides similarly 

 orientated at 1-4 metres above the ground. Kites were also successfully 

 used in India by Mehta (1952) to catch spores of the cereal rusts, Puccinia 

 graminis, P. triticina^ and P. glumarum^ and small balloons were used for 

 the same purpose by Chatterjee (1931). 



SAMPLING from BALLOONS 



Cristiani (1893) obtained bacteria and a few moulds by volumetric 

 sampling from a balloon at up to 1,300 metres above Geneva (at a total 

 of 1,700 metres above sea-level). He was obviously puzzled by his results, 

 which he regarded as inconclusive, and he attributed most of his catch to 

 contamination from the surface of the balloon and its rigging — remaining 

 convinced that the upper air is extremely pure. 



The credit for first demonstrating the existence of a microbial popula- 

 tion in the upper air should probably go to the mycologist Harz (1904), 

 who sampled during a balloon ascent over southern Bavaria on a sunny 

 morning in March. At altitudes of between 1,500 and 2,300 metres he 

 aspirated air through a Miquel-type filter of powdered sodium sulphate by 

 suction obtained with a horse's stomach-pump; culturing the catch in 

 nutrient gelatine, he found a few moulds, and bacterial concentrations 

 ranging from 179,000 to 2,870,000 per cubic metre. At 1,800 to 2,000 

 metres there was a zone with 16 times the concentration at 1,500 metres 

 and 5 times that at 2,300 metres. These phenomenally large bacterial 

 concentrations were associated with a large temperature lapse and strong 

 convection from hot dry soil. Moulds were identified as: PenicilUum 

 glaucum, P. cinereum, P. atro-viride^ Sporidesjiiium sp., Acreinonimn alter- 

 7tans, Mucor racemosus, M. mucedo^ Oospora ochracea, 0. ferruginea, 

 Perkonia arta^ Hormodendrum {Cladosporium) penicillioides, Arthrococciis 

 lactis, Aspergillus niger, and a sterile mycelium. 



During ascents from Berlin with both captive and free balloons, 

 Flemming (1908) used trapping methods similar to those of Harz. He 

 found viable microbes up to 4,000 metres, averaging 370 per cubic 

 metre above 500 metres, and 12,900 per cubic metre lower down. Sterile 



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