National Geographic : 1936 May
SCIENTIFIC RESULTS OF THE STRATOSPHERE FLIGHT ozone, and low air pressure, the spores of five * of the species returned to earth with vitality unimpaired. They germinated fully as well as others taken f rom the same cul tures before the flight, and the resulting fungi are now growing in test tubes. A sixth fungus, Cladosporium sp., while recovered in pure culture, showed a very low percentage of germination. Final tests of the seventh, Hysperium sp., have not been completed. For a second test we took along a spore collecting device designed by Dr. Lore A. Rogers and M\r. Fred C. Meier, of the De partment of Agriculture, and Dr. Briggs, to find whether we could collect floating living spores from the air of the stratosphere. The apparatus consisted of a glass col lecting tube four inches in diameter and about seven inches long, its inner surface coated with glycerin. The tube was sur rounded by a cylindrical duralumin pro tecting case. The ends of both the tube and the case were provided with sterile plugs, and the whole apparatus, including a parachute, was sterilized and placed in a sterile dust proof bag (see page 697). We released the device after we started down, at an altitude slightly above 70,000 feet. The filling of an exterior parachute opened the bag and allowed the apparatus and its sterile parachute to fall out. A little later this parachute opened, pulled the plugs from the case, and allowed air to stream into the collecting tube and to be deflected against its sticky inner surface. The apparatus was so designed that this passage of stratosphere air through the col lecting tube continued until an altitude of about 36,000 feet was reached. There a small vacuum can (aneroid), set for the air pressure of that altitude, acted as a trigger, allowing springs to clamp the sterilized cot ton-covered disks over each end of the col lecting tube, so protecting it until it could be examined under laboratory conditions. The apparatus was carried safely to earth by its parachute, was recovered by Mr. Frank Brtna, of Academy, South Dakota, and was expressed by him to Washington, D. C., where it was received with the covers safely clamped over the ends of the tube. To avoid all possibility of con taminating the collection tube, a laboratory * Brachysporium sp., Diplodia sp., Rhizo pus nigricans, Aspergillus niger, Helminthosporium sativum. culture room at the Department of Agricul ture had been thoroughly cleaned and kept closed in preparation for the arrival of the apparatus. Inasmuch as only a very few, if any, spores were expected to be caught by the ap paratus, it was obviously hopeless to search for such spores in their normal condition in the tube. It was necessary, therefore, to furnish food to cause them to grow until they multiplied into groups or colonies that could be seen. A MIDNIGHT VIGIL IN A LABORATORY A flask of nutrient agar which had been sterilized several days before and then in cubated as a test for sterility was waiting. At night, when the building was freer from moving dust than at any other time, the glass collecting tube was removed from its case with the cotton-covered disks still held in place over its ends. Using every precaution to prevent con tamination from the air of the laboratory, Dr. Rogers and Mr. Meier melted a small amount of the sterile agar and introduced it into the cylinder, which was quickly closed and then rotated to spread the agar over the surface of the glycerin covering the inside wall. As the agar cooled it formed a soft thin film on the inside of the glass. The cylinder, with both ends still tightly closed, was then placed in an incubator at 30 0C. (860 F.) to encourage the development of any bac teria or mold spores which might be present. Forty-eight hours later growth was visi ble through the glass wall at ten different points. Dr. Rogers determined that five of the colonies were bacteria and trans ferred them to test tubes for study. He found they were all aerobic-that is, they grew in the presence of free oxygen-and that they were all spore formers. These two facts place them in the genus Bacillus. This is a large group of bacteria widely distributed and very common in the soil and on plants and other material ex posed to dust and soil. The specific names of these five cultures were not determined, but it was clear that they were distinct varieties if not five species. The other five colonies in the collection tube were found by Mr. Meier to be mold fungi of types which form spores readily in culture. Hence, by studying the fruiting structures under the microscope, they could easily be identified.