Deep - Sea Bacteria

The presence of living bacteria in some of the deepest parts of the ocean was demonstrated on the Galathea Expedition. Sediment samples taken from the bottom of the Philippine Trench at depths exceeding 10 000 meters were found to contain from 104 to 1Q6 living bacteria per ml. Large bacterial populations were also detected in sediment samples from the floor of the Kermadec-Tonga Trench (6790 to 9820 meters), the Sunda Deep (7020 meters) in the Java Trough, and the Weber Deep (7250 meters) in the Banda Sea. Several hundred microbial analyses were made on nine sediment samples taken from depths exceeding 10 000 meters. The occurrence of bacteria in deep-sea sediment samples was demonstrated by direct microscopic examinations shortly after the samples were hauled aboard the Galathea. Growth or reproduction of the bacteria in nutrient sea water media proved that the bacteria were alive. Their indigenity was indicated by three lines of evidence: (1) Every possible precaution was exercized to prevent the contamination of the deep-sea samples, (2) More bacteria were found in the sediment samples than in the overlying water, and (3) The deep-sea bacteria were unique in their ability to grow preferentially or exclusively at in situ hydrostatic pressures (700 to 1 000 atmospheres) and low temperatures (3 to 5OC). Apparatus is described which was designed to maintain sediment samples and bacterial cultures at any desired pressure in the ship's refrigerator. This apparatus made it possible to send by Air Express deep-sea sediment samples held at 1000 atm to our laboratory at Scripps Institution for further observation.