BACTERIA IN THE DEEP SEA 



205 



Small test tubes about the size of one's little finger, 10 by 50 mm, were 

 used for these cultural tests. After seeding the nutrient medium with mud, 

 each tube was closed with a sterile neoprene stopper. The stoppers pre- 

 vented extraneous microbes from getting into the tubes and also the neo- 

 prene stoppers functioned as pistons which pushed into the tube to com- 

 press the mixture of nutrient medium and mud until the hydrostatic pres- 

 sure approximated that prevailing on the deep-sea floor. These pistons 

 were pushed into the tubes under the influence of hydrostatic pressure in 

 stout steel cylinders designed for this purpose. 



In families of 25, the stoppered tubes were placed in the stainless steel 

 cyhnders designed to withstand internal pressures up to 2,000 atmospheres. 

 After displacing the air from the cylinders with cold water, which also 

 served as the hydraulic fluid, the cylinders were closed pressure-tight and 

 connected by means of a hollow stainless steel tube to a hydraulic pump. 

 The specimens from at depth of 10,060 metres were pumped up to 1,000 

 atmospheres at a temperature of 3° C, approximately the pressure and 

 temperature prevailing at the bottom of the Philippine Trench where 

 the mud samples were collected. 



After several days' incubation in the refrigerator, the pressure was 

 released, the steel cylinders were opened, and the nutrient medium was 

 examined for evidence of bacterial growth. It was found that bacteria 

 from the deep-sea mud had reproduced in great numbers and, further- 

 more, they had affected the chemical composition of the medium. Thus, 

 it was proved that the bacteria from the deep-sea floor were alive and 

 physiologically active at a pressure of 1,000 atmospheres; the first con- 

 clusive proof of living organisms occurring at such great depths and the 



To prevent the bottle from being knocked 

 over by the rolling of the ship. Professor 

 ZoBell iises both fingers and toes when 

 inoculating samples of bacteria. 



