BACTERIA IN THE DEEP SEA 



209 



Plastic tube from Dr. Kullenberg's 

 piston corer with a sample taken 

 from the bottom of the Philip- 

 pine Trench. Professor ^oBell is 

 taking samples for bacterial 

 culture. 



tenes, closely resembling vitamin A, and several produce ergosterol, also 

 known as provitamin D. The synthesis of vitamin B12 by bacteria in the 

 gut of chum salmon and Pacific herring has been reported. 



Although the majority of the bacteria in the sea are beneficial to ani- 

 mals, a few species cause infectious diseases. Bacteriologists on the Gala- 

 thea Expedition obtained no evidence of bacterial infections in deep-sea 

 animals, but judging from observations on diseased animals collected from 

 shallow coastal waters, one might expect to find pathogenic bacteria 

 taking their toll of animal life in the deep sea also. Even though the infec- 

 tion by itself is not fatal, the pathogenic bacteria may incapacitate the 

 host animal to a point where it may more readily fall prey to the ever- 

 present predator. There is no sanctuary in the sea for the ill or the aged 

 where only the fittest survive. 



Certain pathogenic bacteria have the unique property of producing 

 light in infected lesions, causing the latter to glow in the dark. However, 

 only a few species of light-producing bacteria are known to be injurious 

 to marine animals. They are mostly harmless varieties that grow embedded 

 in the surface slime of shrimp, squid, fish, etc., or, in a few cases, in the 

 bioluminescent organs of fish. 



Curiously, the production of light by bacteria is affected by hydrosta- 

 tic pressure. Many more observations will have to be made, however, 

 before we will be able to generalize regarding the behaviour of biolumi- 

 nescent bacteria from the deep sea. We have learned that certain physiolo- 



