Figure 5. Rock sample from 6,000-foot depth showing numerous holes 
made by rock-boring animals. Bryozoa (erect type), tube 
worms, and legs of a brittle star are visible. 
The samplers have been described in Reference 1. The results of the bacterio- 
logical analysis of the sediment samples are presented in Tables III, IV, and V. 
The sulfate reducers found in the sediment samples are anaerobic bacteria 
which obtain their energy by the reduction of sulfate and sulfite in water in the 
absence of free oxygen. The end product of their metabolic process is hydrogen 
sulfide (H2S). These microbes are considered to be responsible for the anaerobic 
corrosion of metals.© Microorganisms other than sulfate reducers, are also found to 
be responsible for metal corrosion./78,? 
The number of aerobic, anaerobic, and sulfate-reducing marine bacteria was 
determined in the laboratory on nutrient agar plates and in test tubes. Because of 
the different nutritional requirements of marine bacteria and the limitation in the 
enumeration procedure employed in this study, only a small percentage of the bacte- 
rial population may have been demonstrated by the analysis of the bottom samples. 
The following media were used for culturing marine microorganisms. 
