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U. S. BUREAU OF FISHERIES 



Occurrence of the bacteria. — Having found that bacteria are present 

 in the slime deposited upon pound nets and that these bacteria digest 

 celhilose, it was deemed advisable to study the occurrence of the 

 organisms. Samples of sterilized gill-net thread, number 70/6 cord, 

 were placed in test tubes containing distilled water, tap water, and 

 lake water, respectively. These media were chosen to see how much 

 of the contamination was water borne. In another series, other 

 test tubes were filled with Lake P^rie water plus 1 cubic centimeter 

 of slime from nets, and with Dubos medium plus the same amount of 

 slime, respectively, so that a comparison could be made concerning 

 the effectiveness of lake water and an artificial medium in propagating 

 the bacteria. Some twine was sterilized in a test tube containing 

 distilled water in order to obtain an idea of the changes taking place 

 in the absence of bacteria. 



At the end of a week, and each week thereafter, samples were 

 removed, dried, and broken in the testing machine. The results of 

 these tests are shown in Figure 4 and Table 1, where it is seen that the 

 sterile control suffered no appreciable change in the two months and 

 that the distilled water and tap water were almost without effect. 



This experiment indicated that the city water was not a source of 

 contamination. The results also show that lake water is an excellent 



Figure o. — Normal cotton fiber in sterile distilled water 



medium for the growth of the cellulose-digesting bacteria, though the 

 growth is not as rapid at first as in the artificial medium of Dubos. 

 The latter preparation was used in subsequent experiments since it 

 was reproducible and easily available if laboratory work were to be 

 done elsewhere than at Lake Erie. 



The lake water inoculated with slime caused the twine to rot until 

 half its strength was gone in about 23 days; inoculated Dubos medium 

 required only 1 1 days to bring the twine to half -strength; and surprising 

 to note, the lake water without added contamination took but 32 days. 

 These tests must not be construed to mean that nets will rot this 

 rapidly in practice, for laboratory conditions are not exactly com- 

 parable with those in nature. These data do, however, allow one to 

 compare in a rough way the effect of the various conditions being 

 inv^estigated. 



Bacterial action on the individual Jiber. — The cultures were examined 

 microscopically and found to contain may bacteria of various forms, 

 expecially very short rods occurring in pairs and ones having a spiral 

 shape. Fibers of the test twine were placed under the microscope and 

 were observed to contain many bacteria. A number of photographs 

 are shown in Figures 5 to 8 . In order to understand them it is necessary 



