Chapter X — 143 — Organic Matter 



not properly refrigerated. The consistency and color of muscle tissue are 

 altered by bacterial activity, and an odor of ammonia, indol, trimethyla- 

 mine, or other protein-decomposition products is manifest. Quantitative 

 tests for ammonia, indol, trimethylamine, histamine, tyrosine, and other 

 protein-decomposition products have been proposed by various workers as 

 a means of detecting the early stages of fish spoilage. A common property 

 of the bacteria associated with spoiled fish is their ability to decompose 

 proteins, peptones, peptides, and amino acids (Bradley and Bailey, 

 1940; Hunter, 1922; Geiger et al., 1944; Griffiths, 1937; Harrison 

 and Kennedy, 1922; Snow and Beard, 1939; Wood, 1940). 



Ostroff and HEJfRY (1939) investigated the ability of 15 represen- 

 tative aerobic bacteria of marine origin to utilize 21 different nitrogen 

 compounds. Asparagine, aspartic acid, glutamic acid, alanine, propiona- 

 mide, acetamide, sodium hippurate, urea, and creatinine were commonly 

 utilized either as a source of nitrogen or energy or both. Cystine, betaine, 

 pyridine, and uric acid were utilized by some of the bacteria. Only one 

 culture utilized tyrosine. Guanidine, anihne, and ethylamine were not 

 utilized by any of the organisms. 



Waksman and Renn (1936) found that from 2 to 4 mgm./L. of 

 glycine, alanine, phenylalanine, glutamic acid, tyrosine, and asparagine 

 were almost quantitatively utilized by raw cultures of bacteria in sea 

 water within 2 to 5 days at 20° C. From these results and others in which 

 they noted the rate of carbohydrate decomposition to be dependent upon 

 an available nitrogen source, they concluded that zooplankton in sea 

 water were decomposed more rapidly than marine algae because of the 

 greater proportion of available nitrogen in the former. Waksman et al. 

 (1933a) noted that marine zooplankton were more susceptible than were 

 marine algae to bacterial decomposition. The green alga, Ulva laduca, 

 which contains about 2 per cent nitrogen on a dry basis, was decomposed 

 more rapidly than the brown alga, Fucus vesiculosis, which contains only 

 half as much nitrogen. The bacterial decomposition of zooplankton pro- 

 ceeded to completion with the liberation of ammonia and CO2, whereas 

 the complete decomposition of Fucus material required the addition of 

 available nitrogen. 



Marine diatom plankton, which is relatively rich in proteinaceous ma- 

 terial, was observed by Waksman et al. (1937) to undergo rapid oxidation 

 and decomposition by bacteria in sea water. This was measured by oxy- 

 gen consumption, nitrogen liberation, phosphate regeneration, and bac- 

 terial multiphcation. Only dead diatoms were attacked by the bacteria. 



Chitin decomposition : — Chitin is the chief constituent of the exo- 

 skeleton of Crustacea and it occurs in some Mollusca, Coelenterata, and 

 Protozoa. Johnstone (1908) estimated that one sub-class of planktonic 

 Crustacea, the Copepoda, produces several million tons of chitin annually. 

 Most of this, as well as the chitin produced by other organisms in the sea, 

 must be decomposed since relatively httle accumulates in the marine 

 sediments, and moreover, if it were not decomposed, it would become a 

 serious drain upon carbon and nitrogen in the cycles of these elements. 

 Chitin is generally believed to be a polymer of glucosamine in which each 

 amino group is acetylated, the composition being C32HB4O21N4. 



There are few if any animals which can assimilate chitin unaided by 

 microorganisms. Although chitinase has been detected in the alimentary 

 tracts of certain chitin-ingesting animals, it may have been produced by 



