Chapter X — 141 — Organic Matter 



The decomposition of alginic acid, a polyuronide occurring abundantly 

 in marine algae, was found by Waksman et al. (1934) to be caused largely 

 by certain specific bacteria. Other microorganisms such as fungi were 

 responsible only to a very limited extent. Bacteria which decompose 

 alginic acid occur abundantly in sea water, marine plankton, and in bot- 

 tom deposits. Three new marine species which decompose alginic acid 

 were described; namely, Bacterium alginicum, Bad. alginovoru?n, and 

 Bad. fiicicola. The last two species also digest agar. 



Pscudomonas hypothcrmis, Ps. marinopcrsica, Ps. perfedomarinus , Ps. 

 pcriphytica, and Flavobaderiiim tdiginosum are agar digesters described by 

 ZoBell and Upham (1944). These organisms tend to lose their ability to 

 digest agar after prolonged laboratory cultivation, even on agar slants. 



According to Kinkel (1936), cellulose-decomposing bacteria occur 

 abundantly in lake mud. She also found in mud from Lake Mendota sev- 

 eral species which fermented pectin. 



Cellulose-decomposing microorganisms, as well as those which attack 

 lignin, are instrumental in the destruction of timbers, wooden pilings, 

 ropes, iish nets, and other cellulose- or lignin-containing structures. Such 

 microorganisms may work symbiotically with shipworms or other wood- 

 borers. Barghoorn (1942) reports the occurrence on the North Atlantic 

 coast of marine fungi which cause the deterioration of both hard and soft 

 woods as well as cordage fibres under marine conditions. 



Lignin decomposition: — Lignin is a complex, carbohydrate-like sub- 

 stance which constitutes part of the woody structure of plants. Ac- 

 cording to Steiner and Meloche (1935), from 10 to 20 per cent of the 

 organic matter in phytoplankton and from 30 to 48 per cent of the organic 

 residue in lake bottom deposits is lignin. Waksman (1933) likewise found 

 a much higher percentage of lignin in marine humus than in marine vegeta- 

 tion. The difference between the lignin content of phytoplankton and 

 bottom deposits is indicative of the relative insusceptibility of lignin to 

 microbial decomposition. 



Lignin is slowly oxidized by certain bacteria. Benson and Partansky 

 (1934) reported that the ligneous materials in sulfite waste liquors dis- 

 charged by pulp mills are slowly decomposed by bacteria in sea water and 

 marine mud. Sulfite waste liquor is primarily a calcium lignosulfate, or 

 the residue of wood after the hemicelluloses are hydrolyzed by acid treat- 

 ment and the cellulose is removed as pulp. The lignosulfate consists 

 chiefly of lignin. When inoculated with marine mud, lignosulfate was 

 found to be fermented with the production of CO2, methane, and H2S. 



ZoBell and Stabler (1940a) present evidence which indicates that, 

 while lignin is oxidized less readily than are other major organic con- 

 stituents occurring in lakes, it is slowly decomposed by bacteria found in 

 water and bottom deposits. Several different purified lignins as well as 

 various ligneous products were examined, using oxygen consumption and 

 the disappearance of lignin as criteria of utilization. Most of the strains 

 of Micromonospora found in lake mud by Erikson (1941) attacked lignin. 



Marine fungi which attack lignin and cellulose are believed by Barg- 

 hoorn and Linder (1944) to be dominantly responsible for the deteriora- 

 tion of hemp, jute, and sisal cordage as well as pilings and other wooden 

 structures in the sea. 



ZoBell (19406) found that, provided some oxygen was present, puri- 

 fied lignin and lignoprotein were slowly oxidized by marine bacteria. The 



