Effects of nitrogen level on survival of Phialophora radicicola and Cochliobolus sativus in pure culture on cellulose
1971; Cambridge University Press; Volume: 57; Issue: 1 Linguagem: Inglês
10.1016/s0007-1536(71)80087-6
ISSN0007-1536
Autores Tópico(s)Microbial Fuel Cells and Bioremediation
ResumoAt nitrogen levels below the optimum for survival in pure culture on filter-paper cellulose, both Phialophora radicicola and Cochliobolus sativus survived much better than Ophiobolus graminis had done in an earlier experiment by the same technique. The better survival of these two species at low nitrogen levels is ascribed to their higher values for the cellulolysis adequacy index (CAI), which expresses the cellulolysis rate of a species in relation to its general metabolic rate. The adverse effect of excess nitrogen on saprophytic survival of these two species in colonized wheat straws buried in soil is attributed to earlier exhaustion of the substrate when nitrogen supply is not limiting rate of decomposition. This effect could be reproduced only partially with P. radicicola in pure culture on cellulose, and so the larger part of the effect is ascribed to decomposition of the straw tissue by other micro-organisms invading the substrate from the surrounding soil. Species with a high CAI value, such as P. radicicola and C. sativus , liberate sugars by cellulolysis in excess of their immediate metabolic needs; when nitrogen and other mineral nutrients are provided by the soil, then nutritional requirements for invasion of the substrate by other micro-organisms are met in full, and so decomposition and ultimate exhaustion of the substrate are thereby accelerated.
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