Ref ID : 1753
Bonnie I. Abrams and Myron J. Mitchell; Role of nematode-bacterial interactions in heterotrophic systems with emphasis on sewage sludge decomposition. OIKOS 35:404-410, 1980
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The role of nematode-bacterial interactions in affecting decomposition was demonstrated utilizing microcosms with sterilized sewage sludge as a substrate. Axenic microcosms were inoculated with the bacterium, Pseudomonas fluorescens (Trevisan), while monoxenic microcosms contained this bacterium and the rhabditid nematode, Pelodera punctata (Cobb). Microcosms were incubated at 5, 15, 22 degrees C. Bacterial density, nematode density, oxygen consumption, and carbon dioxide evolution were determined weekly. Gas flux rates were determined by gas chromatography. For all trials, monoxenic systems had greater (p<0.01) oxygen consumption than axenic systems. Carbon dioxide flux was less (10 to 75%) due to its high solubility. At 22 degrees C, during the period of maximum activity, oxygen consumption was six times greater in those systems containing nematodes, although P. punctata itself accounted for only 5% of the total metabolism. The respiratory metabolism of P. punctata was 7.14 µlO2 hr-1 mg-1 dry weight at 22 degrees C. Over 35 days, percent organic matter losses in axenic microcosms, were 1.37, 2.47 and 3.51 while in monoxenic microcosms they were 2.52, 6.09, and 6.89 at 5, 15, and 22 degrees C, respectively. Bacterial densities were greater (p<0.01) in monoxenic microcosms for all trials, with the exception of one trial at 5 degrees C. Nematode population doubling times were 24, 5, and 2 days for 5, 15, and 22 degrees C, respectively. The time of maximum metabolic activity in the microcosms decreased with the presence of nematodes and/or elevated temperature. The overall importance of nematode-bacterial interactions in heterotrophic systems is discussed.