Selection of surrogates for a genetically engineered microorganism with cellulolytic capability for ecological studies in streams

Abstract

Aerobic cellulolytic bacteria were ranked according to ability to degrade cellulose azure and to clear cellulose agar. Cellulomonas uda NRRL B404 and Cellulomonas sp. NRC 2406 showed greater clearing of cellulose agar than other isolates, but differences in cellulose azure decomposition were not statistically significant. Isolates were tested for ability to accelerate decomposition of tulip poplar (Liriodendron tulipifera) leaves and Cladophora glomerata (Chlorophyta) detritus in stream water. There was significantly more cellulose lost from leaves exposed to Cellulomonas flavigena NRC 2403, Cellulomonas fimi NRRL B402, Cellulomonas sp. NRC 2406, and Cellvibrio gilvus ATCC 13127 and NRC 2407 than in the stream-water control, and the weight losses of leaves exposed to some isolates were significantly greater than in the control. There was significantly more cellulose lost from Cladophora glomerata detritus exposed to these and five other isolates, and there were greater weight losses than in the stream-water control. Cellulomonas uda NRRL B404 was the slowest growing isolate, although growth rates of isolates did not differ statistically. Cellulomonas uda NRRL B404, Cellulomonas sp. NRC 2406, Cellulomonas fimi NRRL B402, Cellulomonas flavigena NRC 2403, and Cellvibrio gilvus ATCC 13127 were selected as the best candidates for larger scale experiments. Persistence of Cellulomonas uda, Cellulomonas sp. NRC 2406, and Cellulomonas sp. CS1-1 in stream-bed sediments was studied in flowing-water microcosms, using fluorescent antibodies and epifluorescence microscopic counts to asses densities of target cells. Isolate densities declined from postinoculation maxima, but organisms were detected 2–4 weeks later in three different experiments. Key words: cellulolytic bacteria, detritus, decomposition, population dynamics, microcosms.