Ref ID : 1118
C.I. Mayfield and W.E. Inniss; Interactions between freshwater bacteria and Ankistrodesmus braunii in batch and continuous culture. Microbial Ecology 4:331-344, 1978
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Batch and continuous cultures of Ankistrodesmus braunii were established in an inorganic medium with growth rate limited by P. In batch culture, inoculation of lake water bacterial isolates of Pseudomonas sp. and Flavobacterium sp. showed that the Pseudomonas isolate was capable of more rapid growth on algal exudates of lytic products than was the Flavobacterium isolate. When inoculated singly into a continuous culture (D=0.267 day-1; P level, 2 uM), the Flavobacterium isolate initially caused a decrease in the population density of the alga, but then steady states for both organisms were obtained. The Pseudomonas isolate under the same conditions caused a rapid washout of the algal culture, and steady-state conditions were never obtained. When the Pseudomonas isolate was added to the two-member, steady-state system of A. braunii and Flavobacterium, the algal population again washed out of the vessel, followed by the Flavobacterium and then the Pseudomonas isolate. A tansient increase in the P concentration to 200 uM in the culture vessel caused the low algal population level to increase, followed by increases in the bacterial isolates when the algal population was high enough to supply the required organic carbon source. The system demonstrated that competition for P between the alga and the bacteria can occur, and the results were dependent on the algal and bacterial relative growth rate. The bacterial growth rate were limited initially by organic substrates produced by the alga, and the different bacterial isolates competed for these substrates.