Pseudomonas aeruginosa Chemotaxis Associated with Blooms of N 2 -Fixing Blue-Green Algae (Cyanobacteria)

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Abstract
Pseudomonas aeruginosa (Schroeter) Migula, a numerically significant bacterium found during N2-fixing blooms of the blue-green algae (cyanobacteria) Anabaena sp. in the Chowan River, North Carolina, was chemotactically attracted to amino acids when tested in a radioassay. The bacterium was labeled with 32Pi, and the disintegrations per minute determined by liquid scintillation counting were proportional to the number of cells accumulating in microcapillaries containing amino acids. Positive chemotaxis was observed toward all of the amino acids tested, although the degrees of response varied. Since many nitrogen-fixing blue-green algae secrete nitrogenous compounds, this attraction may be instrumental in establishing a symbiotic relationship between this bacterium and blue-green algae in freshwater.