Sensitivity of Microcystis Aeruginosa and Other Blue‐green Algae and Associated Bacteria to Selected Antibiotics¹

Sensitivity of 5 blue-green algae, especially Microcystis aeruginosa, and associated bacteria to 32 antibiotics was determined. A combination of neomycin and dihydrostrcptomycin was the most useful in inhibiting bacterial growth while allowing some algal growth. An axenic culture of M. aeruginosa maintainable for an extended time was not obtained. This and other studies indicate that a blue-green chroococcalcan culture should not be reported to be bacteria-free unless repeated rigorous tests for bacteria prove negative.