ANTAGONISTIC ACTION OF THE BACTERIUM BACILLUS-LICHENIFORMIS M-4 TOWARD THE AMEBA NAEGLERIA-FOWLERI

Free-living amoebae belonging to the species Naegleria fowleri are kno wn to be the etiological agents for a form of fulminant meningoencepha litis that is generally fatal (primary amoebic meningoencephalitis). I n a broad bacterial screening from soil and water we have isolated thr ee strains (M-4, D- 1 3 and A- 1 2) belonging to the species Bacillus licheniformis that have remarkable amoebicidal activity against Naegle ria sp. and also against different Gram-positive and Gram-negative bac teria. Physical-chemical characteristics, partial purification and bio logical activities of a substance produced by the M-4 strain have been investigated. This substance (m-4) is stable at high temperature (up to 100-degrees-C) and extremes of pH (2.5-9.5) and also at - 20-degree s-C for months. Its production is greatly influenced by oxygenation of the cultures and is probably related to the sporulation process of th e bacterium. Scanning electron microscope observations reveal that amo ebae are lysed after a few minutes contact with m-4.