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Abstract

Natural populations of L. redekei are accompanied by large amounts of heterotrophic bacteria. Studies with axenic and bacteria-containing L. redekei suspensions showed a narrow correlation between algal growth, release of nitrogenous algal products and bacterial growth while bacteria stimulated algal growth. Type and concentration of extracellular nitrogenous algal products are described as well as their mode of release, the transcellular trichome breakage with lysis of at least one cell. Lysis indicating cell number per trichome and lysis inducing factors as nutrient deficiency were investigated in connection with algal storage capacity for carbon, nitrogen and phosphorus compounds confirmed by observations with natural populations. The growth of the obligate autotrophic L. redekei is stimulated by supply of inorganic nitrogenous compounds released during bacterial degradation of algal lysis products or other organic substrates. Algal-bacterial relations thus have a symbiotic quality.