NOVELTY - A microbial symbiotic association of manganese-oxidizing bacteria and algae, is new.    USE - The symbiotic microbial composition are useful for treating Mn-containing waters to cause oxidation and precipitation of the Mn, which can then be recovered from the water and utilized e.g. in the production of dry battery cells, glazes and enamels, steels and glasses.    ADVANTAGE - The symbiotic combination gives economical and effective recovery of heavy metals, especially Mn, from Mn-containing waters. One or more strains of Mn-oxidizing bacteria were inoculated into artificial sea water to which organic nutrients such as peptone or yeast extract had been added, or into 5 times diluted artificial sea water. An aliquot of the liquid was removed to determine the absorption (optical density) at 660 nanometers and the concentration of dissolved Mn2+. Mn dioxide was precipitated out, even in a liquid with a high concentration of salts, and a high concentration of Mn ions can be removed from solution from which Mn dioxide is not precipitated chemically.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for isolating the symbiotic microbial association comprising:    (i) preparing a filtrate (liquid A) by adding Mn sulfate to a 5 times diluted artificial sea water (Kester (RTM)) to a Mn (II) concentration of about 2 - 3 ppm and filtering the solution through a sterile filter with a pore size of 0.2 micrometers;    (ii) collecting a green, dark green, brown or black microbial carpet in sterilized bottles or flasks;    (iii) transferring the microbial carpet into a sterilized test tube containing liquid A and mixing;    (iv) shaking three test tubes each containing 25 milliliters liquid A and nothing else (tube 1), 2 milliliters of a sterilized test suspension (tube 2) or 2 milliliters of untreated suspension (tube 3) and subjecting them to a stationary culture under natural lighting at 37 degrees Centigrade for 4 days;    (v) filtering each of the tubes through a filter with a pore size of 0.2 micrometers and placing aliquots in test tubes;    (vi) adding formaldoxime solution and a buffer (pH 10) to the test tubes, mixing and allowing to stand for 10 minutes; and    (vii) determining, if the reaction liquid in tube 3 is red colored, whether the coloration is significantly weaker than the coloration in tube 2.    DESCRIPTION OF DRAWING(S) - The figure shows the difference in results of a culture at 20 degrees Centigrade of a filling of one or more Mn-oxidizing bacteria in 20 milliliters 100 percent seawater supplemented with 60 ppm Mn and with organic nutrients, and a non-inoculated (germ-free) system in the same solution.