TECHNOLOGY FOCUS - BIOTECHNOLOGY - Preferred Microbes: The anaerobic microbes are sulfate-reducing microbes, metal-reducing microbes.    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Method: When the anaerobic microbes are thermophilic, mesophilic or psychrotolerant, then the method (M1) is conducted at 40 degrees C. The method is conducted under substantially anaerobic conditions. Preferred Composition: The composition (C1) further indicated by at least one photoluminescent peak of 400-500 nm. Preferred Components: The metal component comprises at least one metal selected from V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, W, Pd, Pt, Au, Ag, Cd, Hg, Ga, In, Tl, Ge, Sn, Pb, Sb, and Bi (preferably Cd, Cu, Fe, Ga, In, or Zn). The non-metal component includes a reducible sulfur-containing, selenium-containing, tellurium-containing, or arsenic-containing compound. The reducible sulfur-containing compound is a sulfate, sulfite, or thiosulfate compound. The reducible selenium-containing compound is a selenate, selenite, or selenosulfate compound. The reducible tellurium-containing compound is a tellurate or tellurite compound. The reducible arsenic-containing compound is an arsenate or arsenite compound. The non-metal component comprises a sulfur-containing, selenium-containing, or tellurium-containing amino acid or nucleic base. The electron donors include at least one carboxylate-containing compound that can be oxidatively consumed by the microbes. The electron donors include at least one sugar compound that can be oxidatively consumed by the microbes. The electron donors include at least one oxidizable gaseous compound or element that can be oxidatively consumed by the microbes.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The non-metal component is comprised of at least one organic compound selected from organsulfur, organoselenium, organotellurium, and organoarsine compounds. EXAMPLE - A ZnS nanoparticles by using metal-reducing microbes was prepared as follows: fluorescent ZnS nanoparticles were synthesized using the thermophilic metal-reducing strain of Thermoanaerobacter ethanolicus strain (TOR-39) cultured in low-NaCl medium for one month. The sulfur-containing non-metal component was added in the form of thiosulfate. Zinc was added as ZnCl2. One experiment used 5 mM thiosulfate and 5 mM ZnCl2, added as sequential aliquots (1 mM/day). A second experiment used 10 mM thiosulfate and 10 mM ZnCl2, added as sequential aliquots (1 mM/day). The two experiments produced highly crystalline ZnS quantum dots with average particle sizes of 6.5 nm and 12 nm, respectively.