TECHNOLOGY FOCUS - BIOTECHNOLOGY - Preferred Method: In converting solid fossil fuels into petroleum, converting organic material or inorganic material (including such contained in water or salt water), petroleum, solid fossil fuels, into carbon, hydrogen or oxygen, or converting hydrogen, carbon and oxygen into fossil fuels, the starting microorganism is Thiobacillus aquaesullis 4255 and 389, Thiosphaera pantotropha 356 or 2944, Thoibacillus thoioparus 55, their mutants and variants, or a microorganism which exists naturally in water including deep water. After transfection, the host microorganism is capable of faster growth, reproduction, enhanced survivability in the production environment, or more production per unit nutrient or starting fossil fuel or oil tar, than is the starting microorganism. The host microorganism can exist in salt water or fresh water, can metabolize glucose or other nutrient media, can exist in rocky, sandy or sand/water environments, can survive heat, cold or acidic or basic environments, can oxidize sulfur, or can exist in aerobic or anaerobic conditions. The genes responsible for conversion are isolated by subtractive hybridization which is performed by representational difference analysis. Before transfection, the genes are selectively altered, and following transfection with such selectively altered genes, the host microorganisms with characteristics best suited to commercial production of petroleum are selected. Improving converting of solid fossil fuels to petroleum, or converting organic or inorganic material (including such contained in water or salt water), petroleum, solid fossil fuels, into carbon, hydrogen or oxygen comprises isolating a starting microorganism capable of the conversion, isolating from the starting microorganism an oligonucleotide probe complementary to a gene responsible for the conversion ability, placing the probe under hybridizing conditions in contact with amplicons from other microorganisms suspected or being capable of the conversion, isolating amplicons which hybridized, and transfecting the isolated amplicons into a host microorganism and determining whether productivity improved.