Abstract: Thermus aquaticus biovar. Nov. SK542 (FERM BP-3382) is an absolute aerobic bacteria. It grows at temperature limit of 40.degree.-82.degree. C. in a normal concentration medium, but its best growth is achieved at 72.degree.-76.degree. C. It produces protein decomposing enzymes functional at a temperature of 75.degree.-85.degree. C. and active in a wide pH range of 4.0-11.3, and a yellow pigment of carotenoid groups. A method for improving the quality of soil comprising applying to the soil a biologically pure culture of an absolute aerobic bacterium Thermus aquaticus biovar. nov. SK542 (FERM BP-3382) having a growth temperature limit of 40.degree.-82.degree. C. in a normal concentration medium, a growth optimum temperature of 72.degree.-76.degree. C., and producing protein decomposing enzymes functional at temperature range of 75.degree.-85.degree. C. and being active in a wide pH range of 4.0-11.3, and a yellow pigment of carotenoid.

Abstract: Clostridium thermocellum biovar. nov. SK522 (FERM BP-345 g) is a thermophilic cellulose decomposing bacteria, capable of solubilizing lignin and fermenting cellulose excellently. Although its temperature limit for growth is 40.degree.-80.degree. C., it grows best at 65.degree.-72.degree. C.Thermus aquaticus biovar. nov. SK542 (FERM BP-3382) is an absolute aerobic bacteria. It grows at temperature limit of 40.degree.-82.degree. C. in a normal concentration medium, but its best growth is achieved at 72.degree.-76.degree. C. It produces protein decomposing enzymes functional at a temperature of 75.degree.-85.degree. C. and active in a wide pH range of 4.0-11.3, and a yellow pigment of carotenoid groups.Both strains can be mix-cultured. Depending on various purposes, as the mix culture is able to decompose organic materials containing cellulose and/or lignin, it can be used for soil improvement.