PHYSIOLOGICAL AND BIOCHEMICAL CHARACTERISTICS OF A FAST-GROWING STRAIN OF LUPINE RHIZOBIA ISOLATED FROM THE SONORAN DESERT (NITROGEN FIXATION, MEXICO).

Abstract

An effective, fast-growing strain of Rhizobium was isolated from a species of Lupinus native to the Sonoran desert near San Felipe, Baja, Mexico (generation time, 3.6 h). Bacteria isolated from the roots of lupines are normally slow growing, however, Lupine 43, is a fast grower, possesses multiple flagella and produces acid in a defined medium. In comparison to a slow-growing lupine strain, Nitragin 96A11, Lupine 43 has a low intrinsic resistance to antibiotics and is able to utilize a wide range of carbon and nitrogen sources. Field and incubator studies were conducted to determine if the adaptation of the characteristics of fast-growing strains enables this strain to survive under the desert conditions of the southwestern United States. In the field, where no moisture was added after initial inoculation, Lupine 43 survived in significantly higher numbers than 96A11 for the first two weeks of the low (19C) and the first month of the high (35C) temperature study. In a laboratory study, at a constant moisture level of 1/3 bar, differences in survival between the two strains were dependent on temperature, pH and soil texture.