A thermosensitive wild-type strain (PP201) of Rhizobium sp. (Cajanus) and its 14 heat-resistant mutants were characterized biochemically with regard to their cell surface (exopolysaccharides (EPSs) and lipopolysaccharides (LPSs)) properties and protein profile. Differences were observed between the parent strain and the mutants in all these parameters under high temperature conditions. At normal temperature (30 degrees C), only half of the mutant strains produced higher amounts of EPSs than the parent strain, but at 43 degrees C, all the mutants produced higher quantities of EPS. The LPS electrophoretic pattern of the parent strain PP201 and the heat-resistant mutants was almost identical at 30 degrees C. At 43 degrees C, the parent strain did not produce LPS but the mutants produced both kinds of LPSs. The protein electrophoretic pattern showed that the parent strain PP201 formed very few proteins at high temperature, whereas the mutants formed additional new proteins. A heat shock protein (Hsp) of 63-74 kDa was overproduced in all mutant strains.
Psoralea corylifolia Linn. is an endangered and medicinally important plant indigenous to tropical and subtropical regions of the world. Its medicinal usage is reported in Indian pharmaceutical codex, the Chinese, British and the American pharmacopoeias and in different traditional system of medicines such as Ayurveda, Unani and Siddha. The review reveals that wide ranges of phytochemical constituents have been isolated from the plant and it possesses important activities like antibacterial, antiinflammatory and antitumer. Various other activities like hepatoprotective, antioxidants and antithelminitic have also been reported. These repots are very encouraging and indicate that herb should be studied more expensively for its therapeutic benefits.This article briefly reviews the botany, pharmacology, biochemistry and therapeutic application of the plant. This is an attempt to compile and document information on different aspects of Psoralea corylifolia and highlight the need for research and development.
Fourteen heat resistant mutant strains were isolated from a wild-type strain (PP201, Nod + Fix + ) of Rhizobium sp. (Cajanus) by giving it a heat shock of 43 0 C. These mutant strains showed a greater increase in optical density (O.D.) and a higher viable cell count in both rhizospheric and non-rhizospheric soil at high temperature. Symbiotic studies showed that pigeon pea plants inoculated with a few mutant strains had ineffective nodules (Nod + Fix -) under controlled temperature (43 o C) conditions, but under natural high temperature (40 -45 o C) conditions, the host plants infected with all the mutant strains showed higher total shoot nitrogen than the plants inoculated with the parent strain. Four mutant strains (HR-3, HR-6, HR-10 and HR-12) were found to be highly effi cient for all the symbiotic parameters, and thus have the potential to be used as bioinoculants in the North-Western regions of India during the summer season.
A .S . Y A DA V, M . V AS U DE VA , K. K. U PA DH Y AY , S . K. SA W HN EY A ND R. K . V AS H IS HA T . 1999. Nitrogen fixing efficiency of sodium azide-resistant strains of Rhizobium leguminosarum bv. trifolii was studied in symbiosis with berseem clover plants in chillum jars. Rate of respiration and glutamine synthetase activity were tested in cultured cells and nodules, respectively. It was observed that shoot dry weight and percentage shoot nitrogen were maximum in plants inoculated with strains resistant to 15 mg ml −1 sodium azide. Rate of respiration in cultured cells was lowest in strains resistant to 15 mg ml −1 sodium azide and highest in strains resistant to 5 mg ml −1 sodium azide. A negative correlation was observed between rate of respiration (in cultured cells) and shoot dry weight of host plants. Glutamine synthetase activity was maximum in nodule extracts of host plants inoculated with strains resistant to 5 and 10 mg ml −1 sodium azide, whereas it was minimum for strains resistant to 15 mg ml −1 sodium azide. Hence, resistance to low doses (15 mg ml ) of sodium azide, together with lower respiratory and glutamine synthetase activities, could be used as a potential method for isolating the symbiotically effective strains of Rh. leguminosarum bv. trifolii.
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