Wielbo J, Skorupska Anna
Department of General Microbiology, M. Curie-Skłodowska University, Lublin, Poland.
Acta Biol Hung. 2008 Mar;59(1):115-27. doi: 10.1556/ABiol.59.2008.1.10.
The Rhizobium-legume interaction is sensitive to a number of environmental factors, among which phosphate (Pi) and ammonium availability are the most important. We investigated the effect of Pi and ammonia concentration on exopolysaccharide production and symbiosis Trifolium pratense with Rhizobium leguminosarum bv. trifolii TA1 (RtTA1). The optimal Pi concentration in the bacterial growth medium for RtTA1 growth and exopolysaccharide production was in the range from 0.9 mM to 8.1 mM. Independently of Pi concentration, ammonium (NH4Cl) concentration above 8.1 mM in the culture medium significantly decreased EPS production, indicating a regulatory role of this nutrient on the EPS production in the RtTA1 strain. Pi availability has a beneficial effect on both partners of symbiosis. Pi concentration in the plant medium in the range from 1.7 mM to 5 mM was optimal for nodule formation, nodule occupancy and nitrogen fixation ability. Despite of T. pratense cv. Bryza tolerance on high Pi concentration, 20 mM Pi occurs to be nearly phytotoxic, which negatively affects almost all symbiotic parameters. Large amounts of starch were accumulated in the nodules formed by clover grown on medium containing high Pi concentration.
根瘤菌与豆科植物的相互作用对许多环境因素敏感，其中磷酸盐（Pi）和铵的有效性最为重要。我们研究了Pi和氨浓度对胞外多糖产生以及三叶草与苜蓿根瘤菌三叶草生物变种TA1（RtTA1）共生的影响。细菌生长培养基中促进RtTA1生长和胞外多糖产生的最佳Pi浓度范围为0.9 mM至8.1 mM。与Pi浓度无关，培养基中铵（NH4Cl）浓度高于8.1 mM会显著降低EPS产生，表明这种养分对RtTA1菌株中EPS产生具有调节作用。Pi的有效性对共生的双方都有有益影响。植物培养基中Pi浓度在1.7 mM至5 mM范围内最有利于结瘤、根瘤占据和固氮能力。尽管三叶草品种Bryza对高Pi浓度具有耐受性，但20 mM Pi几乎具有植物毒性，对几乎所有共生参数都有负面影响。在高Pi浓度培养基上生长的三叶草形成的根瘤中积累了大量淀粉。
