Drouin P, Prévost D, Antoun H
Soils and Crops Research and Development Centre, Agriculture and Agri-Food Canada, 2560 Hochelaga Blvd., Sainte-Foy, Canada
FEMS Microbiol Ecol. 2000 Apr 1;32(2):111-120. doi: 10.1111/j.1574-6941.2000.tb00705.x.
Strains of Rhizobium leguminosarum bv. viciae, isolated from the legume species Lathyrus japonicus and Lathyrus pratensis in northern Quebec (Canada), showed different capacities for growing at low temperature. In the present study, we investigated some mechanisms related to cold adaptation. Two cold-adapted strains (psychrotrophs) were compared to a poorly adapted strain and to a cold-sensitive strain (reference strain) for freezing survival, protein induction and fatty acid composition under low temperature. Following cold shocks (25 degrees C to 10, 5 and 0 degrees C), a common 6.1-kDa CSP (cold shock protein) was induced in all strains, but the total number of CSPs synthesized at 0 degrees C was higher in cold-adapted strains than in the cold-sensitive strain. The synthesis of CAPs (cold acclimation proteins) was observed under continuous growth at 5 degrees C in all three strains capable of growth at this temperature. Levels of survival after 24 h at -80 degrees C where higher in cold- (79%) and poorly adapted (64%) strains than in the cold-sensitive strain (33%), but a 2-h acclimation period at 5 degrees C before freezing doubled the survival of the cold-sensitive strain. Low temperature conditions affected similarly the fatty acid composition of all strains, regardless of their cold adaptation level. The proportion of unsaturated fatty acids increased significantly with the lowering of growth temperature from 25 to 5 degrees C, but showed a tendency to decrease after a cold shock from 25 to 5 degrees C. A specific unsaturated fatty acid, cis-12 octadecanoic acid, was produced during growth at 5 degrees C. The unsaturated cis-vaccenic acid was the principal component under all conditions. The cold adaptation trait was weakly reflected in symbiosis with the agronomic legume, Lathyrus sativus, with which one cold-adapted strain showed a slightly higher nitrogenase activity and shoot dry matter yield than a commercial strain under a sub-optimal temperature regime.
从加拿大魁北克省北部的豆科植物日本山黧豆和草原山黧豆中分离出的豌豆根瘤菌蚕豆生物型菌株，在低温下表现出不同的生长能力。在本研究中，我们调查了一些与冷适应相关的机制。将两株冷适应菌株（嗜冷菌）与一株适应不良的菌株和一株冷敏感菌株（参考菌株）在低温下的冷冻存活率、蛋白质诱导和脂肪酸组成进行了比较。在冷休克（25℃至10℃、5℃和0℃）后，所有菌株均诱导出一种常见的6.1 kDa冷休克蛋白（CSP），但在0℃时合成的CSP总数在冷适应菌株中高于冷敏感菌株。在所有能够在5℃连续生长的三个菌株中，均观察到冷驯化蛋白（CAP）的合成。在-80℃下24小时后的存活率，冷适应菌株（79%）和适应不良菌株（64%）高于冷敏感菌株（33%），但在冷冻前在5℃下进行2小时的驯化期可使冷敏感菌株的存活率加倍。低温条件对所有菌株的脂肪酸组成影响相似，无论其冷适应水平如何。不饱和脂肪酸的比例随着生长温度从25℃降至5℃而显著增加，但在从25℃至5℃的冷休克后呈下降趋势。在5℃生长期间产生了一种特定的不饱和脂肪酸，顺式-12-十八碳烯酸。不饱和顺式-十八碳烯酸在所有条件下都是主要成分。冷适应特性在与农艺豆科植物栽培山黧豆的共生中反映较弱，在次优温度条件下，一株冷适应菌株的固氮酶活性和地上部干物质产量略高于商业菌株。
