Bhargava S, Kachouli R K, Maithil R, Kaithwas V
Division of Microbiology, Department of Botany, Government Motilal Science College, Bhopal 462003 (M.P.), India.
Mikrobiologiia. 2011 Jul-Aug;80(4):454-8.
The cyanobacterium Nostoc muscorum is able to utilized proline and glycine-betaine as a nitrogen source under unstressed growth conditions. This cyanobacterium when grow in modified Chu No. 10 medium (without Na+) unable to utilized proline and glycine-betaine as a nitrogen source. Spontaneously occurring mutant clones defective in Na+ transport (Na+-R) were isolated and analyzed for proline and glycine-betaine utilization. The mutant phenotype showed normal heterocyst frequency and nitrogenase activity even in the medium containing 1 mM proline or 1 mM glycine-betaine, indicates the role of Na+ for proline/glycine-betaine uptake. The Na+-R mutant showed 100% survival at pH 11 and was simultaneously able to uptake and utilize proline/glycine-betaine at higher alkaline pH. This indicates that proline and glycine-betaine uptake systems are more efficient at higher alkaline pH. Since, the hypersaline environments are rich in Na+ contents and have alkaline pH, therefore it is suggested that the origin and evolution of specific compatible solutes may not depend only on the osmoregulatory role they play, but also on the other ecological factors operating simultaneously in the organism's niche.
蓝藻念珠藻在无胁迫生长条件下能够利用脯氨酸和甘氨酸 - 甜菜碱作为氮源。这种蓝藻在改良的朱氏10号培养基（不含Na +）中生长时，无法利用脯氨酸和甘氨酸 - 甜菜碱作为氮源。分离出了在Na +转运方面存在缺陷的自发突变克隆（Na + -R），并对其脯氨酸和甘氨酸 - 甜菜碱利用情况进行了分析。突变表型即使在含有1 mM脯氨酸或1 mM甘氨酸 - 甜菜碱的培养基中也显示出正常的异形胞频率和固氮酶活性，这表明Na +在脯氨酸/甘氨酸 - 甜菜碱摄取中起作用。Na + -R突变体在pH 11时存活率为100%，并且能够在较高碱性pH下同时摄取和利用脯氨酸/甘氨酸 - 甜菜碱。这表明脯氨酸和甘氨酸 - 甜菜碱摄取系统在较高碱性pH下效率更高。由于高盐环境富含Na +且呈碱性pH，因此有人提出特定相容性溶质的起源和进化可能不仅取决于它们所起的渗透调节作用，还取决于生物体生态位中同时起作用的其他生态因素。
