Meza Beatriz, de-Bashan Luz E, Bashan Yoav
Environmental Microbiology Group, Northwestern Center for Biological Research (CIBNOR), Calle IPN 195, La Paz, B.C.S. 23096, Mexico.
Environmental Microbiology Group, Northwestern Center for Biological Research (CIBNOR), Calle IPN 195, La Paz, B.C.S. 23096, Mexico; The Bashan Foundation, 3740 NW Harrison Blvd., Corvallis, OR 97330, USA; Department of Entomology and Plant Pathology, 209 Life Sciences Building, Auburn University, Auburn, AL 36849, USA.
Res Microbiol. 2015 Feb-Mar;166(2):72-83. doi: 10.1016/j.resmic.2014.12.010. Epub 2014 Dec 29.
Accumulation of intracellular ammonium and activities of the enzymes glutamine synthetase (GS) and glutamate dehydrogenase (GDH) were measured when the microalgae Chlorella vulgaris was immobilized in alginate with either of two wild type strains of Azospirillum brasilense or their corresponding indole-3-acetic acid (IAA)-attenuated mutants. After 48 h of immobilization, both wild types induced higher levels of intracellular ammonium in the microalgae than their respective mutants; the more IAA produced, the higher the intracellular ammonium accumulated. Accumulation of intracellular ammonium in the cells of C. vulgaris followed application of four levels of exogenous IAA reported for A. brasilense and its IAA-attenuated mutants, which had a similar pattern for the first 24 h. This effect was transient and disappeared after 48 h of incubation. Immobilization of C. vulgaris with any bacteria strain induced higher GS activity. The bacterial strains also had GS activity, comparable to the activity detected in C. vulgaris, but weaker than when immobilized with the bacteria. When net activity was calculated, the wild type always induced higher GS activity than IAA-attenuated mutants. GDH activity in most microalgae/bacteria interactions resembled GS activity. When complementing IAA-attenuated mutants with exogenous IAA, GS activity in co-immobilized cultures matched those of the wild type A. brasilense immobilized with the microalga. Similarity occurred when the net GS activity was measured, and was higher with greater quantities of exogenous IAA. It is proposed that IAA produced by A. brasilense is involved in ammonium uptake and later assimilation by C. vulgaris.
当普通小球藻与两株野生型巴西固氮螺菌菌株或其相应的吲哚 - 3 - 乙酸（IAA）减弱突变体一起固定在藻酸盐中时，测定了细胞内铵的积累以及谷氨酰胺合成酶（GS）和谷氨酸脱氢酶（GDH）的活性。固定48小时后，两种野生型菌株在微藻中诱导的细胞内铵水平均高于各自的突变体；产生的IAA越多，细胞内积累的铵就越高。普通小球藻细胞内铵的积累遵循报道的巴西固氮螺菌及其IAA减弱突变体的四个外源IAA水平，在前24小时具有相似的模式。这种效应是短暂的，培养48小时后消失。用任何一种细菌菌株固定普通小球藻都会诱导更高的GS活性。这些细菌菌株也具有GS活性，与在普通小球藻中检测到的活性相当，但比与细菌一起固定时弱。计算净活性时，野生型总是比IAA减弱突变体诱导更高的GS活性。大多数微藻/细菌相互作用中的GDH活性与GS活性相似。用外源IAA补充IAA减弱突变体时，共固定培养物中的GS活性与用微藻固定的野生型巴西固氮螺菌的GS活性相匹配。测量净GS活性时也出现了相似性，外源IAA量越大，相似性越高。有人提出，巴西固氮螺菌产生的IAA参与了普通小球藻对铵的吸收和随后的同化作用。
