Francisco J Choix1, Yoav Bashan2, Alberto Mendoza3, Luz E de-Bashan4. 1. Environmental Microbiology Group, Northwestern Center for Biological Research (CIBNOR), Av. Instituto Politécnico Nacional 195, Col. Playa Palo de Santa Rita Sur, La Paz, B.C.S. 23096, Mexico. 2. Environmental Microbiology Group, Northwestern Center for Biological Research (CIBNOR), Av. Instituto Politécnico Nacional 195, Col. Playa Palo de Santa Rita Sur, La Paz, B.C.S. 23096, Mexico; The Bashan Foundation, 3740 NW Harrison Boulevard, Corvallis, OR 97330, USA. 3. Centro de Biotecnología Genómica, Instituto Politécnico Nacional, Blvd. Del Maestro S/N, Col N. Mendoza, Reynosa, Tam. 88710, Mexico. 4. Environmental Microbiology Group, Northwestern Center for Biological Research (CIBNOR), Av. Instituto Politécnico Nacional 195, Col. Playa Palo de Santa Rita Sur, La Paz, B.C.S. 23096, Mexico; The Bashan Foundation, 3740 NW Harrison Boulevard, Corvallis, OR 97330, USA. Electronic address: luzb@cals.arizona.edu.
Abstract
ADP-glucose pyrophosphorylase (AGPase) regulates starch biosynthesis in higher plants and microalgae. This study measured the effect of the bacterium Azospirillum brasilense on AGPase activity in the freshwater microalga Chlorella vulgaris and formation of starch. This was done by immobilizing both microorganisms in alginate beads, either replete with or deprived of nitrogen or phosphorus and all under heterotrophic conditions, using d-glucose or Na-acetate as the carbon source. AGPase activity during the first 72h of incubation was higher in C. vulgaris when immobilized with A. brasilense. This happened simultaneously with higher starch accumulation and higher carbon uptake by the microalgae. Either carbon source had similar effects on enzyme activity and starch accumulation. Starvation either by N or P had the same pattern on AGPase activity and starch accumulation. Under replete conditions, the population of C. vulgaris immobilized alone was higher than when immobilized together, but under starvation conditions A. brasilense induced a larger population of C. vulgaris. In summary, adding A. brasilense enhanced AGPase activity, starch formation, and mitigation of stress in C. vulgaris.
ADP-glucose pyrophosphorylase (AGPase) regulates n class="Chemical">starch biosynthesis in n class="Species">higher plants and microalgae. This study measured the effect of the bacterium Azospirillum brasilense on AGPase activity in the freshwater microalga Chlorella vulgaris and formation of starch. This was done by immobilizing both microorganisms in alginate beads, either replete with or deprived of nitrogen or phosphorus and all under heterotrophic conditions, using d-glucose or Na-acetate as the carbon source. AGPase activity during the first 72h of incubation was higher in C. vulgaris when immobilized with A. brasilense. This happened simultaneously with higher starch accumulation and higher carbon uptake by the microalgae. Either carbon source had similar effects on enzyme activity and starch accumulation. Starvation either by N or P had the same pattern on AGPase activity and starch accumulation. Under replete conditions, the population of C. vulgaris immobilized alone was higher than when immobilized together, but under starvation conditions A. brasilense induced a larger population of C. vulgaris. In summary, adding A. brasilense enhanced AGPase activity, starch formation, and mitigation of stress in C. vulgaris.