Department of Microbiology, Montana State University, Bozeman, Montana 59717.
Appl Environ Microbiol. 1988 Jul;54(7):1738-43. doi: 10.1128/aem.54.7.1738-1743.1988.
Photosynthesis by Synechococcus lividus, the sole oxygenic phototroph inhabiting the surface of the 55 degrees C cyanobacterial mat in Mushroom Spring, Yellowstone National Park, causes superoxic and alkaline conditions which promote glycolate photoexcretion. At O(2) concentrations characteristic of the top 2 mm of mat during the day, up to 11.8% of NaHCO(3) fixed in the light was excreted, and glycolate accounted for up to 58% of the excreted photosynthate. Glycolate was neither incorporated nor metabolized by S. lividus, but it was incorporated by filamentous microorganisms in the mat. Incubation of mat samples with NaHCO(3) resulted in labeling of both S. lividus and filaments, but the addition of nonradioactive glycolate increased the level of C in the aqueous phase and decreased the extent of labeling of filaments. This suggests that cross-feeding of glycolate from S. lividus to filamentous heterotrophs occurs and that underestimation of the extent of photoexcretion is probable.
绿硫菌是唯一栖息在黄石国家公园蘑菇泉 55°C 蓝藻垫表面的产氧光合作用生物，它的光合作用导致超氧和碱性条件，促进了甘醇酸的光分泌。在白天蓝藻垫顶层 2 毫米处的 O2 浓度特征下，高达 11.8%的固定在光中的 NaHCO3 被分泌出来，而甘醇酸占分泌的光合作用产物的 58%。绿硫菌既不摄取也不代谢甘醇酸，但它被垫中的丝状微生物摄取。用 NaHCO3 孵育垫样品导致绿硫菌和丝状微生物都被标记，但添加非放射性甘醇酸会增加水相中的 C 水平，并降低丝状微生物的标记程度。这表明甘醇酸从绿硫菌到丝状异养生物的交叉喂养确实存在，而且可能低估了光分泌的程度。
