The lectin family is composed of mono- and oligosaccharide binding proteins that could activate specific cellular activities, such as cell-cell attachment and toxin production. In the present study, the effect of the external addition of lectins to culture media containing the freshwater cyanobacterium Microcystis aeruginosa on its metabolic activities, such as iron uptake and toxin production was investigated. Among the three lectins examined in this study (concanavalin A [Con A], wheat germ agglutinin [WGA] and peanut agglutinin [PNA]), PNA substantially increased the accumulated intracellular and extracellular iron content. The binding of PNA and Con A to M. aeruginosa cells was visualized via fluorescence microscopy using a lectin adjunct with fluorescein isothiocyanate, and resulted in carbohydrate and protein accumulation in the cellular capsule. Given that the highest carbohydrate accumulation was seen in the Con A system (where iron accumulation was relatively lower), carbohydrate quality is likely important factor that influences cellular iron accumulation. Since PNA specifically binds to sugars such as galactose and N-acetylgalactosamine, these saccharide species could be important candidates for intracellular and extracellular iron accumulation and transport. Microcystin biosynthesis was stimulated in the presence of PNA and WGA, whereas cellular iron uptake increased only in the presence of PNA. Thus, the iron uptake was not necessarily congruent with the upregulation of microcystin synthesis, which suggested that the positive effect of lectin on iron uptake is probably attributable to the PNA-assisted iron accumulation around the cell surface. Overall, the present study provides insights into the interactions of lectin that influence cellular metabolic activities such as iron uptake, extracellular polymeric substance accumulation, and toxin production.

凝集素家族由单糖和寡糖结合蛋白组成，它们可以激活特定的细胞活性，例如细胞与细胞的结合和毒素的产生。在本研究中，研究了向含有淡水蓝藻微囊藻的培养基中外加凝集素对其代谢活性（如铁吸收和毒素产生）的影响。在这项研究中检查的三种凝集素（伴刀豆球蛋白A [Con A]，小麦胚芽凝集素[WGA]和花生凝集素[PNA]）中，PNA大大增加了细胞内和细胞外累积的铁含量。PNA和Con A与铜绿假单胞菌的结合通过使用凝集素与异硫氰酸荧光素的辅助物，通过荧光显微镜观察细胞，并导致碳水化合物和蛋白质在细胞膜中积聚。假设在Con A系统中观察到最高的碳水化合物积累（铁的积累相对较低），则碳水化合物的质量可能是影响细胞铁积累的重要因素。由于PNA与半乳糖和N-乙酰半乳糖等糖类特异性结合，因此这些糖类物质可能是细胞内和细胞外铁蓄积和运输的重要候选物。微囊藻毒素的生物合成在PNA和WGA存在的情况下被刺激，而细胞铁的摄取仅在PNA存在的情况下增加。因此，铁的摄取不一定与微囊藻毒素合成的上调一致，这表明凝集素对铁摄取的积极作用可能归因于PNA辅助的铁在细胞表面的蓄积。总的来说，本研究提供了凝集素相互作用影响细胞代谢活动（例如铁吸收，细胞外聚合物质积累和毒素产生）的见解。