Global Centre for Environmental Remediation (GCER), College of Engineering, Science and Environment, The University of Newcastle, ATC Building, University Drive, Callaghan, NSW, 2308, Australia.
Cooperative Research Centre for Contamination Assessment and Remediation of Environment (CRC CARE), The University of Newcastle, ATC Building, Callaghan, NSW, 2308, Australia.
Microb Ecol. 2022 Apr;83(3):596-607. doi: 10.1007/s00248-021-01772-1. Epub 2021 Jun 16.
The importance of several factors that drive the symbiotic interactions between bacteria and microalgae in consortia has been well realised. However, the implication of extracellular polymeric substances (EPS) released by the partners remains unclear. Therefore, the present study focused on the influence of EPS in developing consortia of a bacterium, Variovorax paradoxus IS1, with a microalga, Tetradesmus obliquus IS2 or Coelastrella sp. IS3, all isolated from poultry slaughterhouse wastewater. The bacterium increased the specific growth rates of microalgal species significantly in the consortia by enhancing the uptake of nitrate (88‒99%) and phosphate (92‒95%) besides accumulating higher amounts of carbohydrates and proteins. The EPS obtained from exudates, collected from the bacterial or microalgal cultures, contained numerous phytohormones, vitamins, polysaccharides and amino acids that are likely involved in interspecies interactions. The addition of EPS obtained from V. paradoxus IS1 to the culture medium doubled the growth of both the microalgal strains. The EPS collected from T. obliquus IS2 significantly increased the growth of V. paradoxus IS1, but there was no apparent change in bacterial growth when it was cultured in the presence of EPS from Coelastrella sp. IS3. These observations indicate that the interaction between V. paradoxus IS1 and T. obliquus IS2 was mutualism, while commensalism was the interaction between the bacterial strain and Coelastrella sp. IS3. Our present findings thus, for the first time, unveil the EPS-induced symbiotic interactions among the partners involved in bacterial‒microalgal consortia.
几种驱动细菌和微藻在共生体中相互作用的因素的重要性已经得到很好的认识。然而，合作伙伴释放的细胞外聚合物物质 (EPS) 的影响仍然不清楚。因此，本研究集中于研究 EPS 在由从家禽屠宰废水分离的细菌 Variovorax paradoxus IS1 与微藻 Tetradesmus obliquus IS2 或 Coelastrella sp. IS3 形成的共生体中的影响。细菌通过增强硝酸盐（88-99%）和磷酸盐（92-95%）的吸收，显著提高了微藻物种在共生体中的比生长速率，同时积累了更多的碳水化合物和蛋白质。从细菌或微藻培养物中收集的分泌物中获得的 EPS 含有许多植物激素、维生素、多糖和氨基酸，这些物质可能参与种间相互作用。将从 V. paradoxus IS1 中获得的 EPS 添加到培养基中，使两种微藻的生长增加了一倍。从 T. obliquus IS2 中收集的 EPS 显著增加了 V. paradoxus IS1 的生长，但当它在 Coelastrella sp. IS3 的 EPS 存在下培养时，细菌的生长没有明显变化。这些观察结果表明，V. paradoxus IS1 和 T. obliquus IS2 之间的相互作用是互利共生，而细菌菌株与 Coelastrella sp. IS3 之间的相互作用是共生关系。因此，我们目前的发现首次揭示了细菌-微藻共生体中参与共生体的 EPS 诱导的共生相互作用。
