Budamagunta Vivekananda, Shameem Nowsheen, Irusappan Sivaraj, Parray Javid A, Thomas Merin, Marimuthu Santhosh, Kirubakaran Rangasamy, Arul Jothi K N, Sayyed R Z, Show Pau Loke
Department of Genetic Engineering, SRM Institute of Science and Technology, Chennai, 603203, India.
Department of Environmental Science, Cluster University Srinagar 190001, India.
Environ Res. 2023 Feb 15;219:114997. doi: 10.1016/j.envres.2022.114997. Epub 2022 Dec 15.
Heavy metal toxicity affects aquatic plants and animals, disturbing biodiversity and ecological balance causing bioaccumulation of heavy metals. Industrialization and urbanization are inevitable in modern-day life, and control and detoxification methods need to be accorded to meet the hazardous environment. Microorganisms and plants have been widely used in the bioremediation of heavy metals. Sporosarcina pasteurii, a gram-positive bacterium that is widely known for its calcite precipitation property in bio-cementing applications has been explored in the study for its metal tolerance ability for the first time. S. pasteurii SRMNP1 (KF214757) can tolerate silver stress to form nanoparticles and can remediate multiple heavy metals to promote the growth of various plants. This astounding property of the isolate warranted extensive examinations to comprehend the physiological changes during an external heavy metal stress condition. The present study aimed to understand various physiological responses occurring in S. pasteuriiSRMNP1 during the metal tolerance phenomenon using electron microscopy. The isolate was subjected to heavy metal stress, and a transmission electron microscope examination was used to analyze the physiological changes in bacteria to evade the metal stress. S. pasteurii SRMNP1 was tolerant against a wide range of heavy metal ions and can withstand a broad pH range (5-9). Transmission Electron Microscopy (TEM) examination of S. pasteurii SRMNP1 followed by 5 mM nickel sulfate treatment revealed the presence of nanovesicles encapsulating nanosized particles in intra and extracellular spaces. This suggests that the bacteria evade the metal stress by converting the metal ions into nanosized particles and encapsulating them within nanovesicles to efflux them through the vesicle budding mechanism. Moreover, the TEM images revealed an excessive secretion of extracellular polymeric substances by the strain to discharge the metal particles outside the bacterial system. S. pasteurii can be foreseen as an effective bioremediation agent with the potential to produce nanosized particles, nanovesicles, and extracellular polymeric substances. This study provides physiological evidence that, besides calcium precipitation applications, S. pasteurii can further be explored for its multidimensional roles in the fields of drug delivery and environmental engineering.
重金属毒性会影响水生植物和动物，扰乱生物多样性和生态平衡，导致重金属生物累积。工业化和城市化在现代生活中不可避免，因此需要采取控制和解毒方法来应对危险环境。微生物和植物已被广泛用于重金属的生物修复。巴氏芽孢八叠球菌是一种革兰氏阳性菌，因其在生物胶结应用中的方解石沉淀特性而广为人知，本研究首次探索了其金属耐受能力。巴氏芽孢八叠球菌SRMNP1（KF214757）能够耐受银胁迫以形成纳米颗粒，并且能够修复多种重金属以促进各种植物的生长。该菌株的这一惊人特性值得进行广泛研究，以了解外部重金属胁迫条件下的生理变化。本研究旨在利用电子显微镜了解巴氏芽孢八叠球菌SRMNP1在金属耐受现象期间发生的各种生理反应。将该菌株置于重金属胁迫下，并使用透射电子显微镜检查来分析细菌为规避金属胁迫而发生的生理变化。巴氏芽孢八叠球菌SRMNP1对多种重金属离子具有耐受性，并且能够在较宽的pH范围（5 - 9）内生存。对经5 mM硫酸镍处理后的巴氏芽孢八叠球菌SRMNP1进行透射电子显微镜（TEM）检查，结果显示在细胞内和细胞外空间存在包裹着纳米尺寸颗粒的纳米囊泡。这表明细菌通过将金属离子转化为纳米尺寸颗粒并将其包裹在纳米囊泡中，通过囊泡出芽机制将它们排出细胞外，从而规避金属胁迫。此外，TEM图像显示该菌株会过量分泌细胞外聚合物，以将金属颗粒排出细菌系统之外。巴氏芽孢八叠球菌有望成为一种有效的生物修复剂，具有产生纳米颗粒、纳米囊泡和细胞外聚合物的潜力。本研究提供了生理学证据，表明除了钙沉淀应用外，巴氏芽孢八叠球菌在药物递送和环境工程领域的多维作用还有待进一步探索。
