Scientists find that mangrove seedlings inoculated with diesel-degrading bacteria are more tolerant to diesel contamination.
Diesel is an important driver of economic growth but also has negative impacts on estuarine ecosystems that are hard to ignore. In this regard, the potential of mangrove ecosystems for phytoremediation of diesel-contaminated soil remains unknown. Scientists have now found that Bacillus safensis-SH10, Sphingomonas sp.-LK11, Rhodococcus corynebacterioides-NZ1, and Bacillus subtilis-EP1 can significantly improve mangrove seedling tolerance to diesel contamination, opening the door for managing pollutants in estuarine ecosystems with bacterial-enhanced phytoremediation.
Soil bacteria can degrade diesel contaminants and mitigate oxidative stress.
Long-chain n-alkanes in diesel are damaging to plant growth. Scientists have found that augmenting mangrove seedlings with a bacterial inoculum can improve their tolerance to diesel contamination and overall growth.
Image credit: In-Jung Lee from Kyungpook National University
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Fostering beneficial relationships can pay dividends in the long run. In plant-microbe associations, relationships that impact ecosystems in the context of mitigating hydrocarbon pollutants are receiving plenty of attention. Diesel has a prominent role in propping up most economies. However, diesel contamination from spills poses a significant threat to many estuarine ecosystems. As a result of these spills, estuarine ecosystems face threats to soil aeration, infiltration, and permeability. These spills also take a heavy toll on mangroves and the ecosystem services they provide a habitat to live in and a sanctuary to breed for a diverse group of marine organisms.
While plant species like alfalfa harbor the capacity for hydrocarbon phytoremediation a process where plants decontaminate and detoxify the affected environment the potential for mangroves to do so remains untapped. However, research has shown that detoxifying diesel contaminants using microbial species in tandem with natural vegetation can be a viable approach to mitigating the effects of hydrocarbon pollution.
Recently, a group of researchers led by Professor In-Jung Lee from the Department of Applied Biosciences at Kyungpook National University, South Korea, and Professor Abdul Latif Khan from the Department of Engineering Technology at the University of Houston, USA, has identified a microbial consortium that degrades diesel components and improves mangrove growth in the presence of diesel contamination. Their findings were made available online on August 28, 2021, and published in the Journal of Hazardous Materials on February 05, 2022.
“The rhizosphere is the region in the immediate periphery of the root, and a plethora of microbial species reside here. We were keen to enhance the degradation of diesel contaminants by engineering the rhizosphere with specific bacterial species that could degrade the alkanes found in diesel and reprogram the host’s metabolism to bolster tolerance to the contamination,” says Prof. Lee.
The team first set out to identify bacteria capable of degrading diesel by isolating species from the rhizosphere and oil-contaminated soil. Following this screening, they narrowed down their analyses to Bacillus safensis-SH10, Sphingomonas sp.-LK11, Rhodococcus corynebacterioides-NZ1, and Bacillus subtilis-EP1. These bacteria rapidly degraded diesel into less harmful products. They also showed high expression of alkane monooxygenase, an enzyme that catalyzes the breakdown of n-alkanes.
When mangrove seedlings were treated with the bacteria and grown in the presence of diesel, SH10 was inherently more effective in improving the morphology, anatomy, and growth of the seedlings compared to the other strains.
The mangrove seedling defenses also exhibited an unexpected effect upon treatment with SH10-diesel inoculation. “On profiling the expression of anti-oxidative stress response genes and enzyme activities in the leaf, stem, and root, we found the mangrove seedlings had reprogrammed their metabolism. The inoculum reduced the expression and activity of the enzymes. This suggested that the hosts were exposed to less diesel-contamination-induced oxidative stress,” explains Prof. Lee.
Following treatment with SH10 and diesel, the researchers found that mangrove seedlings produced higher soil-enzyme activities and secreted essential metabolites in the rhizosphere. This observation reflected the positive effects of the plant-microbe association when challenging the host with the contaminant.
Prof. Lee foresees a bright future for research that aims to demystify such plant-microbe-contaminant interactions and believes it is the key to understanding pollutant detoxification, stabilization, and transformation in natural environments. In conclusion, he remarks, “In the not-too-distant future, we could see the widespread application of rhizosphere bacteria to reprogram host physiology in agriculture. With the extensive degradation of natural habitats, this strategy can ensure food safety and safeguard important crops.”
Reference
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Authors |
Abdul Latif Khana,b, Muhammad Numanc, Saqib Bilalb, Sajjad Asafb, Kerri Crafwordd, Muhammad Imrane, Ahmed Al-Harrasib, Jamal Nasser Al-Sabahif, Najeeb ur Rehmanb, Ahmed A-Rawahib, and In-Jung Leee,* |
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Title of original paper: |
Mangrove’s rhizospheric engineering with bacterial inoculation improve degradation of diesel contamination |
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Journal: |
Journal of Hazardous Materials |
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DOI: |
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Affiliations |
aNatural & Medical Sciences Research Center, University of Nizwa, 616, Oman eSchool of Applied Biosciences, Kyungpook National University, Daegu Korea, South Korea |
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Corresponding author’s email |
About Kyungpook National University
Kyungpook National University (KNU) is a national university located in Daegu, South Korea.
Founded in 1946, it is committed to becoming a leading global university based on its proud and lasting tradition of truth, pride, and service. As a comprehensive national university representing the regions of Daegu and Gyeongbuk Province, KNU has been striving to lead Korea’s national and international development by fostering talented graduates who can serve as global community leaders.
Website: https://en.knu.ac.kr/main/main.htm
About Prof. In-Jung Lee
Dr. In-Jung Lee is a senior Professor in the Department of Applied Biosciences at Kyungpook National University, South Korea. He earned his Ph.D. from Texas A&M University, USA. Prof. Lee researches plant physiology, and his team focuses on pioneering approaches to understand plant growth regulation, phytohormonal signaling, and plant-microbe interactions, particularly under stressful conditions. Professor Lee's research delves into the intricate roles of plant hormones in growth and development, especially in response to changing environmental factors. A key focus of his work is investigating how microorganisms can mitigate environmental stressors.
About Prof. Abdul Latif Khan
Dr. Abdul Latif Khan is an Assistant Professor of Plant Physiology and Genomics in the Department of Engineering Technology at the University of Houston, USA. He completed his postdoctoral training and earned a Ph.D. from Kyungpook National University, South Korea. Before coming to the University of Houston, he was an Assistant Professor at the University of Nizwa, Oman, where he gained experience with plant-microbe interactions and genomics. His group is developing approaches to studying plant-microbe interactions, gas exchange, and genomics of plants under stressful conditions.
About Prof. Ahmed Al-Harrasi
Dr. Al-Harrasi is a Professor at the Natural & Medical Sciences Research Center, University of Nizwa, Oman. He has obtained an MSc. and Ph.D. in Chemistry from the Free University of Berlin. He received the Fulbright award for postdoctoral research in Chemistry at Cornell University. His research group at the University of Nizwa, Oman, extensively works in plant and soil chemistry.
