High prevalence of antibiotic and heavy metal resistance genes found in Indian mangrove microbial ecosystem
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Mangroves are trees with high tolerance to saline environments. Hence, they flourish in coastal or brackish areas where most trees fail to grow. As a result, mangroves play a pivotal role in preserving the coastal ecosystem by acting as a physical barrier in the shoreline to prevent erosion. In addition, they have several benefits such as biodiversity, livelihood to the rural communities and water management. The Indian state of Kerala is a hotspot for mangrove tourism. The long coastline and brackish water serve as an ideal mangrove ecosystem. Mangroves cover up to 152,000 km2 globally. However, their range is decreasing due to pollution, urbanization and other human activities. There is an increasing urgency to understand the structural and functional architecture that underlies the mangrove ecosystem, and the microbial community is an important component that remains unexplored.
Two recent articles published in Nature Scientific Reports by a team of researchers from Central University of Kerala, Kasaragod, India; Institute of Integrative Omics and Applied Biotechnology (IIOAB), India; NITTE University Center for Science Education and Research, India; Universidade Federal de Minas Gerais Brazil; Virginia Commonwealth University and Virginia Tech University, USA, have shown that the mangrove ecosystem of Kerala harbors a rich reservoir of microbial communities distinct from other mangroves around the globe.
The research team also found a high prevalence of antibiotic resistance genes as well as heavy metal resistance genes in the Keralan Mangrove microbiome as compared to the Brazilian and Saudi Arabian mangrove microbial ecosystems. Increasing antibiotic resistance is a global health issue. However, the good news is that the antibiotic resistance genes found in these mangrove sediments, rather than resisting drugs, are involved in basic physiological functions needed to survive in the environment where they compete with a number of other microbes.
The negative aspect of this discovery is that such antibiotic resistance genes can have serious consequences if they “move” from non-harmful microbes to human pathogens through horizontal gene transfer. On the other hand, the heavy metal resistance genes of these microbial ecosystems can be wisely used in developing transgenic organisms towards bioremediation.
Further studies are currently being designed to evaluate the dissemination of such antibiotic resistance genes to pathogens. The rich microbial diversity is an addition to the myriad of benefits that mangroves provide to us. Unfortunately, the mangrove ecosystem is gradually being depleted around the globe due to urbanization and deforestation. Furthermore, household as well as industrial waste has made the mangrove ecosystem inhospitable to many species of migratory and shore birds, fish such as Mugil, Sciaena, Lates, Liza, Polynemus, Setipinna, and other aquatic animals such as Penaeus, Metapenaeus, Scylla serrata that are consumed as food. Hence, preservation of mangroves should be encouraged and maintained. In addition, research on fundamental science should be encouraged.
The study was funded by the Indian Science and Engineering Research Board (SERB). The works were led by Dr. Ranjith Kumavath from Central University of Kerala, Kasaragod, India and coordinated by Debmalya Barh from the Institute of Integrative Omics and Applied Biotechnology (IIOAB), and NITTE University Center for Science Education and Research, India.
From left: Dr. Ranjith Kumavath and Dr.
1. Imchen M, Kumavath R, Barh D, Azevedo V, Ghosh P, Viana M, Wattam AR. Searching for signatures across microbial communities: Metagenomic analysis of soil samples from mangrove and other ecosystems. Sci Rep. 2017 Aug 18;7(1):8859. https://www.ncbi.nlm.nih.gov/pubmed/28821820
2. Imchen M, Kumavath R, Barh D, Vaz A, Góes-Neto A, Tiwari S, Ghosh P, Wattam AR, Azevedo V. Comparative mangrove metagenome reveals global prevalence of heavy metals and antibiotic resistome across different ecosystems. Sci Rep. 2018 Jul 25;8(1):11187. https://www.ncbi.nlm.nih.gov/pubmed/30046123