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ORIGINAL RESEARCH article

Front. Microbiol.
Sec. Aquatic Microbiology
Volume 15 - 2024 | doi: 10.3389/fmicb.2024.1324188
This article is part of the Research Topic Women in Aquatic Microbiology: 2023 View all 17 articles

Estuarine mangrove niches select cultivable heterotrophic diazotrophs with diverse metabolic potentials -A prospective cross-dialogue for functional diazotrophy

Provisionally accepted
Sumana Mondal Sumana Mondal 1Biswajit Biswas Biswajit Biswas 1,2Rajojit Chowdhury Rajojit Chowdhury 1Rudranil Sengupta Rudranil Sengupta 1Anup Mandal Anup Mandal 1Hemendra N. Kotal Hemendra N. Kotal 1CHAYAN K. GIRI CHAYAN K. GIRI 1Subhajit Saha Subhajit Saha 1Mst Momtaj Begam Mst Momtaj Begam 1Chandan Mukherjee Chandan Mukherjee 1Ipsita Das Ipsita Das 1Sandip Kumar Basak Sandip Kumar Basak 3Mahasweta Mitra Ghosh Mahasweta Mitra Ghosh 2Krishna Ray Krishna Ray 1*
  • 1 West Bengal State University, Barasat, West Bengal, India
  • 2 St. Xavier's College, Kolkata, West Bengal, India
  • 3 Sarat Centenary College, Dhaniakhali, West Bengal, India

The final, formatted version of the article will be published soon.

    Biological nitrogen fixation (BNF), an unparalleled metabolic novelty among living microorganisms on earth, globally contributes ~88-101 Tg N year -1 to natural ecosystems, ~56% sourced from symbiotic BNF while ~22-45% derived from free-living nitrogen fixers (FLNF). The success of symbiotic BNF is largely dependent on its interaction with hostplant, however ubiquitous environmental heterotrophic FLNFs face many limitations in their immediate ecological niches to sustain unhindered BNF. The autotrophic FLNFs like cyanobacteria and oceanic heterotrophic diazotrophs have been well studied about their contrivances acclimated/adapted by these organisms to outwit the environmental constraints for functional diazotrophs. However, FLNF heterotrophs face more adversity in executing BNF under stressful estuarine/marine/aquatic habitats. In this study a large-scale cultivationdependent investigation was accomplished with 190 NCBI accessioned and 45 nonaccessioned heterotrophic FLNF cultivable bacterial isolates (total 235) from halophilic estuarine intertidal mangrove niches of Indian Sundarbans, a Ramsar site and UNESCO proclaimed World Heritage Site. Assuming ~1% culturability of the microbial community, the respective niches were also studied for representing actual bacterial diversity via cultivation-independent next-generation sequencing of V3-V4 rRNA regions. Both the studies revealed a higher abundance of culturable Gammaproteobacteria followed by Firmicutes, the majority of 235 FLNFs studied belonging to these two classes. The FLNFs displayed comparable selection potential in media for free nitrogen fixers and iron-oxidizing bacteria, linking diazotrophy with iron oxidation, siderophore production, phosphorus solubilization, phosphorus uptake and accumulation as well as denitrification. This observation validated the hypothesis that under extreme estuarine mangrove niches, diazotrophs are naturally selected as a specialized multidimensional entity, to expedite BNF and survive. Earlier metagenome data from mangrove niches demonstrated a microbial metabolic coupling among C, N, P, S, and Fe cycling in mangrove sediments, as an adaptive trait, evident with the co-abundant respective functional genes, which corroborates our findings in cultivation mode for multiple interrelated metabolic potential facilitating BNF in a challenging intertidal mangrove environment.

    Keywords: biological nitrogen fixation, Free-living heterotrophic diazotroph, Estuarine mangrove ecosystem, Indian Sundarbans, stringent narrow niche, multidimensional specialization

    Received: 19 Oct 2023; Accepted: 10 May 2024.

    Copyright: © 2024 Mondal, Biswas, Chowdhury, Sengupta, Mandal, Kotal, GIRI, Saha, Begam, Mukherjee, Das, Basak, Mitra Ghosh and Ray. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

    * Correspondence: Krishna Ray, West Bengal State University, Barasat, 700126, West Bengal, India

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