Marasco Ramona, Michoud Grégoire, Sefrji Fatmah O, Fusi Marco, Antony Chakkiath P, Seferji Kholoud A, Barozzi Alan, Merlino Giuseppe, Daffonchio Daniele
Red Sea Research Center, Biological and Environmental Sciences and Engineering Division (BESE), King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia.
Front Microbiol. 2023 May 2;14:1155381. doi: 10.3389/fmicb.2023.1155381. eCollection 2023.
The geological isolation, lack of freshwater inputs and specific internal water circulations make the Red Sea one of the most extreme-and unique-oceans on the planet. Its high temperature, salinity and oligotrophy, along with the consistent input of hydrocarbons due to its geology (e.g., deep-sea vents) and high oil tankers traffic, create the conditions that can drive and influence the assembly of unique marine (micro)biomes that evolved to cope with these multiple stressors. We hypothesize that mangrove sediments, as a model-specific marine environment of the Red Sea, act as microbial hotspots/reservoirs of such diversity not yet explored and described.
To test our hypothesis, we combined oligotrophic media to mimic the Red Sea conditions and hydrocarbons as C-source (i.e., crude oil) with long incubation time to allow the cultivation of slow-growing environmentally (rare or uncommon) relevant bacteria.
This approach reveals the vast diversity of taxonomically novel microbial hydrocarbon degraders within a collection of a few hundred isolates. Among these isolates, we characterized a novel species, sp. nov., namely, Nit1536. It is an aerobic, heterotrophic, Gram-stain-negative bacterium with optimum growth at 37°C, 8 pH and 4% NaCl, whose genome and physiological analysis confirmed the adaptation to extreme and oligotrophic conditions of the Red Sea mangrove sediments. For instance, Nit1536 metabolizes different carbon substrates, including straight-chain alkanes and organic acids, and synthesizes compatible solutes to survive in salty mangrove sediments. Our results showed that the Red Sea represent a source of yet unknown novel hydrocarbon degraders adapted to extreme marine conditions, and their discovery and characterization deserve further effort to unlock their biotechnological potential.
地质隔离、缺乏淡水输入以及特定的内部水循环使得红海成为地球上最极端且独特的海洋之一。其高温、高盐度和贫营养状态，再加上由于地质原因（如深海热液喷口）以及油轮频繁通行导致的碳氢化合物持续输入，创造了能够驱动和影响独特海洋（微）生物群落组装的条件，这些生物群落经过进化以应对这些多重压力源。我们假设，作为红海特定模式的海洋环境，红树林沉积物是尚未被探索和描述的此类多样性的微生物热点/储存库。
为了验证我们的假设，我们将模拟红海条件的贫营养培养基与作为碳源的碳氢化合物（即原油）相结合，并延长培养时间，以培养生长缓慢的与环境相关（稀有或不常见）的细菌。
这种方法揭示了在几百个分离菌株中存在大量分类学上全新的微生物碳氢化合物降解菌。在这些分离菌株中，我们鉴定出一个新物种，即 sp. nov.，命名为Nit1536。它是一种需氧、异养、革兰氏染色阴性的细菌，在37°C、pH值为8和4%氯化钠的条件下生长最佳，其基因组和生理分析证实了它对红海红树林沉积物极端贫营养条件的适应性。例如，Nit1536能够代谢不同的碳底物，包括直链烷烃和有机酸，并合成相容性溶质以在含盐的红树林沉积物中生存。我们的结果表明，红海是适应极端海洋条件的未知新型碳氢化合物降解菌的来源，对它们的发现和鉴定值得进一步努力，以挖掘其生物技术潜力。
