Marine Ecology and Systematics (MarES), Department of Biology, University of the Balearic Islands, Palma, Spain.
Department of Infectious Diseases, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
Microb Ecol. 2022 Feb;83(2):296-313. doi: 10.1007/s00248-021-01766-z. Epub 2021 May 5.
Bacteria are essential in the maintenance and sustainment of marine environments (e.g., benthic systems), playing a key role in marine food webs and nutrient cycling. These microorganisms can live associated as epiphytic or endophytic populations with superior organisms with valuable ecological functions, e.g., seagrasses. Here, we isolated, identified, sequenced, and exposed two strains of the same species (i.e., identified as Cobetia sp.) from two different marine environments to different nutrient regimes using batch cultures: (1) Cobetia sp. UIB 001 from the endemic Mediterranean seagrass Posidonia oceanica and (2) Cobetia sp. 4B UA from the endemic Humboldt Current System (HCS) seagrass Heterozostera chilensis. From our physiological studies, both strains behaved as bacteria capable to cope with different nutrient and pH regimes, i.e., N, P, and Fe combined with different pH levels, both in long-term (12 days (d)) and short-term studies (4 d/96 h (h)). We showed that the isolated strains were sensitive to the N source (inorganic and organic) at low and high concentrations and low pH levels. Low availability of phosphorus (P) and Fe had a negative independent effect on growth, especially in the long-term studies. The strain UIB 001 showed a better adaptation to low nutrient concentrations, being a potential N-fixer, reaching higher growth rates (μ) than the HCS strain. P-acquisition mechanisms were deeply investigated at the enzymatic (i.e., alkaline phosphatase activity, APA) and structural level (e.g., alkaline phosphatase D, PhoD). Finally, these results were complemented with the study of biochemical markers, i.e., reactive oxygen species (ROS). In short, we present how ecological niches (i.e., MS and HCS) might determine, select, and modify the genomic and phenotypic features of the same bacterial species (i.e., Cobetia spp.) found in different marine environments, pointing to a direct correlation between adaptability and oligotrophy of seawater.
细菌在海洋环境（例如底栖系统）的维持和支撑中至关重要，它们在海洋食物网和营养循环中起着关键作用。这些微生物可以作为附生或内生种群与具有有价值生态功能的优势生物共存，例如海草。在这里，我们从两个不同的海洋环境中分离、鉴定、测序并暴露了两个相同物种（即鉴定为 Cobetia sp.）的菌株，使用批量培养方法，将它们置于不同的营养环境中：（1）来自特有地中海海草波西多尼亚海草的 Cobetia sp. UIB 001，（2）来自特有洪堡海流系统（HCS）海草异枝麒麟菜的 Cobetia sp. 4B UA。从我们的生理研究来看，这两个菌株都表现出能够适应不同营养物质和 pH 值环境的细菌特性，即在长期（12 天（d））和短期研究（4 d/96 h（h））中，N、P 和 Fe 与不同的 pH 值相结合。我们表明，分离的菌株对低浓度和高浓度以及低 pH 值下的氮源（无机和有机）敏感。低磷（P）和铁（Fe）的可用性对生长有负面影响，尤其是在长期研究中。菌株 UIB 001 对低营养浓度的适应能力更好，是潜在的固氮菌，比 HCS 菌株达到更高的生长率（μ）。我们深入研究了获取磷的机制，即在酶（即碱性磷酸酶活性，APA）和结构水平（例如碱性磷酸酶 D，PhoD）。最后，我们用生化标志物（即活性氧物质（ROS））研究补充了这些结果。总之，我们展示了生态位（即 MS 和 HCS）如何决定、选择和改变在不同海洋环境中发现的相同细菌物种（即 Cobetia spp.）的基因组和表型特征，指出了海水的适应性和贫营养性之间的直接相关性。
