Different Elemental Compositions and Potential Functions of Vacuoles in Bolivina spissa (Foraminifera, Rhizaria) Based on Cryo-SEM-EDS Analyses

IF 2.6 4区 生物学 Q3 MICROBIOLOGY
Julien Richirt, Satoshi Okada, Yoshiyuki Ishitani, Nicolaas Glock, Katsuyuki Uematsu, Hidetaka Nomaki
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引用次数: 0

Abstract

Benthic Foraminifera exhibit diverse adaptations to low oxygen (O2) environments, including denitrification, a rare trait among eukaryotes. Denitrifying species store intracellular nitrate (NO3), possibly within vacuoles, and contribute significantly to the global marine nitrogen (N) cycle. Additionally, widespread phosphate (PO43−) accumulation suggests a role in supporting metabolism under O2-depleted conditions. However, the organelles storing NO3 and PO43− remain unknown, limiting the mechanistic understanding of these alternative metabolic pathways. To investigate the intracellular NO3 and PO43− localization in the benthic foraminifera Bolivina spissa, experimental incubations under varying O2 and NO3 conditions followed by cryogenic fixation and scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) analyses were carried out. Most vacuoles were enriched in N relative to the surrounding cytoplasm, likely representing the intracellular NO3 reservoir. The elemental mapping also confirmed phosphorus (P) enrichment in organelles resembling acidocalcisomes, likely as PO43−, which may serve as a readily available energy source used over NO3 storage during the transition between aerobic and anaerobic respiration. Additionally, barium-rich vacuoles of unknown function(s) display a unique spatial distribution. This study emphasizes the effectiveness of cryogenic techniques in elucidating metabolic processes in foraminifers and other large and/or testate unicellular organisms, particularly for studying soluble compounds that have rarely been investigated.

Abstract Image

基于冷冻扫描电镜-能谱(sem - eds)分析的有孔虫根瘤菌液泡不同元素组成及势功能
底栖有孔虫表现出对低氧(O2)环境的多种适应,包括反硝化,这是真核生物中罕见的特征。反硝化物种在细胞内(可能在液泡内)储存硝酸盐(NO3−),并对全球海洋氮(N)循环做出重要贡献。此外,广泛存在的磷酸(PO43−)积累表明在缺氧条件下支持代谢的作用。然而,储存NO3 -和PO43 -的细胞器仍然未知,限制了对这些替代代谢途径的机制理解。为了研究底栖有孔虫Bolivina spissa细胞内NO3 -和PO43 -的定位,在不同的O2和NO3 -条件下进行了实验培养,然后进行了低温固定和扫描电子显微镜-能量色散光谱(SEM-EDS)分析。大多数液泡相对于周围的细胞质富含氮,可能代表细胞内NO3 -库。元素映射还证实了磷(P)富集在类似酸钙体的细胞器中,可能是PO43−,在有氧呼吸和厌氧呼吸之间的过渡期间,PO43−可能作为一种容易获得的能量来源,用于NO3−的储存。此外,功能未知的富钡液泡具有独特的空间分布。这项研究强调了低温技术在阐明有孔虫和其他大型和/或雄性单细胞生物代谢过程中的有效性,特别是在研究很少被研究的可溶性化合物方面。
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来源期刊
CiteScore
4.30
自引率
4.50%
发文量
85
审稿时长
6-12 weeks
期刊介绍: The Journal of Eukaryotic Microbiology publishes original research on protists, including lower algae and fungi. Articles are published covering all aspects of these organisms, including their behavior, biochemistry, cell biology, chemotherapy, development, ecology, evolution, genetics, molecular biology, morphogenetics, parasitology, systematics, and ultrastructure.
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