Whole cell affinity for 4-amino-5-hydroxymethyl-2-methylpyrimidine (HMP) in the marine bacterium Candidatus Pelagibacter st. HTCC7211 explains marine dissolved HMP concentrations

IF 3.6 4区 生物学 Q2 ENVIRONMENTAL SCIENCES
Elizabeth Brennan, Stephen Noell, Edward W. Davis II, Stephen J. Giovannoni, Christopher P. Suffridge
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引用次数: 0

Abstract

Vitamin B1 is a universally required coenzyme in carbon metabolism. However, most marine microorganisms lack the complete biosynthetic pathway for this compound and must acquire thiamin, or precursor molecules, from the dissolved pool. The most common version of Vitamin B1 auxotrophy is for thiamin's pyrimidine precursor moiety, 4-amino-5-hydroxymethyl-2-methylpyrimidine (HMP). Frequent HMP auxotrophy in plankton and vanishingly low dissolved concentrations (approximately 0.1–50 pM) suggest that high-affinity HMP uptake systems are responsible for maintaining low ambient HMP concentrations. We used tritium-labelled HMP to investigate HMP uptake mechanisms and kinetics in cell cultures of Candidatus Pelagibacter st. HTCC7211, a representative of the globally distributed and highly abundant SAR11 clade. A single protein, the sodium solute symporter ThiV, which is conserved across SAR11 genomes, is the likely candidate for HMP transport. Experimental evidence indicated transport specificity for HMP and mechanistically complex, high-affinity HMP uptake kinetics. Km values ranged from 9.5 pM to 1.2 nM and were dramatically lower when cells were supplied with a carbon source. These results suggest that HMP uptake in HTCC7211 is subject to complex regulation and point to a strategy for high-affinity uptake of this essential growth factor that can explain natural HMP levels in seawater.

Abstract Image

海洋细菌 Candidatus Pelagibacter st. HTCC7211 对 4-amino-5-hydroxymethyl-2-methylpyrimidine (HMP) 的全细胞亲和力解释了海洋溶解 HMP 的浓度。
维生素 B1 是碳代谢过程中普遍需要的辅酶。然而,大多数海洋微生物缺乏这种化合物的完整生物合成途径,必须从溶解池中获取硫胺素或前体分子。最常见的维生素 B1 辅酶是硫胺素的嘧啶前体分子--4-氨基-5-羟甲基-2-甲基嘧啶(HMP)。浮游生物中频繁出现的 HMP 辅助营养和极低的溶解浓度(约 0.1-50 pM)表明,高亲和力 HMP 吸收系统是维持低环境 HMP 浓度的原因。我们使用氚标记的 HMP 来研究全球分布的高含量 SAR11 支系的代表--天竺鹅膏菌 HTCC7211 的细胞培养物中 HMP 的吸收机制和动力学。在 SAR11 基因组中保持一致的单个蛋白质钠溶质合流体 ThiV 可能是 HMP 运输的候选蛋白。实验证据表明了 HMP 的转运特异性和机制复杂的高亲和性 HMP 吸收动力学。Km 值从 9.5 pM 到 1.2 nM 不等,当向细胞提供碳源时,Km 值显著降低。这些结果表明,HTCC7211 对 HMP 的摄取受到复杂的调控,并指出了一种高亲和力摄取这种重要生长因子的策略,可以解释海水中天然 HMP 水平的原因。
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来源期刊
Environmental Microbiology Reports
Environmental Microbiology Reports ENVIRONMENTAL SCIENCES-MICROBIOLOGY
CiteScore
6.00
自引率
3.00%
发文量
91
审稿时长
3.0 months
期刊介绍: The journal is identical in scope to Environmental Microbiology, shares the same editorial team and submission site, and will apply the same high level acceptance criteria. The two journals will be mutually supportive and evolve side-by-side. Environmental Microbiology Reports provides a high profile vehicle for publication of the most innovative, original and rigorous research in the field. The scope of the Journal encompasses the diversity of current research on microbial processes in the environment, microbial communities, interactions and evolution and includes, but is not limited to, the following: the structure, activities and communal behaviour of microbial communities microbial community genetics and evolutionary processes microbial symbioses, microbial interactions and interactions with plants, animals and abiotic factors microbes in the tree of life, microbial diversification and evolution population biology and clonal structure microbial metabolic and structural diversity microbial physiology, growth and survival microbes and surfaces, adhesion and biofouling responses to environmental signals and stress factors modelling and theory development pollution microbiology extremophiles and life in extreme and unusual little-explored habitats element cycles and biogeochemical processes, primary and secondary production microbes in a changing world, microbially-influenced global changes evolution and diversity of archaeal and bacterial viruses new technological developments in microbial ecology and evolution, in particular for the study of activities of microbial communities, non-culturable microorganisms and emerging pathogens.
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