Institute for Chemistry and Biology of the Marine Environment, University of Oldenburg, Carl von Ossietzky Str. 9-11, D-26129, Oldenburg, Germany.
Helmholtz Institute for Functional Marine Biodiversity at the University of Oldenburg (HIFMB), Ammerländer Heerstraße 231, D-26129, Oldenburg, Germany.
ISME J. 2022 Nov;16(11):2599-2609. doi: 10.1038/s41396-022-01304-w. Epub 2022 Aug 13.
Biotin (vitamin B) is involved in a wide range of essential biochemical reactions and a crucial micronutrient that is vital for many pro- and eukaryotic organisms. The few biotin measurements in the world's oceans show that availability is subject to strong fluctuations. Numerous marine microorganisms exhibit biotin auxotrophy and therefore rely on supply by other organisms. Desthiobiotin is the primary precursor of biotin and has recently been detected at concentrations similar to biotin in seawater. The last enzymatic reaction in the biotin biosynthetic pathway converts desthiobiotin to biotin via the biotin synthase (BioB). The role of desthiobiotin as a precursor of biotin synthesis in microbial systems, however, is largely unknown. Here we demonstrate experimentally that bacteria can overcome biotin auxotrophy if they retain the bioB gene and desthiobiotin is available. A genomic search of 1068 bacteria predicts that the biotin biosynthetic potential varies greatly among different phylogenetic groups and that 20% encode solely bioB and thus can potentially overcome biotin auxotrophy. Many Actino- and Alphaproteobacteria cannot synthesize biotin de novo, but some possess solely bioB, whereas the vast majority of Gammaproteobacteria and Flavobacteriia exhibit the last four crucial biotin synthesis genes. We detected high intra- and extracellular concentrations of the precursor relative to biotin in the prototrophic bacterium, Vibrio campbellii, with extracellular desthiobiotin reaching up to 1.09 ± 0.15*10 molecules per cell during exponential growth. Our results provide evidence for the ecological role of desthiobiotin as an escape route to overcome biotin auxotrophy for bacteria in the ocean and presumably in other ecosystems.
生物素（维生素 B）参与广泛的基本生化反应，是一种至关重要的微量营养素，对许多原核生物和真核生物都至关重要。世界海洋中的少数生物素测量结果表明，其可用性会发生剧烈波动。许多海洋微生物表现出生物素营养缺陷，因此依赖其他生物体提供。脱硫生物素是生物素的主要前体，最近在海水中的浓度与生物素相似。生物素生物合成途径中的最后一个酶反应通过生物素合酶（BioB）将脱硫生物素转化为生物素。然而，脱硫生物素作为微生物系统生物素合成前体的作用在很大程度上尚不清楚。在这里，我们通过实验证明，如果细菌保留 bioB 基因并且有脱硫生物素可用，它们就可以克服生物素营养缺陷。对 1068 种细菌的基因组搜索表明，生物素生物合成潜力在不同的系统发育群体中差异很大，其中 20%仅编码 bioB，因此有可能克服生物素营养缺陷。许多放线菌和α变形菌不能从头合成生物素，但有些仅拥有 bioB，而绝大多数γ变形菌和黄杆菌则具有最后四个关键的生物素合成基因。我们在原养型细菌弧菌属中检测到了相对于生物素而言前体的高细胞内和细胞外浓度，其中细胞外脱硫生物素在指数生长期可达到每细胞 1.09 ± 0.15*10 个分子。我们的结果为脱硫生物素作为一种逃避途径的生态作用提供了证据，以克服海洋中以及可能在其他生态系统中的细菌的生物素营养缺陷。
