Biotin (vitamin B₇) 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*10⁶ 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 ₇) 参与广泛的基本生化反应和对许多亲核生物和真核生物至关重要的重要微量营养素。世界海洋中为数不多的生物素测量表明，可用性会受到强烈波动的影响。许多海洋微生物表现出生物素营养缺陷，因此依赖于其他生物的供应。脱硫生物素是生物素的主要前体，最近在海水中检测到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促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中生物素合成前体的作用在很大程度上是未知的。在这里，我们通过实验证明，如果细菌保留bioB ，它们可以克服生物素营养缺陷。基因和脱硫生物素可用。对 1068 种细菌的基因组搜索预测，生物素生物合成潜力在不同的系统发育群体之间差异很大，20% 只编码bioB，因此有可能克服生物素营养缺陷。许多Actino - 和Alphaproteobacteria不能从头合成生物素，但有些仅具有bioB，而绝大多数Gammaproteobacteria和Flavobacteriia表现出最后四个关键的生物素合成基因。我们在原养细菌坎贝氏弧菌中检测到相对于生物素的前体细胞内和细胞外浓度较高，在指数生长期间，细胞外脱硫生物素达到每个细胞高达 1.09 ± 0.15*10 ^{6 个分子。}我们的结果为脱硫生物素的生态作用提供了证据，证明它是克服海洋和其他生态系统中细菌生物素营养缺陷的逃生途径。