AZTI, Marine Research Division, Txatxarramendi Irla s/n, 48395 Sukarrieta, Spain.
AZTI, Food Research Division, Astondo Bidea, Building 609, 48160 Derio, Spain.
Mar Drugs. 2020 Feb 1;18(2):99. doi: 10.3390/md18020099.
Omega-3 long-chain polyunsaturated fatty acids (LC-PUFAs), such as eicosapentaenoic acid (EPA) (20:5n-3) and docosahexaenoic acid (DHA) (22:6n-3), are considered essential for human health. Microorganisms are the primary producers of omega-3 fatty acids in marine ecosystems, representing a sustainable source of these lipids, as an alternative to the fish industry. Some marine bacteria can produce LC-PUFAs de novo via the Polyunsaturated Fatty Acid ( synthase/ Polyketide Synthase (PKS) pathway, which does not require desaturation and elongation of saturated fatty acids. Cultivation-independent surveys have revealed that the diversity of microorganisms harboring a molecular marker of the gene cluster (i.e., A-KS domain) is high and their potential distribution in marine systems is widespread, from surface seawater to sediments. However, the isolation of PUFA producers from marine waters has been typically restricted to deep or cold environments. Here, we report a phenotypic and genotypic screening for the identification of omega-3 fatty acid producers in free-living bacterial strains isolated from 5, 500, and 1000 m deep coastal seawater from the Bay of Biscay (Spain). We further measured EPA production in pelagic sp. strains collected at the three different depths. sp. EPA-producers and non-producers were simultaneously isolated from the same water samples and shared a high percentage of identity in their 16S rRNA genes, supporting the view that the gene cluster can be horizontally transferred. Within a cluster of EPA-producers, we found intraspecific variation in the levels of EPA synthesis for isolates harboring different genetic variants of the A-KS domain. The maximum production of EPA was found in a sp. strain isolated from a 1000 m depth (average 4.29% ± 1.07 of total fatty acids at 10 °C, without any optimization of culturing conditions).
ω-3 长链多不饱和脂肪酸（LC-PUFAs），如二十碳五烯酸（EPA）（20:5n-3）和二十二碳六烯酸（DHA）（22:6n-3），被认为对人类健康至关重要。微生物是海洋生态系统中ω-3 脂肪酸的主要生产者，是这些脂质的可持续来源，可作为鱼类产业的替代品。一些海洋细菌可以通过多不饱和脂肪酸（synthase/Polyketide Synthase（PKS）途径从头合成 LC-PUFAs，该途径不需要饱和脂肪酸的去饱和和延伸。非培养调查显示，携带基因簇分子标记（即 A-KS 结构域）的微生物多样性很高，其在海洋系统中的潜在分布广泛，从表层海水到沉积物。然而，从海洋水中分离 PUFA 生产者通常仅限于深海或寒冷环境。在这里，我们报告了一种表型和基因型筛选方法，用于从比斯开湾（西班牙）5、500 和 1000 米深的沿海海水中分离的自由生活细菌菌株中鉴定 ω-3 脂肪酸生产者。我们进一步测量了在三个不同深度采集的浮游 sp.菌株的 EPA 产量。从同一水样中同时分离出 EPA 生产者和非生产者，并在其 16S rRNA 基因中具有很高的同源性，支持基因簇可以水平转移的观点。在一组 EPA 生产者中，我们发现携带 A-KS 结构域不同遗传变异的分离株中 EPA 合成水平存在种内变异。在从 1000 米深度分离的一株 sp.菌株中发现 EPA 的最大产量（在 10°C 时，不优化培养条件下，平均总脂肪酸的 4.29%±1.07）。
