Laboratory of Anoxygenic Phototrophs, Institute of Microbiology of the Czech Acad Sci, Třeboň, Czechia.
mSystems. 2024 Sep 17;9(9):e0070624. doi: 10.1128/msystems.00706-24. Epub 2024 Aug 27.
The first phototrophic member of the bacterial phylum , AP64, received all its photosynthesis genes via distant horizontal gene transfer from a purple bacterium. Here, we investigated how these acquired genes, which are tightly controlled by oxygen and light in the ancestor, are integrated into the regulatory system of its new host. grew well under aerobic and semiaerobic conditions, with almost no difference in gene expression. Under aerobic conditions, the growth of was optimal at 80 µmol photon m s, while higher light intensities had an inhibitory effect. The transcriptome showed only a minimal response to the dark-light shift at optimal light intensity, while the exposure to a higher light intensity (200 µmol photon m s) induced already stronger but still transient changes in gene expression. Interestingly, a singlet oxygen defense was not activated under any conditions tested. Our results indicate that possesses neither the oxygen-dependent repression of photosynthesis genes known from purple bacteria nor the light-dependent repression described in aerobic anoxygenic phototrophs. Instead, has evolved as a low-light species preferring reduced oxygen concentrations. Under these conditions, the bacterium can safely employ its photoheterotrophic metabolism without the need for complex regulatory mechanisms.
Horizontal gene transfer is one of the main mechanisms by which bacteria acquire new genes. However, it represents only the first step as the transferred genes have also to be functionally and regulatory integrated into the recipient's cellular machinery. , a member of bacterial phylum Gemmatimonadota, acquired its photosynthesis genes via distant horizontal gene transfer from a purple bacterium. Thus, it represents a unique natural experiment, in which the entire package of photosynthesis genes was transplanted into a distant host. We show that lacks the regulation of photosynthesis gene expressions in response to oxygen concentration and light intensity that are common in purple bacteria. This restricts its growth to low-light habitats with reduced oxygen. Understanding the regulation of horizontally transferred genes is important not only for microbial evolution but also for synthetic biology and the engineering of novel organisms, as these rely on the successful integration of foreign genes.
细菌门 AP64 是第一个光合成员，它的所有光合作用基因都是通过与远缘的水平基因转移从紫色细菌获得的。在这里，我们研究了这些获得的基因是如何整合到其新宿主的调控系统中的，在其祖先中，这些基因受到氧和光的严格控制。 在好氧和兼性好氧条件下生长良好，基因表达几乎没有差异。在好氧条件下， 在 80 µmol 光子 m s 时生长最佳，而更高的光强度则具有抑制作用。在最佳光强下，转录组对暗-光转换的响应极小，而暴露于更高的光强（200 µmol 光子 m s）则会引起更强但仍然是短暂的基因表达变化。有趣的是，在任何测试条件下都没有激活单线态氧防御。我们的结果表明， 既没有紫色细菌中已知的依赖氧的光合作用基因抑制作用，也没有有氧厌氧光合生物中描述的光依赖性抑制作用。相反， 已经进化为喜欢低氧浓度的低光物种。在这些条件下，细菌可以安全地利用其光合作用异养代谢，而无需复杂的调节机制。
水平基因转移是细菌获得新基因的主要机制之一。然而，它只是第一步，因为转移的基因也必须在功能上和调控上整合到受体的细胞机制中。 Gemmatimonadota 门的成员 通过远缘水平基因转移从紫色细菌获得其光合作用基因。因此，它代表了一个独特的自然实验，其中整个光合作用基因包被移植到一个遥远的宿主中。我们表明， 缺乏对氧气浓度和光强度的光合作用基因表达的调节，这在紫色细菌中很常见。这限制了它在低氧环境中的生长。了解水平转移基因的调控不仅对微生物进化很重要，对合成生物学和新型生物的工程设计也很重要，因为这依赖于外源基因的成功整合。
