Kobayashi Kazuo, Kurata Rie, Tohge Takayuki
Division of Biological Science, Graduate School of Science and Technology, Nara Institute of Science and Technology, 8916-5 Takayama-cho, Ikoma, Nara, 630-0192, Japan.
NAIST Life Science Collaboration Center (LiSCo), Graduate School of Science and Technology, Nara Institute of Science and Technology, 8916-5 Takayama-cho, Ikoma, Nara, 630-0192, Japan.
Nat Commun. 2025 Jul 1;16(1):5446. doi: 10.1038/s41467-025-60560-4.
Non-photosynthetic bacteria often respond to changes in light. These responses are usually regulated by photoreceptor proteins, but the mechanism of light response in biofilms is poorly understood. Here, we show that colony biofilms of Bacillus subtilis display light responses that are not dependent on typical photoreceptor proteins. Under light, B. subtilis biofilms do not mature and instead keep on expanding, resulting in thin, smooth colonies with low pigmentation. Similar effects have been previously observed upon inhibition of the biosynthesis or export of pulcherriminic acid, an iron chelator known to inhibit colony expansion by reducing extracellular iron levels. We show that light induces spontaneous degradation of pulcherriminic acid. In addition, Fe-bound pulcherriminic acid upregulates the yvmC operon (which is responsible for pulcherriminic acid biosynthesis) by inhibiting the binding of a repressor protein (PchR) to the yvmC promoter. Thus, the photosensitivity of pulcherriminic acid enables this metabolite to control iron availability, yvmC expression, and biofilm development in response to changes in light conditions.
非光合细菌常常对光照变化做出反应。这些反应通常由光感受器蛋白调控，但生物膜中光反应的机制却鲜为人知。在此，我们表明枯草芽孢杆菌的菌落生物膜表现出不依赖于典型光感受器蛋白的光反应。在光照下，枯草芽孢杆菌生物膜不会成熟，而是持续扩张，形成色素沉着低的薄而光滑的菌落。此前在抑制铁载体杆菌肽酸的生物合成或输出时也观察到了类似的效果，铁载体杆菌肽酸是一种已知通过降低细胞外铁水平来抑制菌落扩张的铁螯合剂。我们发现光照会诱导铁载体杆菌肽酸的自发降解。此外，与铁结合的铁载体杆菌肽酸通过抑制阻遏蛋白（PchR）与yvmC启动子的结合，上调yvmC操纵子（负责铁载体杆菌肽酸的生物合成）。因此，铁载体杆菌肽酸的光敏性使这种代谢物能够根据光照条件的变化来控制铁的可用性、yvmC的表达以及生物膜的发育。
