Claudi Riccardo, Alei Eleonora, Battistuzzi Mariano, Cocola Lorenzo, Erculiani Marco Sergio, Pozzer Anna Caterina, Salasnich Bernardo, Simionato Diana, Squicciarini Vito, Poletto Luca, La Rocca Nicoletta
Osservatorio Astronomico di Padova, INAF, 35122 Padova, Italy.
Institute for Particle Physics and Astrophysics, ETH Zurich, 8093 Zurich, Switzerland.
Life (Basel). 2020 Dec 24;11(1):10. doi: 10.3390/life11010010.
In a few years, space telescopes will investigate our Galaxy to detect evidence of life, mainly by observing rocky planets. In the last decade, the observation of exoplanet atmospheres and the theoretical works on biosignature gasses have experienced a considerable acceleration. The most attractive feature of the realm of exoplanets is that 40% of M dwarfs host super-Earths with a minimum mass between 1 and 30 Earth masses, orbital periods shorter than 50 days, and radii between those of the Earth and Neptune (1-3.8 R⊕). Moreover, the recent finding of cyanobacteria able to use far-red (FR) light for oxygenic photosynthesis due to the synthesis of chlorophylls and , extending in vivo light absorption up to 750 nm, suggests the possibility of exotic photosynthesis in planets around M dwarfs. Using innovative laboratory instrumentation, we exposed different cyanobacteria to an M dwarf star simulated irradiation, comparing their responses to those under solar and FR simulated lights. As expected, in FR light, only the cyanobacteria able to synthesize chlorophyll and could grow. Surprisingly, all strains, both able or unable to use FR light, grew and photosynthesized under the M dwarf generated spectrum in a similar way to the solar light and much more efficiently than under the FR one. Our findings highlight the importance of simulating both the visible and FR light components of an M dwarf spectrum to correctly evaluate the photosynthetic performances of oxygenic organisms exposed under such an exotic light condition.
在未来几年内，太空望远镜将对我们的星系进行探测，以寻找生命迹象，主要是通过观测岩石行星来实现。在过去十年中，系外行星大气观测以及生物特征气体的理论研究取得了显著进展。系外行星领域最吸引人的特点是，40%的M型矮星拥有超级地球，其最小质量在1至30个地球质量之间，轨道周期短于50天，半径介于地球和海王星之间（1 - 3.8 R⊕）。此外，最近发现的蓝细菌能够利用远红光（FR）进行有氧光合作用，这是由于合成了叶绿素f和叶绿素g，使得体内光吸收范围扩展至750纳米，这表明在M型矮星周围的行星上可能存在奇异的光合作用。我们使用创新的实验室仪器，将不同的蓝细菌暴露于模拟的M型矮星辐射下，比较它们与在太阳光和FR模拟光下的反应。正如预期的那样，在FR光下，只有能够合成叶绿素f和叶绿素g的蓝细菌能够生长。令人惊讶的是，所有菌株，无论能否利用FR光，在M型矮星产生的光谱下都能生长并进行光合作用，其方式与太阳光下相似，且比在FR光下更高效。我们的研究结果强调了模拟M型矮星光谱的可见光和FR光成分对于正确评估在这种奇异光照条件下暴露的有氧生物光合性能的重要性。
