Abstract
Ultraviolet A (UV-A) is the major component of UV radiation reaching the Earth’s surface, causing indirect damage to photosynthetic organisms via the production of reactive oxygen species (ROS). In comparison, UV-B causes both direct damage to biomolecules and indirect damage. UV-B is well studied in cyanobacterial research due to their long evolutionary history and adaptation to high levels of UV, with less work on the effects of UV-A. In this study, the response of key metabolites in Chlorogloeopsis fritschii (C. fritschii) during 48 h of photosynthetically active radiation (PAR, 15 µmol·m−2·s−1) supplemented with UV-A (11 µmol·m−2·s−1) was investigated using gas chromatography- mass spectrometry (GC-MS). Results showed an overall significant increase in metabolite levels up to 24 h of UV-A exposure. Compared with previously reported UV-B (PAR + UV-B) and PAR only results, UV-A showed more similarity compared to PAR only exposure as opposed to supplemented UV-B. The amino acids glutamate, phenylalanine and leucine showed differences in levels between UV (both supplemented UV-A and supplemented UV-B) and PAR only (non-supplemented PAR), hinting to their relevance in UV stress response. The fatty acids, palmitic and stearic acid, showed positive log2 fold-change (FC) in supplemented UV-A and PAR only experiments but negative log2 FC in UV-B, indicating the more harmful effect of UV-B on primary metabolism. Less research has been conducted on UV-A exposure and cyanobacteria, a potential environmental stimuli for the optimisation of metabolites for industrial biotechnology. This study will add to the literature and knowledge on UV-A stress response at the metabolite level in cyanobacteria, especially within the less well-known species C. fritschii.
Highlights
Introduction iationsCyanobacteria are known to survive in extreme environments and have adaptive mechanisms to cope with these conditions due to their evolution over 3.5 billion years [1].During this time, they have been exposed to an array of abiotic factors such as an absence of the ozone layer in the Precambrian era, which led to the adaptation to high solar ultraviolet (UV) radiation [2]
Intracellular metabolite levels within C. fritschii were investigated during 48 h of Ultraviolet A (UV-A) exposure using gas chromatography- mass spectrometry (GC-MS) analysis
The effect of UV-B on cyanobacteria is widely researched compared to the effect of UV-A
Summary
Cyanobacteria are known to survive in extreme environments and have adaptive mechanisms to cope with these conditions due to their evolution over 3.5 billion years [1]. During this time, they have been exposed to an array of abiotic factors such as an absence of the ozone layer in the Precambrian era, which led to the adaptation to high solar ultraviolet (UV) radiation [2]. Sunlight reaching the Earth’s surface (terrestrial and marine environments) consists of UV-A (315–400 nm), UV-B (280–315 nm), photosynthetically active radiation (PAR, 400–700 nm) and infrared radiation (IR, >700 nm). UV-A differs from UV-B as it has a longer wavelength and is, lower in energy; unlike UV-B, it does not directly damage cells by reacting with biomolecules such as DNA
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