| Congresso Brasileiro de Microbiologia 2023 | Resumo: 659-1 | ||||
Resumo:Phototropism is a behavior exhibited by plants and some fungi in response to light stimulus. This directional growth is related to a better light harvesting yield and occurs via hormone accumulation in eukaryotic cells. In prokaryotes, phototropism might happen when pigments act as photoreceptive structures, moving around the cytoplasm causing an osmotic pressure towards the light. Gliding motility and buoyancy in the water column can move cells closer to light sources or away from it, depending on the amount of photosynthetic active radiation (PAR). In order to evaluate if ten strains of cyanobacteria from diverse ecological backgrounds and with distinct morphologies display positive phototropism, a cage-like apparatus was constructed inside a Bio-Oxygen Demand (BOD) incubator, creating a unidirectional light flux. Each strain was inoculated in a marked area of a Petri dish with BG-11 solid medium and movement was monitored for 14 days. As expected, Geminocystis sp. CENA526, a unicellular strain, shown no motion while three of the filamentous strains tested (Arthrospira platensis CENA650, Pantanalinema rosanae CENA516 and Sphaerospermopsis torques-reginae ITEP-024) presented positive phototropism and considerable gliding skills, with an average speed of 3 mm.day-1. The remaining strains reached less than 35 mm during the complete experimental period and some displayed an erratic drift unrelated to phototropism. The results point to the idea that phototropism in cyanobacteria might be a species-specific strategy related to both motility capabilities and light demand. Filamentous strains isolated from shaded habitats (both Brasilonema strains CENA114 and UFV-OR1, from the Brazilian rainforest) showed less responses to directional light than others. Phototropism and photoprotective strategies in cyanobacteria seem to vary according to each strain, being related to specific genetic and morphophysiological traits. Palavras-chave: directional light, photosynthetic active light, photosynthesis, phototropism Agência de fomento: CNPq - Conselho Nacional de Desenvolvimento Científico e Tecnológico (140892/2020-6); FAPESP – Fundação de Amparo à Pesquisa do Estado de São Paulo (2016/14227-5) | |||||