Plasticidade morfológica de Cronbergia Amazonensis (Nostocales): respostas á adição de carbono e interação com macrófitas e desmonostoc Sp. (Nostocales)

Abstract

Cyanobacteria were the first organisms to perform oxygenic photosynthesis and, therefore, contributed to the great event of atmospheric oxygenation. They have great morphological and ecological plasticity and are found everywhere on the planet. Among the cyanobacteria, we highlight the heterocytous filamentous ones, with the ability to differentiate specialized cells that increase their adaptive plasticity, such as akinetes (cells that act as resistance spores) and heterocysts. Heterocysts are cells capable of performing biological nitrogen fixation (BNF) in situations of low nitrogen availability in the environment or imbalance in the carbon-nitrogen (C-N) ratio. Heterocytous filamentous cyanobacteria can establish relationships with macrophytes, such as epiphytic cyanobacteria, which adhere to the roots of these plants and provide fixed nitrogen, forming, together with other cyanobacteria and microalgae, part of the periphyton. The present study aimed to evaluate the effects of carbon addition to the medium and the interaction with different species of macrophytes (Pistia stratiotes and Salvinia auriculata), in addition to the presence of another heterocytous filamentous cyanobacteria, Desmonostoc sp., on the morphological plasticity of Cronbergia amazonensis. The addition of carbon in two concentrations (1% glucose and 3% glucose) did not increase the number of heterocysts produced in relation to the control, caused the detachment of heterocysts (non-functional) and decreased the number of heterocysts adhered to the filament, in addition to the production of akinetes, indicating that C. amazonensis was subjected to stress. However, although the cyanobacteria in the treatment with 3% glucose died after 10 days, in the treatment with 1% glucose, C. amazonensis grew again approximately 45 days after the end of the experiment, producing new filaments and evidencing its adaptive plasticity. In consortium with Desmonostoc sp., inoculated in the medium containing ramets of S. auriculata, C. amazonensis presented smaller filaments. In the consortium between Desmonostoc sp. and C. amazonensis inoculated in medium with P. stratiotes, both the number of heterocysts and the ratio between heterocysts and vegetative cells increased. In addition, C. amazonensis presented larger heterocysts in interaction with P. stratiotes, regardless of the presence or absence of another cyanobacteria. C. amazonensis presented morphological plasticity both with the addition of carbon in the medium and in the interaction with different macrophytes and with another cyanobacteria, demonstrating its adaptive capacity in the face of different environmental changes.