TY - JOUR A1 - Guljamow, Arthur A1 - Barchewitz, Tino A1 - Große, Rebecca A1 - Timm, Stefan A1 - Hagemann, Martin A1 - Dittmann, Elke T1 - Diel Variations of Extracellular Microcystin Influence the Subcellular Dynamics of RubisCO in Microcystis aeruginosa PCC 7806 JF - Microorganisms : open access journal N2 - The ubiquitous freshwater cyanobacterium Microcystis is remarkably successful, showing a high tolerance against fluctuations in environmental conditions. It frequently forms dense blooms which can accumulate significant amounts of the hepatotoxin microcystin, which plays an extracellular role as an infochemical but also acts intracellularly by interacting with proteins of the carbon metabolism, notably with the CO2 fixing enzyme RubisCO. Here we demonstrate a direct link between external microcystin and its intracellular targets. Monitoring liquid cultures of Microcystis in a diel experiment revealed fluctuations in the extracellular microcystin content that correlate with an increase in the binding of microcystin to intracellular proteins. Concomitantly, reversible relocation of RubisCO from the cytoplasm to the cell’s periphery was observed. These variations in RubisCO localization were especially pronounced with cultures grown at higher cell densities. We replicated these effects by adding microcystin externally to cultures grown under continuous light. Thus, we propose that microcystin may be part of a fast response to conditions of high light and low carbon that contribute to the metabolic flexibility and the success of Microcystis in the field. KW - cyanobacterial bloom KW - Microcystis KW - microcystin KW - RubisCO KW - extracellular signaling Y1 - 2021 U6 - https://doi.org/10.3390/microorganisms9061265 SN - 2076-2607 VL - 9 IS - 6 PB - MDPI CY - Basel ER - TY - JOUR A1 - Köker, Latife A1 - Akçaalan, Reyhan A1 - Dittmann, Elke A1 - Albay, Meriç T1 - Depth profiles of protein-bound microcystin in Küçükçekmece Lagoon JF - Toxicon : an international journal devoted to the exchange of knowledge on the poisons derived from the tissues of plants and animals ; official journal of the International Society on Toxinology N2 - Microcystis is the most commonly found toxic cyanobacterial genus around the world and has a negative impact on the ecosystem. As a predominant producer of the potent hepatotoxin microcystin (MC), the genus causes outbreaks in freshwaters worldwide. Standard analytical methods that are used for the detection of microcystin variants can only measure the free form of microcystin in cells. Since microcystin was found as free and proteinbound forms in the cells, a significant proportion of microcystin is underestimated with analytical methods. The aim of the study was to measure protein-bound microcystins and determine the environmental factors that affect the binding of microcystin to proteins. Samples were taken at depths of surface, 1 m, 5 m, 10 m, 15 m, and 18 m in Kucukcekmece Lagoon to analyze depth profiles of two different microcystin forms from June to September 2012 at regular monthly intervals. Our findings suggest that the most important parameter affecting proteinbound microcystin at surface water is high light. Due to favorable environmental conditions such as temperature, light, and physicochemical parameters, the higher microcystin contents, both free and protein-bound MCs, were found in summer periods. KW - Microcystis KW - Microcystin KW - Protein-bound microcystin KW - Mcy gene KW - Kucukcekmece Lagoon Y1 - 2021 U6 - https://doi.org/10.1016/j.toxicon.2021.05.005 SN - 0041-0101 SN - 1879-3150 VL - 198 SP - 156 EP - 163 PB - Elsevier CY - Oxford ER -