The pH tolerance range of the airborne species Tetracystis vinatzeri (Chlorophyceae, Chlamydomonadales)

ABSTRACTTo decipher the dispersal range of the cosmopolitan green microalga Tetracystis vinatzeri, two airborne-collected strains were barcoded using the 18S ribosomal DNA gene (18S) and the mitochondrial cytochrome c oxidase I subunit (COI), and their survival capacities were investigated across a stepwise acidic to alkaline pH gradient. Genetic fingerprinting confirmed the identity of the strains as representing the same biological species. Investigations of the tolerance of T. vinatzeri to pH levels refined the delimitation of its ecological niche. T. vinatzeri showed optimal growth in freshwater habitats at pH 4.3–9.6 and strains could cope with exposure to slightly more acidic (down to 3.8) and alkaline (up to 10.4) conditions. However, organismal survival was drastically affected by exposure to pH < 3 and > 11. Morphological observations showed that T. vinatzeri could better cope with exposure to acidic pH, exhibiting less cell membrane damage. Genetic analysis showed that the two airborne strains shared the same haplotype, suggesting that they either originated from the same air mass or that the haplotype has a widespread distribution. Further phylogeographic and physiological investigations are required to define the spreading dynamic of T. vinatzeri.Highlights Tetracystis vinatzeri can grow at pH from 3.8–10.4.Strains from different habitats showed sexual compatibility.Low genetic diversity and cosmopolitan distribution suggest widespread dispersal.KEYWORDS: Chlorophyceaedispersalecologymicroalgaesurvival AcknowledgementsFlow cytometry was performed at the FACS Core Facility, Aarhus University, Denmark. The authors are grateful to A. Champeau for proofreading the manuscript.Disclosure statementNo potential conflict of interest was reported by the author(s).Supplementary informationThe following supplementary material is accessible via the Supplementary Content tab on the article’s online page at https://doi.org/10.1080/09670262.2023.2260444Supplementary fig. S1. Pigment profile of Tetracystis vinatzeri for chlorophyll and the phycobilins (phycoerythrin and allophycocyanin).Supplementary fig. S2. Cell signal distribution for chlorophyll pigment and size fraction,distributed by pH category: acid (A, pH 1-4), neutral (B, pH 7-9), and basic (C, pH 10-13).Positive signal for chlorophylls (red) and propidium iodide (blue, dead cells).Author contributionsS. Tesson: original concept, culture experiment, data analysis, drafting and editing manuscript; S. Sildever: molecular data, editing manuscript.Data availability statementGenetic sequences are available in GenBank for both 18S (OQ402668-OQ402669) and COI (OQ412808-OQ412809) markers. S3MWC-21 and S3MWC-29 strains are deposited at the Norwegian Culture Collection of Algae (NIVA-CHL 196 and NIVA-CHL 197).Additional informationFundingThis research and S.T. are funded by the European Union’s Horizon 2020 Research and Innovation Programme under the Marie Skłodowska-Curie grant agreement no. [754513] and The Aarhus University Research Foundation. S.S. is funded by the Estonian Research Council grant [PSG735].