Photosynthetic efficiency and acid tolerance in Pumiliosphaera acidicola KMJ isolated from a geothermal spring in West Java, Indonesia
Abstract
Background: Acidophilic microalgae represent a promising yet underexplored resource for biotechnological carbon capture in low-pH environments such as geothermal springs and industrial effluents. However, few strains have been physiologically characterized, and most biotechnologically relevant microalgae remain neutrophilic.
Objective: This study aimed to isolate and characterize an acid-tolerant green microalga from a geothermal spring in Kamojang, West Java, Indonesia, and assess its growth, acid tolerance, and photosynthetic performance across a range of inorganic carbon (Ci: CO₂, HCO₃⁻, and CO₃²⁻) concentrations.
Methods: Mud samples were enriched in Allen medium under continuous illumination. Isolates were identified via 18S rRNA sequencing and phylogenetic analysis. Growth was tested across pH 2.3 to 7.0 in media acidified with either HCl or H₂SO₄. Photosynthetic performance was evaluated by O₂ evolution under various Ci concentrations.
Results: The isolated strain, designated Pumiliosphaera acidicola KMJ, exhibited robust growth from pH 2.3 to 7.0 and showed comparable tolerance to both HCl and H₂SO₄. Morphologically, KMJ displayed compact, spherical green cells (2–5 µm diameter). Oxygen evolution measurements revealed consistently higher photosynthetic rates than Chlamydomonas reinhardtii, particularly under sub-saturating Ci levels, indicating efficient CO₂ assimilation under acidic, low-Ci conditions. To our knowledge, this is the first study to directly quantify Ci-dependent O₂ evolution in an acidophilic chlorophyte.
Conclusion: P. acidicola KMJ combines broad acid tolerance with high photosynthetic efficiency, positioning it as a strong candidate for CO₂ capture in acidic environments. Its physiology also provides a basis for future molecular studies into acidophilic CO₂ assimilation.
References
Trends in Atmospheric Carbon Dioxide [Internet]. US Department of Commerce, National Oceanic and Atmospheric Administration. 2025 [cited May 18, 2025]. Available from: https://gml.noaa.gov/ccgg/trends/global.html.
Woolway RI, Sharma S, Smol JP. Lakes in Hot Water: The Impacts of a Changing Climate on Aquatic Ecosystems. Bioscience. 2022;72(11):1050-61. https://doi.org/10.1093/biosci/biac052.
Wrona FJ, Prowse TD, Reist JD, Hobbie JE, Lévesque LMJ, Vincent WF. Climate Change Effects on Aquatic Biota, Ecosystem Structure and Function. AMBIO: A Journal of the Human Environment. 2006;35(7):359-69, 11. doi: https://doi.org/10.1579/0044-7447(2006)35[359:CCEOAB]2.0.CO;2.
Field CB, Behrenfeld MJ, Randerson JT, Falkowski P. Primary Production of the Biosphere: Integrating Terrestrial and Oceanic Components. Science. 1998;281(5374):237-40. https://doi.org/doi:10.1126/science.281.5374.237.
Sayre R. Microalgae: The Potential for Carbon Capture. BioScience. 2010;60(9):722-7. https://doi.org/10.1525/bio.2010.60.9.9.
Zeng X, Danquah MK, Chen XD, Lu Y. Microalgae bioengineering: From CO2 fixation to biofuel production. Renewable and Sustainable Energy Reviews. 2011;15(6):3252-60. https://doi.org/10.1016/j.rser.2011.04.014.
de Morais MG, Costa JAV. Carbon dioxide fixation by Chlorella kessleri, C. vulgaris, Scenedesmus obliquus and Spirulina sp. cultivated in flasks and vertical tubular photobioreactors. Biotechnology Letters. 2007;29(9):1349-52. https://doi.org/10.1007/s10529-007-9394-6.
Qiu R, Gao S, Lopez PA, Ogden KL. Effects of pH on cell growth, lipid production and CO2 addition of microalgae Chlorella sorokiniana. Algal Research. 2017;28:192-9. https://doi.org/10.1016/j.algal.2017.11.004.
Zeebe RE, Wolf-Gladrow D. CO2 in Seawater: Equilibrium, Kinetics, Isotopes, Chapter 1 Equilibrium. In: Zeebe RE, Wolf-Gladrow D, editors. Elsevier Oceanography Series. 65: Elsevier; 2001. p. 1-84.
Trias R, Ménez B, le Campion P, Zivanovic Y, Lecourt L, Lecoeuvre A, et al. High reactivity of deep biota under anthropogenic CO2 injection into basalt. Nature Communications. 2017;8(1):1063. https://doi.org/10.1038/s41467-017-01288-8.
Hirooka S, Higuchi S, Uzuka A, Nozaki H, Miyagishima S-y. Acidophilic Green Alga Pseudochlorella sp. YKT1 Accumulates High Amount of Lipid Droplets under a Nitrogen-Depleted Condition at a Low-pH. PLOS ONE. 2014;9(9):e107702. https://doi.org/10.1371/journal.pone.0107702.
Dean AP, Hartley A, McIntosh OA, Smith A, Feord HK, Holmberg NH, et al. Metabolic adaptation of a Chlamydomonas acidophila strain isolated from acid mine drainage ponds with low eukaryotic diversity. Science of The Total Environment. 2019;647:75-87. https://doi.org/10.1016/j.scitotenv.2018.07.445.
Delmelle P, Bernard A. Geochemistry, mineralogy, and chemical modeling of the acid crater lake of Kawah Ijen Volcano, Indonesia. Geochimica et Cosmochimica Acta. 1994;58(11):2445-60. https://doi.org/10.1016/0016-7037(94)90023-X.
Aditiawati P, Yohandini H, Madayanti F, Akhmaloka. Microbial Diversity of Acidic Hot Spring (Kawah Hujan B) in Geothermal Field of Kamojang Area, West Java-Indonesia. The Open Microbiology Journal. 2009;3:121–8. https://doi.org/10.2174/1874285800903010058.
Allen MB. Studies with Cyanidium caldarium, an anomalously pigmented chlorophyte. Arch Mikrobiol. 1959;32(3):270-7. https://doi.org/10.1007/bf00409348.
Gross W, Schnarrenberger C. Heterotrophic Growth of Two Strains of the Acido-Thermophilic Red Alga Galdieria sulphuraria. Plant and Cell Physiology. 1995;36(4):633-8. https://doi.org/10.1093/oxfordjournals.pcp.a078803.
Chen CC, Bates R, Carlson J. Effect of environmental and cultural conditions on medium pH and explant growth performance of Douglas-fir ( Pseudotsuga menziesii) shoot cultures. F1000Res. 2014;3:298. https://doi.org/10.12688/f1000research.5919.2.
Kono A, Spalding MH. LCI1, a Chlamydomonas reinhardtii plasma membrane protein, functions in active CO2 uptake under low CO2. The Plant Journal. 2020;102(6):1127-41. doi: https://doi.org/10.1111/tpj.14761.
Cao M, Fu Y, Guo Y, Pan J. Chlamydomonas (Chlorophyceae) colony PCR. Protoplasma. 2009;235(1-4):107-10. https://doi.org/10.1007/s00709-009-0036-9.
Madeira F, Madhusoodanan N, Lee J, Eusebi A, Niewielska A, Tivey ARN, et al. The EMBL-EBI Job Dispatcher sequence analysis tools framework in 2024. Nucleic Acids Res. 2024;52(W1):W521-W5. https://doi.org/10.1093/nar/gkae241
Ronquist F, Teslenko M, van der Mark P, Ayres DL, Darling A, Höhna S, et al. MrBayes 3.2: Efficient Bayesian Phylogenetic Inference and Model Choice Across a Large Model Space. Systematic Biology. 2012;61(3):539-42. https://doi.org/10.1093/sysbio/sys029.
Rambaut A. FigTree v1.4.4. Institute of Evolutionary Biology, University of Edinburgh; 2009.
Gorman DS, Levine RP. Cytochrome f and plastocyanin: their sequence in the photosynthetic electron transport chain of Chlamydomonas reinhardi. Proc Natl Acad Sci U S A. 1965;54(6):1665-9. https://doi.org/10.1073/pnas.54.6.1665
Wintermans JFGM, De Mots A. Spectrophotometric characteristics of chlorophylls a and b and their phenophytins in ethanol. Biochimica et Biophysica Acta (BBA) - Biophysics including Photosynthesis. 1965;109(2):448-53. https://doi.org/10.1016/0926-6585(65)90170-6.
Darienko T, Pröschold T. Genetic variability and taxonomic revision of the genus Auxenochlorella (Shihira et Krauss) Kalina et Puncocharova (Trebouxiophyceae, Chlorophyta). Journal of Phycology. 2015;51(2):394-400. https://doi.org/10.1111/jpy.12279.
Li X, Hou Z, Xu C, Shi X, Yang L, Lewis LA, et al. Large Phylogenomic Data sets Reveal Deep Relationships and Trait Evolution in Chlorophyte Green Algae. Genome Biology and Evolution. 2021;13(7). https://doi.org/10.1093/gbe/evab101.
Johnson DB. Acidophilic algae isolated from mine-impacted environments and their roles in sustaining heterotrophic acidophiles. Frontiers in Microbiology. 2012;Volume 3 - 2012. https://doi.org/10.3389/fmicb.2012.00325.
Abiusi F, Trompetter E, Pollio A, Wijffels RH, Janssen M. Acid Tolerant and Acidophilic Microalgae: An Underexplored World of Biotechnological Opportunities. Frontiers in Microbiology. 2022;Volume 13 - 2022. https://doi.org/10.3389/fmicb.2022.820907.
Oesterhelt C, Schmälzlin E, Schmitt JM, Lokstein H. Regulation of photosynthesis in the unicellular acidophilic red alga Galdieria sulphuraria†. The Plant Journal. 2007;51(3):500-11. https://doi.org/10.1111/j.1365-313X.2007.03159.x.
Steensma AK, Shachar-Hill Y, Walker BJ. The carbon-concentrating mechanism of the extremophilic red microalga Cyanidioschyzon merolae. Photosynthesis Research. 2023;156(2):247-64. https://doi.org/10.1007/s11120-023-01000-6.
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