Cultivation, isolation and characterisation of thermophilic and acidophilic red algae, Cyanidiales.

Abstract

Cyanidiales is the oldest extant order of the red alga, which diverged from the ancestral lineage of Rhodaphyta approximately 1.4 billion years ago. These asexual, unicellular microalgae are thermophilic and acidophilic, making them unique among all known photosynthetic micro-organisms. These species grow in geothermal streams and soils, at acidities below pH 3.0 and at temperatures exceeding 45°C. This unique physiology means that Cyanidiales have the potential for a variety of biotechnological applications, from pigment production to bioremediation of wastewater. Cyanidiales are found at geothermal sites globally, including New Zealand. However, the diversity and taxonomy of the New Zealand Cyanidiales population has been understudied. In this MSc thesis, Cyanidiales were sampled and isolated from New Zealand geothermal sites in the Taupō Volcanic Zone. Once isolated genetic, morphological and physiological data was gathered in order to describe the strains and resolve taxonomy. The physiological characterisation involved determining the temperature range and the pH range of the isolates, as well as carbon and nitrogen source utilization of these isolates. The chemotaxonomic characterisation involved determining the fatty acid profile and polar lipid profile of the isolates. Additionally, to resolve the taxonomy of Cyanidiales, five genes will be sequenced which are four conserved plastid genes; psaA (photosystem I P700 chlorophyll a apoprotein A1), psbA (photosystem II reaction center protein D1), rbcL (RUBISCO Large subunit), 16S rRNA gene, and one nuclear gene, the 18S rRNA gene. In total, 10 Cyanidiales representatives were isolated and, with the combination of phenotypic and genetic data, it was determined that the isolates represent three lineages. These three lineages included One Galdieria maxima lineage from Russia, as well as two Galdieria sulphuraria lineages from a European lineage and an American lineage. The European G. sulphuraria lineage had not been observed before in New Zealand, which as such is significant as it indicates that the New Zealand Cyanidiales population is more diverse than previous evidence suggested, despite the geographic isolate of New Zealand. This is strong evidence for multiple Cyanidiales colonization events to NZ and a long-distance dispersal mechanism that is yet to be described. The NZ G. maxima strain is also significant as genetic data indicates the closest described relative is G. maxima IPPAS P507, however the morphological, physiological and biochemical characteristics of the strain are closer to Cyanidium caldarium and Cyanidioschyzon merolae. Therefore, these strains are an evolutionary link and an opportunity to revise the nomenclature and the taxonomy. Additionally, this MSc thesis is part of a research program into the development of a proposed photobioreactor that will use New Zealand native Cyanidiales and extremophilic methanotrophs strains in consortium, to sequester the carbon emissions from flue gas. In a desktop assessment, using data from both the literature and this thesis, it was determined that the NZ G.maxima strain is the most suitable for application in the proposed bioreactor. In summary, the data from this MSc thesis contributes to understanding of the dispersal, diversity and evolution of Cyanidiales, both in New Zealand and globally. The characterised NZ Cyanidiales are also an asset to the research and development of New Zealand biotechnologies.