Thermosynechococcus guangdongensis HY-01 sp. nov., a convenient easily transformable thermophilic chassis for photothermobiology

Abstract

This study describes the isolation and characterization of Thermosynechococcus guangdongensis HY-01, a novel thermophilic cyanobacterium developed as a microbial chassis for photothermobiology. The strain was isolated from a top stratum of a microbial mat collected at a geothermal area Tangjiaoqiaotou in Guangdong province of China. Its genome, sequenced using a hybrid approach, is the largest reported in the genus at 2.75 Mbp. The expansion of genome could be attributed to the presence of 180 unique genes, many acquired via horizontal gene transfer. These unique genes are often organised into genomic clusters, four of which are composed exclusively of HY-01-specific genes, including two implicated in exopolysaccharide biosynthesis. This genomic feature may contribute to the strain's ecological niche and physiological robustness. Strain delineation as a new species was performed based on the Botanical Code, encompassing 16S rRNA phylogeny, GTDB, Average Nucleotide and Amino Acid Identities together with morphological and habitat data. The polyphasic approach confirmed its status as a new species within the family. Morphologically and physiologically, HY-01 exhibited typical Thermosynechococcus characteristics. Growth profiling demonstrated robust performance across 37–57 °C, with peak at 52 °C and broad optimum between 47 and 57 °C. Critically, a simplified genetic transformation system based on electroporation was successfully established, achieving fully segregated transgenic lines within a fortnight, as validated by diagnostic PCR and protein immunoblotting of His-tagged photosystem I protein psaJ. We conclude that Thermosynechococcus guangdongensis HY-01 represents a genetically tractable and thermotolerant new species, expanding the portfolio of model organisms for studying thermostable photosynthesis and for developing high-temperature biotechnological applications.