Fig. 3: Screening, isolation, and regulation of key HGT donor bacteria in P. haitanensis and verification of their ability to enhance the thermal tolerance of thalli.

a Changes in the Chao1 and Shannon indices in water and thallus samples from the HS strain and HR strain under high-temperature conditions. T and W represent thallus and water samples, respectively, whereas C and H represent normal- and high-temperature treatments, respectively. b Relative abundance of the community composition (phylum) in the algal intermicrobial environment. c Venn diagram and heatmap illustrating the differences in the number and abundance of shared and unique bacteria between the thallus samples of the HS strain and HR strain. d Analysis of the composition of the macrogenomic community (phylum) and sample clusters. P represents the addition of Saccharothrix sp. e Analysis of the correlation between different treatments of intermicrobial microorganisms and HGT homologous genes. The thickness of the line segment represents the size of Mantel’s r. The color of the line segment represents the size of Mantel’s p, with red representing p < 0.01, green representing 0.01 < p < 0.05, and gray representing p ≥ 0.05; The color of the square represents the correlation between genes, with red indicating a positive correlation and blue indicating a negative correlation, and the size of the square reflects the magnitude of the correlation. HRH: HR strain; HSH: HS strain; PHSH: HS strain supplemented with Saccharothrix sp. “★” denotes actinomycetota as the candidate donors for these HGT genes. Gene abbreviations are provided in Supplementary Data 6f–i) Effects of the addition of proline (Pro) and Saccharothrix sp. (PHS) on the physiological and biochemical indices of the HS strain (CK) thallus under high-temperature conditions. Measurements include f relative growth rate, g maximum quantum yield (Fv/Fm), h superoxide dismutase (SOD) activity, and i free proline content.