Ammonifying and phosphorus-solubilizing function of Aliikangiella maris sp. nov. isolated from Phaeocystis globosa blooms and algal-bacterial interaction

Fei Li ^1,2* Ming-Ben Xu ^2* Liang-Hao Pan ^3* Jie LI ² Cai-Bi Lan ^2* Zhe Li ^2* Shan Lu ¹ Jun-Xiang Lai ^2,4* Peng-Fu Li ^1*

• ¹ State Key Laboratory of Pharmaceutical Biotechnology, School of Life Science, Nanjing University, Nanjing, Jiangsu Province, China
• ² Guangxi Key Laboratory of Marine Environmental Science, Guangxi Academy of Marine Sciences, Guangxi Academy of Sciences, Nanning, China
• ³ Guangxi Key Lab of Mangrove Conservation and Utilization, Guangxi Mangrove Research Center, Guangxi Academy of Marine Sciences, Beihai, China
• ⁴ Beibu Gulf Marine Industry Research Institute, Fangchenggang, China

Phaeocystis globosa blooms are of escalating global concern due to their substantial ecological impacts on marine ecosystem. Emerging evidence indicates that algae-bacterial interactions play pivotal roles in shaping the ecology and evolution of harmful algal blooms, though much of this interplay remains unexplored. We successfully isolated and propagated two novel bacterial strains from Phaeocystis globosa blooms. Two novel Gram-negative, non-spore-forming, motile, rod shaped and yellow-pigmented bacteria, were designated strains GXAS 306 T and GXAS 311. According to phenotypic, chemotaxonomic, phylogenomic, and comparative genomic analyses data, strains GXAS 306 T and GXAS 311 are considered to represent a novel species of the genus Aliikangiella. Genomic analysis revealed that strain GXAS 306 T had many potential functions favorable for interacting with algae, and the further experimental evidence confirmed the ammonifying and phosphorus-solubilizing function. Co-culture experiments showed that strain GXAS 306 T resulted in significant improvements in algal growth parameters of two typical P. globosa strains (Pg293 and PgV01), particularly under nitrogen or phosphorus deficiency. Specifically, cell densities were observed to increase by 19.6-86.0%, accompanied by substantial enhancements in photosynthetic performance with increases of 8.0-30.6% in Fv/Fm and 10.9-27.9% in rETRmax. Overall, these results shed light on intricate relationships between P. globosa and its associated bacterial partners, which may influence the growth characteristics of algae. Key points: • A novel bacterium (GXAS 306 T ) was isolated from phycosphere in P. globosa blooms • GXAS 306 T had many potential functions in favor of interacting with algae • GXAS 306 T was demonstrated to have actual ammonifying and phosphorussolubilizing function • GXAS 306 T positively regulated growth and physiological status of two typical P.