Limnospira platensis (formerly Arthrospira platensis) was cultured for 14 days under simulated microgravity (SMG) generated by a three-dimensional clinostat and compared with motion-matched controls using optical density, live/dead staining and real-time RT-PCR. Control cultures appeared to proliferate faster initially but declined after day 8 and died by day 14, whereas SMG cultures maintained a prolonged exponential phase and reached a final OD₇₅₀ of 1.43 ± 0.05, approximately 29% above the control maximum (1.11 ± 0.12; p = 0.040). Specific growth rates did not differ over days 0–6 (p = 0.13), but between days 8 and 12, the control declined (−0.111 ± 0.008 day⁻¹) while SMG cultures continued to grow (0.025 ± 0.011 day⁻¹; p < 0.000001). Live/dead staining confirmed that SMG-cultured cells retained normal pigmentation and viability throughout, whereas control cells exhibited progressive cell death from day 10 onward. ftsZ was significantly lower under SMG on day 2 and higher on day 12. Eleven of 19 photosystem and open reading frame genes were significantly higher in the control on day 2, in SMG on day 10 and in the control again on day 12. At matched cell density (control day 6 versus SMG day 10; OD₇₅₀p = 0.52), 19 of the 20 genes remained significantly higher under SMG, so this divergence is not an artefact of the growth stage. Reducing mechanical shear stress through SMG thus maintains physiological integrity, prolongs the productive growth phase and enhances biomass accumulation, supporting the use of L. platensis in bioregenerative life-support systems.

This study aimed to characterize the draft genome of Arthrospira platensis NH isolated in Vietnam and evaluate its phylogenetic position within cyanobacteria. Phylogenetic analysis based on 16S rRNA gene sequences confirmed that A. platensis NH belongs to the Arthrospira clade. The assembled genome comprises 5,548,511 bp and contains 4728 genes, including 4683 protein-coding sequences, 42 tRNA genes, and 3 rRNA genes. Genome mapping revealed conserved gene organization with an overall GC content of 44.45%. A comparative genomic analysis with other Arthrospira strains (A. platensis NIES-39 and C1) demonstrated high sequence conservation, supporting their close genetic relationships. Secondary structure prediction showed that all 42 tRNA types adopt typical cloverleaf structures, while the ribosomal RNA genes (16S, 23S, and 5S rRNA) exhibit conserved base composition. An analysis of 16S rRNA sequences from 13 cyanobacterial taxa identified 230 polymorphic sites, providing informative markers for phylogenetic divergence among genera. Collectively, these results establish a comprehensive genomic and phylogenetic framework for A. platensis NH and provide insights into its genetic relationships and potential biotechnological applications.