Phenotypic, transcriptomic and metabolomic changes in Klebsiella pneumoniae after long term exposure to simulated microgravity.

Klebsiella pneumoniae (K. pneumoniae) has been detected on space stations. Microgravity is a key environmental factor in spaceflight, however, research on the phenotypic, genetic, and metabolic changes K. pneumoniae undergoes due to long-term exposure to microgravity is still limited. K. pneumoniae was cultured under normal gravity (NG) and simulated microgravity (SMG) for 56 days, showing phenotypic changes like slower growth, larger and rounder cell morphology, and increased biofilm formation in SMG. RNA sequencing analysis revealed that the DEGs were associated primarily with metabolic and growth pathways, including those involved in biofilm formation. Metabolomic analysis revealed changes in the activity of the phenylalanine metabolic pathway, which was the most significantly enriched pathway, due to the interaction between the mhp gene cluster and related DEMs. Co-expression network analysis revealed intricate relationships between DEGs and DEMs, notably in arginine and proline metabolism. This study provides insights into K. pneumoniae's response mechanisms to microgravity.