Decreased biofilm formation in Proteus mirabilis after short-term exposure to a simulated microgravity environment.

BACKGROUND: Microbes threaten human health in space exploration. Studies have shown that Proteus mirabilis has been found in human space habitats. In addition, the biological characteristics of P. mirabilis in space have been studied unconditionally. The simulated microgravity environment provides a platform for understanding the changes in the biological characteristics of P. mirabilis. OBJECTIVE: This study intends to explore the effect of simulated microgravity on P. mirabilis, the formation of P. mirabilis biofilm, and its related mechanism. METHODS: The strange deformable rods were cultured continuously for 14 days under microgravity simulated in high-aspect rotating vessels (HARVs). The morphology, growth rate, metabolism, and biofilm formation of the strain were measured, and the phenotypic changes of P. mirabilis were evaluated. Transcriptome sequencing was used to detect differentially expressed genes under simulated microgravity and compared with phenotype. RESULTS: The growth rate, metabolic ability, and biofilm forming ability of P. mirabilis were lower than those of normal gravity culture under the condition of simulated microgravity. Further analysis showed that the decrease of growth rate, metabolic ability, and biofilm forming ability may be caused by the downregulation of related genes (pstS, sodB, and fumC). CONCLUSION: The simulated microgravity condition enables us to explore the potential relationship between bacterial phenotype and molecular biology, thus opening up a suitable and constructive method for medical fields that have not been explored before. It provides a certain strategy for the treatment of P. mirabilis infectious diseases in space environment by exploring the microgravity of P. mirabilis.

Identification of genes differentially expressed in the roots of rubber tree (Hevea brasiliensis Muell. Arg.) in response to phosphorus deficiency.

Phosphorus (P) is an essential macronutrient for plant growth and development. P deficiency could affect rubber tree productivity seriously, and understanding the mechanism responses of the rubber tree under the P deficiency will be helpful to improving rubber tree productivity. The molecular mechanism by which the rubber trees respond to a P-deficiency is a complex network involving many processes. To identify the genes differentially expressed in that response, we constructed subtractive suppression hybridization libraries for roots of plants growing under deficient or sufficient conditions. We identified 94 up-regulated genes from the forward library and 45 down-regulated from the reverse library. These differentially expressed genes were categorized into eight groups representing functions in metabolism, transcription, signal transduction, protein synthesis, transport, stress responses, photosynthesis, and development. We also performed quantitative real-time PCR to investigate the expression profiles of eight randomly selected clones. Our results provide useful information for further study of the molecular mechanism for adaptations to a P-deficiency in this species. Further characterization and functional analysis of these differentially expressed genes will help us improve its phosphorus utilization and overall productivity.