Differential Gene Expression of Acidovorax sp.1,608,163 under Simulated Microgravity

Previous studies reported that microorganisms, including several bacterial species, under microgravity stress undergo differential gene expression leading to diverse physiological responses such as increased growth, virulence, antibiotic resistance, and biofilm production. This study examines the gene-expression differences of Acidovorax sp. 1,608,163 under normal and simulated microgravity conditions. Strains of the Acidovorax species are free-living, environmental commensals, plant or human opportunistic pathogens that can infect a variety of crops, including corn, rice, oats, and wheat. The hypothesis that “Acidovorax grown under microgravity alters the gene expression patterns” is tested by comparing transcriptomic data of bacterial cultures at the log (42 h) and stationary (72 h) phases grown under normal and microgravity conditions. Total RNA was extracted and reverse transcribed, and then the cDNA was sequenced using the Illumina HiSeq 4000 platform. Results revealed the difference in growth rates, which were significantly higher under microgravity conditions than under normal gravity conditions. Of the total of 678 differentially expressed genes, 232 (34.22%) and 446 (65.78%) genes were up- and down-regulated in the log phase, respectively, whereas the total of 231 differentially expressed genes at the stationary phase, 32 (13.85%) and 199 (86.15%) genes were up- and down-regulated, respectively. Furthermore, results also indicated that genes coding for several COGs functions, especially in metabolism, signal-transduction, transcription, translation, chemotaxis, and cell motility, were down-regulated in response to microgravity stress, and therefore, the downregulation of genes seems to be the central mechanism for cells to cope under stimulated microgravity.