Abstract
This study demonstrates the effects of simulated microgravity on E. coli K 12 MG1655 grown on LB medium supplemented with glycerol. Global gene expression analysis indicated that the expressions of hundred genes were significantly altered in simulated microgravity conditions compared to that of normal gravity conditions. Under these conditions genes coding for adaptation to stress are up regulated (sufE and ssrA) and simultaneously genes coding for membrane transporters (ompC, exbB, actP, mgtA, cysW and nikB) and carbohydrate catabolic processes (ldcC, ptsA, rhaD and rhaS) are down regulated. The enhanced growth in simulated gravity conditions may be because of the adequate supply of energy/reducing equivalents and up regulation of genes involved in DNA replication (srmB) and repression of the genes encoding for nucleoside metabolism (dfp, pyrD and spoT). In addition, E. coli cultured in LB medium supplemented with glycerol (so as to protect the cells from freezing temperatures) do not exhibit multiple stress responses that are normally observed when cells are exposed to microgravity in LB medium without glycerol.
Highlights
Microbes have the ability to sense and respond to environmental changes occurring in their vicinity
Growth of E. coli in the Clinostat Growth of E. coli was monitored under both simulated microgravity conditions and normal gravity conditions
Expression of Genes in E. coli Grown in a Clinostat In E. coli grown under simulated microgravity conditions hundred genes were differentially expressed with a fold change $1.5 (P#0.05)
Summary
Microbes have the ability to sense and respond to environmental changes occurring in their vicinity. This adaptability confers on them the capacity to thrive under various extreme environmental niches including microgravity. When exposed to microgravity cells experience reduced gravity resulting in a relative lack of sedimentation, low shear stress and low turbulence [1]. These physical effects of microgravity may influence the growth and induce other physiological changes. Resistance towards antibiotics and increase in virulence was reported in different bacteria exposed to microgravity [4,5,6]. The above effects of microgravity on bacteria are possibly dependent on the specific media used for culturing the bacteria [7,8,9]
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