Microbial-Observatory-Mini-Book-04-28-14-508

LSMMG-cultured S. Typhimurium suffered an increased percent mortality,increased time to death, and required a lower LD50 as compared to controlcultures (Nickerson et al. 2000). The success of the flight analog studies using theRWV resulted in the aforementioned two spaceflight experiments involving S.Typhimurium. One outcome of these investigations was the documented increasedvirulence of the bacterium in response to spaceflight, paralleling the bacterium’sresponse to LSMMG as produced by the RWV (Nickerson et al. 2000, Wilson etal. 2007) and validating its use as a spaceflight analog.In addition to the similarities between S. Typhimurium cultured in-flight and withinthe RWV bioreactor, other commonalities have been demonstrated. For example,scanning electron microscopy images revealed an unidentified extracellular matrixaround S. Typhimurium cells following spaceflight culture (Wilson et al. 2007), inresponse to the modeled microgravity conditions within the RWV bioreactor P.aeruginosa, S. aureus, E. coli, and C. albicans have all demonstrated increased biofilmformation (Lynch et al. 2006, Crabbe et al. 2008, Castro et al. 2011, Searles et al.2011). With multiple reports of changes in phenotype following exposure to bothtrue microgravity and simulated microgravity, differences in gene expression inresponse to culture in these environments is not unexpected. What was surprisingwas the identification of the involvement of Hfq, an RNA chaperone protein thatexerts post-transcriptional regulation by binding messenger RNA with small noncodingRNA (Valentin-Hansen et al. 2004), with the mechanism governing thespaceflight response of S. Typhimurium (Wilson et al. 2007). The role for Hfq wasvalidated with the RWV bioreactor and has since been shown to be involved in themodeled microgravity response of both P. aeruginosa and S. aureus (Crabbe et al.2010, Castro et al. 2011). While first identified in spaceflight, the use of the RWVbioreactor on Earth produced evidence that suggests that the ability to sense andrespond to mechanical stimuli such as microgravity and simulated microgravity maybe evolutionarily conserved among structurally diverse prokaryotes.24Figure 4. Increasedextracellular matrixproduction as a resultof A) spaceflightculture in S.Typhimurium andmodeled microgravityin B) P. aeruginosaand in C) S. aureus(Wilson et al. 2007,Crabbe et al. 2008,Castro et al. 2011).