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A Global Transcriptional Analysis of Streptococcus pneumoniae in Response to Low-Shear Modeled Microgravity.     C.A. Allen1, C.L. Galindo1, U. Pandya1, D.A. Watson2, A.K. Chopra1, and D.W. Niesel1,     1Dept. of Microbiology & Immunology, University of Texas Medical Branch, Galveston, TX. and 2InDyne Inc., Houston, TX.

    To facilitate ground-based microgravity analogue studies, NASA developed high aspect ratio vessels (HARVs) which model low-shear microgravity conditions (LSMMG).  To investigate how LSMMG affects global transcriptional activity in opportunistic bacterial pathogens, DNA microarray analysis was carried out on Streptococcus pneumoniae grown in HARVs under LSMMG and compared to 1 x g and static conditions. Analysis of the array data was carried out using multiple analysis methods (Genepix Pro 6.0, Spotfire 7.3, SAM, and ANOVA).  SAM analysis revealed 138 significant LSMMG-responsive genes.  Among the responsive genes (threshold ≥ 1.5-fold), 81 genes representing different functional groups were down-regulated under LSMMG.  Distinct expression patterns were revealed using hierarchical clustering methods (Cluster/Treeview, CLUSFAVOR 6.0, and Spotfire 7.3).  Quantitative RT-PCR was used to confirm gene expression changes.  Computational analyses revealed 101 genes which were differentially expressed under static versus 1 x g conditions. Among these genes, 46 were altered between 1 x g and LSMMG conditions while 9 were altered between static and LSMMG conditions.  SAM analysis revealed 147 genes which exhibited significant changes between static and 1 x g groups.  These results indicate LSMMG represents a unique environment which can alter the transcriptional profile and subsequent physiology of bacteria.  Further, differences in gene expression between the static and 1 x g controls clearly impact the analysis and must be taken into consideration in the assignment of LSMMG responsive genes.

(Supported by NASA: 98-HEDS-02-291 and GSRP Fellowship 424490)