 coli* in space flight indicated shortened lag phase, increase in the duration of exponential growth phase and approximately doubled final cell density population ([@b0085]). The final cell population of *E. coli* and *Bacillus subtilis* grown abroad space shuttle was found to be higher than the static 1 g controls. These studies suggested that access of bacteria to nutrients and removal of waste products is more favorable under microgravity due to lack of sedimentation of the bacterial cells at the bottom of the culture flasks. The low gravity also makes the metabolism of nutrients more efficient and cells multiply repeatedly before the nutrients are depleted ([@b0080]). But increase in growth pattern was not observed with *S. pyogenes* under low shear modeled microgravity. The kind of nutrient medium either the complex media or the minimal essential media and the motility of the bacterium was also found to play a role in varying the growth pattern of bacteria under microgravity conditions ([@b0175], [@b0030]). *S. pyogenes* cannot be cultured on minimal essential medium so the influence of medium composition on growth of the bacteria under low shear modeled microgravity was not studied in detail.

4.2. Structural analysis of *S. pyogenes* under normal and low shear modeled microgravity {#s0090}
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From the images obtained from TEM and SEM analysis, alteration in the morphology of *S. pyogenes* was not noticed. This could be attributed by the presence of thick peptidoglycan layer in *S. pyogenes*, which protects from low shear modeled microgravity. No variation in the size and shape was observed with *Salmonella typhimurium* during the space flight, but the aggregation of the cells and clumping of bacteria associated with the extracellular matrix formation was observed in SEM studies ([@b0180]). In the present study no aggregation of *S. pyogenes* cells was observed under low shear modeled microgravity compared with normal c