ravity vector ([@b0125]). Oxygenation of the bioreactor was achieved through the gas permeable membrane present on back of the HARV reactor.

2.2. Bacterial strains and culture conditions {#s0020}
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Experiments were performed with *S. pyogenes* obtained from Korean Agricultural Culture Collection (KACC 11858). Brain heart infusion agar was used to maintain the culture and stored at 4 °C until use. The overnight liquid cultures were cultured in brain heart infusion at 37 °C. Overnight cultures were used as starter cultures to perform further experiments. 100 μl of culture was inoculated into the HARV vessel for culturing *S. pyogenes* under low shear modeled microgravity and into the conical flask for culturing bacteria under normal gravity which served as control. HARV bioreactor was packed with brain heart infusion broth and removed the air bubbles formed to maintain the low shear modeled microgravity conditions. The normal gravity cultures were grown at 37 °C in the incubator as shake flask cultures shaking at 25 rpm. HARV reactor was also maintained at same 37 °C, rotating at an rpm of 25.

2.3. Growth analysis {#s0025}
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Sampling was done by injecting 1 ml of sterile brain heart infusion medium into one of the sampling ports which displaced 1 ml of culture into the other syringe inserted at other sampling ports. The reactor was rocked well before collecting sample, to obtain representative sample for the growth analysis. Similarly for normal gravity grown culture, the flasks were shaken well and 1 ml of the culture was collected and 1 ml of fresh brain heart infusion medium was introduced into culture flask to maintain a uniform volume of 50 ml and to maintain same culture volume as of the low shear modeled microgravity culture throughout the study. The cultures were collected at every 4 h of intervals until 24 h and absorbance was measured at 600 nm in UV--Vis spectrophotometer.

2.4. Bio-SEM and Bio-TEM analysis {#s0030}
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