The paper contains comparative analysis of microbial communities formed by probiotic lactobacteria L. plantarum 8PA-3 on various carriers (space experiment Biofilm) during ISS missions 53, 54 and 56. Object of the investigations was L. plantarum 8PA-3 cells inoculated on microcellulose sorbates, polystyrene and a variety of powder and laminar-type polymer substrates. Simultaneously, same culture and substrates were used in the laboratory experiment. Resulted biofilms were investigated using transmission (TEM) and scanning (SEM) electron microscopy. Comparative analysis was aimed to detect difference in the development of microbial communities resided on various carriers in space and ground-based laboratories. The obtained data about the ultrathin structure of biofilm and plankton-like L. plantarum 8PA-3 cells involved in formation of microbial communities in microgravity make us think of distinctive morphophysiological properties of these cells, as well as the biofilm structure.