Bacteria are micro- and nanoorganisms that spatially colonize the plant organism and comprise various types of interactions with the host ranging from pathogenic to mutualistic and symbiotic. The presence of these exo- and endosymbionts may affect the plant host physiology. Non-pathogenic bacteria can enhance defensive capacity in plants that provides protection against phytopathogens and herbivores, as well as makes a valuable contribution to the protection of plants from abiotic stressors. Endophytes demonstrate the protection of photosystem in plants under environmental challenges. The putative mechanisms of bacterial effects on plant photosystem are discussed in this paper.