점액세균 Myxococcus xanthus의 C-신호전달에 작용하는 A-신호물질에 대한 연구
Study on A-signals for the C-signaling in Myxococcus xanthus
점액세균 Myxococcus xanthus C-신호전달 A-신호물질;
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Myxococcus xanthus is a Gram-negative soil bacterium that has a complex life cycle and social behaviors, including fruiting body development. On a nutrient-rich surface, rod-shaped cells grow vegetatively. However, the cells form multicellular fruiting bodies under starved conditions. During early fruiting body development, a group of more than 100,000 starved cells aggregate to form a raised mound of cells. Individual rode-shaped cells then transform into environmentally resistant spherical spores in the mound, resulting a mature fruiting body. The fruiting body development needs cooperative activities of about 100,000 cells, so it consists of complex signaling between cells. Five groups of extracellular signaling mutants(A∼E-signaling mutants) have been reported. The developmental defects of the A-signaling mutants are rescued by a group of amino acids known as A-factor amino acids, while the developmental defects of the C-signaling mutants are rescued by the CsgA protein. In this study, I found that leucine, one of A-factor amino acids, caused aggregation-independent early sporulation of M. xanthus under starved conditions. The aggregation-independent early sporulation has been known to be caused by overexperession of the CsgA protein in the cells or by inactivation of the espA gene previously. Since the leucine effect was similar to the phenotype of the CsgA-overproducing mutant, I tested whether leucine could rescue the developmental defects of the C-signaling mutant or not. Then, it appeared that leucine rescued the developmental defects of the csgA mutant, a C-signaling mutant. This result has suggested that leucine, a signal for A-signaling, plays a role as a signal for C-signaling and the CsgA protein is not the only signal for C-signaling.