Frontier Research Institute for Interdisciplinary Sciences
Tohoku University

Interior and exterior of living organism is separated by cell envelope. Therefore, the structure and function of the cell envelope are critical for various aspects of cellular activity such as transport, morphogenesis, response to extracellular environment, and so on. I've been interested in the cell surface of Gram-negative bacteria, which comprises cytoplasmic membrane, peptidoglycan (cell wall) layer, and outer membrane. During my Ph. D. study, I examined molecular basis of the interaction between the outer membrane and underlying peptidoglycan layer, an “anchor” crucial for maintaining structural integrity of the outer membrane (Kojima et al. 2010, 2011). As a postdoc, with the aim of understanding quantitatively the function of the outer membrane, I examined the permeability of the outer membrane by analyzing the movement of substances across the outer membrane, using β-lactam antibiotics as substrates (Kojima & Nikaido 2013, 2014).

Because the outer membrane directly affects the speed of flux of various substances to/from the cell, its permeability is quantitatively linked to the cellular physiology, survival and responses to the external environment. My current researches focus on the molecular basis of the permeability and stability of the outer membrane, in the context of nutrient uptake and also the antibiotic resistance of Gram-negative bacteria. Also, I started recently the research on the outer membrane of chloroplasts, an organelle descended from endosymbiotic cyanobacteria (Gram-negative bacteria that conduct oxygenic photosynthesis). The aim of this research is to understand how the function of the outer membrane has changed (or preserved) during the course of evolution from free living cyanobacteria to chloroplasts. Current projects are: 1) Mechanism of antibiotic resistance of Gram-negative bacteria, 2) Function of the outer membrane of primitive chloroplast, and 3) Outer membrane structure and function of ruminal bacteria.
(for detailed information: http://www.ige.tohoku.ac.jp/tekio/wordpress/wp-content/themes/lsab_wp/img/Kojima_HP/Kojima_eng.html)

[References]

Kojima S, et al. (2010) J Bacteriol 192(22): 5953-5961

Kojima S, et al. (2011) J Bacteriol 193(9):2347-2350

Kojima S, Nikaido H (2013) Proc Natl Acad Sci U S A 110(28): E2629-E2634

Kojima S, Nikaido H (2014) J Biol Chem 289(38): 26464-2647

Kojima et al. (2016) J. Biol. Chem. 291:20198-20209.