Research Topics

1. The food composition and compornent drastically change human microbiota. Furthermore, recent insights on the link between the intestinal microbiota and human health are provided and changes in composition and diversity of human intestinal microbiota are related to disease. In our laboratory, we analyze the human intestinal gut and oral microbiota (human microbiome) and the genomics of human origine bacteria, bifidobacteria and lactic acid bacteria.

2. From ancient times, lactic acid bacteria (LAB) are widely used as microbial starter cultures for fermented foods to improve the taste and flavor, change the texture, and extend the shelf life. In the last several decades, it has been revealed that LAB have many beneficial effects not only for food processing and preservation but also for health maintenance and promotion (by working as probiotics and/or biogenics). In our laboratory, isolation, characterization and food application, particularly for milk and egg products, of beneficial LAB strains are performed.

Analysis of human intestinal and oral microbiota (human microbiome)

Human and animal gut/oral microbiota are analyzed by next generation sequencer and their functions are studied by statistics (dry) and wet lab experiments. In particular, we research about the key bacteria in patient or excellent athlete microbiota by the comparison of healthy microbiota. In these researches, germ-free/gnotobiotic mice are powerful tools.

Genomics of Human origine bacteria, bifidobacteria and lactic acid bacteria

In general, the properties and functions of bacteria are different as not the species but the strains. The genome analysis of bacteria is the base of the various researches including their functional analysis. We also promote to contribute to exhaustive gene expression profiling analysis and epigenetics.

Studies on protein metabolism of lactic acid bacteria

Lactic acid bacteria (LAB) are known as fastidious microorganisms that require a wide variety of exogenous free amino acids or peptides as nitrogen sources for growth. Most of Food stuffs such as milk generally contain proteins but very low amount of free amino acids and peptides. Therefore, LAB first hydrolyze the proteins to get nutritious oligopeptides using their own cell-envelope proteinases (CEP). The oligopeptides released are subsequently taken up by the LAB cells via specific transport systems for further degradation into shorter peptides and free amino acids using various intracellular peptidases. The CEP, transporters and peptidases are species- or strain-specific, and their functional and enzymatic differences are an important factor to produce the diversity on taste, flavor and health-promoting effect of fermented food products. In our laboratory, we are studying the protein metabolism of LAB; particularly focusing on characterization of CEP and function of the oligopeptides released by CEP on fermented foods.

Studies on antimicrobial substances produced by lactic acid bacteria

Lactic acid bacteria (LAB) are known as safe producers of antimicrobial substances such as lactic acid and bacteriocins. Bacteriocins, ribosomally biosynthesized antibacterial peptides, have strong activity with a very small quantity and are easily degraded by digestive enzymes in the animal gut. Food-derived antimicrobial peptides are also produced by LAB. Food proteins such as milk caseins are good origins of functional peptides, including with antimicrobial activity, released by hydrolysis using cell-envelope proteinases (CEP) of LAB. These antimicrobial peptides are expected to be used as a safe natural preservative (biopreservative) for foods and feeds. In our laboratory, we isolated some LAB strains with bacteriocin productivity and high CEP activity for production of food-derived antimicrobial peptides, and characterized the bacteriocins and the food-derived antimicrobial peptides for application to foods and feeds.

Publication List

• A. Khasnobish, L. Takayasu, K. Watanabe, T. T. T. Nguyen, K. Arakawa, O. Hotta, K. Joh, A. Nakano, S. Hosomi, M. Hattori, W. Suda, H. Morita. 2021. Dysbiosis in the salivary microbiome associated with IgA nephropathy – A Japanese cohort study. Microbes and Environ. 36, ME21006.
• E. Miyauchi, S. Kim, W. Suda, M. Kawasumi, S. Onawa, N. Taguchi-Atarashi, H. Morita, T. D. Taylor, M. Hattori, H. Ohno. 2020. Gut microorganisms act together to exacerbate inflammation in spinal cords. Nature 585, 102-106.
• R. Takagaki, C. Yoshizane, Y. Ishida, T. Sakurai, Y. Taniguchi, H. Watanabe, H. Mitsuzumi, S. Ushio, H. Morita. 2020. Inhibitory effect of isomaltodextrin on tyrosine metabolite production in rat gut microbiota. Biosci. Biotechnol. Biochem. 84, 824-831.
• M. Takahara, A. Takaki, S. Hiraoka, T. Adachi, Y. Shimomura, H. Matsushita, T. Nguyen, K. Koike, A. Ikeda, S. Takashima, Y. Yamasaki, T. Inokuchi, H. Kinugasa, Y. Sugihara, K. Harada, S. Eikawa, H. Morita, H. Udono, H. Okada. 2019. Berberine improved experimental chronic colitis by regulating interferon-γ- and IL-17A-producing lamina propria CD4+ T cells through AMPK activation. Sci. Rep. 9, 11934.
• Y. Fujii, T. T. T. Nguyen, Y. Fujimura, N. Kameya, S. Nakamura, K. Arakawa, H. Morita. 2019. Fecal metabolite of a gnotobiotic mouse transplanted with gut microbiota from a patient with Alzheimer’s disease. Biosci. Biotechnol. Biochem. 83, 2144-2152.
• G. Kasuga, M. Tanaka, Y. Harada, H. Nagashima, T. Yamato, A. Wakimoto, K. Arakawa, Y. Kawai, J. Kok, T. Masuda. 2019. Homologous expression and characterization of gassericin T and gassericin S, a novel class IIb bacteriocin produced by Lactobacillus gasseri LA327. Appl. Environ. Microbiol. 85, e02815-18.
• T. T. T. Nguyen, Y. Fujimura, I. Mimura, Y. Fujii, N. L. Nguyen, K. Arakawa, H. Morita. 2018. Cultivable butyrate-producing bacteria of elderly Japanese diagnosed with Alzheimer’s disease. J. Microbiol. 56, 760-771.
• A. Sukma, H. Toh, T. T. T. Nguyen, N. Fitria, I. Mimura, R. Kaneko, K. Arakawa, H. Morita. 2018. Microbiota community structure in traditional fermented milk dadiah in Indonesia: Insights from high-throughput 16S rRNA gene sequencing. Milchwissenschaft 71, 1-3.
• K. Arakawa, S. Yoshida, H. Aikawa, C. Hano, T. Bolormaa, S. Burenjargal, Taku Miyamoto. 2016. Production of a bacteriocin-like inhibitory substance by Leuconostoc mesenteroides subsp. dextranicum 213M0 isolated from Mongolian fermented milk, airag. Anim. Sci. J. 87, 449-456.
• K. Arakawa, K. Matsunaga, S. Takihiro, A. Moritoki, S. Ryuto, Y. Kawai, T. Masuda, T. Miyamoto. 2015. Lactobacillus gasseri requires peptides, not proteins or free amino acids, for growth in milk. J. Dairy Sci. 98, 1593-1603.