Atypical Catabolite Repression Mechanism in the Thermophilic Gram-Positive Bacterium Geobacillus kaustophilus
Generally speaking, in conventional catabolite repression (CCR) in Gram-positive bacteria, the metabolism of hexoses such as glucose is prioritised, and as a result, the expression of genes encoding other carbon source metabolism is repressed. However, we have discovered that in the thermophilic Gram-positive bacterium Geobacillus kaustophilus (GK), an atypical CCR operates that does not prioritise the metabolism of hexoses; instead, the metabolism of pentoses, such as ribose, is prioritised [1]. In this atypical CCR, the involvement of HPr—which plays a central role in conventional CCRs—is extremely limited, and it is thought that its paralogue, Crh, functions as the primary regulatory factor.
In this study, we are conducting a detailed analysis of the atypical CCR mechanism specific to GK, both in vivo and in vitro. In vivo, we are verifying the physiological importance of Crh by using hprK-, crh- and ccpA-deficient strains to evaluate how expression of the myo-inositol catabolism genes (iol genes), which is repressed by ribose, is restored. Meanwhile, in vitro analyses are being conducted to elucidate the phosphorylation of Crh and to determine whether the phosphorylated Crh-CcpA complex binds to the iol promoter regions, which may contain the cre sequences.
The aim of this study is to elucidate the molecular mechanisms and physiological significance of the atypical CCR in GK and to establish the fundamental principles of global carbon metabolism regulation, which are essential for utilising GK as an advanced cellular factory.
[1] Yoshida KI, Fukui K, Osawa T, Tsuji M, Kado-Matsushita M, Asahi N, Ishikawa S, Shiwa Y, Yoshikawa H. Atypical catabolite repression of Geobacillus kaustophilus iol operons in the presence of ribose. Microbiology (Reading). 2026;172(4):001702. doi: 10.1099/mic.0.001702.
Short bio
After obtaining a Master of Science in Agriculture at Kyoto University in 1989, he got an Assistant professor position at Fukuyama University in 1990. He was given a PhD at Kyoto University in 1993 and served as a Postdoc fellow at INRA, France, in 1996-97. He moved to Kobe University in 2004 as an Associate professor and became a Full professor of Applied Microbiology in 2009. He received the prize for Encouragement of Young Scientists (2002) and twice for Excellent papers from the Japan Society for Bioscience, Biotechnology, and Agrochemistry (2008 and 2014). He received the Fermentation and Metabolism Research Award (2006) from the Japan Bioindustry Association (JBA) and a prize from the NAGASE Science Technology Foundation (2009). He received the Hyogo Science Prize (2023). He has served in the Research Promotion Bureau in the Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT) (2005-2007). He has acted as an honourable FEMS Ambassador since 2019 to date. He served at Kobe University Brussels European Centre as one of the directors (2013-2019 and 2022-2023) and as Executive Director of the Centre for EU Academic Collaboration/ Office for International Strategic Planning, Head of the Europe & Africa Division (2019 to 2023). Recently, he became Deputy Dean of the Graduate School of Science, technology and Innovation (2024-).
Laboratory of the speaker
