Browsing by Author "Nomura, Nobuhiko"

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Correlation of Carotenoid Accumulation with Aggregation and Biofilm Development in Rhodococcus sp SD-74
(2013-08-06)
Zheng, Yi-Ting
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Toyofuku, Masanori
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Nomura, Nobuhiko
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Shigeto, Shinsuke
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應用化學系
Aggregation of bacterial populations substantially influences their characteristic properties and functions compared with the planktonic counterpart. It is also involved in the initial stages of biofilm development. Many studies have revealed important roles of bacterial aggregation in microbial production and biodegradation. Nevertheless, mechanistic understanding of bacterial aggregation in vivo and at the molecular level is far from complete. Here, we present a noninvasive, label-free Raman microspectroscopic approach to investigate the aggregation and biofilm development of the biotechnologically important Rhodococcus sp. SD-74. We found that the concentration of intracellular carotenoids increases more than 3-fold within 1 week as the biofilm develops. Raman imaging experiments confirmed that the carotenoid accumulation occurs throughout the Rhodococcus sp. SD-74 biofilm. The correlation between the carotenoid Raman intensities and biofilm development found in the present study provides a new means for quantitative, molecular-level assessment of the level of biofilm development, which is not possible with dye staining assay or electron microscopy. Moreover, our results suggest that microbial production of carotenoids in pigmented bacteria such as Rhodococcus sp. SD-74 may potentially be controlled via bacterial aggregation and biofilm formation.
Leucine pools in Escherichia coli biofilm discovered by Raman imaging
(2011-11-01)
Venkata, Hemanth Nag Noothalapati
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Nomura, Nobuhiko
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Shigeto, Shinsuke
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應用化學系
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應用化學系分子科學碩博班
In structured communities of bacteria known as biofilms, a variety of biomolecules have been shown to play a unique role as signals and/or regulators in biofilm formation. Here, we report that high levels of the amino acid leucine ( leucine pool) were detected, for the first time, within microcolonies in a 30-h-old Escherichia coli biofilm by Raman imaging. Localization of leucine revealed by multifrequency Raman images indicates leucine accumulation during the early stage of the E. coli biofilm formation, which may have resulted from physiological environment-specific metabolic adaptation. We demonstrate that our label-free Raman imaging method provides a useful platform for directly identifying still unknown natural products produced in biofilms as well as for visualizing heterogeneous distributions of biofilm constituents in situ. Copyright (C) 2011 John Wiley & Sons, Ltd.