What is it about?

Rhamnose is a sugar constituent of various plant-derived compounds, and Bacillus subtilis is a soil bacterium that has been shown to contribute to plant growth-promotion by associating with plant roots. We have revealed the transcriptional regulation of the rhamnose catabolic genes in this bacterium.

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Why is it important?

Rhamnose is a potential carbon source for plant-associating bacteria. In addition, it is suggested that rhamnose catabolism plays a significant role in some bacteria-plant interactions, e.g., invasion of plant pathogens and nodulation of rhizobia. Despite physiological importance of rhamnose catabolism for various bacterial species, the transcriptional regulation of the relevant genes has been poorly understood, except for the regulatory system of Escherichia coli. The regulatory system of rhamnose catabolic genes in B. subtilis can be another standard model for better understanding those in the other bacterial species such as rhizobia.


Some Gram-negative bacterial species are known as plant pathogens that possess the rhamnose catabolic genes likely regulated by the E. coli-type system; some Bacillus species are Gram-positive plant growth-promoting rhizobacteria, and their rhamnose catabolic genes are likely to be under the control of the B. subtilis-type system. Since rhamnose catabolic enzymes are assumed to play a significant role in the invasion of such pathogens into plant tissues, an antagonist specific to the E. coli-type system is expected to be an effective pesticide without preventing growth of the Gram-positive plant growth-promoting rhizobacteria. Moreover, in E. coli, the regulatory system of the promoter of the rhamnose catabolic genes is applied to the heterologous expression system, in which the expression of the target gene is capable of being strictly controlled by the addition of rhamnose or glucose. Similar expression system can be created in the cells of B. subtilis and related species by using the B. subtilis-type regulatory system for rhamnose catabolism.

Dr Kazutake Hirooka
Fukuyama Daigaku

Read the Original

This page is a summary of: Regulation of therhaEWRBMAOperon Involved in l-Rhamnose Catabolism through Two Transcriptional Factors, RhaR and CcpA, in Bacillus subtilis, Journal of Bacteriology, December 2015, ASM Journals, DOI: 10.1128/jb.00856-15.
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