Departmental Bulletin Paper Morphological change of rhizoids in Bacillus species caused by interaction with various salts and strategies for acquiring nutrition through root-like rhizoids

Akari, SAKAGAWA  ,  Ryuki, AJICHI  ,  Toshiyuki, KAWAMURA

The Bacillus sp. isolated in our laboratory reverses the spiral direction and regularly transforms into various patterns,depending on the salt type and concentration in the culture medium. It is also called a rhizoid because it adopts a structure similar to plant roots. In this study, we analyzed the composition of secretions of this bacterium to help elucidate the significance of these morphologically characteristic colonies to the bacterial life in the environment and some of the mechanisms involved in the morphological transformation. Optical and electron microscopic observations revealed that the rhizoid comprised rows of contiguous, rod-shaped cells, which were covered with secretions.Because the spiral direction of the colonies changes depending on salts in the medium, we believed that the secretions covering the cell surface may interact with the salts in the medium, and therefore identified the secretions. The results of the experiments indicated that the bacterium is likely to secrete polyglutamic acid. In addition, in this study we indicated that the Bacillus sp. has a structure of rhizoids like plant roots and indeed, this bacterium transported the compounds to the center of the surrounding colonies, similar to the action in plants.

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