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Applied and Environmental Microbiology, April 2005, p. 1811-1815, Vol. 71, No. 4
0099-2240/05/$08.00+0     doi:10.1128/AEM.71.4.1811-1815.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

Roles of Four Chitinases (ChiA, ChiB, ChiC, and ChiD) in the Chitin Degradation System of Marine Bacterium Alteromonas sp. Strain O-7

Hideyuki Orikoshi, Shigenari Nakayama, Katsushiro Miyamoto, Chiaki Hanato, Masahide Yasuda, Yoshihiko Inamori, and Hiroshi Tsujibo^*

Department of Microbiology, Osaka University of Pharmaceutical Sciences, Takatsuki, Osaka, Japan

Received 15 July 2004/ Accepted 22 October 2004

Alteromonas sp. strain O-7 secretes four chitinases (ChiA, ChiB, ChiC, and ChiD) in the presence of chitin. To elucidate why the strain produces multiple chitinases, we studied the expression levels of the four genes and proteins, their enzymatic properties, and their synergistic effects on chitin degradation. Among the four chitinases, ChiA was produced in the largest quantities, followed by ChiD, and the production of ChiB and ChiC changed at lower levels than those of ChiA and ChiD. The expression of the chiA, chiB, chiC, and chiD genes was investigated at the transcriptional level. The RNA transcript of chiA was most strongly induced in the presence of chitin, the expression of chiD followed, and the RNA transcripts of chiB and chiC changed at low levels. The hydrolyzing activities of the four chitinases against various substrates were examined. ChiA was the most active enzyme against powdered chitin, whereas ChiC was the most active against soluble chitin among the four chitinases. ChiD had activities closer to those of ChiA than to those of ChiB and ChiC. ChiB showed no distinctive feature against the chitinous substrates tested. When powdered chitin was treated with the proper combination of four chitinases, an approximately 2.0-fold increase in the hydrolytic activity was observed. These results, together with the results described above, indicate that ChiA plays a central role in chitin degradation for this strain.

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* Corresponding author. Mailing address: Department of Microbiology, Osaka University of Pharmaceutical Sciences, 4-20-1 Nasahara, Takatsuki, Osaka 569-1094, Japan. Phone: (81-726) 90-1057. Fax: (81-726) 90-1057. E-mail: tsujibo{at}gly.oups.ac.jp.

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Applied and Environmental Microbiology, April 2005, p. 1811-1815, Vol. 71, No. 4
0099-2240/05/$08.00+0     doi:10.1128/AEM.71.4.1811-1815.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

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