Microaerophilic property of Actinobacillus actinomycetemcomitans in fructose-limited chemostat cultures |
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Authors: | Hiroyuki Ohta Daisuke Moriki Atsushi Miyagi Tatsuo Watanabe Keijiro Kato Kazuhiro Fukui |
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Affiliation: | Departments of Microbiology, Okayama University Dental School, Shikata-cho 2-chome, Okayama 700, Japan; Departments of Preventive Dentistry, Okayama University Dental School, Shikata-cho 2-chome, Okayama 700, Japan |
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Abstract: | Abstract The effect of oxygen on the growth, metabolism, and leukotoxin production of Actinobacillus actinomycetemcomitans 301-b was examined using a chemostat equipped with a redox potential control system. Steady states were obtained with fructose-limited cultures grown at a dilution rate of 0.1 h−1 under strictly anaerobic ( E h=−460 mV) and microaerobic conditions ( E h≤ 150 mV) but not under highly aerated conditions ( E h≥ 100 mV). The optimum growth was recorded at E h=−300 to − 200 mV and the recorded Y fructose value was about 1.3 times the Y fructose of anaerobic cultures. Although the organism contains a respiratory chain, the increased Y fructose under the microaerobic conditions might result from the increased substrate-level phosphorylation at the site of acetate kinase but not from electron transport phosphorylation. After passing threshold aeration ( E h=−100 mV), the culture yielded a variant with transparent colony morphology. Under anaerobic conditions, the Y fructose of the variant was about 1.6 times that of the original opaque colony-forming cells. The optimum growth of the variant was also recorded at E h=− 300 to − 200 mV. In both types of cells, the production of leukotoxin reached a maximum at E h=−350 to − 200 mV. These findings suggested the microaerophilic nature of A. actinomycetemcomitans . |
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Keywords: | Actinobacillus actinomycetemcomitans Leukotoxin Chemostat culture Microaerophilic growth |
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