HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Ohta, H. Articles by Fukui, K. Search for Related Content PubMed PubMed Citation Articles by Ohta, H. Articles by Fukui, K. Agricola Articles by Ohta, H. Articles by Fukui, K.

Energy metabolism of Actinobacillus actinomycetemcomitans during anaerobic and microaerobic growth in low- and high-potassium continuous culture

Department of Bioresource Science, Ibaraki University College of Agriculture, Ami-machi, Ibaraki 300-0393, Japan¹
Department of Microbiology, Okayama University Dental School, Shikata-cho 2-chome, Okayama 700-8525, Japan²

Author for correspondence: Hiroyuki Ohta. Tel: +81 298 88 8684. Fax: +81 298 88 8525. e-mail: hohta{at}acs.ibaraki.ac.jp

Actinobacillus actinomycetemcomitans, a member of the gamma subclass of the Proteobacteria, has been implicated as the agent responsible for human periodontitis. In this study, A. actinomycetemcomitans 301-b was grown in fructose-limited chemostat cultures under anaerobic [redox potential (E_h)<-400 mV] and microaerobic (E_h=-200 mV) conditions to characterize its energy metabolism. Effects of K⁺ and Na⁺ on growth and metabolism were also examined. In a control medium containing 5·2 mM K⁺ and 24 mM Na⁺, the molar growth yield on fructose (Y_fructose) of microaerobic cultures was 1·3 times higher than the yield of anaerobic cultures at D0·10 h^-1, but the difference in the Y_fructose between microaerobic and anaerobic cultures decreased at D0·10 h^-1. When the ATP yield from fermentation was estimated from the amounts of fructose consumed and acetate formed, the value of the microaerobic culture (2·49 mol ATP produced per mol fructose consumed) was lower than the anaerobic value [3·13 mol ATP (mol fructose)^-1]. Therefore, ATP production from fermentation could not account for the increase in the Y_fructose at D>0·10 h^-1 and thus additional ATP was expected to be generated via respiration. Assuming that the Y_ATP (g cells formed per mol ATP synthesized) was similar between anaerobic and microaerobic cultures, the estimated ATP yield from respiration was between 1·2 and 2·0 mol ATP (mol fructose)^-1 below D=0·10 h^-1 and decreased to 0·3 mol ATP (mol fructose)^-1 when D was increased to 0·19 h^-1. Such growth-rate-dependent decreases in the Y_fructose and the estimated ATP production from respiration were also observed in a high-Na⁺ (5·2 mM K⁺ and 106 mM Na⁺) culture but not in a high-K⁺ (81 mM K⁺ and 24 mM Na⁺) culture. In the high-K⁺ culture, the microaerobic Y_fructose was 1·4–2·0 times higher than the anaerobic value and the respiration-derived ATP yield was estimated to be between 1·2 and 1·9 mol ATP (mol fructose)^-1 over a wide range of dilution rate. These results suggest that higher concentrations of extracellular K⁺ are required for the respiration to occur in rapidly growing cells of A. actinomycetemcomitans.

Keywords: fructose metabolism, microaerophile, chemostat culture, potassium ion, periodontopathogen

This article has been cited by other articles:

				S. A. Brown and M. Whiteley A Novel Exclusion Mechanism for Carbon Resource Partitioning in Aggregatibacter actinomycetemcomitans J. Bacteriol., September 1, 2007; 189(17): 6407 - 6414. [Abstract] [Full Text] [PDF]

				P. Valverde, T. Kawai, and M.A. Taubman Potassium Channel-blockers as Therapeutic Agents to Interfere with Bone Resorption of Periodontal Disease Journal of Dental Research, June 1, 2005; 84(6): 488 - 499. [Abstract] [Full Text] [PDF]