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

Citation
H. Ohta et al., Energy metabolism of Actinobacillus actinomycetemcomitans during anaerobicand microaerobic growth in low- and high-potassium continuous culture, MICROBI-SGM, 147, 2001, pp. 2461-2468
Citations number
26
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Microbiology
Journal title
MICROBIOLOGY-SGM
ISSN journal
1350-0872 → ACNP
Volume
147
Year of publication
2001
Part
9
Pages
2461 - 2468
Database
ISI
SICI code
1350-0872(200109)147:<2461:EMOAAD>2.0.ZU;2-I
Abstract
Actinobacillus actinomycetemcomitans, a member of the gamma subclass of the Proteobacteria, has been implicated as the agent responsible for human per iodontitis. In this study, A. actinomycetemcomitans 301-b was grown in fruc tose-limited chemostat cultures under anaerobic [redox potential (E-h) < -4 00 mV] and microaerobic (E-h = -200 mV) conditions to characterize its ener gy metabolism. Effects of K+ and Na+ on growth and metabolism were also exa mined. 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 ti mes higher than the yield of anaerobic cultures at D less than or equal to 0(.)10 h(-1), but the difference in the Y-fructose between microaerobic and anaerobic cultures decreased at D > 0(.)10 h(-1). When the ATP yield from fermentation was estimated from the amounts of fructose consumed and acetat e formed, the value of the microaerobic culture (2(.)49 mol ATP produced pe r 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 less than or equal to 0(.) 10 h(-1) and thus additional ATP was expected to be generated via respirati on. Assuming that the Y-ATP (g cells formed per mol ATP synthesized) was si milar between anaerobic and microaerobic cultures, the estimated ATP yield from respiration was between 1(.)2 and 2(.)0 mol ATP (mol fructose)(-1) bel ow 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 th e Y-fructose and the estimated ATP production from respiration were also ob served 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 microaero bic Y-fructose was 1(.)4-2(.)0 times higher than the anaerobic value and th e 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 resul ts suggest that higher concentrations of extracellular K+ are required for the respiration to occur in rapidly growing cells of A. actinomycetemcomita ns.