Metabolic Changes in Thiobacillus denitrificans Accompanying the Transition from Aerobic to Anaerobic Growth in Continuous Chemostat Culture

Abstract

Thiobacillus denitrijicans grew exclusively aerobically in thiosulphate-limited chemostat culture at all dissolved oxygen concentrations between 12 and 216 ,UM. Nitrate reduction did not occur in aerobic cultures and nitrate and nitrite reductases only reached high levels under complete anaerobiosis. Growth yield was greatest [11.50 g dry wt (mol thicsulphate oxidized)-l] at the lowest dissolved oxygen concentration (12 ,UM) and decreased at higher dissolved oxygen concentrations, indicating oxygen to be a growth-inhibitory substrate; the anaerobic yield was only 77 yo of the maximum aerobic yield (all tested at a dilution rate of 0.08 h-l) in agreement with thermodynamic calculations. Low activities of thiosulphateoxidizing enzyme and sulphur-oxidizing enzyme were detected in aerobic cultures, but activities were even lower in anaerobic cultures. Efficient energy coupling mechanisms with respect to sulphur and thiosulphate oxidations are indicated.

Whole-Genome Transcriptional Analysis of Chemolithoautotrophic Thiosulfate Oxidation by Thiobacillus denitrificans under Aerobic versus Denitrifying Conditions

“…In a general sense, the microarray results for T. denitrificans are consistent with the well-documented transcriptional activation of denitrification genes as a function of low O 2 tension and the presence of a nitrogen oxide (NO 3 Ϫ , NO 2 Ϫ , NO, or N 2 O) (reviewed in reference 36). With respect to T. denitrificans specifically, the microarray results are generally consistent with greatly increased NAR and NIR enzyme activities (in crude extracts) that were observed to accompany the transition from aerobic to denitrifying conditions in continuous culture (18). Furthermore, the decreasing trend in upregulation shown in However, for nos genes in particular, the results for T. denitrificans appear to deviate from findings for other denitrifying species for which data are available, namely, Pseudomonas stutzeri, Paracoccus denitrificans, and Paracoccus pantotrophus (formerly Thiosphaera pantotropha).…”

Influence of Oxygen Tension on Nitrate Reduction by a Klebsiella sp. Growing in Chemostat Culture

“…This effect was more marked at 8 to 9 mmHg and below, with increased enzyme activities, increased product excretion and a decrease in the culture population density. This suggests that oxygen and nitrate are used simultaneously as electron acceptors, evidence which contrasts with the behaviour of cultures of T. denitriJicans mentioned in the Introduction (Justin & Kelly, 1978). The 'critical' oxygen tension at which oxygen no longer acts as principal electron acceptor correlates well with the report of Harrison (1972) for the change from oxidative to fermentative metabolism of cultures of K. aerogenes growing on glucose.…”

Growth Kinetics of Thiobacillus denitrificans in Anaerobic and Aerobic Chemostat Culture

“…The detailed response of T. denitrzjicans to progressive transition from aerobic to anaerobic continuous culture is described in the following paper (Justin & Kelly, 1978).…”