Enzymic comparisons of the inorganic sulfur metabolism in autotrophic and heterotrophic Thiobacillus ferrooxidans

Activities of enzymes which mediate the oxidation of thiosulfate to sulfate and the assimilation of sulfate to sulfide were assayed in various cell-free fractions of Thiobacillus ferrooxidans grown autotrophically on either ferrous iron or thiosulfate or heterotrophically on glucose. There was no activity of the thiosulfate-oxidizing enzyme in extracts of bacteria grown with ferrous iron. Comparable activities for ATP-sulfurylase (EC 2.7.7.4), ADP-sulfurylase (EC 2.7.7.5), and adenylate kinase (EC 2.7.4.3) were found in the bacteria grown autotrophically with either Fe2+ or S2O32− or heterotrophically with glucose.

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The Mycobacterium tuberculosis cysD and cysNC genes form a stress-induced operon that encodes a tri-functional sulfate-activating complex

Microbiology ◽

10.1099/mic.0.26894-0 ◽

2004 ◽

Vol 150 (6) ◽

pp. 1681-1686 ◽

Cited By ~ 45

Author(s):

Rachel Pinto ◽

Quing Xui Tang ◽

Warwick J. Britton ◽

Thomas S. Leyh ◽

James A. Triccas

Keyword(s):

Mycobacterium Tuberculosis ◽

Sulfur Metabolism ◽

Enzyme Complex ◽

Sulfur Assimilation ◽

Atp Sulfurylase ◽

Catalytic Activities ◽

Disease Relevance ◽

Anti Oxidant ◽

Sulfate Activation ◽

Reductive Assimilation

Sulfur metabolism has been implicated in the virulence, antibiotic resistance and anti-oxidant defence of Mycobacterium tuberculosis. Despite its human disease relevance, sulfur metabolism in mycobacteria has not yet been fully characterized. ATP sulfurylase catalyses the synthesis of activated sulfate (adenosine 5′-phosphosulfate, APS), the first step in the reductive assimilation of sulfate. Expression of the M. tuberculosis cysD gene, predicted to encode the adenylyl-transferase subunit of ATP sulfurylase, is upregulated by the bacilli inside its preferred host, the macrophage. This study demonstrates that cysD and cysNC orthologues exist in M. tuberculosis and constitute an operon whose expression is induced by sulfur limitation and repressed by the presence of cysteine, a major end-product of sulfur assimilation. The cysDNC genes are also induced upon exposure to oxidative stress, suggesting regulation of sulfur assimilation by M. tuberculosis in response to toxic oxidants. To ensure that the cysDNC operon encoded the activities predicted by its primary sequence, and to begin to characterize the products of the operon, they were expressed in Escherichia coli, purified to homogeneity, and tested for their catalytic activities. The CysD and CysNC proteins were shown to form a multifunctional enzyme complex that exhibits the three linked catalytic activities that constitute the sulfate activation pathway.

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Growth of Thiobacillus ferrooxidans on various substrates

Canadian Journal of Microbiology ◽

10.1139/m69-024 ◽

1969 ◽

Vol 15 (1) ◽

pp. 135-138 ◽

Cited By ~ 50

Author(s):

C. J. M. McGoran ◽

D. W. Duncan ◽

C. C. Walden

Keyword(s):

Ferrous Iron ◽

Generation Time ◽

Bacterial Population ◽

Thiobacillus Ferrooxidans ◽

Growth Curves ◽

Insoluble Material ◽

Growth System ◽

Ph Range

When Thiobacillus ferrooxidans was grown on ferrous iron and chalcopyrite (CuFeS2) in excess of 96% of the bacterial population was associated with the insoluble material. When sulfur was the substrate 77% of the bacteria were so associated. This necessitated consideration of the complete growth system to obtain accurate growth curves. By using total bacterial nitrogen as the measure of growth, it was shown that T. ferrooxidans had a minimum generation time of 6.5 to 10 hours on a ferrous iron substrate, 7 to 8 days on a sulfur substrate, and 14 to 17 hours on a chalcopyrite substrate. The pH range for growth was dependent on the substrate used.

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