In vivo role of adenosine-5 '-phosphosulfate reductase in the purple sulfur bacterium Allochromatium vinosum

Citation
O. Sanchez et al., In vivo role of adenosine-5 '-phosphosulfate reductase in the purple sulfur bacterium Allochromatium vinosum, ARCH MICROB, 176(4), 2001, pp. 301-305
Citations number
20
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Microbiology
Journal title
ARCHIVES OF MICROBIOLOGY
ISSN journal
0302-8933 → ACNP
Volume
176
Issue
4
Year of publication
2001
Pages
301 - 305
Database
ISI
SICI code
0302-8933(200110)176:4<301:IVROA'>2.0.ZU;2-8
Abstract
Adenosine-5'-phosphosulfate (APS) reductase participates in the oxidation o f sulfite to APS in Allochromatium vinosum. Oxidation of sulfite via the AP S pathway yields ATP through substrate-level phosphorylation. An alternativ e enzyme for the oxidation of sulfite to sulfate, sulfite:acceptor oxidored uctase, has also been reported in Ach. vinosum. Oxidation of sulfite throug h this enzyme does not yield ATP. APS reductase is expressed constitutively in Ach. vinosum, suggesting that it performs an important role in this org anism. However, studies carried out with batch cultures of an APS reductase mutant showed little or no differences in growth or in the rates of substr ate oxidation when compared to the wild-type, therefore questioning the rol e of this enzyme. In an attempt to establish whether the ATP gain derived f rom APS-reductase-mediated oxidation of sulfite is relevant for energy-limi ted cultures, we compared growth of the wild-type SM50 and the A-PS-reducta se-deficient mutant D3 when grown in continuous culture under different deg rees of illumination. Little differences in the specific growth rates of th e two strains were observed at light-limiting irradiances, suggesting that the ATP gained during sulfite oxidation through the APS reductase pathway d oes not constitute a significant energy input. However, at saturating irrad iances, wild-type Ach. vinosum grew considerably faster than the mutant. In creasing the irradiance even further resulted in inhibition of the wild-typ e strain down to the level of the APS reductase mutant. The implications of these results are discussed.