Six strains of moderately thermophilic sulfur-oxidizing bacteria were isolated from several different typical environments in China. The identities of the isolates were confirmed by analyses of their 16S rRNA genes, a...Six strains of moderately thermophilic sulfur-oxidizing bacteria were isolated from several different typical environments in China. The identities of the isolates were confirmed by analyses of their 16S rRNA genes, and some key physiological traits. The isolates are Gram negative, rod-shaped bacteria, their optimal temperature and pH value for growth are 45-50℃ and 2.5-3.5 respectively. They are autotrophic and used elemental sulfur, sodium thiosulfate and potassium tetrathionate as electron donor, while a little glucose stimulated their growth. 16S rDNA sequences analysis reveals that the strains are phylogenetically clustered to Acidithiobacillus caldus.展开更多
Acidithiobacillus caldus,a typical sulfur oxidizer,derives the majority of its energy from sulfur oxidation.And the essential enzyme for sulfide oxidation catalysis is sulfide quinone oxidoreductase(SQR),an ancient fl...Acidithiobacillus caldus,a typical sulfur oxidizer,derives the majority of its energy from sulfur oxidation.And the essential enzyme for sulfide oxidation catalysis is sulfide quinone oxidoreductase(SQR),an ancient flavoprotein.Here,the catalytic mechanism of SQR generated from A.caldus was investigated(SQR^(Ac)).According to phylogenetic study,SQR^(Ac)(ACAty RS11315)is closely related to SQR(BAD99305)of Acidithiobacillus ferrooxidans NASF-1 and is classified as a type I Sqr enzyme.SQR^(Ac)heterologously produced in Escherichia coli exhibits the distinctive absorption peaks(375,450 nm)of the flavoproteins family of proteins in its absorption spectrum.Utilizing site-directed mutagenesis,the function of conserved cysteines in the catalytic pathway was determined.Based on the sulfide quinone redox reactions in vitro of SQR^(Ac)and variations,Cys160 and Cys356 have been identified as enzyme-active residues.Mutation of another cysteine present in all type I SQRs(Cys128)decreased enzyme activity by 56%,indicating that this residue plays an important but non-essential role in enzyme function.In addition,the binding affinities of SQR^(Ac),the visualization of its 3D structure,and the interaction between receptors and ligands were investigated.Finally,a suitable sulfide quinone redox catalytic mechanism for A.caldus was proposed.展开更多
Acidithiobacillus caldus is one of the dominant sulfur-oxidizing bacteria in bioleaching reactors. It plays the essential role in maintaining the high acidity and oxidation of reduced inorganic sulfur compounds during...Acidithiobacillus caldus is one of the dominant sulfur-oxidizing bacteria in bioleaching reactors. It plays the essential role in maintaining the high acidity and oxidation of reduced inorganic sulfur compounds during bioleaching process. In this report, the complete genome sequence of A. caldus SM-1 is presented. The genome is composed of one chromosome （2,932,225 bp） and four plasmids （pLAtcl, pLAtc2, pLAtc3, pLAtcm） and it is rich in repetitive sequences （accounting for 11% of the total genome）, which are often associated with transposable genetic elements. In particular, twelve copies of ISAtfe and thirty-seven copies of ISAtcl have been identified, suggesting that they are active transposons in the genome. A. caldus SM-1 encodes all enzymes for the central metabolism and the assimilation of carbon compounds, among which 29 proteins/enzymes were identifiable with proteomic tools. The SM-1 fixes CO2 via the classical Calvin-Bassham--Benson （CBB） cycle, and can operate complete Embden-Meyerhof pathway （EMP）, pentose phosphate pathway （PPP）, and gluconeogenesis. It has an incomplete tricarboxylic acid cycle （TCA）. Four putative transporters involved in carbohydrate uptake were identified. Taken together, the results suggested that SM-1 was able to assimilate carbohydrates and this was subsequently confirmed experimentally because addition of 1% glucose or sucrose in basic salt medium significantly increased the growth of SM-1. It was concluded that the complete genome of SM-1 provided fundamental data for further investigation of its physiology and genetics, in addition to the carbon metabolism revealed in this study.展开更多
基金Project (50321402) supported by the National Natural Science Foundation of China Project(2004CB619204) supported by the State Basic Research Development Program of China Project (DY105-02-04-05) supported by the China Ocean Mineral Resources Research and Development Association
文摘Six strains of moderately thermophilic sulfur-oxidizing bacteria were isolated from several different typical environments in China. The identities of the isolates were confirmed by analyses of their 16S rRNA genes, and some key physiological traits. The isolates are Gram negative, rod-shaped bacteria, their optimal temperature and pH value for growth are 45-50℃ and 2.5-3.5 respectively. They are autotrophic and used elemental sulfur, sodium thiosulfate and potassium tetrathionate as electron donor, while a little glucose stimulated their growth. 16S rDNA sequences analysis reveals that the strains are phylogenetically clustered to Acidithiobacillus caldus.
基金the National Key Research and Development Program of China(2022YFC3401300)the National Natural Science Foundation of China(No.21878128,21,776,113,31,701,582+2 种基金21,606,110)the Fundamental Research Funds for the Central Universities(No.2050205)Program of Introducing Talents of Discipline to Universities(No.111-2-06).
文摘Acidithiobacillus caldus,a typical sulfur oxidizer,derives the majority of its energy from sulfur oxidation.And the essential enzyme for sulfide oxidation catalysis is sulfide quinone oxidoreductase(SQR),an ancient flavoprotein.Here,the catalytic mechanism of SQR generated from A.caldus was investigated(SQR^(Ac)).According to phylogenetic study,SQR^(Ac)(ACAty RS11315)is closely related to SQR(BAD99305)of Acidithiobacillus ferrooxidans NASF-1 and is classified as a type I Sqr enzyme.SQR^(Ac)heterologously produced in Escherichia coli exhibits the distinctive absorption peaks(375,450 nm)of the flavoproteins family of proteins in its absorption spectrum.Utilizing site-directed mutagenesis,the function of conserved cysteines in the catalytic pathway was determined.Based on the sulfide quinone redox reactions in vitro of SQR^(Ac)and variations,Cys160 and Cys356 have been identified as enzyme-active residues.Mutation of another cysteine present in all type I SQRs(Cys128)decreased enzyme activity by 56%,indicating that this residue plays an important but non-essential role in enzyme function.In addition,the binding affinities of SQR^(Ac),the visualization of its 3D structure,and the interaction between receptors and ligands were investigated.Finally,a suitable sulfide quinone redox catalytic mechanism for A.caldus was proposed.
基金supported by the National Science Foundation of China(No.30870039)the National Basic Research Program of China(973 Program,No.2010CB630903)
文摘Acidithiobacillus caldus is one of the dominant sulfur-oxidizing bacteria in bioleaching reactors. It plays the essential role in maintaining the high acidity and oxidation of reduced inorganic sulfur compounds during bioleaching process. In this report, the complete genome sequence of A. caldus SM-1 is presented. The genome is composed of one chromosome （2,932,225 bp） and four plasmids （pLAtcl, pLAtc2, pLAtc3, pLAtcm） and it is rich in repetitive sequences （accounting for 11% of the total genome）, which are often associated with transposable genetic elements. In particular, twelve copies of ISAtfe and thirty-seven copies of ISAtcl have been identified, suggesting that they are active transposons in the genome. A. caldus SM-1 encodes all enzymes for the central metabolism and the assimilation of carbon compounds, among which 29 proteins/enzymes were identifiable with proteomic tools. The SM-1 fixes CO2 via the classical Calvin-Bassham--Benson （CBB） cycle, and can operate complete Embden-Meyerhof pathway （EMP）, pentose phosphate pathway （PPP）, and gluconeogenesis. It has an incomplete tricarboxylic acid cycle （TCA）. Four putative transporters involved in carbohydrate uptake were identified. Taken together, the results suggested that SM-1 was able to assimilate carbohydrates and this was subsequently confirmed experimentally because addition of 1% glucose or sucrose in basic salt medium significantly increased the growth of SM-1. It was concluded that the complete genome of SM-1 provided fundamental data for further investigation of its physiology and genetics, in addition to the carbon metabolism revealed in this study.
