Based on analysis of gene structure of mamXY operon in Magnetospirillum gryphiswaldense strain MSR-1,we constructed a mamZ deletion mutant strain(ΔmamZ)and four complemented strains with different mamZ fragment lengt...Based on analysis of gene structure of mamXY operon in Magnetospirillum gryphiswaldense strain MSR-1,we constructed a mamZ deletion mutant strain(ΔmamZ)and four complemented strains with different mamZ fragment lengths.Various cell phenotypic and physiological parameters were evaluated and compared among the wild-type(WT),mutant,and complemented strains.Cell growth rates were not notably different;however,magnetic response(Cmag)and iron uptake ability were significantly lower inΔmamZ.High-resolution transmission electron microscopy(HR-TEM)showed that magnetosomes inΔmamZ were small and irregular,and rock magnetic measurements suggested that they contained immature particles.In comparison to WT of MSR-1,intracellular iron content ofΔmamZ and the complemented strains cultured with 20mmol/L iron source was similar or slightly higher.The complemented strains were unable to synthesize mature or normal amounts of magnetosomes,apparently because of abnormal expression of the transmembrane domain of MamZ protein.Real-time reverse transcription polymerase chain reaction(RTqPCR)analysis showed that relative transcription levels of mamX and ftsZ-like genes inΔmamZ were higher at 18 h than at 12 h,suggesting that MamXY proteins play cooperative functional roles in the magnetosome maturation process.Transcription level of mms6 was significantly upregulated inΔmamZ(incubated at 12 h)and the complemented strains(incubated at 12 and 18 h),refl ecting possible interaction between MamXY and Mms6 proteins during magnetosome biosynthesis.These findings,taken together,demonstrate the essential role of MamZ in the magnetosome maturation process in MSR-1.展开更多
Magnetotactic bacteria reside in sediments and stratified water columns.They are named after their ability to synthesize internal magnetic particles that allow them to align and swim along the Earth’s magnetic field ...Magnetotactic bacteria reside in sediments and stratified water columns.They are named after their ability to synthesize internal magnetic particles that allow them to align and swim along the Earth’s magnetic field lines.Here,we show that two magnetotactic species,Magnetospirillum magneticum strain AMB-1 and Magnetospirillum gryphiswaldense strain MSR-1,are electroactive.Both M.magneticum and M.gryphiswaldense were able to generate current in microbial fuel cells with maximum power densities of 27 and 11μW/m^(2),respectively.In the presence of the electron shuttle resazurin both species were able to reduce the crystalline iron oxide hematite(Fe_(2)O_(3)).In addition,M.magneticum could reduce poorly crystalline iron oxide(FeOOH).Our study adds M.magneticum and M.gryphiswaldense to the growing list of known electroactive bacteria,and implies that electroactivity might be common for bacteria within the Magnetospirillum genus.展开更多
A submerged culture technique for Magneto-spirillum gryphiswaldense under the nitrogen-fixing condition (microaerobic and N-limited) was set up. In N-limited medium with Na-lactate as a sole carbon source, the optical...A submerged culture technique for Magneto-spirillum gryphiswaldense under the nitrogen-fixing condition (microaerobic and N-limited) was set up. In N-limited medium with Na-lactate as a sole carbon source, the optical density (A600 nm) and activity of nitrogen fixation of cells were 1.3 and 217 nmol of ethylene produced per hour per A600nm respectively within 21 h by three times of feeds. The pH and temperature were controlled at 7.2 and 30℃ respectively, and the oxygen concentration was controlled by sparging with N2 containing 0.4%-0.8% of O2. The activity of nitrogen fixation of cells was obviously inhibited by oxygen and ammonium. It indicated that the posttranslational regulation of nitrogenase existed in M. gryphiswaldense.展开更多
A magnetosome deleted mutant NM4 of Magnetospirillum gryphiswaldense MSR-1 was generated by mini-Tn5 transposon mutagenesis, and a 5045-bp fragment flanking mini-Tn5 in NM4 was cloned by Anchored PCR. Sequencing analy...A magnetosome deleted mutant NM4 of Magnetospirillum gryphiswaldense MSR-1 was generated by mini-Tn5 transposon mutagenesis, and a 5045-bp fragment flanking mini-Tn5 in NM4 was cloned by Anchored PCR. Sequencing analysis showed that this fragment involved six putative open reading frames (ORFs); the mini-Tn5 was inserted into ORF4. Functional complementary test indicated that the 5045-bp fragment was required for biosynthesis of mag-netosomes in M. gryphiswaldense MSR-1. The protein encoded by ORF4 had 25% of identity with the chemotaxis protein CheYIII of Caulobacter crescentus CB15, and the protein encoded by ORF4 contained a conserved signal receiver domain that can receive the signal from the sensor partner of the bacterial two-component systems. It was suggested that the protein en-coded by ORF4 may take part in the signal transduction relating to biosynthesis of magneto-somes.展开更多
基金Supported by the National Natural Science Foundation of China(No.31270093)the Innovation Team of Scientific Research Platform of Anhui Province(No.KJ2015TD001)the Open Project Program of the Collaborative Innovation Center for Modern Bio-manufacture,Anhui University(No.BM2015010)。
文摘Based on analysis of gene structure of mamXY operon in Magnetospirillum gryphiswaldense strain MSR-1,we constructed a mamZ deletion mutant strain(ΔmamZ)and four complemented strains with different mamZ fragment lengths.Various cell phenotypic and physiological parameters were evaluated and compared among the wild-type(WT),mutant,and complemented strains.Cell growth rates were not notably different;however,magnetic response(Cmag)and iron uptake ability were significantly lower inΔmamZ.High-resolution transmission electron microscopy(HR-TEM)showed that magnetosomes inΔmamZ were small and irregular,and rock magnetic measurements suggested that they contained immature particles.In comparison to WT of MSR-1,intracellular iron content ofΔmamZ and the complemented strains cultured with 20mmol/L iron source was similar or slightly higher.The complemented strains were unable to synthesize mature or normal amounts of magnetosomes,apparently because of abnormal expression of the transmembrane domain of MamZ protein.Real-time reverse transcription polymerase chain reaction(RTqPCR)analysis showed that relative transcription levels of mamX and ftsZ-like genes inΔmamZ were higher at 18 h than at 12 h,suggesting that MamXY proteins play cooperative functional roles in the magnetosome maturation process.Transcription level of mms6 was significantly upregulated inΔmamZ(incubated at 12 h)and the complemented strains(incubated at 12 and 18 h),refl ecting possible interaction between MamXY and Mms6 proteins during magnetosome biosynthesis.These findings,taken together,demonstrate the essential role of MamZ in the magnetosome maturation process in MSR-1.
基金the Carlsberg Foundation Distinguished Fellowships(No.CF18-0084)the Research Grant(No.00023110)from VILLUM FONDENthe Independent Research Fund Denmark(DFF-Project 1 No.1032-00028B).
文摘Magnetotactic bacteria reside in sediments and stratified water columns.They are named after their ability to synthesize internal magnetic particles that allow them to align and swim along the Earth’s magnetic field lines.Here,we show that two magnetotactic species,Magnetospirillum magneticum strain AMB-1 and Magnetospirillum gryphiswaldense strain MSR-1,are electroactive.Both M.magneticum and M.gryphiswaldense were able to generate current in microbial fuel cells with maximum power densities of 27 and 11μW/m^(2),respectively.In the presence of the electron shuttle resazurin both species were able to reduce the crystalline iron oxide hematite(Fe_(2)O_(3)).In addition,M.magneticum could reduce poorly crystalline iron oxide(FeOOH).Our study adds M.magneticum and M.gryphiswaldense to the growing list of known electroactive bacteria,and implies that electroactivity might be common for bacteria within the Magnetospirillum genus.
基金This work was supported by the National Natural Science Foundation of China (Grant No. 30170012)the National Key Basic Research Development Program (Grant No. 001CB 108904).
文摘A submerged culture technique for Magneto-spirillum gryphiswaldense under the nitrogen-fixing condition (microaerobic and N-limited) was set up. In N-limited medium with Na-lactate as a sole carbon source, the optical density (A600 nm) and activity of nitrogen fixation of cells were 1.3 and 217 nmol of ethylene produced per hour per A600nm respectively within 21 h by three times of feeds. The pH and temperature were controlled at 7.2 and 30℃ respectively, and the oxygen concentration was controlled by sparging with N2 containing 0.4%-0.8% of O2. The activity of nitrogen fixation of cells was obviously inhibited by oxygen and ammonium. It indicated that the posttranslational regulation of nitrogenase existed in M. gryphiswaldense.
基金This work was supported by the Chinese National Programs for High Technology Research and Development(Grant No.2001AA218041).
文摘A magnetosome deleted mutant NM4 of Magnetospirillum gryphiswaldense MSR-1 was generated by mini-Tn5 transposon mutagenesis, and a 5045-bp fragment flanking mini-Tn5 in NM4 was cloned by Anchored PCR. Sequencing analysis showed that this fragment involved six putative open reading frames (ORFs); the mini-Tn5 was inserted into ORF4. Functional complementary test indicated that the 5045-bp fragment was required for biosynthesis of mag-netosomes in M. gryphiswaldense MSR-1. The protein encoded by ORF4 had 25% of identity with the chemotaxis protein CheYIII of Caulobacter crescentus CB15, and the protein encoded by ORF4 contained a conserved signal receiver domain that can receive the signal from the sensor partner of the bacterial two-component systems. It was suggested that the protein en-coded by ORF4 may take part in the signal transduction relating to biosynthesis of magneto-somes.
