Cultivable magnetotactic bacteria(MTB) in laboratory can provide sufficient samples for molecular microbiological and magnetic studies.However,a cold-stored MTB strain,such as Magnetospirillum magneticum AMB-1,often l...Cultivable magnetotactic bacteria(MTB) in laboratory can provide sufficient samples for molecular microbiological and magnetic studies.However,a cold-stored MTB strain,such as Magnetospirillum magneticum AMB-1,often loses its ability to synthesize magnetosomes and consequently fails to sense the external magnetic field.It is therefore important to quickly recover vigorous bacteria cells that highly capable of magnetosome producing.In this study,a modified capillary magnetic separation system was designed to recover a deteriorating strain of Magnetospirillum magneticum AMB-1 that long-term cold-stored in a refrigerator.The results show that all cells obtained after a 3-cycle treatment were vigorous and had the ability to produce magnetosomes.Moreover,the 3rd-cycle recovered cells were able to form more magnetosome crystals.Compared with the colony formation method,this new method is time-saving,easily operated,and more efficient for recovering vigorous MTB cells.展开更多
Magnetospirillum magneticum strain AMB-1 belongs to the family of magnetotactic bacteria. It possesses a magnetosome chain aligning, with the assistance of cytoskeleton filaments MamK, along the long axis of the spira...Magnetospirillum magneticum strain AMB-1 belongs to the family of magnetotactic bacteria. It possesses a magnetosome chain aligning, with the assistance of cytoskeleton filaments MamK, along the long axis of the spiral cells. Most fresh M. magneticum AMB-1 cells exhibit spiral morphology. In addition, other cell shapes such as curved and spherical were also observed in this organism. Interestingly, the spherical cell shape increased steadily with prolonged incubation time. As the actin-like cytoskeleton protein MreB is involved in maintenance of cell shapes in rod-shaped bacteria such as Escherichia coli and Bacillus subtilis, the correlation between MreB protein levels and cell shape was investigated in this study. Immunoblotting analysis showed that the quantity of MreB decreased when the cell shape changed along with incubation time. As an internal control, the quantity of MamA was not obviously changed under the same conditions. Cell shape directs cell-wall synthesis during growth and division. MreB is required for maintaining the cell shape. Thus, MreB might play an essential role in maintaining the spiral shape of M. magneticum AMB-1 cells.展开更多
The magnetic properties of magnetosome magnetite are of interdisciplinary interest because magnetosomes are potential carriers of natural remanent magnetization and paleoenvironment, as well as novel nano-biomaterials...The magnetic properties of magnetosome magnetite are of interdisciplinary interest because magnetosomes are potential carriers of natural remanent magnetization and paleoenvironment, as well as novel nano-biomaterials in biotechnological and biomedical applications. We carried out magnetic and electron transmission microscopy analyses of fresh Magnetospirillum magneticum AMB-1 whole cells and isolated magnetosomes. Results revealed that AMB-1 synthesized single-domain magnetite magneto-somes, which are arranged in the form of linear fragmental chain. The distinct differences of magnetic properties between these two samples can be faithfully interpreted in terms of spatial arrangement of magnetosomes and magnetostatic interaction. For the whole cells, the strong intra-chain interactions and weak inter-chain interactions generate behaviors of non-interacting uniaxial single-domain particles. Its δ-ratio is 3.0 and passes the Moskowitz test. In contrast, the isolated magnetosome sample has reduced values of coercivity and δ-ratio (1.5), due to increasing three-dimensional magnetostatic interactions and collapse of magneto-some chains. These observations provide useful insights into applications of the biogenic magnetite (magnetosomes) in magnetic nano-materials and magnetofossils in the paleomagnetic and environmental magnetism.展开更多
基金Supported by the Natural Science Foundation of Shandong Province,China(No.2006ZRB01973)the National Natural Science Foundation of China(Nos.40821091,40325011)
文摘Cultivable magnetotactic bacteria(MTB) in laboratory can provide sufficient samples for molecular microbiological and magnetic studies.However,a cold-stored MTB strain,such as Magnetospirillum magneticum AMB-1,often loses its ability to synthesize magnetosomes and consequently fails to sense the external magnetic field.It is therefore important to quickly recover vigorous bacteria cells that highly capable of magnetosome producing.In this study,a modified capillary magnetic separation system was designed to recover a deteriorating strain of Magnetospirillum magneticum AMB-1 that long-term cold-stored in a refrigerator.The results show that all cells obtained after a 3-cycle treatment were vigorous and had the ability to produce magnetosomes.Moreover,the 3rd-cycle recovered cells were able to form more magnetosome crystals.Compared with the colony formation method,this new method is time-saving,easily operated,and more efficient for recovering vigorous MTB cells.
基金Supported by the CAS/SAFEA International Partnership Program for Creative Research Teams (Research and Applications of Marine Functional Genomics)the Haiwaijie chuxuezhe-Fund of the Chinese Academy of Sciences (2006-1-15)+1 种基金the fund from MATHAB (No. MH200804)a CNRS scholarship for FZ, and National Natural Science Foundation of China (No. 40776094)
文摘Magnetospirillum magneticum strain AMB-1 belongs to the family of magnetotactic bacteria. It possesses a magnetosome chain aligning, with the assistance of cytoskeleton filaments MamK, along the long axis of the spiral cells. Most fresh M. magneticum AMB-1 cells exhibit spiral morphology. In addition, other cell shapes such as curved and spherical were also observed in this organism. Interestingly, the spherical cell shape increased steadily with prolonged incubation time. As the actin-like cytoskeleton protein MreB is involved in maintenance of cell shapes in rod-shaped bacteria such as Escherichia coli and Bacillus subtilis, the correlation between MreB protein levels and cell shape was investigated in this study. Immunoblotting analysis showed that the quantity of MreB decreased when the cell shape changed along with incubation time. As an internal control, the quantity of MamA was not obviously changed under the same conditions. Cell shape directs cell-wall synthesis during growth and division. MreB is required for maintaining the cell shape. Thus, MreB might play an essential role in maintaining the spiral shape of M. magneticum AMB-1 cells.
基金supported by the National Natural Science Foundation of China (Grant Nos. 40821091 and 40325011)Hundred Talents Program of the Chi-nese Academy of Sciences and Marie-Curie Fellowship (IIF) Return Phase of (Grant No. MIF1-CT-2005-007555)
文摘The magnetic properties of magnetosome magnetite are of interdisciplinary interest because magnetosomes are potential carriers of natural remanent magnetization and paleoenvironment, as well as novel nano-biomaterials in biotechnological and biomedical applications. We carried out magnetic and electron transmission microscopy analyses of fresh Magnetospirillum magneticum AMB-1 whole cells and isolated magnetosomes. Results revealed that AMB-1 synthesized single-domain magnetite magneto-somes, which are arranged in the form of linear fragmental chain. The distinct differences of magnetic properties between these two samples can be faithfully interpreted in terms of spatial arrangement of magnetosomes and magnetostatic interaction. For the whole cells, the strong intra-chain interactions and weak inter-chain interactions generate behaviors of non-interacting uniaxial single-domain particles. Its δ-ratio is 3.0 and passes the Moskowitz test. In contrast, the isolated magnetosome sample has reduced values of coercivity and δ-ratio (1.5), due to increasing three-dimensional magnetostatic interactions and collapse of magneto-some chains. These observations provide useful insights into applications of the biogenic magnetite (magnetosomes) in magnetic nano-materials and magnetofossils in the paleomagnetic and environmental magnetism.
