Magnetospirillum Gryphiswaldense MSR-1 Research Articles

Purified and sterilized magnetosomes from Magnetospirillum gryphiswaldense MSR-1 were not toxic to mouse fibroblasts in vitro

To establish a criterion for measuring the purity of purified and sterilized magnetosomes from Magnetospirillum gryphiswaldense and to evaluate their toxicity for mouse fibroblasts in vitro. The purification of magnetosomes involves disrupting bacterial cells with a French Press, washing directly with PBS buffer accompanied by treatment with low power ultrasonication, and using a magnet to collect the magnetosomes. Five characteristic peaks were displayed by Fourier-transform infrared spectroscopy (FT-IR), which was used to detect the quality of the purified magnetosomes, at 3273, 2921, 1735, 1645 and 1531 cm(-1). The purified magnetosomes showed no evidence of impurities when observed by transmission electron microscopy and energy disperse spectroscopy. The particles could be stored at -20 degrees C after lyophilization and treatment by gamma-rays. Purified and sterilized magnetosomes had no obvious negative effects on the viability of mouse fibroblasts by 3-(4,5-dimethylthiazolyl)-2,5-diphenyl-tetrazolium bromide assay. Purified and sterilized magnetosomes were not toxic to mouse fibroblasts in vitro. This study provides methods for evaluating the purity and safety of magnetosomes from M. gryphiswaldense. The magnetosomes have the potential to be used as novel drug or gene carriers for tumour therapy.

Cloning and functional analysis of the sequences flanking mini-Tn5 in the magnetosomes deleted mutant NM4 of Magnetospirillum gryphiswaldense MSR-1

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 magnetosomes 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 encoded by ORF4 may take part in the signal transduction relating to biosynthesis of magnetosomes.

Iron-limited growth and kinetics of iron uptake in Magnetospirillum gryphiswaldense.

Growth and magnetite formation in Magnetospirillum gryphiswaldense MSR-1 were found close to the maximum at an extracellular iron concentration of 15-20 microM. Ferrous iron was incorporated by a slow, diffusion-like process. Several iron chelators including various microbial siderophores were unable to promote transport of iron into the cells. In contrast, spent culture fluids stimulated the uptake of ferric iron in iron-depleted cells at a high rate, whereas fresh medium and transport buffer were unable to promote iron uptake. However, no siderophore-like compound could be detected in spent culture fluids by the Chrome Azurol S assay. Ferric iron uptake followed Michaelis-Menten kinetics with a Km of 3 microM and a Vmax of 0.86 nmol min-1 (mg dry weight)-1, suggesting a comparatively low-affinity, but high-velocity transport system. Iron incorporation was sensitive to 2,4-dinitrophenol and carbonylcyanide-m-chlorophenylhydrazone, indicating an energy-dependent transport process.