It is widely believed that magnetotactic bacteria (MTB) form membrane-enveloped magnetite crystals (magnetosomes) under strict genetic control.

Postdoctor LI JInhua and his teacher PAN Yongxin find that the Magnetospirillum magneticum strain AMB-1 was cultured in the same growth medium, but under four different growth conditions: Anaerobic static, aerobic static, aerobic 80-rpm rotating, and aerobic 120-rpm rotating to investigate possible environmental influences on magnetite magnetosome formation.

Given that all samples are prepared and measured in the same way, the changes in physical and magnetic properties indicate that environmental factors (oxygen) affected the biomineralization of magnetite magnetosomes in magnetotactic bacteria, which supports the previous findings. In all experiments, only magnetite with the geometry of truncated octahedron is formed within magnetosomes, which suggests that the mineral phase and crystal habit remain to be genetically controlled.

These results also imply the physical and magnetic properties of magnetite magnetosomes may, to some extent, reflect the external growth environments.

FIG. 1. HRTEM images of individual magnetite magnetosomes recorded along the [011] zone axis of magnetite (left), and their corresponding Fast Fourier transform (FFT) images (middle) and morphological models (right). (Image by LI)

FIG. 2. Room-temperature FORC diagrams (left) and low-temperature magnetic properties (right) for the bulk sample of AMB-1 cells after 48 h cultivation. (Image by LI)

Li et al. Environmental factors affect magnetite magnetosome synthesis in Magnetospirillum magneticum AMB-1: Implications for biologically controlled mineralization. Geomicrobiology Journal. 2012, 29: 362-373, doi: 10.1080/01490451.2011.565401 (Download Here)