Carbon sequestration assessment using varying concentrations of magnetotactic bacteria

Abstract

Carbon cycling processes on Earth are many and complex, and several continental and oceanic environments remain poorly studied. Consequently, major uncertainties affect carbon-cycling models which limit our ability to understand and predict climate dynamics. The first assessment of carbon sequestration for magnetotactic bacteria (MTB) was carried out in this study. MTB produce magnetosomes which are intracellular organelles containing nanometer-sized, membrane-bound magnetite crystals. These crystals are arranged into single or multiple chains within the cell, which enable MTB to align themselves along a magnetic field (magnetotaxis). MTB are well known in the biological sciences, and their magnetic remains are widely studied in earth sciences as magnetofossils. Rock magnetic techniques provide indirect and non-destructive identification of magnetosomes in a sample. It is very crucial to understand the magnetic response of different types of magnetosomes produced by distinct MTB species with varying concentrations. Magnetic properties of lysed and whole MTB cells, the cultured Magnetovibrio blakemorei strain MV-1T and Magnetofaba australis strain IT-1, with concentrations varying from 102 to 109 per sample are presented here. Magnetic properties of quantified bacterial magnetite depend largely on the quantity of MTB cells rather than on the bacterial species or cell type (lysed or whole). Magnetic values are significantly higher for the samples containing 107 cells or higher, FORC diagrams have no measurable magnetic fingerprint for the samples containing less than 107 cells. Therefore, unmeasurable magnetic signals may compromise detection of lower magnetic particle concentrations in a sample. This study estimates the carbon content of MTB cells and discusses its relationship to the global carbon cycle.

Keywords

• Carbon cycling
• Magnetic techniques
• Magnetotactic bacteria
• Magnetofossils