Morphological changes in magnetotactic bacteria in presence of magnetic fields

Nanomagnets manufactured by magnetotactic bacteria hold immense promise in magnetically directed drug delivery. In spite of discovery of these bacteria nearly three decades ago, it is not known how the bacteria are able to keep the nanomagnets trapped inside biological membranes (vesicles called magnetosomes). Understanding the physical nature of interactions, which these nanomagnets are capable of, is essential for envisaging any directed drug delivery application. We analyzed the morphology of two magnetic bacterial strains, Magnetospirillum magnetotacticum and Magnetospirillum gryphiswalden e, by defining the features of individual bacteria in two dimensions as length and width (in microns) under different magnetic fields using bar magnets. The control morphologies were taken to be the features of bacteria not under the influence of any magnetic field other than the earth's own. Using analysis of variance (ANOVA), we found statistically significant morphological changes in the M. magnetotacticum under different conditions. In contrast, there were no morphological differences observed for M. gryphiswaldense under any conditions. The width of M. magnetotacticum was found to be significantly higher for the control conditions compared to any magnetic condition. The length of M. magnetotacticum was found to be significantly lower when only south poles of the bar magnets (single or couple) were towards the bacteria. These results reflect a possible difference in packaging of magnetosomes inside two different strains of magnetic bacteria and imply that it may be important to select the right microbial source of nanomagnets (in contrast to using just any strain), trapped inside biological membranes, for potential targeted drug delivery applications, whereby enhanced sensitivity to external magnetic fields would be preferred.