Magnetotaxis Enables Magnetotactic Bacteria to Navigate in Flow

Abstract

Magnetotactic bacteria (MTB) play an important role in Earth's biogeochemical cycles by transporting minerals in aquatic ecosystems, and have shown promise for controlled transport of microscale objects in flow conditions. However, how MTB traverse complex flow environments is not clear. Here, using microfluidics and high-speed imaging, it is revealed that magnetotaxis enables directed motion of Magnetospirillum magneticum over long distances in flow velocities ranging from 2 to 1260 µm s , corresponding to shear rates ranging from 0.2 to 142 s -a range relevant to both aquatic environments and biomedical applications. The ability of MTB to overcome a current is influenced by the flow, the magnetic field, and their relative orientation. MTB can overcome 2.3-fold higher flow velocities when directed to swim perpendicular to the flow as compared to upstream, as the latter orientation induces higher drag. The results indicate a threshold drag of 9.5 pN, corresponding to a flow velocity of 550 µm s , where magnetotaxis enables MTB to overcome counterdirectional flow. These findings bring new insights into the interactions of MTB with complex flow environments relevant to aquatic ecosystems, while suggesting opportunities for in vivo applications of MTB in microbiorobotics and targeted drug delivery.

Unlocking the Potential of Magnetotactic Bacteria as Magnetic Hyperthermia Agents

“…In the last years, a few groups have started to investigate the possibility of using magnetotactic bacteria as nanobiots for cancer treatment . These groups have focused mainly on tracking and analyzing the movement of bacteria in different environments, studying the potential penetration of bacteria into tumors, developing novel magnetic systems to remotely control and guide these bacteria, analyzing their biocompatibility and navigation in blood stream, etc. The initial results have been very positive and there have already been in vivo tests demonstrating the efficiency of these bacteria in tumors targeting …”

Chemotaxis in external fields: Simulations for active magnetic biological matter

“…We show that forces improve chemotaxis for angles smaller than 90˚and totally hinder it for values higher than a threshold value (Fig 2b), for both run and reverse and run and tumble motions. This could be of particular interest when considering bacteria or biohybrids actuated and directed by external forces, such as magnetic swimmers in a magnetic gradient [17] and under the influence of magnetic tweezers [39], or when considering chemotactic swimmers inside a fluid flow [36,52], for which previous studies ignored the complexity given by chemotactic behaviors.…”

A Review of Planar PIV Systems and Image Processing Tools for Lab-On-Chip Microfluidics

“…The challenge is that often that the drug needs to be administered locally to attack the cancer cells. For this reason, substantial research is focused on bio-microfluidics, micro-robotics and micro-mechanical systems that can be released in the bloodstream to perform targeted drug delivery [ 24 ]. In particular, research is focused on the design of magnetotactic biomicrofluidics [ 23 , 24 , 25 ], biologically-inspired micro propulsion systems [ 26 , 27 ], and programmable self-assembling micro-systems [ 28 ].…”

“…For this reason, substantial research is focused on bio-microfluidics, micro-robotics and micro-mechanical systems that can be released in the bloodstream to perform targeted drug delivery [ 24 ]. In particular, research is focused on the design of magnetotactic biomicrofluidics [ 23 , 24 , 25 ], biologically-inspired micro propulsion systems [ 26 , 27 ], and programmable self-assembling micro-systems [ 28 ]. As a consequence, the importance of research efforts put on the swimming behavior and hydrodynamics of small marine organisms using flagella and appendages [ 29 , 30 , 31 ] have increased.…”