Bionanotechnology research is focused on functional structures synergistically integrating a broad range of nanomaterials with multicellular assemblies, cells, or macromolecules. When micrometer-sized cells are provided with miniature nanodevices, it expands the application of the cultured microorganisms and requires nanoassembly on every single live cell.
(a, b) Targeted movement of magnetic cells was facilitated by external magnetic field (in liquid media); (c) sedimentation of magnetically concentrated cells; (d) targeted movement and growth of magnetic cells on solid surface (inset shows a higher-magnification view of cells arranged on the surface). (Photo Credit: From the research article)
In surface engineering, the cell walls with polymer layers or/and nanosized particles are functionalized and have been widely used to modify the fundamental properties of microbial cells. Cell encapsulation enables live microbial cells to be fabricated with magnetic nanoparticles onto cell walls, which imitate natural magnetotactic bacteria.
Kazan Federal University and Louisiana Tech University chose to study Alcanivorax borkumensis marine bacteria as a target microorganism for cell surface engineering using magnetic nanoparticles.
The reasons for this selection include - (a) Hydrocarbon-degrading bacteria form a major tool in marine oil spill remediation, and can probably be employed in industrial oil-processing bioreactors, making the outer magnetic manipulations practically relevant with these cells; (b)
A. borkumensis are marine Gram-negative species that possess moderately delicate and thin cell walls, therefore engineering the cell walls of these bacteria is complicated.
Delivering oil-degrading bacteria with synthetically added magnetic functionality is crucial for attenuating their properties and increasing their practical application.
By employing polycation-coated magnetic nanoparticles, the cell surface engineering was accomplished. This is a rapid and simple process, which uses the direct deposition of positively charged iron oxide nanoparticles onto microbial cells when there is a short incubation in higher concentrations of nanoparticles.
Gram-negative bacteria cell walls are constructed from the thin peptidoglycan layer sandwiched between the inner plasma membrane and the external membrane, with lipopolysaccharides offering the complete negative cell charge so cationic particles will fasten to the cell walls because of electrostatic interactions.
A. borkumensis, a gram-negative bacteria is rod shaped measuring 0.5 μm in diameter were covered with 70 - 100 nm magnetite shells. The nanoparticles deposition was conducted with great care to guarantee the survival of magnetized cells.
The progress of biofilms on hydrophobic surface is a vital feature of
A. borkumensis cells, as this is the manner by which these cells fasten to the oil droplets in natural environments.
As a result, any cell surface change must not minimize their capacity to fasten and multiply as biofilms. The researchers have identified related biofilm growth patterns in every tested concentration of PAH- magnetite nanoparticles. The magnetized cells were capable multiplying and exhibiting typical physiological activity.
The subsequent generations of the bacteria have the tendency to remove the artificial shell returning to the original form. Such magnetic nanoencapsulation could be utilized for the
A. Borkumensis movement in the bioreactors to upgrade the spill oil decomposition at specific areas.