Identifying whether individual bacteria cells are alive or dead is important in a lot of industries from food safety to clinical diagnostics. Current methods typically involve culturing the bacteria to see if anything grows. Now a French collaboration has developed a nanotechnology technique that focuses on the physical properties of bacterial walls to differentiate between the dead from the alive.
The researchers set up a fast and simple procedure – based on a conventional microcontact printing and a simple incubation technique to generate functionalized patterns so as to induce local bacteria deposition – that allowed them to produce reliable chemical patterns exhibiting different surface properties to induce selective adsorption of individual bacteria in liquid media at registered positions.
"We have evidenced a selective adsorption of bacteria on these local chemical patterns, producing highly ordered arrays of single living bacteria with a success rate close to 100%," says Cerf.
The team then used this controlled immobilization method to study the mechanical properties of dead or alive bacterial cell in aqueous environment. Using force spectroscopy before and after heating , they measured the Young moduli of the same cell. The cells with a damaged membrane (after heating) present a Young modulus twice as high (6.1 ± 1.5 MPa versus 3.0 ± 0.6 MPa) as that of healthy bacteria. At the same time it has been impossible to evidence a difference between the AFM images of the living and the dead cell.
More from Michael Berger at Nanowerk…
Abstract in Langmuir:Nanomechanical Properties of Dead or Alive Single-Patterned Bacteria
Image: Untreated bacteria deposition on a microstructured surface with APTES functionalized patterns (1100 µm x 1000 µm dark field image. Scale bar corresponds to 30 µm).