Helium ions image viruses attacking bacteria
Image: Bacteriophages (green) attached on E. coli bacteria (blue) on an agar substrate (brown), imaged with a helium ion microscope.
Finland-based researchers have used helium ion microscopy to image viruses attacking bacteria, producing some of the first such images of these interactions at different stages of infection.
To date, microbial interactions have been imaged using electron microscopy methods but Professor Ilari Maasilta and colleagues from the Nanoscience Center at University of Jyvaskyla have now discovered that bacteria and viruses can also be imaged with helium ions.
As they point out, thanks to the heavier mass of helium ions compared to electrons, HIM reaches sub-nanometre resolutions, provides a greater depth of field, has a greater surface sensitivity than SEM and can be used to image non-conductive samples.
What's more, by controlling the helium beam dose, or be using heavier neon atoms, the researchers can use the helium ion microscope to mill out material in the samples, enabling sub-surface imaging and in situ sectioning.
They demonstrated the method be by imaging hard-to-see interactions between E. Coli and bacteriophages, clearly showing the the different stages in which these viruses attack the bacteria.
Using helium and neon milling they also revealed the sub-surface structure of bacterial colonies on an agar substrate as well as the structure inside some individual bacteria after cross-sectioning.
"HIM offers great opportunities to advance the studies of microbial imaging, in particular in the area of interaction of viruses with cells," says Maasilta.
Research is published in Advanced Biosystems.