Label-Free Raman Microspectroscopy for Identifying Prokaryotic Virocells

Area of Science:

• Microbiology
• Biochemistry
• Spectroscopy

Background:

• Prokaryotic cell chemistry during viral infection (virocells) is poorly understood.
• Raman microspectroscopy offers potential for single-cell analysis.

Purpose of the Study:

• Investigate biochemical changes in bacterial and archaeal cells upon infection with virulent viruses.
• Develop a method for identifying virocells using single-cell Raman microspectroscopy.

Main Methods:

• Single-cell Raman microspectroscopy was applied to bacterial and archaeal cultures before and after viral addition.
• Multivariate and univariate statistical analyses were used to interpret spectral data.
• A wavenumber ratio was defined as an indicator for virocells.

Main Results:

• Significant spectral differences were observed in Pseudomonas syringae infected with dsRNA phage phi6, indicating increased nucleic acid to protein ratio.
• Bacillus subtilis infected with dsDNA phage phi29 showed a decreased ratio, suggesting a cellular stress response.
• The method was less effective for archaeal virocells due to autofluorescence.

Conclusions:

• Raman microspectroscopy is a promising, label-free tool for chemically identifying Gram-positive and Gram-negative virocells.
• The technique can reveal biochemical changes and stress responses in single cells during viral infection.
• This method advances the study of virus-host interactions in prokaryotes.