Label-free bacterial imaging with deep-UV-laser-induced native fluorescence

Area of Science:

• Microbiology
• Optical Imaging
• Spectroscopy

Background:

• Microbial detection often requires fluorescent dyes or tags, which can alter samples.
• Autofluorescence from natural materials can interfere with imaging.
• Existing methods may lack the sensitivity or speed for real-time analysis.

Purpose of the Study:

• To develop a near-real-time optical imaging method for detecting microbes using intrinsic fluorescence.
• To enable non-invasive, dye-free visualization of bacteria in their native state.
• To demonstrate the application of this technique in diverse environments, including the deep ocean.

Main Methods:

• Utilizing deep-ultraviolet (DUV, <250 nm) laser excitation to induce native fluorescence in microorganisms.
• Employing a DUV source to minimize background autofluorescence from natural materials.
• Achieving rapid imaging with short exposure times (100 μs) and low excitation intensities.

Main Results:

• Demonstrated detection of bacteria on opaque surfaces across a range of spatial scales (micrometers to tens of centimeters).
• Successfully imaged bacterial communities and individual cells without irreversible sample alteration.
• Achieved the first noninvasive, in situ detection of bacteria in deep-ocean environmental samples.

Conclusions:

• DUV-induced native fluorescence is a powerful tool for rapid, non-invasive microbial detection.
• The technique is effective on various surfaces and applicable to nutrient-limited environments like the deep biosphere.
• This method offers a significant advancement for microbial imaging in ecological and biomedical research.