Published In
Astrobiology
Document Type
Article
Publication Date
4-2024
Subjects
Fluorescence microscope -- microorganisms
Abstract
We report a simple, inexpensive design of a fluorescence microscope with light-emitting diode (LED) excitation for detection of labeled and unlabeled microorganisms in mineral substrates. The use of deep UV (DUV) excitation with visible emission requires no specialized optics or slides and can be implemented easily and inexpensively using an oblique illumination geometry. DUV excitation (<280 >nm) is preferable to near UV (365 nm) for avoidance of mineral autofluorescence. When excited with DUV, unpigmented bacteria show two emission peaks: one in the near UV ∼320 nm, corresponding to proteins, and another peak in the blue to green range, corresponding to flavins and/or reduced nicotinamide adenine dinucleotide (NADH). Many commonly used dyes also show secondary excitation peaks in the DUV, with identical emission spectra and quantum yields as their primary peak. However, DUV fails to excite key biosignature molecules, especially chlorophyll in cyanobacteria. Visible excitation (violet to blue) also results in less mineral autofluorescence than near UV, and most autofluorescence in the minerals seen here is green, so that red dyes and red autofluorescence of chlorophyll and porphyrins are readily distinguished. The pairing of DUV and near UV or visible excitation, with emission across the visible, represents the most thorough approach to detection of labeled and unlabeled bacteria in soil and rock.
Rights
Copyright (c) 2024 The Authors
This work is licensed under a Creative Commons Attribution 4.0 International License.
Locate the Document
DOI
10.1089/ast.2023.0020
Persistent Identifier
https://archives.pdx.edu/ds/psu/41584
Citation Details
Case, N., Johnston, N., & Nadeau, J. (2024). Fluorescence Microscopy with Deep UV, Near UV, and Visible Excitation for In Situ Detection of Microorganisms. Astrobiology, 24(3), 300-317.