Quantitative SIMS Imaging of Agar-Based Microbial Communities

Sage J.B. Dunham, Joseph F. Ellis, Nameera F. Baig, Nydia Morales-Soto, Tianyuan Cao, Joshua D. Shrout, Paul W. Bohn, Jonathan V Sweedler

Research output: Contribution to journalArticle

Abstract

After several decades of widespread use for mapping elemental ions and small molecular fragments in surface science, secondary ion mass spectrometry (SIMS) has emerged as a powerful analytical tool for molecular imaging in biology. Biomolecular SIMS imaging has primarily been used as a qualitative technique; although the distribution of a single analyte can be accurately determined, it is difficult to map the absolute quantity of a compound or even to compare the relative abundance of one molecular species to that of another. We describe a method for quantitative SIMS imaging of small molecules in agar-based microbial communities. The microbes are cultivated on a thin film of agar, dried under nitrogen, and imaged directly with SIMS. By use of optical microscopy, we show that the area of the agar is reduced by 26 ± 2% (standard deviation) during dehydration, but the overall biofilm morphology and analyte distribution are largely retained. We detail a quantitative imaging methodology, in which the ion intensity of each analyte is (1) normalized to an external quadratic regression curve, (2) corrected for isomeric interference, and (3) filtered for sample-specific noise and lower and upper limits of quantitation. The end result is a two-dimensional surface density image for each analyte. The sample preparation and quantitation methods are validated by quantitatively imaging four alkyl-quinolone and alkyl-quinoline N-oxide signaling molecules (including Pseudomonas quinolone signal) in Pseudomonas aeruginosa colony biofilms. We show that the relative surface densities of the target biomolecules are substantially different from values inferred through direct intensity comparison and that the developed methodologies can be used to quantitatively compare as many ions as there are available standards.

Original languageEnglish (US)
Pages (from-to)5654-5663
Number of pages10
JournalAnalytical chemistry
Volume90
Issue number9
DOIs
StatePublished - May 1 2018

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Secondary ion mass spectrometry
Agar
Imaging techniques
Biofilms
Ions
Molecular imaging
Molecules
Quinolones
Biomolecules
Dehydration
Oxides
Optical microscopy
Nitrogen
Thin films

ASJC Scopus subject areas

  • Analytical Chemistry

Cite this

Dunham, S. J. B., Ellis, J. F., Baig, N. F., Morales-Soto, N., Cao, T., Shrout, J. D., ... Sweedler, J. V. (2018). Quantitative SIMS Imaging of Agar-Based Microbial Communities. Analytical chemistry, 90(9), 5654-5663. https://doi.org/10.1021/acs.analchem.7b05180

Quantitative SIMS Imaging of Agar-Based Microbial Communities. / Dunham, Sage J.B.; Ellis, Joseph F.; Baig, Nameera F.; Morales-Soto, Nydia; Cao, Tianyuan; Shrout, Joshua D.; Bohn, Paul W.; Sweedler, Jonathan V.

In: Analytical chemistry, Vol. 90, No. 9, 01.05.2018, p. 5654-5663.

Research output: Contribution to journalArticle

Dunham, SJB, Ellis, JF, Baig, NF, Morales-Soto, N, Cao, T, Shrout, JD, Bohn, PW & Sweedler, JV 2018, 'Quantitative SIMS Imaging of Agar-Based Microbial Communities', Analytical chemistry, vol. 90, no. 9, pp. 5654-5663. https://doi.org/10.1021/acs.analchem.7b05180
Dunham SJB, Ellis JF, Baig NF, Morales-Soto N, Cao T, Shrout JD et al. Quantitative SIMS Imaging of Agar-Based Microbial Communities. Analytical chemistry. 2018 May 1;90(9):5654-5663. https://doi.org/10.1021/acs.analchem.7b05180
Dunham, Sage J.B. ; Ellis, Joseph F. ; Baig, Nameera F. ; Morales-Soto, Nydia ; Cao, Tianyuan ; Shrout, Joshua D. ; Bohn, Paul W. ; Sweedler, Jonathan V. / Quantitative SIMS Imaging of Agar-Based Microbial Communities. In: Analytical chemistry. 2018 ; Vol. 90, No. 9. pp. 5654-5663.
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