Gas chromatography-mass spectrometry of headspace of natural bacterial isolates, <i>E</i>. <i>coli</i> HB101 and LB media control.

<p>Overnight liquid cultures of bacteria were spotted on NGM agar plates (OD600 = 10) and incubated for 1 hour, then NGM agar squares with bacterial suspension were placed inside a GC-MS glass vial for five hours. A SPME fiber was inserted into the vial containing the bacteria to sample the volatile compounds in the headspace. Top, representative total ion chromatograms (TIC), from top to bottom: JUb4, JUb5, JUb12, JUb39, JUb43, JUb93, JUb38, JUb68, <i>E</i>. <i>coli</i> HB101and LB media control. Peaks present in bacterial samples, but not LB media, are numbered. Peaks present in LB media are labeled with letters. One asterisk indicates “fiber peaks,” volatile siloxanes released by the SPME fiber; two asterisks indicate contamination because also present in fiber blank control run prior to JUb43 sample analysis. Bottom, volatile organic compounds (VOCs) corresponding to labelled peaks. Peaks were identified tentatively with NIST 11 (National Institute of Standards and Technology) mass spectral library and confirmed with known standards. Retention times of VOCs in samples JUb43, JUb38, and JUb68 are shorter by approximately 0.1 minute compared to other samples analyzed because a small, contaminated segment of the column was removed from the inlet. See sample retention times in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0201158#pone.0201158.s001" target="_blank">S1 Table</a>. All bacterial samples were prepared and analyzed two or more times on different days.</p

Chemotaxis to volatile organic compounds released by natural bacterial isolates.

<p>All volatile organic compounds were diluted in ethanol. (<b>A</b>) 2-methyl-1-butanol (<b>B)</b> Ethyl isovalerate. *** p < 0.001, ** p < 0.01 ANOVA with Dunnett compared to chemotaxis between ethanol (the diluent) on both sides of the chemotaxis plate (last bar), n ≥ 6 assays. Assays conducted on at least two different days. Error bars represent SEM.</p

Summary of most abundant bacterial volatile organic compounds.

<p>VOCs were identified by SPME-GC-MS and confirmed with known standards. +++ indicates high abundance VOC with total ion chromatogram (TIC) peak area greater than 6.0 × 10⁷ counts; + indicates low abundance VOC with TIC peak area between 1.0 × 10⁷ and 6.0 × 10⁷counts; n.d. indicates not detected. Data from at least two different experimental replicates on different days. Attraction to <i>C</i>. <i>elegans</i> determined by bacterial odor choice assay (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0201158#pone.0201158.g001" target="_blank">Fig 1D</a>).</p