## 4 Materials and Methods
### Identification of Microbial Volatiles Using GC-MS  
_Paenibacillus polymyax_ strains DSM 32871 and M1 were grown in 20 mL headspace vials (75.5 \(\times\) 22.5 mm; Chromtech, Idstein, Germany) filled with 8 mL of (a) nutrient agar (Sifin Diagnostic GmbH, Berlin, Germany), (b) Lysogeny broth (Luria-Bertani) (LB) medium, (c) Landy medium [82] and (d) TSA medium. Equal distribution was assured by parallel application of cell material in three vials per organism. After 24 h of incubation at 30 \({}^{\circ}\)C, the volatiles accumulating inside the vials were measured by headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME GC-MS). Compound separation and detection was performed on a system combining a gas chromatograph 7890A with a quadruppol mass spectrometer 5975C (Agilent Technologies, Waldbronn, Germany). A SPME fiber consisting of divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) was used for sampling (Sigma-Aldrich, St. Louis, MO, USA). HS samples were separated in a (5%-phenyl)methylpolysiloxane column (60 m \(\times\) 0.25 mm i.d.; 0.25 \(\upmu\)m film thickness; DB-5 MS; Agilent Technologies, Waldbronn, Germany). Subsequently, electron ionization with 70 eV and detection in the mass range 25-350 Da were performed. The fiber was desorbed at 200 \({}^{\circ}\)C for 8 min to eliminate potential residues before initial measurements. The inlet temperature was set to 270 \({}^{\circ}\)C. The temperature gradient of the column was maintained at 70 \({}^{\circ}\)C for 1.5 min, raised to 200 \({}^{\circ}\)C at a rate of 16 \({}^{\circ}\)C/min and finally kept at 200 \({}^{\circ}\)C for 0.5 min. The helium flow rate was adjusted to 1.2 mL/min. For identification of the volatiles the received spectra were matched to the NIST Mass Spectral Database.  
The following are available online at [[https://www.mdpi.com/article/10.3390/pathogens10111485/s1](https://www.mdpi.com/article/10.3390/pathogens10111485/s1)]([https://www.mdpi.com/article/10.3390/pathogens10111485/s1](https://www.mdpi.com/article/10.3390/pathogens10111485/s1)), Figure S1: MALDI-TOF mass spectra of the fusaricidins in surface extracts and culture filtrates of _P. polymyax_ DSM 32871 and M1, Figure S2: MALDI-TOF mass spectra of the products found in fractions 22 until 31 of the HPLC fractionation of the culture filtrate of DSM 32871, Figure S3: Upper part of the LIFT-MALDI-TOF/TOF product ion spectra of fusaricidin A ([M + H]\({}^{+}\) = 883.74) (A) and its derivatives with molecular masses [M + H + 71]\({}^{+}\) = 954.63 and [M + H + 16]\({}^{+}\) = 899.43, respectively, in the range from 280 Da up to the parent ion.  
**Author Contributions:** [PERSON], [PERSON], [PERSON] and [PERSON] designed and developed the experimental strategy and the concept of the manuscript. [PERSON], [PERSON], [PERSON] and [PERSON] performed the microbiological work (strain management and sample preparation). [PERSON], [PERSON] and [PERSON] performed the generation, evaluation and presentation of the mass spectrometric data. [PERSON] studied the volatilomes of the tested _P. polymyna_ strains. [PERSON] performed the HPLC analysis. [PERSON] and [PERSON] wrote the manuscript. [PERSON], [PERSON] and [PERSON] were involved in preparation and discussion of the manuscript. All authors have read and agreed to the published version of the manuscript.  
**Funding:** Funding was received from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 676480.  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** The data presented in this article are available on request from the corresponding author.  
**Conflicts of Interest:** The authors declare no conflict of interest.