Serratia odorifera: analysis of volatile emission and biological impact of volatile compounds on Arabidopsis thaliana

Abstract

Bacteria emit a wealth of volatiles. The combination of coupled gas chromatography/mass spectrometry (GC/MS) and proton-transfer-reaction mass spectrometry (PTR-MS) analyses provided a most comprehensive profile of volatiles of the rhizobacterium Serratia odorifera 4Rx13. An array of compounds, highly dominated by sodorifen (approximately 50%), a bicyclic oligomethyl octadiene, could be detected. Other volatiles included components of the biogeochemical sulfur cycle such as dimethyl disulfide (DMDS), dimethyl trisulfide and methanethiol, terpenoids, 2-phenylethanol, and other aromatic compounds. The composition of the bouquet of S. odorifera did not change significantly during the different growth intervals. At the beginning of the stationary phase, 60 μg of volatiles per 24 h and 60 easily detectable components were released. Ammonia was also released by S. odorifera, while ethylene, nitric oxide (NO) and hydrogen cyanide (HCN) could not be detected. Dual culture assays proved that 20 μmol DMDS and 2.5 μmol ammonia, individually applied, represent the IC(50) concentrations that cause negative effects on Arabidopsis thaliana.

Dimethyl Disulfide Produced by the Naturally Associated Bacterium Bacillus sp B55 Promotes Nicotiana attenuata Growth by Enhancing Sulfur Nutrition

“…Our observations that DMDS promotes plant growth differ in part from those of Kai et al (2010) in that fumigation of Arabidopsis seedlings with DMDS suppressed growth irrespective of the concentration applied. In our experimental setup (MM2 medium supplemented with different amounts of SO 4 22 ), we found positive effects of 500 µg DMDS per Petri dish on the growth of Arabidopsis, as we did with N. attenuata seedlings (see Supplemental Figure 10 online).…”

“…We cannot exclude the possibility that other S-containing VOCs, not detected by methods we used (SPME coupled to GC-MS), might also have been transferred through the headspace and assimilated. For example, other sulfurous VOCs, such as methanethiol, dimethyl sulfide, and dimethyl trisulfide, are commonly produced by a range of microbes (Farag et al, 2006;Kai et al, 2010;Minerdi et al, 2011). Furthermore, S-methyl pentanethioate (see Supplemental Table 2 online), which is emitted in trace amounts, might have contributed to the radioactive signal.…”

“…The PGP effects were largely attributed to two volatiles, namely, 3-hydroxybutan-2-one (acetoin) and 2,3-butanediol. Several other studies have examined bacterial bioactive volatile compounds that promote or suppress plant growth (Farag et al, 2006;Splivallo et al, 2007;Vespermann et al, 2007;Kai et al, , 2010Gutiérrez-Luna et al, 2010;Zou et al, 2010;Blom et al, 2011aBlom et al, , 2011bVelazquez-Becerra et al, 2011;Weise et al, 2012;Yu and Lee, 2013), but the underlying mechanisms of these effects remain largely unknown (Wenke et al, 2012b). Profiling studies in Arabidopsis seedlings provided the first insights into changes in the transcriptome and proteome elicited by exposure to bacterial VOCs (Zhang et al, 2007;Kwon et al, 2010) and revealed the importance of hormone signaling, particularly that of indole-3-acetic acid and abscisic acid (Zhang et al, 2007(Zhang et al, , 2008.…”

Proton Transfer Reaction Mass Spectrometry: Applications in the Life Sciences

“…In addition to the plant roots, there are other natural sources that may contribute to sulfide emissions. Several soil-dwelling microorganisms are known to produce volatile sulfides, including DMDS ( [126], [127]). The low levels of sulfides emerging from control plants show that the direct contribution -if anyof soil dwelling microorganisms to these emissions is small (Fig.…”

“…Head space analysis would in principle allow bacterial cultures to be characterized on line without manual manipulation. It has been shown that it is possible to measure Volatile Organic Compounds (VOCs) from the headspace of bacterial cultures using Proton Transfer Reaction Mass Spectrometry (PTR-MS) ( [131]; [40]; [127]) or related methods [132]. Those systems have provided consistent evidence that various microbes and mycobacteria produce distinctive patterns of VOCs.…”