Volatile affairs in microbial interactions

Abstract

Microorganisms are important factors in shaping our environment. One key characteristic that has been neglected for a long time is the ability of microorganisms to release chemically diverse volatile compounds. At present, it is clear that the blend of volatiles released by microorganisms can be very complex and often includes many unknown compounds for which the chemical structures remain to be elucidated. The biggest challenge now is to unravel the biological and ecological functions of these microbial volatiles. There is increasing evidence that microbial volatiles can act as infochemicals in interactions among microbes and between microbes and their eukaryotic hosts. Here, we review and discuss recent advances in understanding the natural roles of volatiles in microbe-microbe interactions. Specific emphasis will be given to the antimicrobial activities of microbial volatiles and their effects on bacterial quorum sensing, motility, gene expression and antibiotic resistance.

Figure 1

Main metabolic pathways for the production of microbial volatiles. Volatiles are depicted in coloured dashed rectangles indicating different chemical classes. Representative examples are given per class: alcohols (for example, ethanol), aldehydes (for example, benzaldehyde), alkanes (for example, undecane), alkenes (1-undecene), aromatic compounds (for example, 2-phenylethanol), esters (for example, 2-phenylethyl ester), fatty acids (for example, butyric acid), isoprene, lactic acid, lactones (for example, gamma-butyrolactone), methylketones (for example, acetone), monoterpenes (for example, farnesol), nitrogen compounds (for example, benzonitrile), sesquiterpenes (for example, pinene) and sulphur compounds (for example, dimethyl disulphide).