Volatiles in Inter-Specific Bacterial Interactions

Abstract

The importance of volatile organic compounds for functioning of microbes is receiving increased research attention. However, to date very little is known on how inter-specific bacterial interactions effect volatiles production as most studies have been focused on volatiles produced by monocultures of well-described bacterial genera. In this study we aimed to understand how inter-specific bacterial interactions affect the composition, production and activity of volatiles. Four phylogenetically different bacterial species namely: Chryseobacterium, Dyella, Janthinobacterium, and Tsukamurella were selected. Earlier results had shown that pairwise combinations of these bacteria induced antimicrobial activity in agar media whereas this was not the case for monocultures. In the current study, we examined if these observations were also reflected by the production of antimicrobial volatiles. Thus, the identity and antimicrobial activity of volatiles produced by the bacteria were determined in monoculture as well in pairwise combinations. Antimicrobial activity of the volatiles was assessed against fungal, oomycetal, and bacterial model organisms. Our results revealed that inter-specific bacterial interactions affected volatiles blend composition. Fungi and oomycetes showed high sensitivity to bacterial volatiles whereas the effect of volatiles on bacteria varied between no effects, growth inhibition to growth promotion depending on the volatile blend composition. In total 35 volatile compounds were detected most of which were sulfur-containing compounds. Two commonly produced sulfur-containing volatile compounds (dimethyl disulfide and dimethyl trisulfide) were tested for their effect on three target bacteria. Here, we display the importance of inter-specific interactions on bacterial volatiles production and their antimicrobial activities.

The ecological role of volatile mediated interactions belowground

“…The relationship between community composition and VOCs production is in accordance with previous studies (Garbeva et al 2014a;Hol et al 2015;Tyc et al 2015;Van Agtmaal et al 2015;El Ariebi et al 2016). In this regard, the presence of low-abundant species in the microbial community, such as observed for the Paenibacillus strain in Chapter 3, can significantly contribute to the emission of certain VOCs such as pyrazines with antifungal activity .…”

“…The shifts in fungalassociated bacterial community led to shifts in volatile production of the original and the The composition and abundance of volatiles was affected by the nutrient conditions with more volatiles produced on the nutrient-rich PDA media. Several independent studies have reported that the volatile profiles of bacteria and fungi are strongly dependent on growth conditions, interactions and nutrient availability (Garbeva et al 2014b;Tyc et al 2015;Schmidt et al 2016;Weikl et al 2016). Hence, it is questionable whether the same volatile-mediated interactions will occur in nature under nutrient-limited conditions.…”

“…For instance, shifts in the fungus-associated bacterial community led to changes in VOCs emission that stimulated growth and motility of bacterial competitors such as the fungusfeeding Collimonas fungivorans (Chapter 5). (Garbeva et al 2014a;Tyc et al 2015) and (3) VOCs emitted by one organism can be consumed or degraded by interacting partners. The latter can be linked to the detoxification of VOCs with antimicrobial activity (Cooney et al 2001;Chapter 6).…”

“…Several recent studies reported that the production of certain mVOCs can be induced or suppressed during inter-specific microbial interactions (Garbeva et al 2014a;Tyc et al 2015;Piechulla et al 2017).mVOCs were often considered to be by-products of primary metabolism, but recent findings revealed that many mVOCs demonstrate biological activity (Schmidt et al 2015;Tyc et al 2017a). Furthermore, in bacteria, the production of certain mVOCs is dependent on the GacS/GacA two-component regulatory system (Cheng et al 2016;Ossowicki et al 2017).…”

Causes and consequences of soil bacterial rarity

“…In addition to indirect suppression of potential invading pathogens through resource competition, rare species can be involved directly in pathogen suppression through the production of volatile organic compounds (VOCs). VOCs are one important way of communication among microorganisms and different species and even species combinations have been found to produce their own specific blend of compounds (Tyc et al 2015). The presence of rare bacterial species may alter the volatile profile of the microbial community and thereby affect the growth of a fungal pathogen (Hol et al 2015b).…”