Throughout the natural world, terpenes work their magic. They discharge pleasing fragrances from enumerable plants like hops, flowers, cannabis, grapefruits, or tea. The fragrances float on air finding their way into our noses where they might invoke nostalgias for past experiences or make us marvel at a mesmerizing new scent. Once encountered by our bodies, terpenes provide many medicinal opportunities to us such as their anti-cancer [1], antiviral, or anti-anxiety properties.
One of the most interesting aspects of the terpene is it’s use for communication throughout nature. Honeybees use terpenes to talk to each other and rear their young, while plants wield a powerful arsenal of terpenes to defend themselves and to warn their neighbors of impending trouble from plant-eaters. As such, terpenes have been labeled as “infochemicals.” [2]
Terpenes are utilized by microscopic life as well, such as bacteria and fungi. Just like in the macro world, terpenes may be used to modulate microorganism behavior or to suppress or eradicate potential microscopic enemies. The lines of communication can be amongst similar organisms or across species, such as the effects of fungal molecules on bacteria.
The pathogenic fungi Fusarium culmorum, for example, uses α-terpinene, β-phellandrene, 3-carene, and camphene to alter the swarming and swimming mobility of the bacterium Serratia plymuthica PRI-2C. [3] Swarming is defined as “direct, signal-dependent movement powered by rotating flagella” whereas swimming relates “individual cells moving in more liquid environments.”
The terpene cocktail released by the fungus can penetrate bacterial cell wall membranes, increasing permeability thereby decreasing cell viability. [4] α-Terpinene, β-phellandrene, 3-carene, and camphene were tested at concentrations of 10 nM, 100 nM, 10 μM, 100 μM, 10 mM, and 100 mM. [2] For some of the pure terpenes, a concentration dependent bacterial response was found. For example, the researchers reported that concentrations of 10 nm, 100 nM, and 100 μM α-terpinene affected the swimming mobility of S. plymuthica PRI-2C, but higher doses were not effective. β-Phellandrene provided a similar effect at concentrations between 10 μM to 100 mM.
3-Carene affected the swarming mobility of the bacterium Collimonas pratensis Ter291 in divergent ways. At 10 nM and 100 nM, swarming motility increased while at 10 μM, this motility decreased. And regardless of the concentration applied, β-phellandrene reduced swarming motility while 3-carene and camphene both inhibited swimming and swarming mobility in S. plymuthica PRI-2C.
So, what does all this mean?
Like little molecular puppeteers, fungal terpenes could promote or prevent the movements of bacteria. Caryophyllene, for example, is used as a fungal defense weapon, while farnesol aids in signaling. Why would they do this? The researchers concluded that fungi utilize their terpenes to “attract mutualistic bacteria” towards them while repelling “competitors from common niches by manipulating their motility through volatiles [volatiles meaning terpenes].” [3] Interestingly, when nutrients were scarcer, F. culmorum produced more terpenes. What’s more, a lack of specific nutrients has been shown to lead to terpene emission. Perhaps this extends to cannabis?
The beauty is in the balance, the yin and yang of terpene functionality in nature. The spectrum of life representing our sentient world – whether advanced beings like you and me, insects, fish, flowers, fungi, or bacteria – depends on terpenes for just about everything under the sun, from communication and controlling the behaviors of neighbors (e.g., allelopathy), to medicinal possibilities, or just to simply enjoy the sweet scent of the inflorescences of Cannabis sativa.
References
[1] Tomko AM, et al. Anti-cancer potential of cannabinoids, terpenes, and flavonoids present in cannabis. Cancers. 2020;12(7):1985. [Journal Impact Factor = 6.639; Times Cited = 13 (Semantic Scholar)] [2] Schmidt R, Jager V, Zühlke D, et al. Fungal volatile compounds induce production of the secondary metabolite Sodorifen in Serratia plymuthica PRI-2C. Sci Rep. 2017;7(1):862. [journal impact factor = 4.379; times cited = 58 (Semantic Scholar)] [3] Schmidt R, Etalo DW, de Jager V, et al. Microbial Small Talk: Volatiles in fungal-bacterial interactions. Front Microbiol. 2016;6:1495. [journal impact factor = 4.235; times cited = 93 (Semantic Scholar)] [4] Nazzaro F, Fratianni F, De Martino L, Coppola R, De Feo V. Effect of essential oils on pathogenic bacteria. Pharmaceuticals. 2013; 6(12):1451-1474. [journal impact factor = 5.863; times cited = 808 (Semantic Scholar)]
Image Credit: Photo by Simon Berger on Unsplash
