Effect of substrate on the production of antifungal volatiles from Bacillus subtilis

Abstract

An antibiotic-producing strain of Bacillus subtilis has been shown to produce potent antifungal volatiles (AFV). These volatiles are active against a range of fungal species and are produced on a range of growth media and in loam-based compost. In vitro antifungal volatile activity on nutrient agar is enhanced with the addition of D-glucose, complex carbohydrates and peptones. The addition of L-glucose led to significantly less AFV activity than comparable levels of D-glucose. Growth studies in liquid culture revealed that B. subtilis failed to grow in response to L-glucose. Further growth studies on solid media showed no clear correlation between enhanced bacterial growth and increases in in vitro AFV activity in response to supply of substrates. Low level AFV activity was also detected from oilseed rape roots inoculated with B. subtilis. Gas chromatography mass spectrometry headspace analysis of B. subtilis cultures grown on various substrates revealed common similarities between substrates promoting AFV activity, although it was not possible to isolate individual antifungal compounds.

Bacterial volatiles promote growth in Arabidopsis

“…Of the PGPR tested, three of seven strains elicited growth promotion of Arabidopsis seedlings (B. subtilis GB03, B. amyloliquefaciens IN937a, and E. cloacae JM22), suggesting that synthesis of bioactive VOCs is a strain-specific phenomenon. The particular medium in which the bacteria are cultured has been shown to impact the VOC emission profile for certain bacterial strains (18). Our initial screening for plant growth-promoting activity by bacterial VOC emissions was run on a nutrient-rich agar medium (assumed to be nonlimiting in nutrients) that resulted in uniform bacterial growth for all strains tested.…”

“…Chromatographic profiles of volatiles from bacteria strains IN937a and GB03, both of which promote growth by the emission of volatile chemicals, compared with a growth-promoting strain that does not trigger promotion by volatile emissions 89B61, a nongrowth-promoting bacterial strain DH5␣, and an uninoculated medium control. Compounds positively identified include 3-hydroxy-2-butanone [1], 2,3-butanediol [2], decane [6], tetramethyl pyrazine [9], undecane [10], decanal [13], dodecane [14], 2-undecanone [16], 2-tridecanone [17], and 2-tridecanol [18]; nonyl acetate was added as an internal standard (IS). Asterisks in the lower chromatograms designate compounds that align with numbered peaks above.…”

Diversity and Distribution of Volatile Secondary Metabolites Throughout Bacillus subtilis Isolates

“…Evidence for nutrient dependent production of many nonvolatile secondary metabolites (Tyc et al, 2017) and volatile metabolites could be yet supplied in vitro for several species of soil bacteria when cultivated on varying nutrient compositions (Fiddaman and Rossall, 1994;Kai et al, 2009;Blom et al, 2011;Weise et al, 2012;Ratiu et al, 2017b). One of the main nutrient resources for bacteria in soil represent plants root exudates (Barber and Martin, 1975;Lynch and Whipps, 1991;Hütsch et al, 2002).…”

Mining the Volatilomes of Plant-Associated Microbiota for New Biocontrol Solutions

“…As an emanation of the metabolome of a given organism in a given condition, the collected volatile blends represent only snapshots of a more complex phenomenon. Different substrate use, various growth conditions and genetic mutations are just some of the factors that directly influence the chemical composition of volatilomes (Fiddaman and Rossall, 1994 ; Blom et al, 2011a ; De Vrieze et al, 2015 ). Furthermore, the natural conditions and environmental cues leading to the production of particular volatile species or signatures have not yet been resolved, and their biological relevance in biocontrol contexts remain to be assessed outside in vitro systems (issues reviewed in Schmidt et al, 2015 ; Chung et al, 2016 ).…”

“…However, the increase in stringent policies regarding copper release into the environment exerts pressure for the continuation of investigations. In vitro work has demonstrated that mVOCs specifically contribute to the inhibition of growth and development of several phytopathogenic fungal or fungal-like genera, including members of Aspergillus (Vespermann et al, 2007 ; Hua et al, 2014 ; Chaves-Lopez et al, 2015 ; Gong et al, 2015 ), Botrytis (Huang et al, 2011 ; Li et al, 2012 ; Rouissi et al, 2013 ; Zhang et al, 2013 ; Parafati et al, 2015 ), Fusarium (Vespermann et al, 2007 ; Minerdi et al, 2009 ; Yuan et al, 2012 ; Tenorio-Salgado et al, 2013 ; Wang et al, 2013 ; Cordero et al, 2014 ), Penicillium (Rouissi et al, 2013 ), Sclerotinia (Fiddaman and Rossall, 1993 , 1994 ; Fernando et al, 2005 ; Vespermann et al, 2007 ; Giorgio et al, 2015 ), Rhizoctonia (Fiddaman and Rossall, 1993 , 1994 ; Kai et al, 2007 ; Vespermann et al, 2007 ; Liu et al, 2008 ), Alternaria (Andersen et al, 1994 ; Chaurasia et al, 2005 ; Trivedi et al, 2008 ; Zhao et al, 2011 ; Groenhagen et al, 2013 ), Pythium (Chaurasia et al, 2005 ; Sanchez-Fernandez et al, 2016 ), and Phytophthora (Zhao et al, 2011 ; Ann, 2012 ; Sharma et al, 2015 ).…”