Lipopolysaccharide (LPS) stimulation of fungal secondary metabolism.
We report on a preliminary investigation of the use the Gram-negative bacterial cell wall constituent lipopolysaccharide (LPS) as a natural chemical cue to stimulate and alter the expression of fungal secondary metabolism. Integrated high-throughput micro-cultivation and micro-analysis methods determined that 6 of 40 (15%) of fungi tested responded to an optimal exposure to LPS (0.6 ng/mL) by activating, enhancing or accelerating secondary metabolite production. To explore the possible mechanisms behind this effect, we employed light and fluorescent microscopy in conjunction with a nitric oxide (NO)-sensitive fluorescent dye and an NO scavenger to provide evidence that LPS stimulation of fungal secondary metabolism coincided with LPS activation of NO. Several case studies demonstrated that LPS stimulation can be scaled from single microplate well (1.5 mL) to preparative (>400 mL) scale cultures. For example, LPS treatment ofPenicilliumsp. (ACM-4616) enhanced pseurotin A and activated pseurotin A1and pseurotin A2biosynthesis, whereas LPS treatment ofAspergillussp. (CMB-M81F) substantially accelerated and enhanced the biosynthesis of shornephine A and a series of biosynthetically related ardeemins and activated production of neoasterriquinone. As an indication of broader potential, we provide evidence that cultures ofPenicilliumsp. (CMB-TF0411),Aspergillus niger(ACM-4993F),Rhizopus oryzae(ACM-165F) andThanatephorus cucumeris(ACM-194F) were responsive to LPS stimulation, the latter two examples being particular noteworthy as neither are known to produce secondary metabolites. Our results encourage the view that LPS stimulation can be used as a valuable tool to expand the molecular discovery potential of fungal strains that either have been exhaustively studied by or are unresponsive to traditional culture methodology.
Institute for Molecular Bioscience, The University of Queensland , St Lucia , QLD 4072 , Australia.
Zeinab G
ZG
Khalil
Institute for Molecular Bioscience, The University of Queensland , St Lucia , QLD 4072 , Australia.
Pabasara
P
Kalansuriya
Institute for Molecular Bioscience, The University of Queensland , St Lucia , QLD 4072 , Australia.
Robert J
RJ
Capon
acceleration; activation; enhancement; lipopolysaccharide; silent secondary metabolism; stimulation