Geosmin

Geosmin

• Slightly reduced degradation of FTC-casein
• By the digestive enzymes excreted by M. xanthus DK1622
• no effect on degradation by a well-characterized human protease, trypsin
• www.biorxiv.org/content/10.1101/2021.03.09.434661v1.full

• Geosmin repels egg-laying Drosophila melanogaster
• Attracts mosquitos and ants
• Attracts springtails to sporulating Streptomyces colonies
• Which then eat the bacteria
• Help disperse bacterial spores
• Non-geosmin secondary metabolites
• Many of these bioactive compounds inhibit the growth of prokaryotes or eukaryotes
• geosmin was non-toxic to the bacteriophagous nematode Caenorhabditis elegans
• Did not prevent the worms from preying on non-toxinogenic Escherichia coli cells
• Geosmin also did not act as a nematode repellent or attractant
• By the ASE gustatory neuron triggered a distinct crawling behaviour with characteristics of both roaming and dwelling movement
• Terpenes were non-toxic to C. elegans
• Triggered sporulation and the expression of a toxic secondary metabolite by S. coelicolor
• Consumption of S. coelicolor or M. xanthus led to a C. elegans stress behaviour and the death of the worms
• High prevalence of geosmin biosynthetic genes in evolutionarily disparate microbes well known for their toxic natural products.
• www.biorxiv.org/content/10.1101/2021.03.09.434661v1.full

• Toxic prey advertise their unpalatability through the use of warning colours
• geosmin is a warning chemical
• Advertise the production of toxic secondary metabolites
• www.biorxiv.org/content/10.1101/2021.03.09.434661v1.full

• geosmin associates with membrane proteins in cyanobacteria
• Might stabilize hydrophobic digestive enzymes in M. xanthus
• Had no discernable effect on BSA stability as measured by circular dichroism, either at elevated temperatures or on heating or cooling
• Did not appear to act as a chemoattractant or chemorepellent
• geosmin strongly altered the worms’ movement
• Adult hermaphrodites exhibited clear roaming behaviour

Geosmin

• Pocit hniloby / plísně ve stravě - např. v červené řepě
• Geosmin production is heavily conserved in
• Actinobacteria,
• Myxobacteria,
• Cyanobacteria
• Some fungi
• geosmin
• Aposematic signal used to indicate the unpalatability of toxin-producing microbes
• Discouraging predation by eukaryotes
• www.biorxiv.org/content/10.1101/2021.03.09.434661v1.full
• Geosmin itself was non-toxic
• First warning chemical to be identified in bacteria or fungi
• The smell of wet earth
• Saprophytic bacterial phylum Actinobacteria
• Predatory/saprophytic bacterial order Myxococcales
• Antarctica
• Range of fungi
• Common contaminant in
• Drinking water
• Farmed fish
• Peel of beets
• www.biorxiv.org/content/10.1101/2021.03.09.434661v1.full

2-methylisoborneol

• Related terpene
• Reduced predation of Streptomyces coelicolor and Myxococcus xanthus
• By the bacteriophagous Caenorhabditis elegans
• Predation was restored by
• Removal of both terpene biosynthetic pathways
• Deletion of the C. elegans ASE sensory neuron
• Resulted in the death of the nematodes