Biosynthetic genes and activity spectrum of antifungal polyynes from Collimonas fungivorans Ter331

Abstract

Summary The antifungal activity of bacteria from the genus Collimonas has been well documented, but the chemistry and gene functions that underlie this phenotype are still poorly understood. Screening of a random plasposon insertion library of Collimonas fungivorans Ter331 for loss‐of‐function mutants revealed the importance of gene cluster K, which is annotated to code for the biosynthesis of a secondary metabolite and which features genes for fatty acid desaturases and polyketide synthases. Mutants in gene cluster K had lost the ability to inhibit hyphal growth of the fungus Aspergillus niger and were no longer able to produce and secrete several metabolites that after extraction and partial purification from wildtype strain Ter331 were shown to share a putative ene‐triyne moiety. Some but not all of these metabolites were able to inhibit growth of A. niger, indicating functional variation within this group of Collimonas‐produced polyyne‐like ‘collimomycins’. Polymerase chain reaction analysis of isolates representing different Collimonas species indicated that the possession of cluster K genes correlated positively with antifungal ability, further strengthening the notion that this cluster is involved in collimomycin production. We discuss our findings in the context of other bacterially produced polyynes and the potential use of collimomycins for the control of harmful fungi.

De novo biosynthesis of terminal alkyne-labeled natural products

“…Terminal alkynes can be formed by acetylenases, a special family of desaturases that catalyze O 2 -dependent dehydrogenation of C-C bonds in a diiron dependent mechanism 12 . Several membrane-bound acetylenases have recently been 3 identified from plants, insects, fungi, and bacteria 4,10,[13][14][15][16][17] , but all of these reports have been limited to bioinformatics or in vivo studies through mutagenesis or heterologous expression in yeasts and plants because it is notoriously difficult to work with the membrane-bound desaturases in vitro. As a result, no definitive information on the reactions catalyzed by these enzymes is available to date.…”

Volatile communication between fungi and bacteria

“…Ter331 and was shown to have strong antifungal activities (Fritsche et al, 2014). The corresponding biosynthesis cluster K, is only partially present in C. fungivorans Ter6, and completely absent in the other four genomes (Fig.…”

“…In Collimonas, the secondary metabolites are thought to play an important role for enabling mycophagous growth, namely by disturbing the fungal membrane integrity (Leveau et al, 2010). Although Collimonas was suggested to represent a valuable resource for the discovery of novel molecules and enzymes (Leveau et al, 2010), to date only two antimicrobial compounds were described for this genus, namely violacein and collimomycin (Hakvag et al, 2009, Fritsche et al, 2014. Violacein was identified in the Collimonas CT strain isolated from an aquatic environment and revealed antibacterial activity against Micrococcus luteus (Hakvag et al, 2009).…”

“…Collimomycin is a polyacetylenic compound with alternating triple and single carbon-carbon bonds (Fritsche et al, 2014) which is produced by C. fungivorans…”

“…This gene is composed of five amino acids without hits to the known lipopeptides indicating a new lipopeptide. Collimonas strains are well known for their ability to suppress a range of fungi and oomycetes (De Boer et al, 1998, Opelt & Berg, 2004, Adesina et al, 2007, Fritsche et al, 2014.…”