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The fungi in the genus Ambrosia are associated with wood boring ambrosia beetles. These beetles bore extensive galleries into the sapwood of the host wood while relying on the fungal symbiont as a source of nutrition, however the mechanism behind this is not completely understood. In this study, the ambrosia fungus was isolated from the mycangia of a female ambrosia beetle. The fungus was observed to be filamentous with dense aerial mycelia and filiform colony margins. Molecular identification was conducted based on the sequence of the internal transcribed spacers (ITS) of ribosomal RNA (rRNA) genes and 5.8S rRNA gene. Sequence analysis by BLAST, sequence alignment and phylogenetic analysis indicated that the isolate belongs to Ambrosiella grosmanniae of the family Ceratocystidaceae. It was hypothesized that A. grosmanniae produces extracellular enzymes involved in the degradation of woody polysaccharides and antimicrobial substances important for its survival against other microorganisms in the gallery. The capability of the fungus to breakdown cellulosic components of the wood was demonstrated by agar plate method to measure regions of enzyme activity and Dinitrosalicylic assay method to measure reducing sugar concentration in liquid media using carboxymethylcellulose as substrate with Saprolegnia parasitica, a known cellulase producer, was used as a positive control. The antibiotic activity of the fungal extracts was analyzed by testing against Staphylococcus aureus, Bacillus subtilis, Shigella flexneri and Escherichia coli. An antibiotic chloramphenicol was used as a positive control. Antibiotic activity was observed against Bacillus subtilis and Shigella flexneri. The results obtained in this study indicate that A. grosmanniae is a dominant fungal symbiont of the ambrosia beetle Xylosandrus germanus, possesses cellulase activity and produces compounds that confer a competitive advantage on the fungi in the gallery. |
