Abstract
An endophyte, designated “AV 17-3”, was isolated from a stem sample of an Australian Prickly Tea Tree, Leptospermum junipae, growing in the coastal area of the state of Victoria, Australia. Isolation of the partial 18S rDNA sequence and a subsequent search in GenBank revealed high homology to the fungal genus Quambalaria. Standard scanning electron microscopy (SEM) as well as environmental SEM of the isolate revealed that it produces widely elliptically shaped spores (4.5–5.5 × 1–2.2 μm) and secondary budding spores (2.0–3.0 × 1.5–1.7μm) on conidiophores, all showing a close similarity to Quambularia pitereka. The fungus produces bioactive compounds that were inhibitory to all and lethal to some pathogenic fungi, such as Phytophthora erythroseptica. It also inhibited or killed other tested bacteria and fungi, including Candida albicans, Escherichia coli, Staphylococcus aureus, Salmonella typhimurium, Pseudomonas aeruginosa, Xanthomonas citri, Mycosphaerella fijiensis, Saccharomyces cerevisae and Bacillus subtilus. It is well known that Quambalaria pitereka is a cause of blight in Australian tree species; however, our isolate of Quambalaria produced no evidence of disease in its host plant and exhibited strong antimicrobial activities against a variety of human and plant pathogens. At least one reddish biologically active product was isolated and shown to be polar and labile.
