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- Svahn, Stefan, 1977-
(författare)
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Analysis of Secondary Metabolites from Aspergillus fumigatus and Penicillium nalgiovense : Antimicrobial Compounds from Filamentous Fungi Isolated from Extreme Environments
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis describes the cultivation and extraction of filamentous fungi isolated from extreme environments in the search for new antibiotic compounds. Filamentous fungi are a rich source of medicines including antibiotics, and it is believed that many currently unknown fungal species and bioactive fungal metabolites remain to be discovered.Aspergillus fumigatus and Penicillium nalgiovense strains were isolated from an antibiotic-contaminated riverbed near Hyderabad, India, and soil taken from a penguin’s nest on Paulete Island, Antarctica, respectively. It was anticipated that the extreme conditions within these environments would exert unusual selective pressures on their filamentous fungi, possibly causing the secretion of new bioactive compounds.The cultivation, extraction and analysis of metabolites from the A. fumigatus strain resulted in the isolation of the antimicrobial substance gliotoxin. Subsequent investigations revealed that this strain’s secretion of gliotoxin was increased by as much as 65 % when it was cultivated in the presence of pathogen-associated molecular patterns. These results indicate the existence of a fungal receptor/signaling system for detecting nearby bacteria. The scope for using gliotoxin and the related metabolite bis(methyl)gliotoxin as biomarker metabolites for diagnosing the lethal pulmonary condition invasive aspergillosis was also investigated. Bronchoalveolar lavage fluid from 42 patients with and without possible invasive aspergillosis was extracted and analyzed. The results obtained suggest that gliotoxin and bis(methyl)gliotoxin are not suitable markers for diagnosing invasive aspergillosis.Studies on the P. nalgiovense strain from Antarctica resulted in the isolation of the antifungal agent amphotericin B. The secretion of this compound increased when P. nalgiovense was cultured on a potato-dextrose agar enriched with coconut flakes rather than liquid RPMI 1640 medium. This was the first time amphotericin B was isolated from any organism other than the bacterium Streptomyces nodosus.The results presented in this thesis will be useful in the continuing search for novel bioactive compounds, the diagnosis of fungal infections, and as a source of insight into the interactions between microorganisms. Moreover, they show that even extensively studied fungal genera such as Aspergillus and Penicillium are not completely understood and may produce unexpected or previously unknown bioactive metabolites under appropriate conditions.
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| 2. |
- Svahn, Stefan, 1977-, et al.
(författare)
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Antimicrobial activity of filamentous fungi isolated from highly antibiotic-contaminated river sediment
- 2012
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Ingår i: Infection Ecology & Epidemiology. - : Informa UK Limited. - 2000-8686. ; 2, s. 11591-
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Tidskriftsartikel (refereegranskat)abstract
- Background:Filamentous fungi are well known for their production of substances with antimicrobial activities, several of which have formed the basis for the development of new clinically important antimicrobial agents. Recently, environments polluted with extraordinarily high levels of antibiotics have been documented, leading to strong selection pressure on local sentinel bacterial communities. In such microbial ecosystems, where multidrug-resistant bacteria are likely to thrive, it is possible that certain fungal antibiotics have become less efficient, thus encouraging alternative strategies for fungi to compete with bacteria.Methods:In this study, sediment of a highly antibiotic-contaminated Indian river was sampled in order to investigate the presence of cultivable filamentous fungi and their ability to produce substances with antimicrobial activity.Results:Sixty one strains of filamentous fungi, predominantly various Aspergillus spp. were identified. The majority of the Aspergillus strains displayed antimicrobial activity against methicillin-resistant Staphylococcus aureus, extended-spectrum beta-lactamase-producing Escherichia coli, vancomycin-resistant Enterococcus faecalis and Candida albicans. Bioassay-guided isolation of the secondary metabolites of A. fumigatus led to the identification of gliotoxin.Conclusion:This study demonstrated proof of principle of using bioassay-guided isolation for finding bioactive molecules
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| 3. |
- Svahn, Stefan, 1977-, et al.
(författare)
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Bis(methyl)gliotoxin and gliotoxin in bronchoalveolar lavage fluids are not suitable markers for invasive aspergillosis
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Introduction: Invasive aspergillosis is challenging to diagnose partly due to shortcomings in sensitivity, reliability, and selectivity of current diagnostic methods, which rely on cultures, assays, and histopathology. This problem may be addressed by chemical analysis of metabolites in lung fluid from infected patients. Gliotoxin and bis(methyl)gliotoxin have been pinpointed as potential marker metabolites in serum and plasma for invasive aspergillosis patients, but whether lung fluid samples could be assessed for these markers is still unknown.Methods: Bronchoalveolar lavage samples were taken from 42 individuals with a variety of pulmonary diseases whereof 20 were diagnosed with possible invasive aspergillosis. The samples were analyzed with ultra high performance liquid chromatography coupled to triple quadropole time-of-flight mass spectrometry to investigate the use of the Aspergillus fumigatus metabolites gliotoxin and bis(methyl)gliotoxin as marker metabolites for invasive aspergillosis.Results: Gliotoxin was not detected in any of the 42 samples, but bis(methyl)gliotoxin in 10 (24%). Bis(methyl)gliotoxin was detected in 5 (25%) of the 20 patients with possible IA and in 5 (23%) in the other 22 samples. One unknown compound (357.30 m/z) with a similar mass spectrum profile to bis(methyl)gliotoxin (357.09 m/z) was found in 32 (76%) of all samples.Conclusions: Neither gliotoxin nor bis(methyl)gliotoxin appears to be an acceptable marker metabolite in bronchoalveolar lavage fluids for invasive aspergillosis. Further development of MS-based analyses should include chromatography.
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| 4. |
- Svahn, Stefan, 1977-, et al.
(författare)
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Penicillium nalgiovense Laxa isolated from Antarctica is a new source of the antifungal metabolite amphotericin B
- 2015
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Ingår i: Fungal biology and biothechnology. - : Springer Science and Business Media LLC. - 2054-3085. ; 2:1
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Tidskriftsartikel (refereegranskat)abstract
- Background: The need for new antibiotic drugs increases as pathogenic microorganisms continue to develop resistance against current antibiotics. We obtained samples from Antarctica as part of a search for new antimicrobial metabolites derived from filamentous fungi. This terrestrial environment in the South Pole is hostile and extreme due to a sparsely populated food web, low temperatures, and insufficient liquid water availability. We hypothesize that this environment could cause the development of fungal defense or survival mechanisms not found elsewhere.Results: We isolated a strain of Penicillium nalgiovense Laxa from a soil sample obtained from an abandoned penguin’s nest. Amphotericin B was the only metabolite secreted from P. nalgiovense Laxa with noticeable antimicrobial activity,with minimum inhibitory concentration of 0.125 µg/mL against Candida albicans. This is the first time that amphotericin B has been isolated from an organism other than the bacterium Streptomyces nodosus. In terms of amphotericin B production, cultures on solid medium proved to be a more reliable and favorable choice compared to a liquid.Conclusions: These results encourage further investigation of the many unexplored sampling sites characterized by extreme conditions, and confirm filamentous fungi as potential sources of metabolites with antimicrobial activity.
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