Riparian ecosystems in the 21st century are likely to play a critical role in determining the vulnerability of natural and human systems to climate change, and in influencing the capacity of these ...systems to adapt. Some authors have suggested that riparian ecosystems are particularly vulnerable to climate change impacts due to their high levels of exposure and sensitivity to climatic stimuli, and their history of degradation. Others have highlighted the probable resilience of riparian ecosystems to climate change as a result of their evolution under high levels of climatic and environmental variability. We synthesize current knowledge of the vulnerability of riparian ecosystems to climate change by assessing the potential exposure, sensitivity, and adaptive capacity of their key components and processes, as well as ecosystem functions, goods and services, to projected global climatic changes. We review key pathways for ecological and human adaptation for the maintenance, restoration and enhancement of riparian ecosystem functions, goods and services and present emerging principles for planned adaptation. Our synthesis suggests that, in the absence of adaptation, riparian ecosystems are likely to be highly vulnerable to climate change impacts. However, given the critical role of riparian ecosystem functions in landscapes, as well as the strong links between riparian ecosystems and human well-being, considerable means, motives and opportunities for strategically planned adaptation to climate change also exist. The need for planned adaptation of and for riparian ecosystems is likely to be strengthened as the importance of many riparian ecosystem functions, goods and services will grow under a changing climate. Consequently, riparian ecosystems are likely to become adaptation 'hotspots' as the century unfolds.
An Australian marine-derived isolate of Aspergillus versicolor (MST-MF495) yielded the known fungal metabolites sterigmatocystin, violaceol I, violaceol II, diorcinol, (−)-cyclopenol, and ...viridicatol, along with a new alkaloid, cottoquinazoline A (1), and two new cyclopentapeptides, cotteslosins A (2) and B (3). Structures for 1−3 and the known compounds were determined by spectroscopic analysis. The absolute configurations of 1−3 were addressed by chemical degradation and application of the C3 Marfey’s method. The use of “cellophane raft” high-nutrient media as a device for up-regulating secondary metabolite diversity in marine-derived fungi is discussed. The antibacterial properties displayed by A. versicolor (MST-MF495) were attributed to the phenols violaceol I, violaceol II, and diorcinol, while cotteslosins 2 and 3 were identified as weak cytotoxic agents.
Natural products play an invaluable role as a starting point in the drug discovery process, and plants and animals use many interesting biologically active natural products as a chemical defense ...mechanism against predators. Among marine organisms, many nudibranch gastropods are known to derive defensive metabolites from the sponges they eat. Here we investigated the putative sequestration of the toxic compound latrunculin A--a 16-membered macrolide that prevents actin polymerization within cellular processes--which has been identified from sponge sources, by five closely related nudibranch molluscs of the genus Chromodoris. Only latrunculin A was present in the rim of the mantle of these species, where storage reservoirs containing secondary metabolites are located, whilst a variety of secondary metabolites were found in their viscera. The species studied thus selectively accumulate latrunculin A in the part of the mantle that is more exposed to potential predators. This study also demonstrates that latrunculin-containing sponges are not their sole food source. Latrunculin A was found to be several times more potent than other compounds present in these species of nudibranchs when tested by in vitro and in vivo toxicity assays. Anti-feedant assays also indicated that latrunculin A was unpalatable to rock pool shrimps, in a dose-dependent manner. These findings led us to propose that this group of nudibranchs has evolved means both to protect themselves from the toxicity of latrunculin A, and to accumulate this compound in the mantle rim for defensive purposes. The precise mechanism by which the nudibranchs sequester such a potent compound from sponges without disrupting their own key physiological processes is unclear, but this work paves the way for future studies in this direction. Finally, the possible occurrence of both visual and chemosensory Müllerian mimicry in the studied species is discussed.
In reviewing a selection of recent case studies from our laboratory, we revealed some lessons learned and benefits accrued from the application of mass spectrometry (MS/MS) molecular networking in ...the field of marine sponge natural products. Molecular networking proved pivotal to our discovery of many new natural products and even new classes of natural product, some of which were opaque to alternate dereplication and prioritization strategies. Case studies included the discovery of: (i) trachycladindoles, an exceptionally rare class of bioactive indole alkaloid previously only known from a single southern Australia sample of
; (ii) dysidealactams, an unprecedented class of sesquiterpene glycinyl-lactam and glycinyl-imide from a
sp., a sponge genera often discounted as having been exhaustively studied; (iii) cacolides, an unprecedented family of sesterterpene α-methyl-γ-hydroxybutenolides from a
sp., all too easily mischaracterized and deprioritized during dereplication as a well-known class of sponge sesterterpene tetronic acids; and (iv) thorectandrins, a new class of indole alkaloid which revealed unexpected insights into the chemical and biological properties of the aplysinopsins, one of the earliest and more extensively reported class of sponge natural products.
Co-cultivation of Chaunopycnis sp. (CMB-MF028) and Trichoderma hamatum (CMB-MF030), fungal strains co-isolated from the inner tissue of an intertidal rock platform mollusc (Siphonaria sp), resulted ...in transcriptional activation of a rare class of 2-alkenyl-tetrahydropyran, chaunopyran A (7), and biotransformation and deactivation of the antifungal pyridoxatin (1), to methyl-pyridoxatin (8). This study illustrates the complexity of offensive and counter-offensive molecular defenses encountered during fungal co-cultivation, and the opportunities for activating new, otherwise transcriptionally silent secondary metabolites.
This study showcases the application of an integrated workflow of molecular networking chemical profiling (GNPS), together with miniaturized microbioreactor cultivation profiling (MATRIX) to ...successfully detect, dereplicate, prioritize, optimize the production, isolate, characterize, and identify a diverse selection of new chemically labile natural products from the Queensland sheep pasture soil-derived fungus
sp. CMB-MRF324. More specifically, we report the new tryptamine enamino tripeptide aspergillamides E-F (
-
), dihydroquinoline-2-one aflaquinolones H-I (
-
), and prenylated phenylbutyrolactone aspulvinone Y (
), along with an array of known co-metabolites, including asterriquinones SU5228 (
) and CT5 (
), terrecyclic acid A (
), and aspulvinones N-CR (
), B (
), D (
), and H (
). Structure elucidation was achieved by a combination of detailed spectroscopic and chemical analysis, biosynthetic considerations, and in the case of
an X-ray crystallographic analysis.
The knowledge that natural products (NPs) are potent and selective modulators of important biomacromolecules (e.g., DNA and proteins) has inspired some of the world's most successful pharmaceuticals ...and agrochemicals. Notwithstanding these successes and despite a growing number of reports on naturally occurring pairs of enantiomers, this area of NP science still remains largely unexplored, consistent with the adage "If you don't seek, you don't find". Statistically, a rapidly growing number of enantiomeric NPs have been reported in the last several years. The current review provides a comprehensive overview of recent records on natural enantiomers, with the aim of advancing awareness and providing a better understanding of the chemical diversity and biogenetic context, as well as the biological properties and therapeutic (drug discovery) potential, of enantiomeric NPs.
A chemical investigation of Australian soil-derived bacteria Actinomadura sp. S4S-00069B08 yielded eight new benzenoid ansamycins, goondansamycins A–H. Goondansamycins feature rare ...1,4-benzoxazin-3-one or o-diamino-p-benzoquinone moieties and can exist as both aglycones or 9-O-α-glycosides of either d-rhodinose or d-amicetose. Structures were solved on the basis of detailed spectroscopy, including X-ray analysis.
Investigation of the secondary metabolites of Streptomyces virginiae CMB-CA091 isolated from the quartz-rich (tepui) soil of a cave in Venezuela yielded two new dimeric phenazine glycosides, ...tepuazines A and B (1 and 2); three new monomeric phenazine glycosides, tepuazines C–E (3–5); and a series of known analogues, baraphenazine G (6), phenazinolin D (7), izumiphenazine C (8), 4-methylaminobenzoyl-l-rhamnopyranoside (9), and 2-acetamidophenol (10). Structures were assigned to 1–10 on the basis of detailed spectroscopic analysis and biosynthetic considerations, with 1 and 2 featuring a rare 2-oxabicyclo3.3.1nonane-like ring C/D bridge shared with only a handful of known Streptomyces natural products. We propose a plausible convergent biosynthetic relationship linking all known members of this structure class that provides a rationale for the observed ring C/D configuration.
Fungal indole diterpenes (IDTs) occupy a valuable region of bioactive natural product chemical space, displaying potent and selective inhibition of therapeutically important ion channels and with ...potential application in the treatment of glaucoma, cancer, and neurodegenerative diseases, as well as insecticides and antivirals. We have employed an integrated workflow of analytical scale chemical profiling using GNPS (Global Natural Products Social molecular networking) and cultivation profiling (also known as “MATRIX” miniaturized microbioreactor) to detect, prioritize, optimize the production, isolate, characterize, and identify a new series of indole diterpenes, noonindoles G–L (7–12), from an Australian marine-derived fungus, Aspergillus noonimiae CMB-M0339. The first reported examples of IDT glycosides, the molecular structures for 7–12, were assigned on the basis of detailed spectroscopic analysis and biosynthetic considerations.
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