RESUMEN
Historically, small molecules biosynthesised by bacteria have been an excellent source for antibacterial drugs. Today, however, the rediscovery of known compounds is a significant hurdle to developing new antimicrobials. Here we use a genome mining and synthetic biology approach to discover the ambocidins: calcium-dependent lipodepsipeptides that are active against drug-resistant Gram-positive pathogens. By cloning a silent biosynthetic gene cluster (the amb cluster) from Streptomyces ambofaciens ATCC 2387 and integrating this into the chromosome of Streptomyces avermitilis we induce expression of ambocidin A and B: two new Nε-hydroxyarginine-containing cyclic lipodepsipeptides active against drug-resistant Gram-positive pathogens. Using a panel of Streptomyces host strains, we show that the choice of heterologous host is critical for producing the biologically active compounds, and that inappropriate host choice leads to aberrant production inactive derivatives. We show that Nε-hydroxyarginine is the product of a haem-dependent oxygenase and that it enhances biological activity. Ambocidin A inhibits cell wall biosynthesis by binding to Lipid II at a different site than vancomycin. Unlike daptomycin, ambocidin A retains antimicrobial activity in the presence of lung-surfactant, giving it the potential to treat bacterial pneumonia. Our work expands the family of calcium-dependent lipopeptide antibiotics with new members exhibiting a distinct mechanism of action.
RESUMEN
Introduced wasps (Vespula germanica and V. vulgaris) are costly invertebrate pests in New Zealand, with large impacts on the local ecology and economy. Wasps eat honeybees (Apis mellifera), which has potentially devastating effects on hive health, as well as agricultural and horticultural industries. Vespex bait, which contains fipronil in a proteinaceous carrier, has recently been introduced for wasp control. In over a decade of reported trials, honeybees have never been observed foraging on Vespex, likely because the bait contains no sugars to serve as a bee food source. However, the potential for the control agent fipronil to enter beehives has not been tested. Therefore, here, we investigated this using a liquid chromatography-mass spectrometry assay of fipronil and two of its environmental breakdown and metabolic derivatives, fipronil desulfinyl and fipronil sulfone. We did not detect fipronil in any of the worker bee, bee larva, honey or pollen samples (n = 120 per product) collected from 30 hives over a 2-year period. Furthermore, although we detected fipronil desulfinyl in one honeybee sample, this is thought to have originated from a single individual, representing a rare occurrence of intoxication, and there was no evidence that Vespex was the toxicant source. There was also no evidence of trophallactic transfer of fipronil or its derivatives in any of the hives sampled. Previous studies have reported the impairment of individual bee performance at fipronil doses similar to the detection limit of our study. However, our results provide confidence that if undetectable intoxication was occurring, it would involve an acute exposure for those few individuals affected, with minimal impairment to colonies. Therefore, we conclude that the use of Vespex in the vicinity of honeybees does not result in significant hive uptake while effectively reducing wasp pressure on honeybee colonies.
Asunto(s)
Abejas , Miel/análisis , Control de Plagas , Proteínas/química , Pirazoles/análisis , Avispas , Animales , Abejas/metabolismo , Pirazoles/metabolismoRESUMEN
Seven new members of the hamigeran family of diterpenoids have been isolated from the New Zealand marine sponge Hamigera tarangaensis. Among the new additions are hamigeran R (1), considered to be the first benzonitrile-based marine natural product, and hamigeran S (2), the first dimeric structure in the series. The formation of 1 and 2 is thought to occur via the reaction of hamigeran G with a nitrogen source, where the nitrile carbon of 1 is derived from the terpenoid skeleton.
Asunto(s)
Diterpenos/química , Naftoquinonas/química , Nitrógeno/química , Poríferos/química , Animales , Productos Biológicos/química , Carbono/química , Nueva Zelanda , Terpenos/químicaRESUMEN
The NMR-directed investigation of the New Zealand marine sponge Hamigera tarangaensis has afforded ten new compounds of the hamigeran family, and a new 13-epi-verrucosane congener. Notably, hamigeran F (6) possesses an unusual carboncarbon bond between C-12 and C-13, creating an unprecedented skeleton within this class. In particular, the structural features of 6, hamigeran H (10) and hamigeran J (12) imply a diterpenoid origin, which has allowed the putative biogenesis of three hamigeran carbon skeletons to be proposed based on geranyl geranyl pyrophosphate. All new hamigerans exhibited micromolar activity towards the HL-60 promyelocytic leukaemic cell line, and hamigeran G also selectively displayed antifungal activity in the budding yeast Saccharomyces cerevisiae. Homozygous deletion profiling (HOP) analysis suggests Golgi apparatus function as a potential target of this unusual class of sponge-derived terpenoids.