Summary Anaerobic ammonium oxidation coupled with iron(III) reduction (Feammox) with dinitrogen, nitrite or nitrate as end‐products is the most recently discovered nitrogen cycling process. This reaction has been observed in tropical forest soils, paddy soils and intertidal wetlands. However, Feammox has not been measured in mangrove wetlands. In this study, sediment slurry incubation experiments were combined with isotope tracing and acetylene inhibition techniques. Feammox was detected in mangrove sediments and ‘bare flats’ (mud flats without mangrove), with potential rates of 0.48 (±0.03 SE) mg N kg−1 day−1 (accounting for 6.4% of the total nitrogen loss through N2) and 0.38 (±0.02 SE) mg N kg−1 day−1 (accounting for 6.7% of the total nitrogen loss through N2), respectively. Microbially reducible iron(III) was added, which significantly (P < 0.01) increased the Feammox rate in contrast to no addition of iron(III). It was estimated that a loss of 12.33 t N year−1 was associated with Feammox in mangrove sediments of the Jiulong River Estuary, accounting for 0.04% of the total external inorganic nitrogen transported into the estuary. Overall, these findings demonstrate that Feammox can act as a nitrogen loss mechanism in mangroves. Highlights Feammox was investigated by ammonium 15N labelled isotopic tracing technique. Feammox rates in mangrove were larger than those in mud flats without mangrove. The nitrogen loss contribution of Feammox in mangrove was less than in other ecosystems. Tidal fluctuations and the large TOC would accelerate the Feammox process.
Aims: To establish a highly efficient methodology for screening high yield strains of cytotoxic deacetylmycoepoxydiene (DAM), to meet the need of research on its mechanism of anti‐tumor properties and in vivo toxicity studies. Methods and Results: A simple, sensitive, and highly repetitive screening procedure ‘Antimicrobial‐TLC–HPLC’ (ATH) was established for the rapid obtaining of high‐yielding DAM mutants to replace the time and labor intensive anti‐tumor activity assay (MTT). With this ATH method, four highly yielding DAM mutants were selected out of 5000 total mutants, one of which, M4‐143, showed yields of more than 300 times (250·3 mg l−1) that of the parent strain A123. Conclusions: The ATH method developed in this work has proven to be both economical and highly efficient with the screening of 1200 mutants in a one week time period, thusly shortening the expenditure of time and labor, without missing a single high‐yield mutant. Due to these characteristics, it is superior to other HTS screening methods described in earlier literature. The mutant M4‐143 has a good genetic stability and can be used for further research. Significance and Impact of the Study: This ATH screening method is not only perfect for screening high‐yield DAM mutants, but also, it is suitable to screen the strain libraries for those strains that have the ability to produce natural metabolites with antitumor activity.
Aims To evaluate whether decoloured cell‐free supernatant of Lysobacter enzymogenes C3 can decrease paper bioreceptivity to fungal attack. Methods and Results To prepare colourless C3 supernatant, single‐factor design and uniform design were applied. The optimum conditions with high decolouration degree and low antifungal activity loss were achieved as follows: carbon granule content 1·6% (M/V), temperature 27°C, decolouring time 1·2 h and pH 8·0. An agar plate bioassay was used to assess the antifungal activity of the decoloured supernatant against the fungal isolates obtained from contaminated books, and strong suppression was observed. Small‐sacle laboratory test was further introduced, in which common book papers were artificially inoculated with the fungal isolates, and then sprayed uniformly with decoloured supernatant or water. The results showed that, after treatment, the paper showed a significantly low extent of fungal colonization and high tensile strength, and maintained the same colour before and after treatment. Conclusion These results suggest that the decoloured C3 supernatant inhibits fungal growth on types of paper commonly used in books. Significance and Impact of the Study Decoloured C3 supernatant could be used as a preventive agent to protect books and other paper‐based items against fungal growth.
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