Xiancui Li
Hong Kong University of Science and Technology
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Publication
Featured researches published by Xiancui Li.
Biofouling | 2006
Xiancui Li; Sergey Dobretsov; Ying Xu; Xiang Xiao; Oi Shing Hung; Pei-Yuan Qian
Abstract Modern antifouling coatings use heavy metals and toxic organic molecules to prevent biofouling, the undesirable growth of marine organisms on man-made substrata. In an ongoing survey of deep-sea microorganisms aimed at finding low toxic antifouling metabolites, an actinomycete bacterium was isolated from the Pacific sediment at the depth of about 5000 m. The bacterium was closely related to Streptomyces fungicidicus (99% similarity) according to 16S ribosomal RNA sequence information. The spent culture medium of this bacterium inhibited barnacle larval attachment. Bioassay-guided fractionation was employed to isolate antifouling compounds. The ethyl acetate extract was fractionated by using an open silica gel column. Active fractions were further purified on a HPLC C18 column. Five diketopiperazines, cyclo-(L-Leu-L-Pro), cyclo-(L-Phe-L-Pro), cyclo-(L-Val-L-Pro), cyclo-(L-Trp-L-Pro), and cyclo-(L-Leu-L-Val) were isolated for the first time from a deep sea bacterium, and the structures of the compounds were elucidated by nuclear magnetic resonance spectroscopy and mass spectrometry. The pure diketopiperazines were tested for antilarval activity using the barnacle Balanus amphitrite. Effective concentrations that inhibited 50% larval attachment (EC50) after 24 h ranged from 0.10 – 0.27 mM. The data suggest that diketopiperazines and other compounds from deep-sea bacteria may be used as novel antifoulants.
Biofouling | 2006
Laihung Yang; On On Lee; Tao Jin; Xiancui Li; Pei-Yuan Qian
Abstract Many soft-bodied sessile marine invertebrates such as sponges and soft corals defend themselves against fouling directly through the production of antifouling compounds, or indirectly through regulating the epibiotic microbes that affect larval settlement. In this study, 10β-formamidokalihinol-A and kalihinol A were isolated and purified from the marine sponge Acanthella cavernosa (Dendy). The results indicated that both compounds inhibited the growth of bacteria isolated from the natural environment whereas kalihinol A suppressed larval settlement of a major fouling polychaete, Hydroides elegans with an EC50 of 0.5 μg ml−1. Kalihinol A was incorporated in Phytagel® that was exposed to the bacterial consortia in natural seawater for biofilm formation. Biofilms that developed on the Phytagel® surfaces were analysed for bacterial abundance and bacterial species composition using a DNA fingerprinting technique, terminal restriction fragment length polymorphism (T-RFLP). The results showed that kalihinol A only slightly reduced bacterial abundance (t-test, p = 0.0497), but modified the bacterial species composition of the biofilms. Inhibition of H. elegans larval settlement was observed when biofilms developed under the influence of kalihinol A were exposed to larvae, suggesting that compounds like kalihinol A from the sponge A. cavernosa may change bacterial community composition on the sponge surface, which in turn, modulates larval settlement of fouling organisms.
Biofouling | 2007
Ying Xu; Li Miao; Xiancui Li; Xiang Xiao; Pei-Yuan Qian
Abstract Deep-sea microorganisms are a new source of bioactive compounds. In this study, crude ethyl acetate extracts of 176 strains of deep-sea bacteria, isolated from sediments of the West Pacific Ocean, were screened for their antibacterial activity against four test bacterial strains isolated from marine biofilms. Of these, 28 deep-sea bacterial strains exhibited antibacterial activity against one or more of the bacteria tested. Active deep-sea bacterial strains belonged mainly to the genera of Pseudomonas, Psychrobacter and Halomonas. Additionally, antilarval activity of 56 deep-sea bacterial strains was screened using Balanus amphitrite larvae. Seven bacterial strains produced metabolites that had strong inhibitive effects on larval settlement. None of these metabolites showed significant toxicity. The crude extract of one deep-sea Streptomyces strain could completely inhibit larval settlement at a concentration of 25 μg ml−1.
International Journal of Systematic and Evolutionary Microbiology | 2005
Stanley C K Lau; Mandy Man Yee Tsoi; Xiancui Li; I. Plakhotnikova; Sergey Dobretsov; Ken W K Lau; Madeline C S Wu; Po Keung Wong; Joseph R. Pawlik; Pei-Yuan Qian
International Journal of Systematic and Evolutionary Microbiology | 2004
Stanley C.K. Lau; Mandy Man Yee Tsoi; Xiancui Li; I. Plakhotnikova; Madeline Chang-sun Wu; Po Keung Wong; Pei-Yuan Qian
Marine Biotechnology | 2009
Ying Xu; Honglei Li; Xiancui Li; Xiang Xiao; Pei-Yuan Qian
International Journal of Systematic and Evolutionary Microbiology | 2006
Stanley C.K. Lau; Mandy Man Yee Tsoi; Xiancui Li; I. Plakhotnikova; Sergey Dobretsov; Madeline Chang-sun Wu; Po Keung Wong; Joseph R. Pawlik; Pei-Yuan Qian
Applied Microbiology and Biotechnology | 2007
Lai Hung Yang; Li Miao; On On Lee; Xiancui Li; Hairong Xiong; Ka-Lai Pang; Lilian L.P. Vrijmoed; Pei-Yuan Qian
International Journal of Systematic and Evolutionary Microbiology | 2006
On On Lee; Stanley C.K. Lau; Mandy Man Yee Tsoi; Xiancui Li; I. Plakhotnikova; Sergey Dobretsov; Madeline C S Wu; Po Keung Wong; Markus G. Weinbauer; Pei-Yuan Qian
International Journal of Systematic and Evolutionary Microbiology | 2005
Stanley C K Lau; Mandy Man Yee Tsoi; Xiancui Li; I. Plakhotnikova; Sergey Dobretsov; Po Keung Wong; Pei-Yuan Qian