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Lee K.-H.,University of Hong Kong | Wang Y.-F.,Guangdong Academy of Forestry | Li H.,East China University of Science and Technology | Gu J.-D.,University of Hong Kong
Ecotoxicology | Year: 2014

Ecophysiological differences between ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) enable them to adapt to different niches in complex freshwater wetland ecosystems. The community characters of AOA and AOB in the different niches in a freshwater wetland receiving municipal wastewater, as well as the physicochemical parameters of sediment/soil samples, were investigated in this study. AOA community structures varied and separated from each other among four different niches. Wetland vegetation including aquatic macrophytes and terrestrial plants affected the AOA community composition but less for AOB, whereas sediment depths might contribute to the AOB community shift. The diversity of AOA communities was higher than that of AOB across all four niches. Archaeal and bacterial amoA genes (encoding for the alpha-subunit of ammonia monooxygenases) were most diverse in the dry-land niche, indicating O2 availability might favor ammonia oxidation. The majority of AOA amoA sequences belonged to the Soil/sediment Cluster B in the freshwater wetland ecosystems, while the dominant AOB amoA sequences were affiliated with Nitrosospira-like cluster. In the Nitrosospira-like cluster, AOB amoA gene sequences affiliated with the uncultured ammonia-oxidizing beta-proteobacteria constituted the largest portion (99 %). Moreover, independent methods for phylogenetic tree analysis supported high parsimony bootstrap values. As a consequence, it is proposed that Nitrosospira-like amoA gene sequences recovered in this study represent a potentially novel cluster, grouping with the sequences from Gulf of Mexico deposited in the public databases. © 2014 Springer Science+Business Media New York. Source

Zhang Q.,Zhejiang University | Zhang Q.,Guangdong Academy of Forestry | Wang C.,Zhejiang University | Tian J.,Zhejiang University | And 2 more authors.
Plant Biology | Year: 2011

Purple acid phosphatases (PAPs) are a family of metallo-phosphoesterases involved in a variety of physiological functions, especially phosphate deficiency adaptations in plants. We identified 26 putative PAP genes by a genome-wide analysis of rice (Oryza sativa), 24 of which have isolated EST sequences in the dbEST database. Amino acid sequence analysis revealed that 25 of these genes possess sets of metal-ligating residues typical of known PAPs. Phylogenetic analysis classified the 26 rice and 29 Arabidopsis PAPs into three main groups and seven subgroups. We detected transcripts of 21 PAP genes in roots or leaves of rice seedlings. The expression levels of ten PAP genes were up-regulated by both phosphate deprivation and over-expression of the transcription factor OsPHR2. These PAP genes all contained one or two OsPHR2 binding elements in their promoter regions, implying that they are directly regulated by OsPHR2. Both acid phosphatase (AP) and surface secretory acid phosphatase (SAP) activity assays showed that the up-regulation of PAPs by Pi starvation, OsPHR2 over-expression, PHO2 knockout or OsSPX1 RNA interference led to an increase in AP and SAP activity in rice roots. This study reveals the potential for developing technologies for crop improvement in phosphorus use efficiency. © 2010 German Botanical Society and The Royal Botanical Society of the Netherlands. Source

Wang Y.-F.,Guangdong Academy of Forestry | Wang Y.-F.,University of Hong Kong | Gu J.-D.,University of Hong Kong
Applied Microbiology and Biotechnology | Year: 2014

Anaerobic ammonium-oxidizing (anammox) bacteria, aerobic ammonia-oxidizing archaea (AOA) and bacteria (AOB) are three groups of ammonia/ammonium-oxidizing prokaryotes (AOPs) involved in the biochemical nitrogen cycling. In this study, the effects of allylthiourea (ATU), pH, and salinity on these three groups from mangrove sediment were investigated through microcosm incubation in laboratory. ATU treatments (50, 100, and 500 mg L-1) obviously affected the community structure of anammox bacteria and AOB, but only slightly for AOA. ATU began to inhibit anammox bacteria growth slightly from day 10, but had an obvious inhibition on AOA growth from the starting of the study. At 100 mg L-1 of ATU or higher, AOB growth was inhibited, but only lasted for 5 days. The pH treatments showed that acidic condition (pH 5) had a slight effect on the community structure of anammox bacteria and AOA, but an obvious effect on AOB. Acidic condition promoted the growth of all groups of AOPs in different extent, but alkaline condition (pH 9) had a weak effect on AOB community structure and a strong effect on both anammox bacteria and AOA. Alkaline condition obviously inhibited anammox bacteria growth, slightly promoted AOA, and slightly promoted AOB in the first 20 days, but inhibited afterward. Salinity treatment showed that higher salinity (20 and 40 ‰) resulted in higher anammox bacteria diversity, and both AOA and AOB might have species specificity to salinity. High salinity promoted the growth of both anammox bacteria and AOB, inhibited AOA between 5 and 10 days, but promoted afterward. The results help to understand the role of these microbial groups in biogeochemical nitrogen cycling and their responses to the changing environments. © 2013 Springer-Verlag Berlin Heidelberg. Source

Wang Y.-F.,Guangdong Academy of Forestry | Wang Y.-F.,University of Hong Kong | Li X.-Y.,University of Hong Kong | Gu J.-D.,University of Hong Kong
Applied Microbiology and Biotechnology | Year: 2014

The effects of acetate and leaf litter powder on ammonia/ammonium-oxidizing microorganisms (AOMs) in mangrove sediment were investigated in a laboratory incubation study for a period of 60 days. The results showed that different AOMs responded differently to the addition of acetate and leaf litter. A higher diversity of anaerobic ammonium-oxidizing (anammox) bacteria was observed when acetate or leaf litter was added than the control. However, acetate and leaf litter generally inhibited the growth of anammox bacteria despite that leaf litter promoted their growth in the first 5 days. The inhibitory effects on anammox bacteria were more pronounced by acetate than by leaf litter. Neither acetate nor leaf litter affected ammonia-oxidizing archaea (AOA) community structures, but promoted their growth. For ammonia-oxidizing bacteria (AOB), the addition of acetate or leaf litter resulted in changes of community structures and promoted their growth in the early phase of the incubation. In addition, the promoting effects by leaf litter on AOB growth were more obvious than acetate. These results indicated that organic substances affect AOM community structures and abundances. The study suggests that leaf litter has an important influence on the community structures and abundances of AOMs in mangrove sediment and affects the nitrogen cycle in such ecosystem. © 2013 Springer-Verlag Berlin Heidelberg. Source

Cao Y.,University of New Brunswick | Cao Y.,Guangdong Academy of Forestry | Chan F.,University of New Brunswick | Chui Y.-H.,University of New Brunswick | Xiao H.,University of New Brunswick
BioResources | Year: 2012

Flax fibres are being considered as an environmentally friendly alternative to synthetic fibres in fibre-reinforced polymer composites due to their low density, biodegradability, and high mechanical strength. Previous work has found that the surface properties of natural fibres can be modified by chemical treatment and other treatment methods. This study focused on the effect of different treatments using alkaline, enzyme, and steam-heat, respectively, on some surface characteristics of flax fibre, e.g. physical, chemical, and thermal stability. Using scanning electron microscopy (SEM), treated fibres were observed to have smoother surfaces than untreated fibres. Chemical composition of fibres was found to be modified after treatment as characterized by Fourier transform infrared spectroscopy (FTIR). The crystallinity index and thermal stability of flax fibres were increased after certain treatments as determined by X-ray diffraction (XRD) and thermogravimetric analysis (TGA), respectively. The wettability of treated fibre by water was improved compared to the untreated sample. Source

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