A total of 131 endophytic actinomycete strains were successfully isolated from surface-sterilized banana roots. These isolates belonged to Streptomyces (n=99), Streptoverticillium (n=28), and Streptosporangium (n=2) spp. The remaining 2 isolates were not identified. About 18.3% of the isolates inhibited the growth of pathogenic Fusarium oxysporum f. sp. cubense on banana tissue extract medium. The most frequently isolated Streptomyces sp. strain S96 was similar to Streptomyces griseorubiginosus. About 37.5% of the S. griseorubiginosus strains were antagonistic to F. oxysporum f. sp. cubense. The antagonism of strain S96 was lost when FeCl(3) was introduced into the inhibition zone. In vivo biocontrol assays showed that the disease severity index (DSI) was significantly (P=0.05) reduced and mean fresh weight increased (P=0.001) in plantlets treated with strain S96 compared to those grown in the absence of the biocontrol strain. These findings indicate the potential of developing siderophore-producing Streptomyces endophytes for the biological control of fusarium wilt disease of banana.

To elucidate fungal diversity in methane hydrate-bearing deep-sea marine sediments in the South China Sea, internal transcribed spacer (ITS) regions of rRNA genes from five different sediment DNA samples were amplified and phylogenetically analyzed. Total five ITS libraries were constructed and 413 clones selected randomly were grouped into 24 restriction patterns by Amplified Ribosomal DNA Restriction Analysis (ARDRA). ITS sequences of 44 representative clones were determined and compared with the GenBank database using gapped-BLAST. The phylogenetic analysis showed that the ITS sequences (71-97% similarity) were similar to those of Phoma, Lodderomyces, Malassezia, Cryptococcus, Cylindrocarpon, Hortaea, Pichia, Aspergillus and Candida. The remaining sequences were not associated to any known fungi or fungal sequences in the public database. The results suggested that methane hydrate-bearing deep-sea marine sediments harbor diverse fungi. This is the first report on fungal communities from methane hydrate-bearing deep-sea marine sediments in South China Sea.

China remains by far the largest aquaculture producer in the world. However, biofilms formed by pathogenic Vibrio strains pose serious problems to marine aquaculture. To provide a strategy for biofilm prevention, control, and eradication, extracts from 88 marine actinomycetes were screened. Thirty-five inhibited the biofilm formation of Vibrio harveyi, Vibrio vulnificus, and Vibrio anguillarum at a concentration of 2.5% (v/v). Thirty-three of the actinomycete extracts dispersed the mature biofilm. Six extracts inhibited the quorum-sensing system of V. harveyi by attenuating the signal molecules N-acylated homoserine lactones' activity. Strain A66, which was identified as Streptomyces albus, both attenuated the biofilms and inhibited their quorum-sensing system. It is suggested that strain A66 is a promising candidate to be used in future marine aquaculture.

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Aims: To isolate endophytic Streptomyces strains from tomato and examine their antimicrobial activity. Methods: Endophytic Streptomyces strains were isolated using surface-sterilization methods and identified by morphological characteristics. Antimicrobial activities were measured by the agar plate sensitivity method. Antifungal activity in vivo was measured by seedling mortality in infested soils. Results: Twenty-one per cent of endophytic streptomycete isolates produced antibacterial metabolites and 41% produced antifungal metabolites in S medium. Sixty-five per cent of the most frequently isolated strains inhibited the growth of Rhizoctonia solani by the antibiosis assay but only 32% produced metabolites active against R. solani in S medium. Growth promotion and enhanced disease resistance of seedlings inoculated with Streptomyces sp. strain S30 were observed in tomato but not in cucumber seedlings. Conclusions: Endophytic Streptomyces spp. strains were successfully isolated using stringent methods and strain S30 promoted growth and enhanced resistance to R. solani in tomato seedlings. Significance and Impact of the Study: Endophytic streptomycetes showing antifungal activity in vitro and in vivo may indicate the potential for their use as biocontrol agents particularly of R. solani disease of tomato seedlings.

The objective of this study was to screen for novel quorum-sensing inhibitors (QSIs) from traditional Chinese medicines (TCMs) that inhibit bacterial biofilm formation. Six of 46 active components found in TCMs were identified as putative QSIs based on molecular docking studies. Of these, three compounds inhibited biofilm formation by Pseudomonas aeruginosa and Stenotrophomonas maltophilia at a concentration of 200 mM. A fourth compound (emodin) significantly inhibited biofilm formation at 20 mM and induced proteolysis of the quorum-sensing signal receptor TraR in Escherichia coli at a concentration of 3-30 mM. Emodin also increased the activity of ampicillin against P. aeruginosa. Therefore, emodin might be suitable for development into an antivirulence and antibacterial agent. INTRODUCTIONPseudomonas aeruginosa, an opportunistic human pathogen, may cause acute infections in hospitalized patients, can be isolated from the environment, particularly from soil and water, and it regularly contaminates medical devices (Stover et al., 2000). It is also the predominant cause of chronic lung infection in cystic fibrosis patients (Frederiksen et al., 1997) and has recently been recognized as one of the main causes of chronic wound infections (Gjødsbøl et al., 2006). P. aeruginosa can infect patients by producing a wide range of virulence factors, the expression levels of which are tightly regulated. Key to this regulation is cell density-dependent cell-to-cell signalling, which is termed quorum sensing (QS) (Rumbaugh et al., 2000). As in many other bacteria, QS controls secretion of virulence factors (Mittal et al., 2006), biofilm formation (Waters et al., 2008) and the exchange of DNA (Fuqua & Winans, 1996) in P. aeruginosa. The biofilm mode of growth is recognized as an important bacterial trait that is relevant to infections (Costerton et al., 1994). Many infections involve the formation of bacterial biofilms, which are bacterial communities that settle and proliferate on surfaces and are covered by exopolymers (Lewis, 2007). Once established, biofilms are difficult to eradicate and become a source of secondary infection (Jones et al., 2009). Moreover, bacteria embedded in biofilms are more tolerant than planktonic cells of antibiotics (Donlan & Costerton, 2002;Drenkard, 2003). The dose of antibiotics needed in this situation will often exceed the highest deliverable dose, which makes efficient treatment impossible.QS, as a regulatory mechanism, enables bacteria to make collective decisions with respect to the expression of a specific set of genes that involve the production, release and subsequent detection of chemical signalling molecules, such as N-acylhomoserine lactones (AHLs) that are commonly used by Gram-negative bacteria. When the concentration of AHLs reaches a certain threshold level, binding to a receptor molecule (for example, LuxR) is promoted and the activated LuxR-AHL complex forms dimers or polymers, which, in turn, act as transcriptional regulators of target genes in the QS regulon (Parsek & Greenbe...

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Traditionally, static units of analysis such as administrative units are used when studying obesity. However, using these fixed contextual units ignores environmental influences experienced by individuals in areas beyond their residential neighborhood and may render the results unreliable. This problem has been articulated as the uncertain geographic context problem (UGCoP). This study investigates the UGCoP through exploring the relationships between the built environment and obesity based on individuals’ activity space. First, a survey was conducted to collect individuals’ daily activity and weight information in Guangzhou in January 2016. Then, the data were used to calculate and compare the values of several built environment variables based on seven activity space delineations, including home buffers, workplace buffers (WPB), fitness place buffers (FPB), the standard deviational ellipse at two standard deviations (SDE2), the weighted standard deviational ellipse at two standard deviations (WSDE2), the minimum convex polygon (MCP), and road network buffers (RNB). Lastly, we conducted comparative analysis and regression analysis based on different activity space measures. The results indicate that significant differences exist between variables obtained with different activity space delineations. Further, regression analyses show that the activity space delineations used in the analysis have a significant influence on the results concerning the relationships between the built environment and obesity. The study sheds light on the UGCoP in analyzing the relationships between obesity and the built environment.