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...

The intestine barrier serves as the front-line defense in shrimp. Clostridium butyricum (CB) can produce butyric acid that provides energy for the intestine epithelial cells of the host. However, the effects of dietary CB on the intestine microbiome and the digestion and immunity of the host is not clear. In this study, we therefore investigated the composition and metabolic activity of the intestine microbiome, and digestive and immune-related gene expression in Litopenaeus vannamei fed with diets containing different levels of CB: basal diet (control), 2.5 × 109 CFU kg−1 diet (CB1), 5.0 × 109 CFU kg−1 diet (CB2), and 1.0 × 1010 CFU kg−1 diet (CB3) for 56 days. Dietary CB altered the composition of the intestine microbiome. Specifically, the dominant bacterial phylum Proteobacteria was enriched in the CB3 group and weakened in the CB1 and CB2 groups. The Bacteroidetes was enriched in the CB1 and CB2 groups and weakened in the CB3 group. The Firmicutes was enriched in all three CB groups. At the genus level, the potential pathogen (Desulfovibrio and Desulfobulbus) were weakened, and beneficial bacteria (Bacillus, Clostridium, Lachmoclostridium, Lachnospiraceae, and Lactobacillus) were enriched in response to dietary CB; these might contribute to the expression of the host digestive genes (α-amylase, lipase, trypsin, fatty acid-binding protein, and fatty acid synthase) and immune-related genes (prophenoloxidase, lipopolysaccharide and β-1,3-glucan binding protein, lysozyme, crustin, and superoxide dismutase). Additionally, CB enhanced the bacterial metabolism, especially that of carbohydrates, polymers, amino acids, carboxylic acids, and amines. These results revealed that dietary CB had a beneficial effect on the intestine health of L. vannamei by modulating the composition of the intestine microbiome, enhancing the microbial metabolism activity, and promoting the digestion and immunity of the host. The optimal dietary supplementation dosage was found to be 5.0 × 109 CFU kg−1 in the diet.

Bacteria are recognized as important drivers of biogeochemical processes in all aquatic ecosystems. Temporal and geographical patterns in ocean bacterial communities have been observed in many studies, but the temporal and spatial patterns in the bacterial communities from the South China Sea remained unexplored. To determine the spatiotemporal patterns, we generated 16S rRNA datasets for 15 samples collected from the five regularly distributed sites of the South China Sea in three seasons (spring, summer, winter). A total of 491 representative sequences were analyzed by MOTHUR, yielding 282 operational taxonomic units (OTUs) grouped at 97% stringency. Significant temporal variations of bacterial diversity were observed. Richness and diversity indices indicated that summer samples were the most diverse. The main bacterial group in spring and summer samples was Alphaproteobacteria, followed by Cyanobacteria and Gammaproteobacteria, whereas Cyanobacteria dominated the winter samples. Spatial patterns in the samples were observed that samples collected from the coastal (D151, D221) waters and offshore (D157, D1512, D224) waters clustered separately, the coastal samples harbored more diverse bacterial communities. However, the temporal pattern of the coastal site D151 was contrary to that of the coastal site D221. The LIBSHUFF statistics revealed noticeable differences among the spring, summer and winter libraries collected at five sites. The UPGMA tree showed there were temporal and spatial heterogeneity of bacterial community composition in coastal waters of the South China Sea. The water salinity (P=0.001) contributed significantly to the bacteria-environment relationship. Our results revealed that bacterial community structures were influenced by environmental factors and community-level changes in 16S-based diversity were better explained by spatial patterns than by temporal patterns.

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Enzyme immunoassays for quantifying hepatitis C virus (HCV) core antigen (Ag) have been proposed as an alternative to HCV RNA detection. The present study aimed to investigate the early kinetics of serum HCVcAg and its usefulness in predicting virological responses.The clinical data of 135 patients with chronic hepatitis C treated with pegylated interferon alpha (PEG-IFN-α) and ribavirin was retrospectively collected. The patients were grouped according to their treatment outcomes as follows: sustained virological response (SVR), nonsustained virological response (N-SVR), and relapse.Higher HCVcAg and HCV RNA levels were observed in patients in the N-SVR group than in the other groups at baseline. HCVcAg better predicted rapid virological response (RVR) compared with HCV RNA and had a predictive value similar to that of HCV RNA for SVR and early virological response. In the relapse group, HCV RNA decreased to 0 after 48 weeks, whereas HCVcAg was still detectable, indicating that HCVcAg more sensitively predicted relapse in antiviral therapy than HCV RNA.For patients treated with PEG-INF-α and ribavirin, HCVcAg may more sensitively predict relapse than HCV RNA.

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Cyanophycin is non-ribosomally synthesized protein-like copolymer. Synthesis of cyanophycin is catalyzed by cyanophycin synthetase (CphA). In this study, a novel cyanophycin synthetase CphA49 belonging to NOR5 clade of Gammaproteobacteria was identified with primer-based screening from a deep-sea sediment metagenomic library. The cphA49 gene contained an open reading frame of 2,637 bp and encoded a protein with a predicted molecular mass of 100 kDa. A recombinant CphA49 was obtained by the functional expression of cphA49 in Escherichia coli BL21 (DE3). The biochemical properties of the purified CphA49 were determined. The optimum pH and temperature of the recombinant CphA49 were 9.0 and 40 °C, respectively. The enzyme was stable at temperatures below 40 °C. The recombinant CphA49 exhibited strict primer dependency and broad substrate specificities. Cyanophycin catalyzed by CphA49 exhibited homogenous molecular mass. The amino acid composition of cyanophycin was determined and constitutes arginine, aspartic acid, and lysine.