(2011). Community assembly during secondary forest succession in a Chinese subtropical forest. Ecological Monographs, 81(1): 25-41. Community assembly during secondary forest succession in a Chinese subtropical forest Abstract Subtropical broad-leaved forests in southeastern China support a high diversity of woody plants. Using a comparative study design with 30330 m plots (n=27) from five successional stages (<20, <40, <60, <80, and ≤80 yr), we investigated how the gradient in species composition reflects underlying processes of community assembly. In particular, we tested whether species richness of adult trees and shrubs decreased or increased and assessed to which degree this pattern was caused by negative density dependence or continuous immigration over time. Furthermore, we tested whether rare species were increasingly enriched and the species composition of adult trees and shrubs became more similar to species composition of seedlings during the course of succession. We counted the individuals of all adult species and shrubs >1 m in height in each plot and counted all woody recruits (bank of all seedlings ≤1 m in height) in each central 10310 m quadrant of each plot. In addition, we measured a number of environmental variables (elevation, slope, aspect, soil moisture, pH, C, N, and C/N ratio) and biotic structural variables (height and cover of layers). Adult species richness varied from 25 to 69 species per plot, and in total 148 woody species from 46 families were recorded. There was a clear successional gradient in species composition as revealed by nonmetric multidimensional scaling (NMDS), but only a poor differentiation of different successional stages with respect to particular species. Adult richness per 100 individuals (rarefaction method) increased with successional stage. None of the measured abiotic variables were significantly correlated with adult species richness. We found no evidence that rare species were responsible for the increasing adult species richness, as richness of rare species among both adults and recruits was independent of the successional stage. Furthermore, the similarity between established adults and recruits did not increase with successional stage. There was a constant number of recruit species and also of exclusive recruit species, i.e., those that had not been present as adult individuals, across all successional stages, suggesting a continuous random immigration over time. variables were significantly correlated with adult species richness. We found no evidence that 41 rare species were responsible for the increasing adult species richness, as richness of rare 42 species amongst both adults and recruits was independent of the successional stage.

Endocarditis isolates of Enterococcus faecalis produced biofilm significantly more often than nonendocarditis isolates, and 39% of 79 versus 6% of 84 isolates produced strong biofilm (P < 0.0001). esp was not required, but its presence was associated with higher amounts of biofilm (P < 0.001). Mutants disrupted in dltA, efaA, ace, lsa, and six two-component regulatory systems were largely unaltered, while disruptions in epa, atn, gelE, and fsr resulted in fewer attached bacteria, as determined using phase-contrast microscopy, and less biofilm (P < 0.0001).

We previously identified a gene cluster, epa (for enterocococcal polysaccharide antigen), involved in polysaccharide biosynthesis of Enterococcus faecalis and showed that disruption of epaB and epaE resulted in attenuation in translocation, biofilm formation, resistance to polymorphonuclear leukocyte (PMN) killing, and virulence in a mouse peritonitis model. Using five additional mutant disruptions in the 26-kb region between orfde2 and OG1RF_0163, we defined the epa locus as the area from epaA to epaR. Disruption of epaA, epaM, and epaN, like prior disruption of epaB and epaE, resulted in alteration in Epa polysaccharide content, more round cells versus oval cells with OG1RF, decreased biofilm formation, attenuation in a mouse peritonitis model, and resistance to lysis by the phage NPV-1 (known to lyse OG1RF), while mutants disrupted in orfde2 and OG1RF_163 (the epa locus flanking genes) behaved like OG1RF in those assays. Analysis of the purified Epa polysaccharide from OG1RF revealed the presence of rhamnose, glucose, galactose, GalNAc, and GlcNAc in this polysaccharide, while carbohydrate preparation from the epaB mutant did not contain rhamnose, suggesting that one or more of the glycosyl transferases encoded by the epaBCD operon are necessary to transfer rhamnose to the polysaccharide. In conclusion, the epa genes, uniformly present in E. faecalis strains and involved in biosynthesis of polysaccharide in OG1RF, are also important for OG1RF shape determination, biofilm formation, and NPV-1 replication/lysis, as well as for E. faecalis virulence in a mouse peritonitis model.Enterococci are among the major causes of endocarditis and nosocomial infections, with Enterococcus faecalis the most commonly identified species (7,22). The antibiotic resistance of enterococci not only causes difficulty in treatment of enterococcal infections but also appears to promote their survival in hospitalized, antibiotic-exposed individuals, helping to explain their important role in the nosocomial milieu.In order to understand the mechanisms of enterococcal pathogenesis, which may lead to development of alternative approaches to prevent and/or treat enterococcal infections, we and other investigators have identified several enterococcal factors important for virulence, including proteins and polysaccharides (11). Polysaccharides are composed of repeating units of oligosaccharides, are important components of bacterial cell walls, and can be associated with bacterial surfaces through linkage to the cell membrane, peptidoglycan, or by other unknown mechanisms. Polysaccharides also play important roles in bacterial pathogenesis. They have been shown to be important for adherence to and invasion of host tissues (10, 19), for resistance to host defense systems such as phagocytosis (1,2,8,12,24,30), and for induction of host inflammatory responses (14,25). Vaccine potential of surface polysaccharides has been shown for different bacteria, such as pneumococci (20), and antibodies against capsular carbohydrates have been shown to promo...

lines 4 and 5: "... while disruptions in epa, atn, gelE, and fsr resulted in fewer attached bacteria," should read "... while disruptions in epa (encoding enterococcal polysaccharide antigen), atn (encoding an autolysin), gelE (encoding gelatinase), and fsr (encoding the E. faecalis regulator) resulted in fewer attached bacteria." 7075

Experimental forest plantations to study biodiversity-ecosystem functioning (BEF) relationships have recently been established in different regions of the world, but subtropical biomes have not been covered so far. Here, we report about the initial survivorship of 26 tree species in the first such experiment in subtropical China. In the context of the joint Sino-German-Swiss Research Unit "BEFChina," 271 experimental forest plots were established using 24 naturally occurring tree species and two native commercial conifers. Based on the survival inventories carried out in November 2009 and June 2010, the overall survival rate was 87 % after the first 14 months. Generalized mixed-effects models showed that survival rates of seedlings were significantly affected by species richness, the species' leaf habit (deciduous or evergreen), species identity, planting date, and altitude. In the first survey, seedling establishment success decreased with increasing richness levels, a tendency that disappeared in the second survey after replanting. Though evergreen species performed less well than deciduous species with establishment rates of 84 versus 93 % in the second survey, their planting success exceeded the general expectation for subtropical broad-leaved evergreen species. These results have important implications for establishing mixed-species plantations for diversity conservation and improvement of ecosystem functioning in the Chinese subtropics and elsewhere. Additional costs associated with mixed-species plantations as compared to conventional plantations also demonstrate the potential of upscaling BEF experiments to large-scale afforestation projects. June 2010, the overall survival rate was 87% after the first 14 months. Generalized mixed-effects 22 models showed that survival rates of seedlings were significantly affected by species richness, the 23 species' leaf habit (deciduous or evergreen), species identity, planting date and altitude. In the first 24 survey, seedling establishment success decreased with increasing richness levels, a tendency that 25 disappeared in the second survey after replanting. Deciduous species had a significantly higher survival 26 than evergreen species (93% vs. 84% in the second survey). These results have implications for 27 establishing Though evergreen species performed less well than deciduous species with establishment 28 rates of 84% vs. 93% in the second survey, their planting success exceeded the general expectation for 29 subtropical broad-leave evergreen species. These results have important implications for establishing 30 mixed species plantations for diversity conservation and improvement of ecosystem functioning in the 31Chinese subtropics and elsewhere. Additional costs associated with mixed -species as compared to 32 conventional plantations also demonstrates the potential of upscaling BEF experiments to large-scale 33 afforestation projects. 34 35

In previous studies, we cloned a cluster of genes involved in polysaccharide biosynthesis (epa) from Enterococcus faecalis strain OG1RF and showed that this gene cluster mediated synthesis of a polysaccharide in Escherichia coli. Disruption of two open reading frames in the epa gene cluster of OG1RF generated two mutants, TX5179 and TX5180, which were attenuated in a mouse peritonitis model. In the current study, Western blotting was performed with serum from a patient with E. faecalis endocarditis and polysaccharide extracts from OG1RF and the mutants TX5179 and TX5180. OG1RF showed a smear in the high-molecularweight region and discrete bands in the low-molecular-weight region, which were missing from the mutants; periodate treatment and carbohydrate staining confirmed the polysaccharide nature of this material. In a neutrophil killing assay using OG1RF-absorbed normal human serum, the mutants TX5179 and TX5180, respectively, were 50 and 2.4 times more susceptible to killing than wild-type OG1RF (P < 0.01). With a fluorescence phagocytosis assay, 2.5 to 3 times more of the mutants were taken up by neutrophils than OG1RF (P < 0.001). Finally, with restriction digestion and hybridization under high-stringency conditions, the epa gene cluster of OG1RF (which is also present in the sequenced E. faecalis strain V583) was detected in 12 of 12 other clonally distinct E. faecalis strains tested: a similar polysaccharide pattern was detected for the 12 strains on Western blots using an E. faecalis endocarditis patient serum, and sera from four other patients with E. faecalis endocarditis all reacted with polysaccharide extracts of OG1RF. These results indicate that the epa gene cluster is widespread among E. faecalis and confers some protection against human host defenses.Enterococci are a leading cause of nosocomial infections in the United States and account for 5 to 15% of cases of infective endocarditis, with most isolates being Enterococcus faecalis (9). Better understanding of the pathogenicity of enterococci may help to develop more effective therapies or preventative modalities for E. faecalis infections.Polysaccharides on bacterial surfaces may interact with the human host and play important roles in bacterial pathogenesis. There is evidence indicating that polysaccharides are involved in hindering leukocyte killing of enterococci. Arduino and colleagues (1, 12) reported that exposure of Enterococcus faecium TX0016 (also called TEX16 as well as DO), a strain resistant to phagocytosis and killing by leukocytes in the presence of normal human sera (NHS); for partial sequence, see http:// www.hgsc.bcm.tmc.edu/microbial/efaecium/), to sodium periodate, but not to trypsin, pronase, or phospholipase C, eliminated its resistance to phagocytosis. Recently, members of our group showed that rabbit antiserum against formalin-killed E. faecium TX0016 promoted opsonization and killing, and this effect was dramatically reduced by adsorption of the antiserum with carbohydrate purified from TX0016, but not by incubation with ...

Eleven PhoP-PhoS homolog pairs were identified by searching the Enterococcus faecalis V583 genome sequence database at The Institute for Genomic Research with the Bacillus subtilis PhoP-PhoS sequences. Each pair appears to be a potential two-component system composed of a response regulator and a sensor kinase. Seven of the homologs were disrupted in E. faecalis strain OG1RF. TX10293, a mutant disrupted in one of these genes (etaR, the first gene of the gene pair designated etaRS), showed delayed killing and a higher 50% lethal dose in a mouse peritonitis model. The predicted EtaR protein sequence showed greatest similarity to LisR of Listeria monocytogenes (77%) and CsrR of Streptococcus pyogenes (70%); EtaS is 53% similar to LisK and 54% similar to CsrS. When grown in vitro, the TX10293 mutant was more sensitive to low pH (pH 3.4) and more resistant to high temperature (55°C) than wild-type OG1RF. In conclusion, many potential two-component systems are identified for E. faecalis, one of which, EtaRS, was shown to be involved in stress response and virulence.Enterococci are normal flora of the human intestine, found in the feces of most healthy adults. These organisms are also one of the leading causes of nosocomial infections, producing various diseases including bacteremia, urinary tract infections, endocarditis, intra-abdominal and pelvic infections, neonatal infections, and central nervous system infections, among others (15). Seventy to ninety percent of clinical enterococcal isolates are Enterococcus faecalis, with Enterococcus faecium playing an increasingly important role in the past decade.Bacteria often use two-component systems to control expression of virulence factors in response to environmental changes throughout the various stages of infection. These twocomponent systems are generally composed of a sensor kinase that recognizes one or more specific environmental signals and a response regulator protein that mediates cell response by regulating expression of specific operons or modulating protein functions (9). The genes encoding the sensor and regulator are often cotranscribed as a single transcript (9). An example is the CsrRS (also called CovRS) system of Streptococcus pyogenes. The CsrRS system is a two-component system that was first identified as a negative regulator of hyaluronic acid capsule synthesis (8,12). In an attempt to identify potential two-component systems in S. pyogenes, PhoP-PhoS, a global regulatory system in Bacillus subtilis, was used as query, and CsrRS was identified as a PhoPS homolog (6) that negatively regulates the transcription of several virulence factors, including ska (encoding streptokinase), sagA (encoding streptolysin S), speMF (encoding mitogenic factor), and hasA, the first gene in the operon for capsule synthesis (6). The phosphorylated CsrR was then found to be able to bind to the promoters of ska, sagA, speMF, and hasA with different affinities, consistent with its function as a response regulator and its differential regulation of these virulence genes (1...

Bi 2 Te 3 -based compounds and derivatives are milestone materials in the fields of thermoelectrics (TEs) and topological insulators (TIs). They have highly complex band structures and interesting lattice dynamics, which are favorable for high TE performance as well as strong spin orbit and band inversion underlying topological physics. This review presents rational calculations of properties related to TEs and provides theoretical guidance for improving the TE performance of Bi 2 Te 3 -based materials. Although the band structures of these TE materials have been studied theoretically and experimentally for many years, there remain many controversies on band characteristics, especially the locations of band extrema and the exact values of bandgaps. Here, the key factors in the theoretical investigations of Bi 2 Te 3 , Bi 2 Se 3 , Sb 2 Te 3 , and their solid solutions are reviewed. The phonon spectra and lattice thermal conductivities of Bi 2 Te 3 -based materials are discussed. Electronic and phonon structures and TE transport calculations are discussed and reported in the context of better establishing computational parameters for these V 2 VI 3 -based materials. This review provides a useful guidance for analyzing and improving TE performance of Bi 2 Te 3 -based materials.nologies, including cooling and power generation. [1] They have been attracting increased attention in the last decade as a promising potential solution for harvesting waste heat to produce useful electrical power. The key challenge is to improve the efficiency of TE energy conversion, which is determined by the dimensionless figure of merit zT = S 2 σT/(κ e + κ L ), where S, σ, T, κ e , and κ L are the Seebeck coefficient, electrical conductivity, absolute temperature, and the electronic and lattice components of total thermal conductivity κ, respectively. [2] In order to improve zT, one can increase the numerator S 2 σ, which is also called power factor, and decrease the denominator κ. However, the tradeoff among the three properties makes it difficult to realize a high zT. [3] Since all three properties (S, σ, κ e ) are carrier concentration dependent, optimizations of the carrier concentration are needed for maximizing zT. [4] It is often convenient to evaluate TE materials through several empirical parameters, which can be combined into a term called the quality factor B ∼ N v /m I *κ L , [5] where N v is the band degeneracy and m I * is the inertial mass (m I * is equal to the band effective mass m b * for an isotropic single band). This suggests that high N v with low m b * and low κ L are beneficial for TE performance. However, materials such as Bi 2 Te 3 -based alloys, with the highest known roomtemperature TE performance, have complex band structures that are not well described in effective mass models. More sophisticated treatments involving the actual electronic structure are imperative.Since the discovery of the Seebeck effect, a rapid progress in TEs has been made in the 1950s and 1960s, when the classic TE materials Bi 2 Te 3 , ...