High-performance Bi(2)Te(3)-based topological insulator film magnetic field detector

Topological insulators with the nanoscaled metallic surface state (3-5 nm) are actually of typical functional nanostructures. Significant efforts have been devoted to study new families of topological insulators and identifications of topological surface state, as well as fundamental physics issues relating to spin-polarized surface electronic states in the past few years. However, transport investigations that can provide direct experimental evidence for potentially practical applications of topological insulators are limited, and realization of functional devices based on topological insulators is still under exploration. Here, using the Sn-doping Bi2Te3 polycrystalline topological insulator films, we fabricated high-performance current-controlled magnetic field detectors. When a parallel magnetic field is applied, the as-fabricated device exhibits a stable and reproducible magneto-resistance (MR) switching behavior, and the corresponding MR ratio can be modulated by the applied current. Even under such a low magnetic field (0.5 kG), the device still shows a distinguishable MR switching performance, suggesting that topological insulator devices are very sensitive to external stimulation and potentially applicable to weak magnetic field detection.

Polymorphisms in the endothelial nitric oxide synthase gene associated with recurrent miscarriage

Endothelial nitric oxide synthase (eNOS) is an enzyme that influences placental human chorionic gonadotropin production during gestation. Previous studies have indicated an association between eNOS activity, implantation, and maintenance of pregnancy, but proposed associations between polymorphisms of the eNOS gene and recurrent miscarriage (RM) are controversial. To identify markers contributing to the genetic susceptibility to RM, we examined the potential association between RM and 8 single nucleotide polymorphisms (SNPs; rs1799983, rs2070744, rs11771443, rs3918188, rs2853796, rs7830, rs1541861, and rs2853792) of the eNOS gene using the MassARRAY system (Sequenom, USA). The enrolled participants included 192 RM patients and 201 women with normal fertility as controls. The results showed that rs1799983 at exon 7 of the eNOS gene was significantly associated with RM (genotype: chi-square = 15.071, P = 0.001; allele: chi-square = 6.250, P = 0.016). Another significant association was observed for rs11771443 in the promoter (genotype: chi-square = 6.259, P = 0.044; allele: chi-square = 7.076, P = 0.008). Furthermore, strong linkage disequilibrium was observed in 3 blocks (D' > 0.9), and significantly fewer T-T-G haplotypes (chi-square = 5.981, P = 0.015) residing in block 1 were found in RM patients. These findings point to a role for eNOS gene polymorphisms in RM in the Chinese Han population and may be informative for future genetic or neurobiological studies of RM.

Limb ischemic preconditioning attenuates cerebral ischemic injury in rat model

Ischemic brain injury is not uncommon after open-heart surgery with cardiopulmonary bypass and seriously undermines the patients' life quality. Therefore, potential protective effects of limb ischemic preconditioning (LIP) on subsequent ischemic injury of the brain were investigated by evaluating anti-inflammatory effects and apoptosis of pyramidal neurons in the CA1 hippocampus. One hundred and eight Sprague-Dawley rats were divided into the middle cerebral artery occlusion (MCAO) group (n=54) and the LIP group (n=54). A thread was used to occlude the middle cerebral artery in the MCAO group and the LIP group animals were pretreated with LIP followed by MCAO. In the two groups, nine samples were collected at each time-point of 0, 6, 12, 24, 48 and 72 h after MCAO to detect IL-6 and IL-17 and their mRNA levels. Neurological severity scores (NSS) were examined before the animals were sacrificed. Compared with the LIP group, cerebral histopathological changes in the MCAO group were most distinct and significantly more infiltrated inflammatory and apoptotic neuronal cells were observed at 24, 48 and 72 h post-surgery. IL-17 and IL-6 mRNA levels analyzed by quantitative real-time polymerase chain reaction (PCR) (qRT-PCR) were significantly reduced in the LIP group compared with the MCAO group at the 12, 24 and 48 h time-points. A significant reduction in IL-17 expression level was determined by enzyme-linked immunosorbent assay (ELISA) in the LIP group at 12, 24 and 48 h, while IL-6 was significantly reduced at the 24 and 48 h time-points. The NSSs were not significantly different between the groups. Therefore, in a MCAO rat model, we have proved that LIP pretreatment can protect the brain from infarction after ischemic injury and induce ischemic tolerance, potentially, by reducing IL-17 to provide anti-inflammatory effects and attenuate apoptosis of hippocampal neuronal cells.

The evolution of polyploid wheats: identification of the A genome donor species

Cytogenetic work has shown that the tetraploid wheats, Triticum turgidum and T. timopheevii, and the hexaploid wheat T. aestivum have one pair of A genomes, whereas hexaploid T. zhukovskyi has two. Variation in 16 repeated nucleotide sequences was used to identify sources of the A genomes. The A genomes of T. turgidum, T. timopheevii, and T. aestivum were shown to be contributed by T. urartu. Little divergence in the repeated nucleotide sequences was detected in the A genomes of these species from the genome of T. urartu. In T. zhukovskyi one A genome was contributed by T. urartu and the other was contributed by T. monococcum. It is concluded that T. zhukovskyi originated from hybridization of T. timopheevii with T. monococcum. The repeated nucleotide sequence profiles in the A genomes of T. zhukovskyi showed reduced correspondence with those in the genomes of both ancestral species, T. urartu and T. monococcum. This differentiation is attributed to heterogenetic chromosome pairing and segregation among chromosomes of the two A genomes in T. zhukovskyi.

Nine polymorphic STR loci in the HLA region in the Shaanxi Han population of China

A large number of microsatellite genetic markers have been identified in the human leukocyte antigen (HLA) region. We investigated genetic polymorphism of the nine short tandem repeat (STR) loci (D6S276, MOGCA, D6S265, MIB, D6S273, G51152, TAP1CA, RING3CA, and D6S291) in the HLA region in the Shaanxi Han population. Using a fluorescence-labeled multiplex-PCR STR typing method, 6-13 alleles were detected in these nine STR loci in 150 unrelated Han Chinese from the region of Shaanxi, China. The distributions of the genotypes at these nine loci were in Hardy-Weinberg equilibrium. We conclude that these nine STR loci have a high level of genetic polymorphism; they would be useful for population genetic studies, pre-transplantation HLA typing, forensic and paternity testing, etc.

Postoperative adjuvant transcatheter arterial chemoembolisation improves survival of intrahepatic cholangiocarcinoma patients with poor prognostic factors: results of a large monocentric series

BACKGROUND

The prognosis of patients with intrahepatic cholangiocarcinoma (ICC) is currently unsatisfactory. The aims of this study were to identify prognostic factors after curative ICC resection, and to evaluate the effects of postoperative transcatheter arterial chemoembolisation (TACE).

METHODS

A retrospective analysis was conducted of 114 ICC patients who underwent curative resection from January 2005 to December 2006. Relationships between survival and clinicopathological factors were evaluated using univariate and multivariate analyses. The benefits of adjuvant TACE were investigated separately.

RESULTS

The cumulative 1-, 3-, and 5-year survival rates were 63%, 26%, and 15%, respectively. Multivariate analysis revealed that tumour size ≥ 5 cm (hazard ratio [HR] 1.875, 95% CI 1.139-3.088, P=0.013) and advanced TNM stage (stage III or IV) (HR 1.681, 95% CI 1.035-2.732, P=0.036) were independently associated with poor prognosis. Fifty-seven patients underwent adjuvant TACE. In patients with poor prognostic factors, TACE improved the survival rate (P<0.001). However, in patients without poor prognostic factors, TACE did not significantly change the survival rate (P=0.724).

CONCLUSIONS

Postoperative adjuvant TACE can prolong survival in ICC patients with tumour size ≥ 5 cm or advanced TNM stage.

Two novel DAX1 gene mutations in Chinese patients with X-linked adrenal hypoplasia congenita: clinical, hormonal and genetic analysis

Mutations in the DAX1 gene result in X-linked congenital adrenal hypoplasia (AHC). Affected boys usually present with primary adrenal failure in early infancy or childhood and hypogonadotropic hypogonadism (HH) at puberty. This paper describes the clinical, hormonal, radiological, and genetic characteristics of 2 Chinese patients with X-linked AHC. Primary adrenal insufficiency occurred in the 2 patients during their childhood and HH was recognized at puberty. Genomic DNA was extracted from their peripheral blood leukocytes and coding sequence abnormalities of the DAX1 gene were assessed by PCR and direct sequencing analysis. Genetic analysis of the DAX1 gene revealed 2 novel mutations c.572-575 dupGGGC, p.Thr193Gly,fs,205X and c.773- 774 dupCC, p.Ser259Pro,fs,264X in exon 1, causing frameshifts and yeilding premature stop codons at 205 and 264, respectively. This study identifies 2 novel mutations in the DAX1 gene which can further expand the mutation database and benefit patients in the diagnosis and treatment of AHC.

Improved tolerance of maize (Zea mays L.) to heavy metals by colonization of a dark septate endophyte (DSE) Exophiala pisciphila

Dark septate endophytes (DSE) are ubiquitous and abundant in stressful environments including heavy metal (HM) stress. However, our knowledge about the roles of DSE in improving HM tolerance of their host plants is poor. In this study, maize (Zea mays L.) was inoculated with a HM tolerant DSE strain Exophiala pisciphila H93 in lead (Pb), zinc (Zn), and cadmium (Cd) contaminated soils. E. pisciphila H93 successfully colonized and formed typical DSE structures in the inoculated maize roots. Colonization of E. pisciphila H93 alleviated the deleterious effects of excessive HM supplements and promoted the growth of maize (roots and shoots) under HM stress conditions, though it significantly decreased the biomass of inoculated maize under no HM stress. Further analysis showed that the colonization of E. pisciphila H93 improved the tolerance of maize to HM by restricting the translocation of HM ions from roots to shoots. This study demonstrated that under higher HM stress, such a mutual symbiosis between E. pisciphila and its host (maize) may be an efficient strategy to survive in the stressful environments.

Distribution of human leukocyte antigen alleles and haplotypes in Oroqen and Ewenki nationality minority in Inner Mongolia Autonomous Region of China

The frequencies of the human leukocyte antigen alleles HLA-A,-B, DRB1 and the A-B, A-DRB1, B-DRB1, A-B-DRB1 haplotypes were investigated through means of PCR-based reverse line-strip sequence specific oligonucleotide hybridization on 108 Oroqen and 104 Ewenki nationality unrelated healthy individuals from the Inner Mongolia Autonomous Region of China. A total of thirteen different HLA-A alleles, 21 different HLA-B alleles and 13 different HLA-DRB1 alleles were detected in the Oroqen ethnic group and the most frequent HLA alleles found were A*24(35.65%), B*15(17.92%), and DRB1*09(17.59%), respectively. The common HLA-A-B-DRB1 haplotypes were A*24-B*40-DRB1*09(5.09%), A*24-B*48-DRB1*12(2.78%) and A*24-B*51-DRB1*04(2.78%); and the HLA-A*33-B*58, A*30-B*13, A*01-B*37, A*33-DRB1*03, A*01-DRB1*10, A*30-DRB1*07, B*37-DRB1*10, B*58-DRB1*03, B*38-DRB1*08, B*13-DRB1*07 were significant positive linkage disequilibrium in the Oroqen nationality group. In total, 14 different HLA-A alleles, 27 B alleles and 12 DRB1 alleles were found in Ewenki nationality group, and the most frequent HLA alleles found were A*24(24.49%), B*40(17.35%), and DRB1*04(14.80%), respectively. The common HLA-A-B-DRB1 haplotypes were A*33-B*58-DRB1*03(6.25%), A*01-B*51-DRB1*11(2.88%) and A*24-B*40-DRB1*09(2.88%); the HLA-A*33-B*58, A*29-B*44, A*03-B*52, A*33-DRB1*03, A*29-DRB1*07, A*24-DRB1*09, B*58-DRB1*03, B*08-DRB1*03, B*46-DRB1*09 were significant positive linkage disequilibrium in Ewenki nationality group. The distribution of HLA A,-B, DRB1, alleles haplotypes frequencies and phylogenetic tree indicated that the Oroqen and Ewenki population groups belongs to northern group of China, together as a group cluster.

Safety and radiation-enhancing effect of sodium glycididazole in locoregionally advanced laryngeal cancers previously treated with platinum-containing chemotherapy regimens: A preliminary report

PURPOSE

To determine the safety and radiation-enhancing effect of sodium glycididazole in laryngeal squamous cell carcinoma (stage T3-4,N0-3,M0) with conventional radiotherapy.

PATIENTS AND METHODS

Patients with locoregional advanced laryngeal cancer (stage T3-4,N0-3,M0) were included: group 1(control, n=30)were not administered of sodium glycididazole; group 2 (test, n=30) received sodium glycididazole at a dose of 700 mg/m(2) intravenous infusion 30 minutes before radiotherapy three times a week. Surrogate end-points of efficacy were tumor and nodal size. Safety parameters were vomiting, nausea, mucositis, laryngeal edema, esophagus and skin reaction, dysphagia, dyspnea, neurological deficit. Patients were evaluated weekly during treatment for 7 weeks and thereafter monthly for 3 months.

RESULTS

In the test, the overall response rate was 88.89% (95%CI, 71.00-97.00%) at 7 weeks and 92.59% (95%CI, 76.00 to 99.00%) at 1 month of follow-up. In the control, the overall response rate was 62.5% (95%CI, 41.00 to 81.00%) at 7 weeks and 58.33% (95%CI, 37.00 to 78.00%) at 1 month of follow-up. The short-term locoregional response rate was better in the test group at 7 weeks (p=0.027) and at 1 month (p=0.005) of follow-up. The test group had significantly more nausea and vomiting in weeks 1 (p=0.047), 2 (p=0.007), and 3 (p=0.01) of treatment.

CONCLUSIONS

The study indicates sodium glycididazole is an effective radiation-enhancing agent that improves short-term locoregional control and is well tolerated in patients with locoregionally advanced laryngeal cancer.

13C labeling reveals multiple amination reactions in the biosynthesis of a novel polyketide polyamine antibiotic zeamine from Dickeya zeae

The structure of zeamine, a novel polyamino-amide antibiotic metabolite of Dickeya zeae has been established by NMR and detailed MS analyses; labelling studies with (13)C-labelled acetates suggest that the repeating secondary amine containing motif may be biosynthesised via a modular PKS containing aminotransferase domains.

Genetic susceptibility to haemorrhagic fever with renal syndrome caused by Hantaan virus in Chinese Han population

We report a significantly higher occurrence of HLA-DRB1*09 (51% vs. 23%, P = 0.002, OR = 3.57) and HLA-B*46-DRB1*09 (26% vs. 8%, P = 0.018, OR = 3.76) in patients with haemorrhagic fever with renal syndrome (HFRS) compared to the control group, suggesting Hantaan virus-induced HFRS is associated with a genetic predisposition in the Chinese Han population.

Generation of multilayered structures for biomedical applications using a novel tri-needle coaxial device and electrohydrodynamic flow

In this short communication, we describe the scope and flexibility of using a novel device containing three coaxially arranged needles to form a variety of novel morphologies. Different combinations of materials are subjected to controlled flow through the device under the influence of an applied electric field. The resulting electrohydrodynamic flow allows us to prepare double-layered bubbles, porous encapsulated threads and nanocapsules containing three layers. The ability to process such multilayered structures is very significant for biomedical engineering applications, for example, generating capsules for drug delivery, which can provide multistage controlled release.

Generation of multilayered structures for biomedical applications using a novel tri-needle coaxial device and electrohydrodynamic flow

In this short communication, we describe the scope and flexibility of using a novel device containing three coaxially arranged needles to form a variety of novel morphologies. Different combinations of materials are subjected to controlled flow through the device under the influence of an applied electric field. The resulting electrohydrodynamic flow allows us to prepare double-layered bubbles, porous encapsulated threads and nanocapsules containing three layers. The ability to process such multilayered structures is very significant for biomedical engineering applications, for example, generating capsules for drug delivery, which can provide multistage controlled release.

Characterization of a pathogenic H9N2 influenza A virus isolated from central China in 2007

The entire genome of the A/Chicken/Hubei/C1/2007 (H9N2) virus, isolated from central China in 2007, was completely sequenced and phylogenetically analyzed. Phylogenetic analysis demonstrated that A/Chicken/Hubei/C1/2007 (H9N2) virus represents multiple reassortant lineages, with genes coming from the early mainland China strain (Ck/Beijing/1/94), an H9N2 virus with special genotype (Ck/shanghai/F/98) and other lineages from poultry in Asia. Infection studies indicated that A/Chicken/Hubei/C1/2007 (H9N2) virus replicated efficiently in MDCK cells and in BALB/c mice. The H9N2 virus also replicated to high titers in chicken respiratory tracts and caused overt clinical signs in chickens. Our results suggest that attention should be paid to the natural evolution of H9N2 influenza viruses and to the control of H9N2 influenza viruses in animals.

Distribution of polycyclic aromatic hydrocarbons in thirty typical soil profiles in the Yangtze River Delta region, east China

Polycyclic aromatic hydrocarbons (PAHs) were quantified in 30 soil profiles from the Yangtze River Delta Region, in east China. Relative concentrations of PAH compounds with different benzene rings and ratios of fluoranthene to fluoranthene plus pyrene and benz(a)anthracene to benz(a)anthracene plus chrysene were used to identify the possible sources of soil PAHs. Total concentrations of 15 PAHs in topsoils ranged from 8.6 to 3881 microg kg(-1) with an average of 397 microg kg(-1). Half of the soil samples were considered to be contaminated with PAHs (>200 microg kg(-1)) and two sampling sites were heavily polluted by PAHs with concentrations >1000 microg kg(-1). Phenanthrene was found in soils below a depth of 100 cm in half of the sampling sites, but the detectable ratio of benzo(a)pyrene decreased sharply from 100% in topsoil to 0 in the 4th horizon.

Seasonality of symptoms in women with postpartum depression

It is important to consider the potential contribution of seasonality to postpartum depression (PPD; Hiltunen et al, 2004). A possible link between seasonality and PPD may have implications for not only choice of treatment, but also in considering pregnancy planning. The objectives of this pilot study were to examine whether women with seasonal mood changes demonstrated greater incidence of PPD, and to determine if seasonality scores were predictive of PPD. The Seasonal Pattern Assessment Questionnaire (SPAQ; Rosenthal et al, 1987) was used to assess seasonality of mood. A logistic regression analysis was conducted to determine the association between clinical factors, SAD diagnosis, SPAQ global seasonality score (GSS) and season of SPAQ administration and PPD. In our sample, twice as many women in the PPD group were found to have SAD compared to the control group. The PPD group also had a higher group GSS mean (10.44) than did the control group (8.84). However, logistic regression analysis showed that higher seasonality scores in women with PPD were not necessarily predictive of PPD. While more women in the PPD group reported increased seasonal weight fluctuation and less sleep in the spring and summer, these items alone did not predict depression after childbirth.

Tumor suppressor in lung cancer-1 (TSLC1) functions as a glioma tumor suppressor

Tumor suppressor in lung cancer-1 (TSLC1) loss is common in many human cancers, including meningioma. In this study, we demonstrate that TSLC1 protein and RNA expression is lost in 60% to 65% of high-grade gliomas, and that TSLC1 reintroduction into glioma cells results in growth suppression. Moreover, Tslc1 loss in mice results in increased astrocyte proliferation in vivo and in vitro. These data indicate that TSLC1 functions as a glioma tumor suppressor.

Distribution of polycyclic aromatic hydrocarbons in soils at Guiyu area of China, affected by recycling of electronic waste using primitive technologies

The concentration, distribution, profile and possible source of polycyclic aromatic hydrocarbons (PAHs) in soil were studied in Guiyu, an electronic waste (E-waste) recycling center, using primitive technologies in Southeast China. Sixteen USEPA priority PAHs were analyzed in 49 soil samples (0-10 cm layer) in terms of individual and total concentrations, together with soil organic matter (SOM) concentrations. The concentrations of a sum of 16 PAHs ranged from 44.8 to 3206 microgkg(-1) (dry weight basis), in the descending order of E-waste open burning sites (2065 microgkg(-1))>areas near burning sites (851microgkg(-1))>rice fields (354 microgkg(-1))>reservoir areas (125microgkg(-1)). The dominant PAHs were naphthalene, phenanthrene and fluoranthene, which were mainly derived from incomplete combustion of E-waste (e.g. wire insulations and PVC materials), and partly from coal combustion and motorcycle exhausts. All individual and total PAH concentrations were significantly correlated with SOM except for naphthalene and acenaphthylene. Principal component analysis was performed, which indicated that PAHs were mainly distributed into three groups in accordance with their ring numbers and biological and anthropogenic source. In conclusion, PAH concentrations in the Guiyu soil were affected by the primitive E-waste recycling activities.

Preparation of microbubble suspensions by co-axial electrohydrodynamic atomization

In this paper we report a novel method, based on co-axial electrohydrodynamic jetting, for the preparation of microbubble suspensions containing bubbles <10 microm in size and having a narrow size distribution. No selective filtration is necessary and the suspensions are produced directly by the process. To demonstrate the method, glycerol was used as the liquid medium, flowing in the outer needle of the co-axial twin needle arrangement and undergoing electrohydrodynamic atomization in the stable cone-jet mode while air flowed through the inner needle at the same time. At zero applied voltage a hollow stream of liquid flowed from the outer needle. When the applied voltage was increased, eventually the hollow stream became a stable cone-jet and emitted a microthread of bubbles, which were collected in a container of glycerol to obtain microbubble suspensions. The size of the microbubbles was measured via optical microscopy and laser diffractometry. Several microbubble suspensions were prepared and characterised and the size distribution was found to be critically dependent on the ratio (n) of flow rates of liquid/air and, in particular the flow rate of the air. At n=1.5, with the flow rate of air set at approximately 1.7 microl/s, a microbubble suspension containing bubbles in the size range 2-8 microm was obtained.

Succinic semialdehyde couples stress response to quorum-sensing signal decay in Agrobacterium tumefaciens

Quorum sensing (QS) signal decay in Agrobacterium tumefaciens occurs in response to starvation or host signals. We have demonstrated that the gamma-aminobutyric acid (GABA) shunt metabolite links stress response to QS signal decay. Mutation of the aldH gene encoding a succinic semialdehyde dehydrogenase (SSADH) that converts succinic semialdehyde (SSA) to succinic acid results in early expression of the signal degrading enzyme, AttM. Exogenous addition of SSA or its precursor GABA induces AttM expression and abolishes Ti plasmid conjugative transfer. SSA acts by binding to the repressor AttJ that regulates the attKLM operon. attK encodes another SSADH. The stress alarmone ppGpp and SSA modulates separately the expression of the two SSADH enzymes, which might control the intracellular SSA level and hence to switch on/off the QS signal decay system in response to environmental changes. These findings document for the first time a sophisticated signalling mechanism of the widely conserved GABA degradation pathway in prokaryotes.

Genome scale analysis of diffusible signal factor regulon in Xanthomonas campestris pv. campestris: identification of novel cell-cell communication-dependent genes and functions

The bacterial pathogen Xanthomonas campestris pv. campestris (Xcc) recruits a diffusible signal factor (DSF), which has recently been structurally characterized as cis-11-methyl-2-dodecenoic acid, as a cell-cell communication signal to synchronize virulence gene expression and biofilm dispersal. In this study, we showed that despite the existance of phenotype variations in different Xcc isolates, the DSF-mediated functions were in general conserved. To investigate the genomic profiles of DSF regulation, we designed and conducted oligomicroarray analysis by comparison of the gene expression patterns of wild-type strain XC1 and its DSF-deficient mutant XC1dF, as well as those of XC1dF in the presence or absence of DSF signals. The analyses led to identification of 165 genes, whose expression was significantly influenced by DSF signals. These genes encode proteins and enzymes belonging to at least 12 functional groups. In addition to those previously known DSF-dependent activities such as production of extracellular enzymes and extracellular polysaccharides, microarray analyses also revealed new functions mediated by DSF, such as flagellum synthesis, resistance to toxins and oxidative stress, and aerobic respiration. Phenotype analyses confirmed that DSF signalling contributed to resistance to toxin acriflavin and hydrogen peroxide, and to the survival of bacterial cells at different temperatures. We conclude that DSF cell-cell signalling is not only essential for co-ordinating the expression of virulence genes but also plays a vital role in keeping up the general competence of the pathogen in ecosystems.

Distributions and concentrations of PAHs in Hong Kong soils

Surface soil (0-10 cm) samples from 53 sampling sites including rural and urban areas of Hong Kong were collected and analyzed for 16 EPA priority polycyclic aromatic hydrocarbons (PAHs). Total PAH concentrations were in the range of 7.0-410 microg kg(-1) (dry wt), with higher concentrations in urban soils than that in rural soils. The three predominant PAHs were Fluoranthene, Naphthalene and Pyrene in rural soils, while Fluoranthene, Naphthalene and Benzo(b + k)fluoranthene dominated the PAHs of urban soils. The values of PAHs isomer indicated that biomass burning might be the major origin of PAHs in rural soils, but vehicular emission around the heavy traffic roads might contribute to the soil PAHs in urban areas. A cluster analysis was performed and grouped the detectable PAHs under 4 clusters, which could be indicative of the PAHs with different origins and PAHs affected by soil organic carbon contents respectively.

Dual control of quorum sensing by two TraM-type antiactivators in Agrobacterium tumefaciens octopine strain A6

Agrobacterium tumefaciens wild-type strains have a unique quorum-sensing (QS)-dependent Ti plasmid conjugative transfer phenotype in which QS signaling is activated by corresponding conjugative opine inducers. Strain K588, with a nopaline-type chromosomal background harboring an octopine-type Ti plasmid, however, is a spontaneous mutant displaying a constitutive phenotype in QS. In this study, we show that a single amino acid mutation (L54P) in the QS antiactivator TraM encoded by the traM gene of Ti plasmid is responsible for the constitutive phenotype of strain K588. Introduction of the L54P point mutation to the TraM of wild-type strain A6 by allelic replacement, however, failed to generate the expected constitutive phenotype in this octopine-type strain. Intriguingly, the QS-constitutive phenotype appeared when the pTiA6 carrying the mutated traM was placed in the chromosomal background of the nopaline-type strain C58C1RS, suggesting an unknown inhibitory factor(s) encoded by the chromosomal background of strain A6 but not by C58C1RS. Low-stringency Southern blotting analysis showed that strain A6, but not strain C58 and its derivatives, contains a second traM homologue. The homologue, designated traM2, has 64% and 65% identities with traM at the DNA and peptide levels, respectively. Similar to TraM, TraM2 is a potent antiactivator that functions by blocking TraR, the QS activator, from specific binding to the tra gene promoters. Deletion of traM2 in strain A6 harboring the mutated traM confers a constitutive QS phenotype. The results demonstrate that the QS system in strain A6 is subjected to the dual control of TraM and TraM2.