Functional Analysis of the Major Pilin Proteins of Type IV Pili in Streptococcus sanguinis CGMH010.

The pil gene cluster for Type IV pilus (Tfp) biosynthesis is commonly present and highly conserved in Streptococcus sanguinis. Nevertheless, Tfp-mediated twitching motility is less common among strains, and the factors determining twitching activity are not fully understood. Here, we analyzed the functions of three major pilin proteins (PilA1, PilA2, and PilA3) in the assembly and activity of Tfp in motile S. sanguinis CGMH010. Using various recombinant pilA deletion strains, we found that Tfp composed of different PilA proteins varied morphologically and functionally. Among the three PilA proteins, PilA1 was most critical in the assembly of twitching-active Tfp, and recombinant strains expressing motility generated more structured biofilms under constant shearing forces compared to the non-motile recombinant strains. Although PilA1 and PilA3 shared 94% identity, PilA3 could not compensate for the loss of PilA1, suggesting that the nature of PilA proteins plays an essential role in twitching activity. The single deletion of individual pilA genes had little effect on the invasion of host endothelia by S. sanguinis CGMH010. In contrast, the deletion of all three pilA genes or pilT, encoding the retraction ATPase, abolished Tfp-mediated invasion. Tfp- and PilT-dependent invasion were also detected in the non-motile S. sanguinis SK36, and thus, the retraction of Tfp, but not active twitching, was found to be essential for invasion.

Nutrient limitation regulates the properties of extracellular electron transfer and hydraulic shear resistance of electroactive biofilm.

Understanding the roles of nutrient restriction in extracellular electron transfer (EET) and stability of mixed electroactive biofilm is essential in pollutant degradation and bioenergy production. However, the relevant studies are still limited so far. Herein, the effect of nutrient restriction on the EET pathways and stability of mixed electroactive biofilm was explored. It was found that the electroactive Pseudomonas and Geobacter genera were selectively enriched in the biofilms cultured under total nutrient and P-constrained conditions, and two EET pathways including direct and indirect were found, while Rhodopseudomonas genus was enriched in the N-constrained biofilm, which only had the direct EET pathway. Moreover, multiple analyses including 2D confocal Raman spectra revealed that P-constrained biofilm was rich in extracellular polymeric substances (EPS) especially for polysaccharide, presented a dense and uniform layered distribution, and had better stability than N-constrained biofilm with lower EPS and biofilm with heterostructures cultured under total nutrient conditions.

Antibacterial Property of Composites of Reduced Graphene Oxide with Nano-Silver and Zinc Oxide Nanoparticles Synthesized Using a Microwave-Assisted Approach.

Graphene oxide (GO) composites with various metal nanoparticles (NPs) are attracting increasing interest owing to their broad scope in biomedical applications. Here, microwave-assisted chemical reduction was used to deposit nano-silver and zinc oxide NPs (Ag and ZnO NPs) on the surface of reduced GO (rGO) at the following weight percentages: 5.34% Ag/rGO, 7.49% Ag/rGO, 6.85% ZnO/rGO, 16.45% ZnO/rGO, 3.47/34.91% Ag/ZnO/rGO, and 7.08/15.28% Ag/ZnO/rGO. These materials were tested for antibacterial activity, and 3.47/34.91% Ag/ZnO/rGO and 7.08/15.28% Ag/ZnO/rGO exhibited better antibacterial activity than the other tested materials against the gram-negative bacterium Escherichia coli K12. At 1000 ppm, both these Ag/ZnO/rGO composites had better killing properties against both E. coli K12 and the gram-positive bacterium Staphylococcus aureus SA113 than Ag/rGO and ZnO/rGO did. RedoxSensor flow cytometry showed that 3.47/34.91% Ag/ZnO/rGO and 7.08/15.28% Ag/ZnO/rGO decreased reductase activity and affected membrane integrity in the bacteria. At 100 ppm, these two composites affected membrane integrity more in E. coli, while 7.08/15.28% Ag/ZnO/rGO considerably decreased reductase activity in S. aureus. Thus, the 3.47/34.91% and 7.08%/15.28% Ag/ZnO/rGO nanocomposites can be applied not only as antibacterial agents but also in a variety of biomedical materials such as sensors, photothermal therapy, drug delivery, and catalysis, in the future.

Antimicrobial effects of zero-valent iron nanoparticles on gram-positive Bacillus strains and gram-negative Escherichia coli strains.

BACKGROUND: Zero-valent iron nanoparticles (ZVI NPs) have been used extensively for the remediation of contaminated soil and groundwater. Owing to their large active surface area, they serve as strong and effective reductants. However, the ecotoxicity and bioavailability of ZVI NPs in diverse ecological media have not been evaluated in detail and most studies have focused on non-nano ZVI or Fe0. In addition, the antimicrobial properties of ZVI NPs have rarely been investigated, and the underlying mechanism of their toxicity remains unknown. RESULTS: In the present study, we demonstrate that ZVI NPs exhibited significant toxicity at 1000 ppm against two distinct gram-positive bacterial strains (Bacillus subtilis 3610 and Bacillus thuringiensis 407) but not against two gram-negative strains (Escherichia coli K12 and ATCC11634). Specifically, ZVI NPs caused at least a 4-log and 1-log reductions in cell numbers, respectively, in the two Bacillus strains, whereas no change was detected in the two E. coli strains. X-ray photoelectron spectroscopy, X-ray absorption near-edge, and extended X-ray absorption fine structure spectra confirmed that Bacillus cells exposed to ZVI NPs contained mostly Fe2O3 with some detectable FeS. This finding indicated that Fe0 nanoparticles penetrated the bacterial cells, where they were subsequently oxidized to Fe2O3 and FeS. RedoxSensor analysis and propidium iodide (PI) staining showed decreased reductase activity and increased PI in both Bacillus strains treated with a high (1000 ppm) concentration of ZVI NPs. CONCLUSION: Taken together, these data show that the toxicity of ZVI NPs was derived from their oxidative properties, which may increase the levels of reactive oxygen species and lead to cell death.

Nicotine contributes to the neural stem cells fate against toxicity of microglial-derived factors induced by Aß via the Wnt/ß-catenin pathway.

Recent studies have demonstrated that the molecules secreted from microglias play important roles in the cell fate determination of neural stem cells (NSCs), and nicotinic acetylcholine receptor agonist treatment could reduce neuroinflammation in some neurodegenerative disease models, such as Alzheimer's disease (AD). However, it is not clear how nicotine plays a neuroprotective role in inflammation-mediated central nervous diseases, and its possible mechanisms in the process remain largely elusive. The aim of this study is to improve the survival microenvironment of NSCs co-cultured with microglias in vitro by weakening inflammation that mediated by accumulation of ß-amyloid peptide (Aß). The viability, proliferation, differentiation, apoptosis of NSCs and underlying mechanisms associated with Wnt signaling pathway were investigated. The results showed that Aß could directly damage NSCs. Furthermore, concomitant to elevated levels of TNF-α, IL-1ß derived from microglias, the NSCs had been damaged more severely with the upregulation of Axin 2, p-ß-catenin and the downregulation of ß-catenin, p-GSK-3ß, microtubule-associated protein-2, choline acetyltransferase. However, addition of 10 µmol/L nicotine before microglias treated with Aß was beneficial to protect the NSCs against neurotoxicity of microglial-derived factors induced by Aß, which partially rescued proliferation, differentiation and inhibited apoptosis of NSCs via activation of Wnt/ß-catenin pathway. Taken together, these data imply that low concentration nicotine attenuates NSCs injury induced by microglial-derived factors via Wnt signaling pathway. Thus, treatment with nicotinic acetylcholine receptor agonist provides a promising research field for neural stem cell fate and therapeutic intervention in neuroinflammation diseases.

Cancer adjuvant chemotherapy strategic classification by artificial neural network with gene expression data: An example for non-small cell lung cancer.

PURPOSE: Adjuvant chemotherapy (ACT) is used after surgery to prevent recurrence or metastases. However, ACT for non-small cell lung cancer (NSCLC) is still controversial. This study aimed to develop prediction models to distinguish who is suitable for ACT (ACT-benefit) and who should avoid ACT (ACT-futile) in NSCLC. METHODS: We identified the ACT correlated gene signatures and performed several types of ANN algorithms to construct the optimal ANN architecture for ACT benefit classification. Reliability was assessed by cross-data set validation. RESULTS: We obtained 2 probes (2 genes) with T-stage clinical data combination can get good prediction result. These genes included 208893_s_at (DUSP6) and 204891_s_at (LCK). The 10-fold cross validation classification accuracy was 65.71%. The best result of ANN models is MLP14-8-2 with logistic activation function. CONCLUSIONS: Using gene signature profiles to predict ACT benefit in NSCLC is feasible. The key to this analysis was identifying the pertinent genes and classification. This study maybe helps reduce the ineffective medical practices to avoid the waste of medical resources.

Stereotactic neurosurgical technique and electrophysiological study in ablating the ventromedial shell of the nucleus accumbens.

OBJECTIVE: To describe in as much detail as possible the method for ablating the ventromedial shell of the nucleus accumbens (NAc) and investigate the efficacy and safety of the ablation treatment. METHODS: Sixty-five patients with drug addictions received operations within the time frame from 2004 to 2009. The ablation targets were located in the bilateral medial posterior inferior shell of the NAc. Intraoperative electrophysiological monitoring was performed. RESULTS: Tissue impedance in the shell of the NAc varied from 185 to 355 Ω. When stimulated with a low frequency (2 Hz) and a voltage above 3 V, 57 out of 65 (87.7%) patients experienced slight throbbing sensations. During the lesion procedure, fever was detected on the head and face of 59 patients (90.8%), the heart rate decreased in 19 cases (29.2%), and restlessness, irritability and hyperalgia were noted for all patients. Among the 65 patients, 52 (80%) no longer experienced a psychological craving for the drug. CONCLUSIONS: The shell of the NAc may be a promising surgical target for psychosurgery. Electrophysiological recordings revealed that the shell is indeed an appropriate structure.

Boosting bioelectricity generation in bioelectrochemical systems with nitrogen-doped three-dimensional graphene aerogel anode.

Bioelectricity generation by electrochemically active bacteria has become particularly appealing due to its vast potential in energy production, pollution treatment, and biosynthesis. However, developing high-performance anodes for bioelectricity generation remains a significant challenge. In this study, a highly efficient three-dimensional nitrogen-doped macroporous graphene aerogel anode with a nitrogen content of approximately 4.38 ± 0.50 at% was fabricated using hydrothermal method. The anode was successfully implemented in bioelectrochemical systems inoculated with Shewanella oneidensis MR-1, resulting in a significantly higher anodic current density (1.0 A/m2) compared to the control one. This enhancement was attributed to the greater biocapacity and improved extracellular electron transfer efficiency of the anode. Additionally, the N-doped aerogel anode demonstrated excellent performance in mixed-culture inoculated bioelectrochemical systems, achieving a high power density of 4.2 ± 0.2 W/m², one of the highest reported for three-dimensional carbon-based bioelectrochemical systems to date. Such improvements are likely due to the good biocompatibility of the N-doped aerogel anode, increased extracellular electron transfer efficiency at the bacteria/anode interface, and selectively enrichment of electroactive Geobacter soli within the NGA anode. Furthermore, based on gene-level Picrust2 prediction results, N-doping significantly upregulated the conductive pili-related genes of Geobacter in the three-dimensional anode, increasing the physical connection channels of bacteria, and thus strengthening the extracellular electron transfer process in Geobacter.

Trend analysis and future development of Taiwan electronic medical records.

The aim of this study was to validate a specially designed electronic medical records (EMRs) questionnaire for use in Taiwan. Published reviews of national trends and EMRs characteristics from seven countries in the Americas, Oceania, Europe, and Asia were used to design the Google-based document. This questionnaire is intended for use by medical institutions, government health units, manufacturers, academic institutions, and the public, and may be administered by information officers, non-IT staff (physicians, nurses, policymakers, vendors), and even people. A modified Delphi method was employed to determine the most appropriate content for the questionnaire. In conclusion, this research demonstrated trend analysis of several national EMRs, and also identified the meaningful use of EMR and establishing governmental EMR office are the important directions for Taiwan EMRs.

Activation of the promoter of the fengycin synthetase operon by the UP element.

Bacillus subtilis F29-3 produces an antifungal peptidic antibiotic that is synthesized nonribosomally by fengycin synthetases. Our previous work established that the promoter of the fengycin synthetase operon is located 86 nucleotides upstream of the translational initiation codon of fenC. This investigation involved transcriptional fusions with a DNA fragment that contains the region between positions -105 and +80 and determined that deleting the region between positions -55 and -42 reduces the promoter activity by 64.5%. Transcriptional fusions in the B. subtilis DB2 chromosome also indicated that mutating the sequence markedly reduces the promoter activity. An in vitro transcription analysis confirmed that the transcription is inefficient when the sequence in this region is mutated. Electrophoretic mobility shift and footprinting analyses demonstrated that the C-terminal domain of the RNA polymerase alpha subunit binds to the region between positions -55 and -39. These results indicated that the sequence is an UP element. Finally, this UP element is critical for the production of fengycin, since mutating the UP sequence in the chromosome of B. subtilis F29-3 reduces the transcription of the fen operon by 85% and prevents the cells from producing enough fengycin to suppress the germination of Paecilomyces variotii spores on agar plates.

Clinical analysis of contrast-enhanced ultrasound combined with serum SMURF1 detection in the diagnosis of thyroid cancer / 局解手术学杂志

Objective To investigate the diagnostic value of contrast-enhanced ultrasound(CEUS)combined with serum Smad ubiquitin regulatory factor 1(SMURF1)detection for thyroid cancer.Methods A total of 144 suspected thyroid cancer patients admitted to Lishui branch of Zhongda Hospital Affiliated to Southeast University from February 2019 to February 2020 were selected as the study subjects.Based on the histopathological results,they were divided into the thyroid cancer group(76 cases)and the benign group(68 cases).All patients underwent contrast-enhanced ultrasound examination and serum SMURF1 level detection;the diagnostic value of contrast-enhanced ultrasound parameters,serum SMURF1 detection alone,and the combination of the two methods for thyroid cancer were analyzed.Results Contrast-enhanced ultrasound parameters peak intensity(PI),mean perfusion intensity(SImean)and maximum perfusion intensity(SImax)in the thyroid cancer group were lower than those in the benign group,and the level of SMURF1 mRNA was higher than that in the benign group(P<0.05).The sensitivity of contrast-enhanced ultrasound parameter SImax in the diagnosis of thyroid cancer was 82.89%,the specificity was 72.06%,the accuracy was 77.78%,and the Kappa value was 0.552.The sensitivity of serum SMURF1 in the diagnosis of thyroid cancer was 65.79%,the specificity was 94.12%,the accuracy was 79.17%,and the Kappa value was 0.589.The sensitivity,specificity,accuracy and Kappa value of SImax combined with serum SMURF1 in the diagnosis of thyroid cancer were 97.37%,85.29%,91.67%and 0.832,respectively,which were higher than those of SImax and SMURF1 alone(P<0.05),the AUC of the combination of the two methods was 0.927,which was significantly higher than that of the two methods alone(Zcombined vs.SImax=3.999,P<0.001;Zcombined vs.SMURF1=3.270,P=0.001).Conclusion Contrast-enhanced ultrasound combined with serum SMURF1 detection can improve the diagnostic efficiency of thyroid cancer,which may avoid the over-diagnosis on the premise of ensuring the effective diagnosis of thyroid cancer patients.

Light-Chain Cardiac Amyloidosis: Cardiac Magnetic Resonance for Assessing Response to Chemotherapy

Objective@#Cardiac magnetic resonance (CMR) is a diagnostic tool that provides precise and reproducible information about cardiac structure, function, and tissue characterization, aiding in the monitoring of chemotherapy response in patients with lightchain cardiac amyloidosis (AL-CA). This study aimed to evaluate the feasibility of CMR in monitoring responses to chemotherapy in patients with AL-CA. @*Materials and Methods@#In this prospective study, we enrolled 111 patients with AL-CA (50.5% male; median age, 54 [interquartile range, 49–63] years). Patients underwent longitudinal monitoring using biomarkers and CMR imaging. At followup after chemotherapy, patients were categorized into superior and inferior response groups based on their hematological and cardiac laboratory responses to chemotherapy. Changes in CMR findings across therapies and differences between response groups were analyzed. @*Results@#Following chemotherapy (before vs. after), there were significant increases in myocardial T2 (43.6 ± 3.5 ms vs. 44.6 ± 4.1 ms; P = 0.008), recovery in right ventricular (RV) longitudinal strain (median of -9.6% vs. -11.7%; P = 0.031), and decrease in RV extracellular volume fraction (ECV) (median of 53.9% vs. 51.6%; P = 0.048). These changes were more pronounced in the superior-response group. Patients with superior cardiac laboratory response showed significantly greater reductions in RV ECV (-2.9% [interquartile range, -8.7%–1.1%] vs. 1.7% [-5.5%–7.1%]; P = 0.017) and left ventricular ECV (-2.0% [-6.0%–1.3%] vs. 2.0% [-3.0%–5.0%]; P = 0.01) compared with those with inferior response. @*Conclusion@#Cardiac amyloid deposition can regress following chemotherapy in patients with AL-CA, particularly showing more prominent regression, possibly earlier, in the RV. CMR emerges as an effective tool for monitoring associated tissue characteristics and ventricular functional recovery in patients with AL-CA undergoing chemotherapy, thereby supporting its utility in treatment response assessment.

Differences of resting-state brain functional connectivity in patients with early-onset and late-onset obsessive compulsive disorder and their correlation with cognitive flexibility / 中华行为医学与脑科学杂志

Objective:To explore the differences of the resting-state functional connectivity(FC) between goal-directed network and habituation networks in patients with early- and late-onset obsessive compulsive disorder (OCD) and the correlation between the strength of FC in the differential brain regions and cognitive flexibility.Methods:From October 2019 to April 2021, 40 patients with OCD were included in this study, including 22 patients with early-onset OCD and 18 patients with late-onset OCD.The cognitive flexibility of all subjects was assessed using the Wisconsin card sorting test (WCST), the Stroop task and the trail making test (TMT). The brain regions which were associated with goal-directed network(caudate, orbitofrontal cortex, ventromedial prefrontal cortex, and anterior cingulate cortex) and the brain regions which were associated with habituation network(putamen, supplementary motor area and insula) were selected as FC regions of interest (ROI). The DPABI and SPM12 plug-ins in the matlab2011a platform were used for whole brain FC analysis to compare the difference of FC between patients with early-onset OCD and patients with late-onset OCD on the two networks.The data were analyzed by SPSS 25.0 with χ2 test, independent samples t-test, and Pearson correlation analysis. Results:Compared with patients with early-onset OCD, patients with late-onset OCD had significantly enhanced FC of the left supplementary motor area with the left putamen and left insula.The total number of persistent errors of WCST in patients with late-onset OCD was greater than that in patients with early-onset OCD ((20.61±11.30), (14.95±8.94), P<0.05). The FC of the left putamen-left supplementary motor area was significantly and positively correlated with the total number of sustained responses ( r=0.678, P=0.003) and the total number of incorrect responses ( r=0.590, P=0.013) in patients with late-onset OCD.The FC of the left supplementary motor area-left insula was significantly positively correlated with the number of responses required to complete the first classification in patients with late-onset OCD ( r=0.485, P=0.049). Conclusion:Patients with late-onset OCD have stronger habituation network FC than patients with early-onset OCD, and the enhanced FC correlates with patients' cognitive flexibility performance, while late-onset OCD has more impaired cognitive flexibility than early-onset OCD.

Changes in Plasma Amyloid-β Level and Their Relationship With White Matter Microstructure in Patients With Mild Cognitive Impairment / 中国医学科学院学报

Objective To investigate the changes in plasma amyloid-β (Aβ) level and their relationship with white matter microstructure in the patients with amnesic mild cognitive impairment(aMCI) and vascular mild cognitive impairment (vMCI).Methods A total of 36 aMCI patients,20 vMCI patients,and 34 sex and age matched healthy controls (HC) in the outpatient and inpatient departments of the First Affiliated Hospital of Anhui Medical University were enrolled in this study.Neuropsychological scales,including the Mini-Mental State Examination,the Montreal Cognitive Assessment,and the Activity of Daily Living Scale,were employed to assess the participants.Plasma samples of all the participants were collected for the measurement of Aβ42 and Aβ40 levels.All the participants underwent magnetic resonance scanning to obtain diffusion tensor imaging (DTI) data.The DTI indexes of 48 white matter regions of each individual were measured (based on the ICBM-DTI-81 white-matter labels atlas developed by Johns Hopkins University),including fractional anisotropy (FA) and mean diffusivity (MD).The cognitive function,plasma Aβ42,Aβ40,and Aβ42/40 levels,and DTI index were compared among the three groups.The correlations between the plasma Aβ42/40 levels and DTI index of aMCI and vMCI patients were analyzed.Results The Mini-Mental State Examination and the Montreal Cognitive Assessment scores of aMCI and vMCI groups were lower than those of the HC group (all P<0.001).There was no significant difference in the Activity of Daily Living Scale score among the three groups (P=0.654).The plasma Aβ42 level showed no significant difference among the three groups (P=0.227).The plasma Aβ40 level in the vMCI group was higher than that in the HC group (P=0.014),while it showed no significant difference between aMCI and HC groups (P=1.000).The plasma Aβ42/40 levels in aMCI and vMCI groups showed no significant differences from that in the HC group (P=1.000,P=0.105),while the plasma Aβ42/40 level was lower in the vMCI group than in the aMCI group (P=0.016).The FA value of the left anterior limb of internal capsule in the vMCI group was lower than those in HC and aMCI groups (all P=0.001).The MD values of the left superior corona radiata,left external capsule,left cingulum (cingulate gyrus),and left superior fronto-occipital fasciculus in the vMCI group were higher than those in HC (P=0.024,P=0.001,P=0.003,P<0.001) and aMCI (P=0.015,P=0.004,P=0.019,P=0.001) groups,while the MD values of the right posterior limb of internal capsule (P=0.005,P=0.001) and left cingulum (hippocampus) (P=0.017,P=0.031) in the aMCI and vMCI groups were higher than those in the HC group.In the aMCI group,plasma Aβ42/40 level was positively correlated with FA of left posterior limb of internal capsule (r=0.403,P=0.015) and negatively correlated with MD of the right fonix (r=-0.395,P=0.017).In the vMCI group,plasma Aβ42/40 level was positively correlated with FA of the right superior cerebellar peduncle and the right anterior limb of internal capsule (r=0.575,P=0.008;r=0.639,P=0.002),while it was negatively correlated with MD of the right superior cerebellar peduncle and the right anterior limb of internal capsule (r=-0.558,P=0.011;r=-0.626,P=0.003).Conclusions Plasma Aβ levels vary differently in the patients with aMCI and vMCI.The white matter regions of impaired microstructural integrity differ in the patients with different dementia types in the early stage.The plasma Aβ levels in the patients with aMCI and vMCI are associated with the structural integrity of white matter,and there is regional specificity between them.

Regions involved in fengycin synthetases enzyme complex formation.

BACKGROUND: Fengycin is a lipopeptide antibiotic synthesized nonribosomally by five fengycin synthetases. These enzymes are linked in a specific order to form the complex. This study investigates how these enzymes interact in the complex and analyzes the regions in the enzymes that are critical to the interactions. METHODS: Deletions were generated in the fengycin synthetases. The interaction of these mutant proteins with their partner enzymes in the complex was analyzed in vitro by a glutathione S-transferase (GST) or nickel pulldown assay. RESULTS: The communication-mediating donor (COM-D) domains of the fengycin synthetases, when fused to GST, specifically pulled down their downstream partner enzymes in the GST-pulldown assays. The communication-mediating acceptor (COM-A) domains were required for binding between two partner enzymes, although the domains alone did not confer specificity of the binding to their upstream partner enzymes. This study found that the COM-A domain, the condensation domain, and a portion of the adenylation domain in fengycin synthetase B (FenB) were required for specific binding to fengycin synthetase A (FenA). CONCLUSION: The interaction between the COM-D and COM-A domains in two partner enzymes is critical for nonribosomal peptide synthesis. The COM-A domain alone is insufficient for interacting with its upstream partner enzyme in the enzyme complex with specificity; a region that contains COM-A, condensation, and a portion of adenylation domains in the downstream partner enzyme is required.

Modulation of Staphylococcus aureus spreading by water.

Staphylococcus aureus is known to spread rapidly and form giant colonies on the surface of soft agar and animal tissues by a process called colony spreading. So far, the mechanisms underlying spreading remain poorly understood. This study investigated the spreading phenomenon by culturing S. aureus and its mutant derivatives on Tryptic Soy Agarose (TSA) medium. We found that S. aureus extracts water from the medium and floats on water at 2.5 h after inoculation, which could be observed using phase contrast microscopy. The floating of the bacteria on water could be verified by confocal microscopy using an S. aureus strain that constitutively expresses green fluorescence protein. This study also found that as the density of bacterial colony increases, a quorum sensing response is triggered, resulting in the synthesis of the biosurfactants, phenolic-soluble modulins (PSMs), which weakens water surface tension, causing water to flood the medium surface to allow the bacteria to spread rapidly. This study reveals a mechanism that explains how an organism lacking a flagellar motor is capable of spreading rapidly on a medium surface, which is important to the understanding of how S. aureus spreads in human tissues to cause infections.

[Usefulness of serum inhibin B measurement for evaluation of ovarian reserve in controlled ovarian hyperstimulation].

OBJECTIVE: To assess usefulness of serum inhibin B (INHB) measurement for evaluation of ovarian function. METHODS: Serum INHB level on day 3 of menstrual cycle was determined by enzyme labeled immunosorbent assay (ELISA) in 96 cases of in vitro fertilization and embryo transfer (IVF-ET). The patients were classified into 3 groups including (1) poor response (n = 6), normal response (n = 72), and over response (n = 18) according to their response to ovary stimulation. In addition, serum follicle-stimulating hormone (FSH), luteinizing hormone (LH) and estradiol (E(2)) levels were also determined by chemiluminescent microparticle immunoassay in these patients. Evaluation of the INHB measurement and related factors was performed by statistical analysis. RESULTS: Serum INHB levels in poor, normal and over-response groups were (28 +/- 20), (85 +/- 42), (92 +/- 34) pg/ml; FSH levels were (11.9 +/- 5.3), (7.5 +/- 2.6), (7.2 +/- 1.7) U/L; E(2) levels on day 3 of human chorionic gonadotropin (hCG) administration were (2558 +/- 2108), (9366 +/- 4472), (18 392 +/- 9655) pmol/L; numbers of retrieved oocytes per cycle were (0.6 +/- 0.4), (8.7 +/- 3.6), (14.3 +/- 2.9); top grade embryos were (0.4 +/- 0.3), (3.8 +/- 1.9), (4.6 +/- 1.7); pregnancy rates were 16.7%, 36.1%, 61.1%, respectively. INHB level was negatively correlated to FSH (r = -0.222, P < 0.05) and FSH/LH (r = -0.371, P < 0.05); while positively correlated to E(2) on the day of hCG administration (r = 0.336, P < 0.05), number of retrieved oocytes (r = 0.404, P < 0.05), number of quality embryos (r = 0.323, P < 0.05) and pregnancy rate (r = 0.246, P < 0.05), respectively. CONCLUSIONS: INHB test may reflect the ovarian reserve which is of clinic importance in the guidance of controlled ovarian hyperstimulation.

Water surface tension modulates the swarming mechanics of Bacillus subtilis.

Many Bacillus subtilis strains swarm, often forming colonies with tendrils on agar medium. It is known that B. subtilis swarming requires flagella and a biosurfactant, surfactin. In this study, we find that water surface tension plays a role in swarming dynamics. B. subtilis colonies were found to contain water, and when a low amount of surfactin is produced, the water surface tension of the colony restricts expansion, causing bacterial density to rise. The increased density induces a quorum sensing response that leads to heightened production of surfactin, which then weakens water surface tension to allow colony expansion. When the barrier formed by water surface tension is breached at a specific location, a stream of bacteria swarms out of the colony to form a tendril. If a B. subtilis strain produces surfactin at levels that can substantially weaken the overall water surface tension of the colony, water floods the agar surface in a thin layer, within which bacteria swarm and migrate rapidly. This study sheds light on the role of water surface tension in regulating B. subtilis swarming, and provides insight into the mechanisms underlying swarming initiation and tendril formation.

ZnO Nanoparticles Affect Bacillus subtilis Cell Growth and Biofilm Formation.

Zinc oxide nanoparticles (ZnO NPs) are an important antimicrobial additive in many industrial applications. However, mass-produced ZnO NPs are ultimately disposed of in the environment, which can threaten soil-dwelling microorganisms that play important roles in biodegradation, nutrient recycling, plant protection, and ecological balance. This study sought to understand how ZnO NPs affect Bacillus subtilis, a plant-beneficial bacterium ubiquitously found in soil. The impact of ZnO NPs on B. subtilis growth, FtsZ ring formation, cytosolic protein activity, and biofilm formation were assessed, and our results show that B. subtilis growth is inhibited by high concentrations of ZnO NPs (≥ 50 ppm), with cells exhibiting a prolonged lag phase and delayed medial FtsZ ring formation. RedoxSensor and Phag-GFP fluorescence data further show that at ZnO-NP concentrations above 50 ppm, B. subtilis reductase activity, membrane stability, and protein expression all decrease. SDS-PAGE Stains-All staining results and FT-IR data further demonstrate that ZnO NPs negatively affect exopolysaccharide production. Moreover, it was found that B. subtilis biofilm surface structures became smooth under ZnO-NP concentrations of only 5-10 ppm, with concentrations ≤ 25 ppm significantly reducing biofilm formation activity. XANES and EXAFS spectra analysis further confirmed the presence of ZnO in co-cultured B. subtilis cells, which suggests penetration of cell membranes by either ZnO NPs or toxic Zn+ ions from ionized ZnO NPs, the latter of which may be deionized to ZnO within bacterial cells. Together, these results demonstrate that ZnO NPs can affect B. subtilis viability through the inhibition of cell growth, cytosolic protein expression, and biofilm formation, and suggest that future ZnO-NP waste management strategies would do well to mitigate the potential environmental impact engendered by the disposal of these nanoparticles.

The Antimicrobial Properties of Silver Nanoparticles in Bacillus subtilis Are Mediated by Released Ag+ Ions.

The superior antimicrobial properties of silver nanoparticles (Ag NPs) are well-documented, but the exact mechanisms underlying Ag-NP microbial toxicity remain the subject of intense debate. Here, we show that Ag-NP concentrations as low as 10 ppm exert significant toxicity against Bacillus subtilis, a beneficial bacterium ubiquitous in the soil. Growth arrest and chromosomal DNA degradation were observed, and flow cytometric quantification of propidium iodide (PI) staining also revealed that Ag-NP concentrations of 25 ppm and above increased membrane permeability. RedoxSensor content analysis and Phag-GFP expression analysis further indicated that reductase activity and cytosolic protein expression decreased in B. subtilis cells treated with 10-50 ppm of Ag NPs. We conducted X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) analyses to directly clarify the valence and fine structure of Ag atoms in B. subtilis cells placed in contact with Ag NPs. The results confirmed the Ag species in Ag NP-treated B. subtilis cells as Ag2O, indicating that Ag-NP toxicity is likely mediated by released Ag+ ions from Ag NPs, which penetrate bacterial cells and are subsequently oxidized intracellularly to Ag2O. These findings provide conclusive evidence for the role of Ag+ ions in Ag-NP microbial toxicity, and suggest that the impact of inappropriately disposed Ag NPs to soil and water ecosystems may warrant further investigation.