The environmentally induced corrosion failure of cable bolts in underground coal mines

The failure of cable bolts, made from high carbon cold-drawn steel wires, is frequently observed in underground coal mines. Hydrogen-induced stress corrosion cracking (HISCC) is known to be the main mechanism of such a failure. The groundwater and geomaterials (mixture of coal and clay) collected from the affected mines have not been found to be corrosive. In this study, we examine the effect of sulfate-reducing bacteria (SRB), which exist in affected mines, on the failure of cable bolts. We make stressed coupons from cable bolt wires and test the coupons in different solutions containing SRB. We find that the hydrogen sulfide produced by SRB promote hydrogen diffusion into the steel and causes HISCC while the steel is under constant load. The fractures in failed coupons show similar features to those failed in underground coal mines. This study provides insights into the role of microorganisms in the failure of underground structures. We recommend future studies to develop prevention measures to stop hydrogen diffusion into steel or microbial activities around the bolts

The role of AHL-mediated quorum sensing system in Chitinase production of Aeromonas sp. strains isolated from a municipal wastewater treatment plant

This thesis explores the role of AHL-mediated quorum sensing system in chitinase production of Aeromonas sp. strains isolated from a municipal wastewater treatment (WWT) plant. AHL production and chitinase activity was assessed in twelve different Aeromonas strains, isolated previously. LuxR and TraR based cross-streaking assays, colloidal chitin plates and colorimetric chitinase activity assays were performed. Six out of twelve isolates were exhibited both AHL and chitinase activity. AHL-mediated chitinase activity was explored by supplementing different AHLs into growing cultures of six selected isolates. Results showed that addition of butanoyl-homoserine lactone (BHL) and 3-oxo-hexanoyl-homoserine lactone (OHHL) induced the expression of chitinase in two of the Aeromonas sp. isolates early in the logarithmic growth phase.Aeromonas sp. strain GC1 was found to produce BHL, hexanoyl-homoserine lactone (HHL), octanoyl-homoserine lactone (OHL) and dodecanoyl-homoserine lactone (dDHL) by Thin Layer Chromatograhy (TLC) overlay plate assay and Mass Spectrometric analysis. PCR amplification and sequencing confirmed the presence of Aeromonas sp. LuxR/I homologues, AhyR/I, and chitinase genes in Aeromonas sp. strain GC1. These experiments are consistent with the hypothesis that AHL mediated quorum sensing plays a role in regulating chitinase activity in Aeromonas sp. and add to our understanding of AHL mediated gene expression in activated sludge

Primers used for sequencing <i>V. fischeri</i> bioluminescence regulatory genes.

a<p>Primers and base numbering based on <i>luxR</i> and <i>luxI</i> (Genbank AF170104.1), ^bPrimers and numbering based on <i>ainR</i> and <i>ainS</i> (Genbank L37404), ^c<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0067443#pone.0067443-Dunn1" target="_blank">[38]</a>.</p

Impact of <i>luxR</i> complementation on bioluminescene during long term culturing of <i>Vibrio fischeri</i>.

<p>Relative bioluminescence output from the dark <i>V. fischeri</i> MJ1 Lineage 10 with a <i>luxR</i> mutation complimented with a functional <i>luxR</i> gene under control of its own promoter on pLS6luxR. Complementation with <i>luxR</i> initially restored the bioluminescence phenotype to wild type levels, however bioluminescence was observed to decrease during subsequent subculturing for 120 days.</p

Impact of <i>luxI</i> deletion on growth of <i>Vibrio fischeri</i> in isolation.

<p>Batch culture growth of <i>V. fischeri</i> wild type strain MJ1 (circles) and <i>luxI</i> deficient mutant strain MJ211 (squares) in the absence (A) and presence (B) of 5 µM <i>N</i>-3-oxohexanoyl-L-homoserine lactone. Values presented are averages of triplicate cultures. Error bars represent standard deviation. Small statistically significant differences were late in the logarithmic phase of growth.</p

Fate of the bioluminescence phenotype during long term culturing in <i>Vibrio fischeri</i>.

<p>Relative bioluminescence output from ten <i>V. fischeri</i> MJ1 cultures, subcultured daily over 325 days. Large fluctuations are observed in bioluminescence in all cultures. Half of the cultures (4, 5, 6, 8 and 10) irreversibly lost the bioluminescence phenotype during the course of the experiment. Quorum sensing regulatory genes (<i>ainS</i>, <i>ainR</i>, <i>luxI</i> and <i>luxR</i>) and the <i>luxI</i>-<i>luxR</i> intergenic region were sequenced to investigate the cause of the loss of phenotype.</p

Experimental design for competition experiments.

<p>Mixtures of <i>Vibrio fischeri</i> wild type (MJ1) and <i>luxI</i> mutant (MJ211) strains at optical density based starting ratios of 1∶1 or 1∶10 were inoculated (100 µl) into 5 ml of fresh media in triplicate. Each replicate culture was subsequently subcultured daily for ten days and wild type to mutant ratios determined every second day.</p

Impact of <i>luxI</i> deletion on competition in <i>Vibrio fischeri</i>.

<p>Percentage of luminescence colonies plated from mixed <i>V. fischeri</i> MJ1 (wild type) and MJ211 (<i>luxI</i> mutant) cultures subcultured daily for ten days. The starting ratio of MJ1 to MJ211 was either 1∶1 (Panel A) or 1∶9 (Panel B). Regardless of the initial ratio of wild type (MJ1) to mutant (MJ211) cells, the wild type lineage dominated the cultures within days suggesting the <i>luxI</i> gene represents a selective advantage independent of the bioluminescence phenotype. Average values from triplicate cultures are presented. Error bars represent standard deviation.</p

N-Acetylglucosamine Inhibits LuxR, LasR and CviR Based Quorum Sensing Regulated Gene Expression Levels

N-acetyl glucosamine, the monomer of chitin, is an abundant source of carbon and nitrogen in nature as it is the main component and breakdown product of many structural polymers. Some bacteria use N-acyl-L-homoserine lactone (AHL) mediated quorum sensing (QS) to regulate chitinase production in order to catalyse the cleavage of chitin polymers into water soluble NAG monomers. In this study, the impact of NAG on QS activities of LuxR, LasR and CviR regulated gene expression was investigated by examining the effect of NAG on QS regulated green fluorescent protein (GFP), violacein and extracellular chitinase expression. It was discovered that NAG inhibits AHL dependent gene transcription in AHL reporter strains within the range of 50% to 80% reduction at low millimolar concentrations (0.25 mM to 5 mM). Evidence is presented supporting a role for both competitive inhibition at the AHL binding site of LuxR type transcriptional regulators and catabolite repression. Further, this study shows that NAG down-regulates CviR induced violacein production while simultaneously up-regulating CviR dependent extracellular enzymes, suggesting that an unknown NAG dependent regulatory component influences phenotype expression. The quorum sensing inhibiting activity of NAG also adds to the list of compounds with known quorum sensing inhibiting activities

Post-recurrence survival analysis of patients with pulmonary recurrence from gynaecologic cancers: a multi-institutional analysis of 122 patients

In this retrospective study, patients with epithelial gynaecologic cancer with pulmonary recurrence (PR) were evaluated from five national gynaecologic oncology clinics. Patients with a diagnosis of primary endometrial, ovarian/fallopian tube/peritoneal, cervical or vaginal/vulvar tumours who developed an initial PR were included in the study A total of 122 patients were included in the study. The median follow-up time after recurrence was 7.5 (range, 1–84) months. The 2-year PRS was 48% in the main cohort. The risk of death was more than seven times higher in patients who did not receive salvage chemotherapy compared with those who did (hazard ratio: 7.6, 95% CI: 3.0–18.9; p < .001). When squamous cell carcinoma was compared with the other tumour types, the risk of death increased more than three times (hazard ratio: 3.7, 95% CI: 1.4–9.6; p = .007).IMPACT STATEMENT What is already known on this subject? Pulmonary recurrence (PR) from gynaecologic malignancies is rare and can cause major clinical problem. Therefore, defining the clinical and pathologic characteristics and recurrence patterns are essential. What the results of this study add? This study demonstrates non-squamous subtype and salvage chemotherapy at PR were associated with improved survival. What of these findings for clinical practice and/or further research? To the best of our knowledge, our study is the largest study to investigate the clinico-pathologic characteristics, recurrence patterns, treatment options, and post-recurrence survival (PRS) in patients with PR from epithelial gynaecologic cancers. Future research should examine the underlying causes of these findings