Production and optimization of alkalostable lipase by alkalophilic Burkholderia cenocepacia ST8

A superior lipase-producing bacterium was isolated from forest soil samples in Setapak, Malaysia and it was identified as Burkholderia cenocepacia with 16S rRNA sequencing technique. Multifactor experimental design based on ‘change-one-factor-at-a-time’ approach was employed to optimize the production of Bukholderia lipase with submerged fermentation technique. Effects of carbon and nitrogen sources, metal ions as well as initial pH of medium on lipase production were extensively investigated. Optimal lipase activity was achieved in medium using combination of sunflower oil and Tween 80 (1% v/v each) as carbon sources. Simple sugars such as glucose and fructose, however, did not promote the production of lipase. Peptone (from meat) at 0.33% (w/v) was the most suitable nitrogen source for lipase production by this Gram-negative bacterium. The presence of Ca2+ in the cultivation medium possessed significant effect on lipase production while Mg2+, Mn2+, Na+, Fe2+, Cu2+ and Co2+ exhibited inhibitory effect towards the enzyme production. Initial culture pH in the range of 5 to 11 were found suitable for lipase production, with the maximum level of lipase activity recorded in the medium with initial culture pH of 9.0.Key words: Alkalostable lipase, alkalophilic Burkholderia cenocepacia, optimization, multifactor experimental design

The Associations of Income, Education and Income Inequality and Subjective Well-Being among Elderly in Hong Kong-A Multilevel Analysis

Background: Higher income and education and lower income inequality in a neighbourhood have been shown to be related to better mental health outcome in developed countries. However, it is not clear whether these factors would affect the subjective well-being of the elderly, especially in a setting with recent rapid economic development. Methods: This study was conducted in 80 community centres with a total of 7552 community-dwelling elderly (mean age 75.9 years (SD = 7.79), 79% female) in Hong Kong. Income at individual level was measured as perceived disposable income. Education level was also collected. At district level, income was measured by district median household income and education was measured as the proportion of the population with no formal schooling. Income inequality was quantified using Gini coefficients. Low subjective well-being was defined as any one or a combination of the following: not satisfied with life, no meaning of life and being unhappy (Likert scale ≤ 2). Multilevel logistic regression was used to assess the association of income, education and income inequality and low subjective well-being. Results: We found that 15.3% (95% confidence interval (CI): 14.5 to 16.1) of the elderly have low subjective well-being. Compared with elderly who reported a very adequate disposable income, those who reported a very inadequate disposable income are at increased risk of low subjective well-being (OR=5.08, 95%CI: 2.44 to 10.59). Compared with elderly with tertiary education, those with no formal schooling were at higher risk (OR=1.60, 95%CI 1.22 to 2.09). Income inequality was not related to subjective well-being. Conclusions: Elderly with inadequate disposable income and lower education level are more likely to suffer from low subjective well-being. At the neighbourhood level, income inequality was not related to subjective well-being. However, the relationships between neighbourhood income and education level and individuals’ subjective well-being are not clear

Transcriptomic Analysis of Laribacter hongkongensis Reveals Adaptive Response Coupled with Temperature

published_or_final_versio

Macrocyclic colibactin induces DNA double-strand breaks via copper-mediated oxidative cleavage.

Colibactin is an assumed human gut bacterial genotoxin, whose biosynthesis is linked to the clb genomic island that has a widespread distribution in pathogenic and commensal human enterobacteria. Colibactin-producing gut microbes promote colon tumour formation and enhance the progression of colorectal cancer via cellular senescence and death induced by DNA double-strand breaks (DSBs); however, the chemical basis that contributes to the pathogenesis at the molecular level has not been fully characterized. Here, we report the discovery of colibactin-645, a macrocyclic colibactin metabolite that recapitulates the previously assumed genotoxicity and cytotoxicity. Colibactin-645 shows strong DNA DSB activity in vitro and in human cell cultures via a unique copper-mediated oxidative mechanism. We also delineate a complete biosynthetic model for colibactin-645, which highlights a unique fate of the aminomalonate-building monomer in forming the C-terminal 5-hydroxy-4-oxazolecarboxylic acid moiety through the activities of both the polyketide synthase ClbO and the amidase ClbL. This work thus provides a molecular basis for colibactin's DNA DSB activity and facilitates further mechanistic study of colibactin-related colorectal cancer incidence and prevention

The Viscoelastic Properties of Passive Eye Muscle in Primates. II: Testing the Quasi-Linear Theory

We have extensively investigated the mechanical properties of passive eye muscles, in vivo, in anesthetized and paralyzed monkeys. The complexity inherent in rheological measurements makes it desirable to present the results in terms of a mathematical model. Because Fung's quasi-linear viscoelastic (QLV) model has been particularly successful in capturing the viscoelastic properties of passive biological tissues, here we analyze this dataset within the framework of Fung's theory

Role of biomechanics in the understanding of normal, injured, and healing ligaments and tendons

Ligaments and tendons are soft connective tissues which serve essential roles for biomechanical function of the musculoskeletal system by stabilizing and guiding the motion of diarthrodial joints. Nevertheless, these tissues are frequently injured due to repetition and overuse as well as quick cutting motions that involve acceleration and deceleration. These injuries often upset this balance between mobility and stability of the joint which causes damage to other soft tissues manifested as pain and other morbidity, such as osteoarthritis

Inhibition of the aquaporin 3 water channel increases the sensitivity of prostate cancer cells to cryotherapy

Aquaporins (AQPs) are intrinsic membrane proteins that facilitate selective water and small solute movement across the plasma membrane. In this study, we investigate the role of inhibiting AQPs in sensitising prostate cancer cells to cryotherapy. PC-3 and DU145 prostate cancer cells were cooled to 0, −5 and −10°C. The expression of AQP3 in response to freezing was determined using real-time quantitative polymerase chain reaction (RT–qPCR) and western blot analysis. Aquaporins were inhibited using mercuric chloride (HgCl2) and small interfering RNA (siRNA) duplex, and cell survival was assessed using a colorimetric assay. There was a significant increase in AQP3 expression in response to freezing. Cells treated with AQP3 siRNA were more sensitive to cryoinjury compared with control cells (P<0.001). Inhibition of the AQPs by HgCl2 also increased the sensitivity of both cell lines to cryoinjury and there was a complete loss of cell viability at −10°C (P<0.01). In conclusion, we have shown that AQP3 is involved directly in cryoinjury. Inhibition of AQP3 increases the sensitivity of prostate cancer cells to freezing. This strategy may be exploited in the clinic to improve the efficacy of prostate cryotherapy

Knee stability assessment on anterior cruciate ligament injury: Clinical and biomechanical approaches

Anterior cruciate ligament (ACL) injury is common in knee joint accounting for 40% of sports injury. ACL injury leads to knee instability, therefore, understanding knee stability assessments would be useful for diagnosis of ACL injury, comparison between operation treatments and establishing return-to-sport standard. This article firstly introduces a management model for ACL injury and the contribution of knee stability assessment to the corresponding stages of the model. Secondly, standard clinical examination, intra-operative stability measurement and motion analysis for functional assessment are reviewed. Orthopaedic surgeons and scientists with related background are encouraged to understand knee biomechanics and stability assessment for ACL injury patients

Structural and Functional Analysis of Phytotoxin Toxoflavin-Degrading Enzyme

Pathogenic bacteria synthesize and secrete toxic low molecular weight compounds as virulence factors. These microbial toxins play essential roles in the pathogenicity of bacteria in various hosts, and are emerging as targets for antivirulence strategies. Toxoflavin, a phytotoxin produced by Burkholderia glumae BGR1, has been known to be the key factor in rice grain rot and wilt in many field crops. Recently, toxoflavin-degrading enzyme (TxDE) was identified from Paenibacillus polymyxa JH2, thereby providing a possible antivirulence strategy for toxoflavin-mediated plant diseases. Here, we report the crystal structure of TxDE in the substrate-free form and in complex with toxoflavin, along with the results of a functional analysis. The overall structure of TxDE is similar to those of the vicinal oxygen chelate superfamily of metalloenzymes, despite the lack of apparent sequence identity. The active site is located at the end of the hydrophobic channel, 9 Å in length, and contains a Mn(II) ion interacting with one histidine residue, two glutamate residues, and three water molecules in an octahedral coordination. In the complex, toxoflavin binds in the hydrophobic active site, specifically the Mn(II)-coordination shell by replacing a ligating water molecule. A functional analysis indicated that TxDE catalyzes the degradation of toxoflavin in a manner dependent on oxygen, Mn(II), and the reducing agent dithiothreitol. These results provide the structural features of TxDE and the early events in catalysis