Production of rhamnolipids-producing enzymes of Pseudomonas in E. coli and structural characterization

Rhamnolipids have a great potential to be utilized in industries due to their surface active properties and non-toxic impact on the enviroment. Accumulated studies have shown that the major producer of rhamnolipids is Pseudomonas aeruginosa (P. aeruginosa) which is a pathogenic strain. Despite efforts spent to improve rhamnolipid yield by screening different organisms, optimizing fermentation conditions, and optimizing strains through metabolic engineering, the cost for rhamnolipid production is still very high compared with chemically synthesized surfactants. Therefore, it is necessary to explore an alternative strategy for rhamnolipids production. Five proteins/enzymes, namely RhlA, RhlB, RhlC, RhlG and RhlI, are critical for the rhamnolipids production in Pseudomonas aeruginosa. Overexpression of RhlA and RhlB in E. coli can result in a strain to produce rhamnolipids. Here we report the high level expression of these proteins in E.coli. We show these genes can be expressed in E. coli and some of them can be purified in large quantities for structural studies. The purified proteins are confirmed to be folded in solution by using NMR spectroscopy. We also analyzed their structures using homology modeling. These results lay a basis for further structural and functional characterization of these proteins in vitro to favor the rhamnolipids production in vitro

Identification of vector-borne diseases in domestic dogs using biomolecular techniques and implications for human health

openThe number of domestic dog owners has been increased in recent years worldwide and domestic dogs are nowadays the closest animal companion to human beings. Due to these aspects, they can represent a potential reservoir of vector-borne diseases. Canine vector-borne diseases (CVBDs) comprise a group of parasitic and infectious diseases caused by several pathogens (e.g., bacteria, protozoa, and helminths), which are transmitted by arthropod vectors, including ticks, fleas, lice, mosquitoes, and phlebotomine sand flies. Because CVBDs causing pathogens (e.g. Hepatozoon spp., Babesia spp., Anaplasma spp., Borrelia spp.) are of major zoonotic concern, they represent an increased public health threat for domestic dogs and their owners. Therefore, the study of CVBDs can help to recognize the disease affecting human health. In this study, 273 blood samples were collected in an area in southern Ethiopia by FTA cards and analyzed by biomolecular techniques (i.e. conventional PCR, real-time PCR and multiple real-time PCR) in order to identify the infection and parasitic/infective agents and emphasized the importance of molecular methods in distinctive CVBD pathogens. Hepatozoon canis DNA and Babesia canis rossi DNA were detected in 141 (51.6%) and 9 (3.3%) samples, respectively. No Anaplasma phagocytophilum DNA and Borrelia burgdorferi s.l. DNA were detected in samples by multiple real-time PCR. In this study, Hepatozoon canis had the highest detection rate, while Anaplasma and Borrelia appeared to be absent in the study area. The relevance of encountered pathogens should be further investigated.The number of domestic dog owners has been increased in recent years worldwide and domestic dogs are nowadays the closest animal companion to human beings. Due to these aspects, they can represent a potential reservoir of vector-borne diseases. Canine vector-borne diseases (CVBDs) comprise a group of parasitic and infectious diseases caused by several pathogens (e.g., bacteria, protozoa, and helminths), which are transmitted by arthropod vectors, including ticks, fleas, lice, mosquitoes, and phlebotomine sand flies. Because CVBDs causing pathogens (e.g. Hepatozoon spp., Babesia spp., Anaplasma spp., Borrelia spp.) are of major zoonotic concern, they represent an increased public health threat for domestic dogs and their owners. Therefore, the study of CVBDs can help to recognize the disease affecting human health. In this study, 273 blood samples were collected in an area in southern Ethiopia by FTA cards and analyzed by biomolecular techniques (i.e. conventional PCR, real-time PCR and multiple real-time PCR) in order to identify the infection and parasitic/infective agents and emphasized the importance of molecular methods in distinctive CVBD pathogens. Hepatozoon canis DNA and Babesia canis rossi DNA were detected in 141 (51.6%) and 9 (3.3%) samples, respectively. No Anaplasma phagocytophilum DNA and Borrelia burgdorferi s.l. DNA were detected in samples by multiple real-time PCR. In this study, Hepatozoon canis had the highest detection rate, while Anaplasma and Borrelia appeared to be absent in the study area. The relevance of encountered pathogens should be further investigated

Microbial production of rhamnolipids from isolate pseudomonas sp. —A mono- rhamnolipid producer

Rhamnolipids are a class of glycolipid biosurfactants containing mono- or di-rhamnose as the sugar moiety linked to β-hydroxylated fatty acid chain(s). Rhamnolipids are used in many consumer products such as cosmetics, food and pesticides, due to their excellent surface and biological activities. The main rhamnolipid producer is Pseudomonas aeruginosa, an opportunistic pathogen which may cause safety and health concerns during large-scale production. Furthermore, cost of microbial production of rhamnolipids is more expensive as compared to that of the chemical surfactants. Therefore, extensive studies have been carried out to explore suitable and economical methods to obtain rhamnolipids in non-pathogenic strains. In our study, we have isolated a rhamnolipid-producing strain capable of producing 2 g/L mono-rhamnolipids when supplemented with 8g/L glucose as the sole carbon source in 72h. The production of only mono-rhamnolipids eliminates the need for costly and laborious separation of mono- and di-rhamnolipids. The mono-rhamnolipid yield can be further improved through optimization of medium composition and fermentation condition

Structure, Application, and Biochemistry of Microbial Keratinases

Keratinases belong to a class of proteases that are able to degrade keratins into amino acids. Microbial keratinases play important roles in turning keratin-containing wastes into value-added products by participating in the degradation of keratin. Keratin is found in human and animal hard tissues, and its complicated structures make it resistant to degradation by common proteases. Although breaking disulfide bonds are involved in keratin degradation, keratinase is responsible for the cleavage of peptides, making it attractive in pharmaceutical and feather industries. Keratinase can serve as an important tool to convert keratin-rich wastes such as feathers from poultry industry into diverse products applicable to many fields. Despite of some progress made in isolating keratinase-producing microorganisms, structural studies of keratinases, and biochemical characterization of these enzymes, effort is still required to expand the biotechnological application of keratinase in diverse fields by identifying more keratinases, understanding the mechanism of action and constructing more active enzymes through molecular biology and protein engineering. Herein, this review covers structures, applications, biochemistry of microbial keratinases, and strategies to improve its efficiency in keratin degradation

Antiviral activity of interleukin-11 as a response to porcine epidemic diarrhea virus infection

International audienceAbstractInterleukin-11 (IL-11), a well-known anti-inflammatory factor, provides protection from intestinal epithelium damage caused by physical or chemical factors. However, little is known of the role of IL-11 during viral infections. In this study, IL-11 expression at mRNA and protein levels were found to be high in Vero cells and the jejunum of piglets during porcine epidemic diarrhea virus (PEDV) infection, while IL-11 expression was found to be positively correlated with the level of viral infection. Pretreatment with recombinant porcine IL-11 (pIL-11) was found to suppress PEDV replication in Vero E6 cells, while IL-11 knockdown promoted viral infection. Furthermore, pIL-11 was found to inhibit viral infection by preventing PEDV-mediated apoptosis of cells by activating the IL-11/STAT3 signaling pathway. Conversely, application of a STAT3 phosphorylation inhibitor significantly antagonized the anti-apoptosis function of pIL-11 and counteracted its inhibition of PEDV. Our data suggest that IL-11 is a newfound PEDV-inducible cytokine, and its production enhances the anti-apoptosis ability of epithelial cells against PEDV infection. The potential of IL-11 to be used as a novel therapeutic against devastating viral diarrhea in piglets deserves more attention and study

Miniaturized-Element Frequency-Selective Rasorber Design Using Characteristic Modes Analysis

A dual-polarization frequency-selective rasorber with two absorptive bands at both sides of a passband is presented. Based on the characteristic mode analysis, a circuit analog absorber is designed using a lossy FSS that consists of miniaturized meander lines and lumped resistors. The positions and values of resistors are determined according to the analysis of modal significances and modal current. After that, the presented rasorber is designed by cascading of the lossy FSS and a lossless bandpass FSS. Equivalent circuits of the frequency-selective rasorber are modelled, and surface current distributions of both FSSs are illustrated to explain the operation mechanism. Measurement results show that, under the normal incidence, a minimum insertion loss of 0.27 dB is achieved at a passband around 6 GHz, and the absorption bands with an absorption rate higher than 80% are 2.5 to 4.6 GHz in the lower band and 7.7 to 12 GHz in the higher band, respectively. Our results exhibit good agreements between measurements and simulations

Numerical investigation of nonlinear wave interaction with a submerged object

Submerged objects are widely occurred in ocean and coastal engineering. Their presence influences the neighbouring flow field and even generates higher harmonic waves. A two-dimensional fully nonlinear numerical wave flume, based on a time-domain higher-order boundary element method is developed to investigate nonlinear interactions between regular waves and a submerged object. The incident wave is generated by the inner-source wavemaker. Fully nonlinear kinematics and dynamics boundary conditions are satisfied on the transient free surface. A mixed Eulerian-Lagrangian technique combined with the fourth- order Runge-Kutta scheme is used as the time marching process. A four-point method is used to separate bound and free harmonic waves. The proposed model is verified against the experimental and other numerical data for nonlinear waves scattering by a submerged trapezoid and a submerged horizontal cylinder, respectively. Numerical tests are performed to investigate the effects of submergence and characterised length of a submerged object, static water depth on the high free harmonics

Individuals’ preference on reading pathways influences the involvement of neural pathways in phonological learning

IntroductionExisting behavioral and neuroimaging studies revealed inter-individual variability in the selection of the two phonological routes in word reading. However, it is not clear how individuals’ preferred reading pathways/strategies modulate the involvement of a certain brain region for phonological learning in a new language, and consequently affect their behavioral performance on phonological access.MethodsTo address this question, the present study recruited a group of native Chinese speakers to learn two sets of artificial language characters, respectively, in addressed-phonology training (i.e., whole-word mapping) and assembled-phonology training conditions (i.e., grapheme-to-phoneme mapping).ResultsBehavioral results showed that the more lexical pathways participants preferred, the better they performed on newly-acquired addressed characters relative to assembled characters. More importantly, neuroimaging results showed that participants who preferred lexical pathway in phonological access show less involvement of brain regions for addressed phonology (e.g., the bilateral orbitofrontal cortex and right pars triangularis) in the processing of newly-acquired addressed characters.ConclusionThese results indicated that phonological access via the preferred pathway required less neural resources to achieve better behavioral performance. These above results provide direct neuroimaging evidence for the influence of reading pathway preference on phonological learning