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A novel strain of coronavirus, SARS-CoV-2, the causative agent of coronavirus disease (COVID-19) was first associated with severe acute respiratory disease in late 2019 and has triggered an ongoing...

The low success rates in the treatment of multidrug-resistant tuberculosis (MDR-TB) and extensively drug-resistant TB (XDR-TB), which account for 55% and 34% respectively, led the WHO to conclude that MDR/XDR-TB is a serious public health crisis. However, the virulence of MDR/XDR-Mycobacterium Tuberculosis(Mtb) has not been analyzed in details, which could provide a specific guidance for the control and prevention. In this review, we discuss different aspects of MDR/XDR-Mtb virulence and its relationship to fitness cost by probing the following questions: (1) what mediates the virulence of MDR/XDR-Mtb? (What is the relationship between fitness and virulence of Mtb? (2) Is it possible that drug-resistant Mtb(DR Mtb) can show higher fitness? (3) What is the definite effect on fitness of each drug-resistant mutant? (4) What other important factors affecting fitness in the mutant strain? (5) How to study the virulence of a large number of DR Mtb?And what prevention and control measures will be taken in the future, especially for the high virulent DR Mtb? We therefore summarized the congruent relationship between drug resistance and fitness from the global response-related genes to antibiotic resistance-contributing mutation, provided methods to explore the virulence of DR Mtb. This review may offer some critical information and concise guide to creating strategies for the prevention and control of drug-resistant Mtb.

The outbreak of the Coronavirus Disease 2019 (COVID-19) has quickly happened worldwide, and mutated. The most typical imaging manifestations of unmutated COVID-19 had been reported by many literatures. However, the imaging manifestations of pneumonia caused by the mutant strain delta are still unfamiliar to us. This article will introduce a typical case of pneumonia caused by Delta Variant of Concern (VOC)through computed tomography (CT) follow-ups in order to improve readers' understanding of its imaging manifestations and changes. This article is protected by copyright. All rights reserved.

It is well known in the literature that human behavior can change as a reaction to disease observed in others, and that such behavioral changes can be an important factor in the spread of an epidemic. It has been noted that human behavioral traits in disease avoidance are under selection in the presence of infectious diseases. Here we explore a complimentary trend: the pathogen itself might experience a force of selection to become less “visible”, or less “symptomatic”, in the presence of such human behavioral trends. Using a stochastic SIR agent-based model, we investigated the co-evolution of two viral strains with cross-immunity, where the resident strain is symptomatic while the mutant strain is asymptomatic. We assumed that individuals exercised self-regulated social distancing (SD) behavior if one of their neighbors was infected with a symptomatic strain. We observed that the proportion of asymptomatic carriers increased over time with a stronger effect corresponding to higher levels of self-regulated SD. Adding mandated SD made the effect more significant, while the existence of a time-delay between the onset of infection and the change of behavior reduced the advantage of the asymptomatic strain. These results were consistent under random geometric networks, scale-free networks, and a synthetic network that represented the social behavior of the residents of New Orleans.

Strain improvement has become an important strategy in large scale microbial fermentation processes to increase the production yield of enzymes at minimal cost. Here, ultraviolet (UV) irradiation-induced mutant strain of Bacillus cereus, identified using 16S rRNA molecular gene sequencing was subjected to cellulolytic potential screening before cultivating it for carboxymethyl cellulase (CMCase) production under submerged fermentation using a cost-effective plantain stalk–based medium. The enzyme was homogenously purified by a combination of ammonium sulphate precipitation and chromatographic techniques on both DEAE Sephadex A-50 anion-exchange and Sephadex G-100 size-exclusion columns. Sodium dodecyl sulphate polyacrylamide gel electrophoresis was used to determine the molecular weight. Remarkably, this 56 kDa purified cellulase was most active at 70°C and pH 6.0. The CMCase retained over 60% of initial activity after pre-incubation at 60°C for 3 h and was also very stable in both acidic and mild basic medium (pH 3.0-9.0). Cellulase activity was enhanced by Mn2+, Na+, Mg2+ and K+ but inhibited by Pb2+, Hg2+ and Cu2+ at 5 mM. The Km and Vmax of the enzyme with carboxymethyl cellulose are respectively, 3.25 mg/mL and 29.76 U/min/mg. The purified cellulase from B. cereus FOA-2 possesses remarkable properties for suitable application in biotechnological industries.

Subacute sclerosing panencephalitis (SSPE) is a late-onset, intractable, and fatal viral disease caused by persistent infection of the central nervous system by a mutant strain of the measles virus. Ribavirin intracerebroventricular therapy has already been administered to several SSPE patients in Japan based on fundamental and clinical research findings from our group, with positive therapeutic effects reported in some patients. However, the efficacy of this treatment approach has not been unequivocally established. Hence, development of more effective therapeutic methods using new antiviral agents is urgently needed. This review describes the current status of SSPE treatment and research, highlighting promising approaches to the development of more effective therapeutic methods.

Background The yeast Phaffia rhodozyma has many desirable properties for astaxanthin production, including rapid heterotrophic metabolism and high cell densities in fermenter culture. The optimal temperature range for cell growth and astaxanthin synthesis in this species is low (17–21 °C), which presents an obstacle to efficient industrial-scale astaxanthin production. The molecular regulatory mechanisms of cell growth and astaxanthin synthesis in P. rhodozyma remain poorly understood, and the regulatory effects of temperature have not been investigated. Results MK19, a mutant P. rhodozyma strain that grows well at moderate temperatures, was generated from wild-type (WT) strain JCM9042, which is unable to grow at 28 °C. MK19 cell growth was also inhibited at 28 °C, but such inhibition was mitigated, and biomass production reached 6 g/L after 100 h culture. Transcriptome analysis indicated that low viability at 28 °C resulted from strong suppression of DNA synthesis. Growth inhibition at 28 °C was due to low mRNA content of fatty acid (f.a.) pathway genes (acc, fas1, fas2), and consequent low f.a. content. Thinning of cell wall and low mannose content (leading to loss of cell wall integrity) also contributed to reduced cell growth at 28 °C. In MK19 cultured for 48 h at 28 °C, levels of astaxanthin and ergosterol, two end-products of isoprenoid biosynthesis (a shunt pathway of f.a. biosynthesis), reached 2000 µg/g and 7500 µg/g respectively; ~2-fold higher than levels at 21 or 25 °C. Abundance of ergosterol, an important cell membrane component, compensated for lack of f.a., making possible the biomass production of 6 g/L for MK19 at 28 °C. Downregulation of crtI mRNA, whose product catalyzes four dehydrogenation steps in the phytoene-to-lycopene process, contributed to inhibition of astaxanthin synthesis in WT at 25 °C. High crtI mRNA content in MK19 (> 10-fold higher than that in WT) counteracted the inhibitory effect of high temperature on crtI transcription, making possible the efficient synthesis of lycopene which was subsequently converted to astaxanthin. Conclusion Inhibition of growth of WT P. rhodozyma at 28 °C results from blocking of DNA, f.a., and cell wall biosynthesis. Growth at this temperature could be increased by enhancement of such biosynthesis. In moderate-temperature strain MK19, precursor molecules accumulated from f.a. pathway are diverted to astaxanthin and ergosterol biosynthesis, making possible biomass production 6 g/L at 28 °C. Strengthening of the MVA pathway to make available more precursors from f.a. pathway is a feasible metabolic engineering approach for enhancement of astaxanthin synthesis in MK19 or other moderate-temperature producer strains. The present findings provide useful mechanistic insights regarding adaptation of P. rhodozyma to 28 °C, and improved understanding of transcription regulatory networks and feasible metabolic engineering techniques for industrial scale astaxanthin production by this economically important yeast species.

HIV-1 RT has been considered as one of the most important targets for the development of anti-HIV-1 drugs for their well-solved three-dimensional structure and well-known mechanism of action. In this study, with HIV-1 RT as target, we used miniaturized parallel click chemistry synthesis via CuAAC reaction followed by in situ biological screening to discover novel potent HIV-1 NNRTIs. A 156 triazole-containing inhibitor library was assembled in microtiter plates and in millimolar scale. The enzyme inhibition screening results showed that 22 compounds exhibited improved inhibitory activity. Anti-HIV-1 activity results demonstrated that A3N19 effected the most potent activity against HIV-1 IIIB (EC50 = 3.28 nM) and mutant strain RES056 (EC50 = 481 nM). The molecular simulation analysis suggested that the hydrogen bonding interactions of A3N19 with the main chain of Lys101 and Lys104 was responsible for its potency. Overall, the results indicated the in situ click chemistry-based strategy was rational and might be amenable for the future discovery of more potent HIV-1 NNRTIs.

The second wave of the COVID-19 pandemic has affected India significantly with country reporting more than 400,000 cases in the month of May 2021 and health system almost collapsing. This was attributed to the new mutant strain also called as the ‘Delta Strain’ which led to high surge of cases across the country. As the country was stabilising over this situation, another imminent threat in the form of Covid Associated Mucormycosis (CAM) challenged the already burdened health system of India. Also called as ‘Black Fungus,’ cases of CAM began to rise rapidly in the last week of May 2021 with multiple states reporting steady rise in the number of cases. Based on the published literature, India contributed to approximately 71% of global cases of CAM from December 2019 to start of April 2021, with majority of the cases occurring during the second wave. The present paper focuses on the epidemic of CAM during the second wave in India highlighting the causes, symptoms and various treatment modalities that have been adopted to cure the disease. Also, spotlight has also been thrown on some other nations where cases of CAM have begun to emerge. Some key recommendations are also mentioned which can prove vital towards disease prevention.

In this announcement, we present the complete annotated genome sequence of an Escherichia coli MC4100 mutant strain, BE104. This strain has several methionine sulfoxide reductase gene deletions, making it ideal for studying enzymes that alter the redox state of methionine.

ObjectivesA new variant ofChlamydia trachomatis(nvCT) was discovered in Sweden in 2006. The nvCT has a plasmid deletion, which escaped detection by two nucleic acid amplification tests (Abbott/Roche, AR), which were used in 14 of 21 Swedish counties. The objectives of this study were to assess when and where nvCT emerged in Sweden, the proportion of nvCT in each county, and the role of a potential fitness difference between nvCT and co-circulating wild-type strains (wtCT).MethodsWe used a compartmental mathematical model describing the spatial and temporal spread of nvCT and wtCT. We parameterised the model using sexual behaviour data and Swedish spatial and demographic data. We used Bayesian inference to fit the model to surveillance data about reported diagnoses of chlamydia infection in each county and data from four counties that assessed the proportion of nvCT in multiple years.ResultsModel results indicated that nvCT emerged in central Sweden (Dalarna, Gävleborg, Västernorrland), reaching a proportion of 1% of prevalent CT infections in late 2002 or early 2003. The diagnostic selective advantage enabled rapid spread of nvCT in the presence of high treatment rates. After detection, the proportion of nvCT decreased from 30-70% in AR counties and 5-20% in counties that Becton Dickinson tests, to around 5% in 2015 in all counties. The decrease in nvCT was consistent with an estimated fitness cost of around 5% in transmissibility or 17% reduction in infectious duration.ConclusionsWe reconstructed the course of a natural experiment in which a mutant strain ofC. trachomatisspread across Sweden. Our modelling study provides support, for the first time, of a reduced transmissibility or infectious duration of nvCT. This mathematical model improved our understanding of the first nvCT epidemic in Sweden and can be adapted to investigate the impact of future diagnostic escape mutants.Key messagesThe dynamics of a new variant ofChlamydia trachomatis(nvCT) that escaped testing and treatment in Sweden can be reconstructed using a mathematical transmission model.Our study for the first time provides support of a reduced transmissibility or infectious duration of the nvCT in Sweden.This mathematical model improved our understanding of the nvCT epidemic in Sweden and can be adapted to investigate the impact of future diagnostic escape mutants.

Three rare carbamate-containing alkaloids, penicimutamides A–C (1–3), were isolated from a fungal mutant from the diethyl sulfate (DES) mutagenesis of marine-derived Penicillium purpurogenum G59. Their structures, including their absolute configurations, were determined by spectroscopic methods, especially the X-ray crystallography and CD analyses. HPLC-UV and HPLC-MS analyses evidenced that 1–3 were only produced in the mutant strain via biosynthetic pathways that were silent in the parental strain and activated by DES mutagenesis.

In the present study, an attempt was made to study the effect of plant extract on Sexual behaviour of Mutant Strain (Curled) of Drosophila melanogaster. The LC50 has been estimated with 1% of the food media. The virgin females and males were isolated and fed with normal food media for three days. Then sub-lethal concentrations of 0.625 μl / 100 ml food, 1.2 μl /100 ml food, 2.5μl /100 / food of nicotine were mixed in food medium and allowed in flies to feed for two days. Then appropriate combination of untreated / treated males and females were introduced into the mating chamber. Courtship latency, mating latency and copulation duration were studied. After observation of the behaviour, mated flies were allowed to produce progeny. The sexual behaviour of bachelor male and virgin female obtained in the progeny was also studied. The pooled data were analyzed by student t-test and the result indicates p-value significant at 0.05 levels. The courtship latency was affected by in treatment but it is neither dose dependent nor sex dependent.

International audience; Objectives - Daptomycin has become a first-line therapeutic option for vancomycin-resistant Enterococcus faecium infective endocarditis (IE). Although high doses (≥8 mg/kg) are often recommended, optimal doses, particularly for strains with MICs close to the susceptibility breakpoint (4 mg/L), are still debated.Methods - Daptomycin efficacy at doses equivalent to 8 mg/kg daptomycin (DAP8) and 12 mg/kg daptomycin (DAP12) in humans was evaluated in a rabbit model of aortic valve IE induced by 108 cfu of E. faecium reference strain Aus0004 (daptomycin MIC = 2 mg/L) or its in vitro mutant strain Mut4 (daptomycin MIC = 4 mg/L). Treatment began 48 h post-inoculation and lasted 5 days.Results - With Aus0004, the median log10 cfu/g of vegetations was significantly lower after DAP8 and DAP12 versus controls [6.05 (n = 12) and 2.15 (n = 10) versus 9.14 (n = 11), respectively; P Conclusions - DAP12 was the most successful strategy against IE due to a WT E. faecium strain (daptomycin MIC = 2 mg/L). To treat IE strains with MIC = 4 mg/L, DAP8 or DAP12 monotherapy was poorly effective with the risk of resistant mutant emergence. Reassessment of the daptomycin susceptibility breakpoint for enterococci seems necessary.

In this study, a microalgae mutant Scenedesmus sp. Z-4 with a lipid content of 28.86% and biomass of 2.876 g L−1 was obtained using 60Co γ-ray mutation. The lipid productivity (138 mg L−1 per day) and content of mutant Z-4 were enhanced by 113% and 71.3% compared to that of the wild strain, respectively. In addition, unlike the wild strain, the microalgae cells were larger and the surface was rougher in mutant Z-4.

Promoters in Escherichia coli include an ‘OFF’ state, during which transcription is halted. Here, we propose a novel empirical method for assessing the time-length spent by promoters in this state. It relies on direct measurements of RNA production kinetics at the single molecule level at different induction levels, followed by an estimation of the RNA production rate under infinite induction, which is then compared to this rate under real, maximum induction. We apply it to the LacO3O1 promoter and infer that, under full induction, on average, 15% of the time between successful transcription events is spent in the OFF state. We verify this result by comparing the kinetics of a mutant strain lacking repressor molecules with that of the inferred rate under infinite induction. We expect this strategy of dissecting the kinetics of transcription repression to be applicable to a wide number of promoters in E. coli. acceptedVersion

New indolylarylsulfone HIV-1 NNRTIs were synthesized to evaluate unexplored substitutions of the benzyl/phenylethyl group linked at the indole-2-carboxamide. Against the NL4-3 HIV-1 WT strain, 17 out 20 compounds were superior to NVP and EFV. Several compounds inhibited the K103N HIV-1 mutant strain at nanomolar concentration and were superior to EFV. Some derivatives were superior to EFV against the Y181C and L100I HIV-1 mutant strains. Against the NL4-3 HIV-1 strain, the enantiomers 24 and 25 showed small differences of activity. In contrast, 24 turned out significantly more potent than 25 against the whole panel of mutant HIV-1 strains. The docking studies suggested that the difference in the observed inhibitory activities of 24 and 25 against the K03N mutation could be due to a kinetic rather than affinity differences.

The R. glutinis NR98 of high-producing β-carotene was treated by ultra high pressure (UHP) of 100~500 MPa for 10~30 min. The survival curve of NR98 treated for 10 min was saddle, which shows that the effect of UHP on this strain maybe was the cumulation of many biology effects. The rate of β-carotene production from mutant G39 (obtained at 300 MPa for 10 min) was increased by 59.87% compared with the initial strain NR98, and its genetic quality was proved to be stable by experiments. The result of restriction fragment length polymorphism analysis suggested that mutant strain G39 was likely to change in nucleic acid level.

Summary Bacteria associated with free-living amoebae have attracted considerable attention because of their role in human disease and as models for studying endosymbiosis. However, the identification and analysis of such novel associations are hindered by the limitations of methods for isolation and axenization of amoebae. Here, we replaced the heat- inactivated Escherichia coli, which is typically used as food source during axenization, with a live E. coli tolC knockout mutant strain hypersensitive to antibi- otics. Together with the addition of otherwise suble- thal amounts of ampicillin, this approach tripled the success rate and reduced the time required for axenization by at least 3 days. Using this method for two environmental samples, 10 Acanthamoeba strains were isolated, seven of which contained bac- terial symbionts. In three cases, amoebae harbouring two phylogenetically distinct symbionts were recov- ered, supporting a more widespread occurrence of multi-partner symbiotic associations among free- living amoebae.

Photoelectrocatalytic (PEC) and photocatalytic (PC) inactivation of ancestor Escherichia coli K-12 and its mutant E. coli BW25113 were systematically compared using a TiO2 nanotubular photoanode. The results showed that PEC inactivation was more effective to both bacterial strains than PC process, and E. coli BW25113 showed higher resistance than E. coli K-12 in both PEC and PC systems. The findings indicate that the two strains with different genes are varied in their susceptibilities and responses to the PEC and PC treatments. The h+ was found to be the major reactive species and predominantly responsible for PEC inactivation. Scanning electron microscopy images demonstrated that the cells were severely damaged and resulted in a leakage of the intracellular components during PEC inactivation process. For a given bacterial strain, no significant effect was found on the PEC inactivation efficiency as different electrolytes were employed. However, in the presence of NaCl or NaBr, PEC inactivation efficiencies of both strains were remarkably enhanced. This phenomenon can be attributed to the efficient formation of halide and dihalide radical anions during PEC process. The different efficiencies of the two bacterial strains under same conditions can be ascribed to their different abilities to resist the inactivation of bacterial strains with different genotypes.

A high molecular weight hyaluronic acid-producing mutant, designated asStreptococcus equiSH-109 that did not produce streptolysin or hyaluronidase was selected from wild-typeStreptococcus equiSH-0 by NTG treatment. The selected mutant could produce high molecular weight HA and had perfect genetic stability after reproduction. Several culture conditions were optimized in a 5-l fermentor for the production of hyaluronic acid. It was found that the optimal pH and agitation speed were 7.6 and 550rpm, respectively. Under the optimized culture condition, hyaluronic acid with a molecular weight of 4.0 x 106was accumulated in the culture broth.

A series of novel N-arylmethyl substituted piperidine-linked aniline derivatives were designed, synthesized and evaluated for their anti-HIV activity in MT-4 cells. All the new compounds showed moderate to potent activities against wild-type (wt) HIV-1 with an EC50 range from 0.022 to 2.1 μM. Among them, compound 5a6 (EC50 = 0.022 ± 0.0091 μM, SI >10,770) was confirmed to be the most potent and selective inhibitor, which proved more potent than DDI and DLV in a cell-based assay against wt HIV-1, and more efficient than NVP in an RT (reverse transcriptase) assay. Besides, it is worth noting that compound 7a1 retained moderate inhibitory activity (EC50 = 4.8 ± 0.95 μM) against the HIV-1 double RT mutant strain (K103N/Y181C). The preliminary structure–activity relationship was discussed and rationalized by molecular simulation.

Mithramycin (MTM) is a potent anti-cancer agent that has recently garnered renewed attention. This manuscript describes the design and development of mithramycin derivatives through a combinational approach of biosynthetic analogue generation followed by synthetic manipulation for further derivatization. Mithramycin SA is a previously discovered analogue produced by the M7W1 mutant strain alongside the improved mithramycin analogues mithramycin SK and mithramycin SDK. Mithramycin SA shows decreased anti-cancer activity compared to mithramycin and has a shorter, two carbon aglycon side chain that is terminated in a carboxylic acid. The aglycon side chain is responsible for an interaction with the DNA-phosphate backbone as mithramycin interacts with its target DNA. It was therefore decided to further functionalize this side chain through reactions with the terminal carboxylic acid in an effort to enhance the interaction with the DNA phosphate backbone and improve the anti-cancer activity. This side chain was modified with a variety of molecules increasing the anti-cancer activity to a comparable level to mithramycin SK. This work shows the ability to transform the previously useless mithramycin SA into a valuable molecule and opens the door to further functionalization and semi-synthetic modification for the development of molecules with increased specificity and/or drug formulation.

wild type strain W3110; in the YS1234 strain defective in ynbD, yeiU, ybjG, and pgpB; in the YS1235 strain defective in ynbD, yeiU, ybjG, and bacA; and in the YS1245 strain defective in ynbD, yeiU, pgpB, and bacA were 78.0% ± 3.5%, 74.7% ± 1.2%, 68.4% ± 6.8%, and 64.0% ± 7.5%, respectively. The quadruple mutant strain that possessed the wild-type bacA showed almost identical UP level as the wild type strain W3110, indicating that sufficient level of UPP phosphatse activity was conferred by a bacA product without the products of ynbD, yeiU, ybjG, and pgpB. However, the mutants defective in bacA showed a slight but significant (p < 0.01) decrease in the UP level.

Staphylococci are Gram-positive spherical bacteria of enormous clinical and biotechnological relevance. Staphylococcus aureus has been extensively studied as a model pathogen. A plethora of methods and molecular tools has been developed for genetic modification of at least ten different staphylococcal species to date. Here we review recent developments of various genetic tools and molecular methods for staphylococcal research, which include reporter systems and vectors for controllable gene expression, gene inactivation, gene essentiality testing, chromosomal integration and transposon delivery. It is furthermore illustrated how mutant strain construction by homologous or site-specific recombination benefits from sophisticated counterselection methods. The underlying genetic components have been shown to operate in wild-type staphylococci or modified chassis strains. Finally, possible future developments in the field of applied Staphylococcus genetics are highlighted.

Three rare carbamate-containing alkaloids, penicimutamides A–C (1–3), were isolated from a fungal mutant from the diethyl sulfate (DES) mutagenesis of marine-derived Penicillium purpurogenum G59. Their structures, including their absolute configurations, were determined by spectroscopic methods, especially the X-ray crystallography and CD analyses. HPLC-UV and HPLC-MS analyses evidenced that 1–3 were only produced in the mutant strain via biosynthetic pathways that were silent in the parental strain and activated by DES mutagenesis.

Side-ring-modified thiostrepton (TSR) derivatives that vary in their quinaldic acid (QA) substitution possess more potent biological activities and better pharmaceutical properties than the parent compound. In this work, we sought to introduce fluorine onto C-7′ or C-8′ of the TSR QA moiety via precursor-directed mutational biosynthesis to obtain new TSR variants. Unexpectedly, instead of the target product, the exogenous chemical feeding of 7-F-QA into the ΔtsrT mutant strain resulted in a unique TSR analog with an incomplete side-ring structure and an unoxidized QA moiety (1). Accordingly, two cytochrome P450 genes, tsrP and tsrR, were in-frame deleted to elucidate the candidate responsible for the monooxidation of the QA moiety in TSR. The unfluorinated analog of compound 1 that was thus isolated from ΔtsrP (2) and the abolishment of TSR production in ΔtsrR revealed not only the biosynthetic logic of the TSR side-ring but also the essential checkpoint in TSR maturation before macro-ring closure.

IS-Tlk/Kyo, a rat mutant strain derived from IS/Kyo strain, exhibits a kinked and/or short tail, in addition to a congenital anomaly of the lumbar vertebrae that is a hallmark of IS/Kyo rats. Homozygotes (Tlk/Tlk) of Tlk dominant gene are known to die during embryonic development. The present report deals with the morphological features of heterozygous IS-Tlk/Kyo rat fetuses in comparison with those of IS/Kyo rat fetuses. One of the morphological features was a high incidence of tail vertebral anomalies in IS-Tlk rats (81.6% versus 0% in IS/Kyo rats). Significantly low values in number of live fetuses and ossified 5th sternebra and sacral and caudal vertebrae were observed in IS-Tlk/Kyo rats compared with those in IS/Kyo rats as well as a low incidence of fetuses with ventral septal defects in IS-Tlk/Kyo (0% versus 54.4% in IS rats). These results suggest that the Tlk gene may be involved in the formation of the vertebral centra and the ventral septum when it expresses on the genetic background of the IS rat.

The aim of the study was to evaluate baseline data of mutant strain of mice and to compare haematological parameters with their background strains. Almost all mutant strains of either sex had statistically significant changes in relation to their background strains. These findings will be useful for researchers in designing experiments on mutant strains for various disease models and interpreting data obtained from those strains.

The rapid spread of a mutant strain of Escherichia coli throughout Europe highlights the need for modern and flexible public health laws to identify, control and treat infections and contamination that give significant concern for the health of the population. In this article, Richard Griffith and Cassam Tengnah outline the amendments to the Public Health (Control of Disease) Act 1984 that adopt an all-hazards approach to threats to public health.

De novo peroxisome formation in peroxisome-deficient yeast cells requires Rho1 and the Pex11 family protein Pex25., We identified two proteins, Pex25 and Rho1, which are involved in reintroduction of peroxisomes in peroxisome-deficient yeast cells. These are, together with Pex3, the first proteins identified as essential for this process. Of the three members of the Hansenula polymorpha Pex11 protein family—Pex11, Pex25, and Pex11C—only Pex25 was required for reintroduction of peroxisomes into a peroxisome-deficient mutant strain. In peroxisome-deficient pex3 cells, Pex25 localized to structures adjacent to the ER, whereas in wild-type cells it localized to peroxisomes. Pex25 cells were not themselves peroxisome deficient but instead contained a slightly increased number of peroxisomes. Interestingly, pex11 pex25 double deletion cells, in which both peroxisome fission (due to the deletion of PEX11) and reintroduction (due to deletion of PEX25) was blocked, did display a peroxisome-deficient phenotype. Peroxisomes reappeared in pex11 pex25 cells upon synthesis of Pex25, but not of Pex11. Reintroduction in the presence of Pex25 required the function of the GTPase Rho1. These data therefore provide new and detailed insight into factors important for de novo peroxisome formation in yeast.

Herpes simplex virus type 1(HSV-1) presents a conundrum to public health worldwide because of its specific pathogenicity and clinical features. Some experimental vaccines, such as the recombinant viral glycoproteins, exhibit the viral immunogenicity of a host-specific immune response, but none of these has achieved a valid epidemiological protective efficacy in the human population. In the present study, we constructed an attenuated HSV-1 strain M3 through the partial deletion of UL7, UL41, and the latency-associated transcript (LAT) using the CRISPR/Cas9 system. The mutant strain exhibited lowered infectivity and virulence in macaques. Neutralization testing and ELISpot detection of the specific T-cell responses confirmed the specific immunity induced by M3 immunization and this immunity defended against the challenges of the wild-type strain and restricted the entry of the wild-type strain into the trigeminal ganglion. These results in rhesus macaques demonstrated the potential of the attenuated vaccine for the prevention of HSV-1 in humans.

Functional foods, of which probiotic- and prebiotic-containing foods are a subset, have recently justified the efforts of health authorities in many countries. Many strains of Leuconostoc mesentero...

Multi drug resistant Klebsiella pneumoniae showed stepwise adaptation when grown in increasing concentration of Cefotaxime eventually reaching a maximum of 2 mg/ml. The resultant Cefotaxime resistant mutant strain was stable and did not revert to susceptibility on frequent subculturing. The response of the cells to different concentration of Cefotaxime was examined by scanning electron microscope which showed that the size of the bacterium increased with increasing concentration of Cefotaxime.

A fundamental possibility of antitumor activity testing in the bacterial system represented by Escherichia coli of the wild type and its MS2-induced mutant has been shown. The initial bacterial strain is an indicator of toxic properties of tested substances and the mutant strain is a specific test culture modeling a tumor cell. The comparison of the data described for eukaryotes with the data obtained using the proposed bacterial test system confirms an adequate response of both strains to substances with proved antitumor properties. The data obtained are considered as very promising for the further improvement of this test system towards its application for primary screening of antitumor substances.

Background: Chronic hepatitis B (CHB) affects 400 million people worldwide and is a major cause of morbidity and mortality. It is known that HBV DNA sequences were detected after the clearance of serum hepatitis B surface antigen (HBsAg) often in serum, liver and peripheral blood mononuclear cells. The objectives of our study were to evaluate the previous measurements of HBsAg titers versus. quantitative hepatitis B virus (HBV) DNA and ALT measurements in order to predict the nonresponse and response in interferon-alpha (IFN-α)-treated HBeAg-positive and HBeAg-negative chronic HBV patients. Methods: We investigate whether the presence of precore mutant affects the response to IFN-α therapy and on the titer of HBsAg or not. Twenty-one HBeAg-positive (group1), 38 HBeAg-negative (group 2), and 47 healthy inactive carriers (group 3) made up this study. Liver biopsy showed chronic hepatitis, there was no cirrhosis and none of the patients had IFN-α therapy before. Results: The decrease in HBsAg titers was found as statistically not significant in groups 1 (p = 0.192) and 3 (p = 0.236) and statistically significant in group 2 (p = 0.0001) within a 6-month interval. Conclusion: HBsAg titer may be a factor to predict the primary responders and nonresponders specially in HBeAg-negative patients.

We report a draft genome sequence of Streptomyces fradiae olg1-1, a mutant strain derived from the model object S. fradiae ATCC 19609, which is resistant to nitrone-oligomycin and has a mutation in the DNA-binding domain of a transcriptional regulator PadR.

It is well known that Escherichia coli executes chemotactic motion in response to chemical cues by modulating the flagellar motor bias alone. However, previous studies have reported the possibility of variation in run speed in the presence of attractants although it is unclear whether bacteria can deliberately modulate their swimming speeds in response to environmental cues or if the motor speeds are hardwired. By studying the detailed motion of cells in a uniform concentration of glucose and its non-metabolizable analogue, we show that changing concentrations may be accompanied by variation in the swimming speed. For a fixed run duration, cells exposed to the attractants achieved a higher peak-swimming speed after a tumble compared with that in plain motility buffer. Our experiments using the mutant strain lacking the Trg sensor show no change in swimming speed with varying concentrations of the non-metabolizable analogue, suggesting that sensing may play a role in the observed variation of swimming speed.

Beef-processing equipment can be contaminated with pathogens such as Escherichia coli O157:H7 and Salmonella spp. The bowl cutter has wide application in particle-size reduction and blending of meat products. This study was undertaken to determine (i) the distribution patterns of E. coli O157:H7 in equipment components and ground beef produced with a table-top bowl cutter under different operational conditions and (ii) the likelihood that pathogen contamination can be transferred to subsequent batches after a batch of beef contaminated with E. coli O157:H7 has been processed in the same bowl cutter. A beef trim (44.6 +/- 29.5 g) inoculated with 2 log CFU of an E. coli O157:H7 mutant strain resistant to rifampicin (E. coli O157:H7rif) was fed by hand into an uncontaminated beef-trim batch under two different batch sizes (2 and 4 kg), three processing times (60, 120, and 240 s), and two feeding modes (running and stoppage fed). There were no significant differences (P > or = 0.05) among all the treatments for the averages of the counts of E. coli O157:H7rif distributed in the ground beef. Regardless of the processing time and the method used to feed the beef trims into the bowl cutter, the whole batch and the following subsequent batch became contaminated when previously contaminated beef was processed. Areas of the bowl cutter most likely to be contaminated with E. coli O157:H7 were (i) the material left on the top of the comb/knife guard and (ii) the knife. Material that overflowed the bowl cutter, when processing the batch with E. coli O157:H7rif, contaminated the equipment surroundings. A Pearson V probability distribution function was determined to describe the distribution of pathogenic organisms in the ground beef, a distribution that can also be applied when conducting process risk analyses on mixing-particle reduction operations for beef trims.

Production of neomycin by a mutant strain of Streptomyces marinensis, under solid state fermentation was optimised. Various substrates were used to study their effect on neomycin production. Wheat rawa was found to be better for optimum production of neomycin. The maximum neomycin yield (10 755 μg/g substrate) was achieved with optimised process parameters such as coarse size of wheat rawa with raspberry seed powder (10% w/w) as additional nutrient, initial moisture content of solid substrate 80%, initial pH of the medium 7.5, incubation temperature 30 °C, inoculum size 0.5% w/w dry cell mass equivalent and 10 days of fermentation time. One hundred and forty percent of higher production was achieved after optimising the process parameters.

A mutant strain of Pseudomonas putida (LU2201) expressing a novel ethylphenylacetate (EPA) esterase was isolated after mutagenesis of P. putida LU6456. The DNA fragment conferring the EPA+ phenotype was cloned and characterized. It included the structural genes of the 2,3-butanediol catabolic pathway, including acoC, which catalyzes the acetyl transfer step (i.e., dihydrolipoamide acetyltransferase). The acoC gene product from LU2201 was expressed in E. coli and shown to be responsible for the novel EPA-esterase activity. Biochemical characterization revealed that the enzyme still retained the natural dihydrolipoamide acetyltransferase activity. Sequence comparison with the corresponding wild-type gene indicated a single-base pair change leading to a I238V replacement in the respective protein. Biochemical characterization of wild-type AcoC enzyme showed that it too was able to catalyze EPA hydrolysis despite the apparent absence of this activity in cells grown in the presence of EPA. Unlike the wild type, EPA serves as an inducer in the mutant strain. Inverse PCR was used to clone the putative regulator acoR from the aco operon in both wild type and mutant strains. Sequence analyses indicated an S14R exchange in the AcoR from the P. putida mutant. This mutation was located in the N-terminal region responsible for regulatory functions, presumably by interaction with signal molecules. This may account for the ability of EPA to induce expression of acoC only in the mutant strain.Key words: Pseudomonas putida, ethylphenylacetate esterase, acetoin cleaving system, acoC gene, dihydrolipoamide acetyl-transferase, E2 component, acoR gene.

Members of the Mycobacterium tuberculosis group synthesize a family of long-chain fatty acids, mycolic acids, which are located in the cell envelope. These include the non-oxygenated α-mycolic acid and the oxygenated keto- and methoxymycolic acids. The function in bacterial virulence, if any, of these various types of mycolic acids is unknown. We have constructed a mutant strain of M. tuberculosis with an inactivated hma (cmaA, mma4) gene; this mutant strain no longer synthesizes oxygenated mycolic acids, has profound alterations in its envelope permeability and is attenuated in mice.

Guided by crystal structures of HIV-1 RT/DAPY complex and molecular modeling studies, a series of novel [1,2,4]triazolo[1,5-a]pyrimidine derivatives were rationally designed via structure-based core refining approach, synthesized through the readily accessible synthetic methods and evaluated for their anti-HIV activities in MT-4 cells. Preliminary biological evaluation indicated that most of the compounds exhibited marked inhibitory activity against the wild-type HIV-1 IIIB. Particularly, compound 7n was the most potent inhibitor against wild-type and K103N/Y181C double resistant mutant strain of HIV-1, possessing EC50 values of 0.02 μM and 7.6 μM, respectively, which were much better than or similar to nevirapine (NVP, EC50 = 0.15 μM, 2.9 μM) and delavirdine (DLV, EC50 = 0.07 μM, >36 μM). Besides, some other compounds, 5b, 7c, 7e, 7f, and 7m, were also endowed with favorable anti-HIV-1 potency (EC50 = 0.07, 0.05, 0.05, 0.07, and 0.05 μM, respectively), which were better than or similar to those of NVP and DLV, suggesting a high potential to further develop this type of bridgehead nitrogen heterocycle as a novel class of NNRTIs with improved antiviral efficacy and resistance profile. The selected compound, 7i, was found moderately inhibitory towards RT (IC50 = 0.39 μM), which was higher than for ETV (IC50 = 0.56 μM). Preliminary structure–activity relationships (SARs) and molecular modeling of these new analogues were detailed in this manuscript.

The open reading frame at 86.7 min on the Escherichia coli chromosome, “ yigC ,” complemented a ubiD mutant strain, AN66, indicating that yigC is the ubiD gene. The gene product, a 497-amino-acid-residue protein, showed extensive homology to the UPF 00096 family of proteins in the Swiss-Prot database.