Three-dimensional models of <Emphasis Type="Italic">Mycobacterium tuberculosis</Emphasis> proteins Rv1555, Rv1554 and their docking analyses with sildenafil,tadalafil, vardenafil drugs,suggest interference with quinol binding likely to affect protein’s function

Background

Earlier based on bioinformatics analyses, we had predicted the Mycobacterium tuberculosis (M.tb) proteins; Rv1555 and Rv1554, among the potential new tuberculosis drug targets. According to the ‘TB-drugome’ the Rv1555 protein is ‘druggable’ with sildenafil (Viagra), tadalafil (Cialis) and vardenafil (Levitra) drugs. In the present work, we intended to understand via computer modeling studies, how the above drugs are likely to inhibit the M.tb protein’s function.

Results

The three-dimensional computer models for M.tb proteins; Rv1555 and Rv1554 constructed on the template of equivalent membrane anchor subunits of the homologous E.coli quinol fumarate reductase respiratory protein complex, followed by drug docking analyses, suggested that the binding of above drugs interferes with quinol binding sites. Also, we experimentally observed the in-vitro growth inhibition of E.coli bacteria containing the homologous M.tb protein sequences with sildenafil and tadalafil drugs.

Conclusions

The predicted binding sites of the drugs is likely to affect the above M.tb proteins function as quinol binding is known to be essential for electron transfer function during anaerobic respiration in the homologous E.coli protein complex. Therefore, sildenafil and related drugs currently used in the treatment of male erectile dysfunction targeting the human phosphodiesterase 5 enzyme may be evaluated for their plausible role as repurposed drugs to treat human tuberculosis.

     

The Inhibition Effect of Lactobacilli Against Growth and Biofilm Formation of <Emphasis Type="BoldItalic">Pseudomonas aeruginosa</Emphasis>

The emergence of antibiotic-resistant and food-spoilage microorganisms has renewed efforts to identify safe and natural alternative agents of antibiotics such as probiotics. The aim of this study was the isolation of lactobacilli as potential probiotics from local dairy products with broad antibacterial and anti-biofilm activities against antibiotic-resistant strains of Pseudomonas aeruginosa and determination of their inhibition mechanism. Antibiotic susceptibility and classification of acquired resistance profiles of 80 P. aeruginosa strains were determined based on Centers for Disease Control and Prevention (CDC) new definition as multidrug-resistant (MDR), extensively drug-resistant (XDR), and pan-drug-resistant (PDR) followed by antibacterial assessment of lactobacilli against them by different methods. Among the 80 P. aeruginosa strains, 1 (1.3%), 50 (62.5%), and 78 (97.5%) were PDR, XDR, and MDR, respectively, and effective antibiotics against them were fosfomycin and polymyxins. Among 57 isolated lactobacillus strains, two strains which were identified as Lactobacillus fermentum using biochemical and 16S rDNA methods showed broad inhibition/killing and anti-biofilm effects against all P. aeruginosa strains. They formed strong biofilms and had bile salts and low pH tolerance. Although investigation of inhibition mechanism of these strains showed no bacteriocin production, results obtained by high-performance liquid chromatography (HPLC) analysis indicated that their inhibitory effect was the result of production of three main organic acids including lactic acid, acetic acid, and formic acid. Considering the broad activity of these two L. fermentum strains, they can potentially be used in bio-control of drug-resistant strains of P. aeruginosa.     

Aloe Emodin Reduces Phthiodiolone Dimycocerosate Potentiating Vancomycin Susceptibility on Mycobacteria

Treatment of tuberculosis still represent a major public health issue. The emergence of multi-and extensively-drug resistant (MDR and XDR) Mycobacterium tuberculosis clinical strains further pinpoint the urgent need for new anti-tuberculous drugs. We previously showed that vancomycin can target mycobacteria lacking cell wall integrity, especially those lacking related phthiocerol and phthiodolone dimycocerosates, PDIM A and PDIM B, respectively. As aloe emodin was previously hypothesized to be able to target the synthesis of mycobacterial cell wall lipids, we tested its ability to potentiate glycopeptides antimycobacterial activity. The aloe emodin with the vancomycin induced a combination effect beyond simple addition, close to synergism, at a concentration lower to reported IC₅₀ cytotoxic value, on M. bovis BCG and on H37Rv M. tuberculosis. Interestingly, out of six MDR and pre-XDR clinical strains, one showed a strong synergic susceptibility to the drug combination. Mycobacterial cell wall lipid analyses highlighted a selective reduction of PDIM B by aloe emodin.     

Connection between proliferation rate and temozolomide sensitivity of primary glioblastoma cell culture and expression of <Emphasis Type="Italic">YB-1</Emphasis> and <Emphasis Type="Italic">LRP/MVP</Emphasis>

Glioblastomas (GBL) are the most common and aggressive brain tumors. They are distinguished by high resistance to radiation and chemotherapy. To find novel approaches for GBL classification, we obtained 16 primary GBL cell cultures and tested them with real-time PCR for mRNA expression of several genes (YB-1, MGMT, MELK, MVP, MDR1, BCRP) involved in controlling cell proliferation and drug resistance. The primary GBL cultures differed in terms of proliferation rate, wherein a group of GBL cell cultures with low proliferation rate demonstrated higher resistance to temozolomide. We found that GBL primary cell cultures characterized by high proliferation rate and lower resistance to temozolomide expressed higher mRNA level of the YB-1 and MDR1 genes, whereas upregulated expression of MVP/LRP mRNA was a marker in the group of GBL with low proliferation rate and high resistance. A moderate correlation between expression of YB-1 and MELK as well as YB-1 and MDR1 was found. In the case of YB-1 and MGMT expression, no correlation was found. A significant negative correlation was revealed between mRNA expression of MVP/LRP and MELK, MDR1, and BCRP. No correlation in expression of YB-1 and MVP/LRP genes was observed. It seems that mRNA expression of YB-1 and MVP/LRP may serve as a marker for GBL cell cultures belonging to distinct groups, each of which is characterized by a unique pattern of gene activity.     

3D QSAR,pharmacophore and molecular docking studies of known inhibitors and designing of novel inhibitors for M18 aspartyl aminopeptidase of <Emphasis Type="Italic">Plasmodium falciparum</Emphasis>

Background

The Plasmodium falciparum M18 Aspartyl Aminopeptidase (PfM18AAP) is only aspartyl aminopeptidase which is found in the genome of P. falciparum and is essential for its survival. The PfM18AAP enzyme performs various functions in the parasite and the erythrocytic host such as hemoglobin digestion, erythrocyte invasion, parasite growth and parasite escape from the host cell. It is a valid target to develop antimalarial drugs. In the present work, we employed 3D QSAR modeling, pharmacophore modeling, and molecular docking to identify novel potent inhibitors that bind with M18AAP of P. falciparum.

Results

The PLSR QSAR model showed highest value for correlation coefficient r² (88 %) and predictive correlation coefficient (pred_r2) =0.6101 for external test set among all QSAR models. The pharmacophore modeling identified DHRR (one hydrogen donor, one hydrophobic group, and two aromatic rings) as an essential feature of PfM18AAP inhibitors. The combined approach of 3D QSAR, pharmacophore, and structure-based molecular docking yielded 10 novel PfM18AAP inhibitors from ChEMBL antimalarial library, 2 novel inhibitors from each derivative of quinine, chloroquine, 8-aminoquinoline and 10 novel inhibitors from WHO antimalarial drugs. Additionally, high throughput virtual screening identified top 10 compounds as antimalarial leads showing G-scores -12.50 to -10.45 (in kcal/mol), compared with control compounds(G-scores -7.80 to -4.70) which are known antimalarial M18AAP inhibitors (AID743024). This result indicates these novel compounds have the best binding affinity for PfM18AAP.

Conclusion

The 3D QSAR models of PfM18AAP inhibitors provided useful information about the structural characteristics of inhibitors which are contributors of the inhibitory potency. Interestingly, In this studies, we extrapolate that the derivatives of quinine, chloroquine, and 8-aminoquinoline, for which there is no specific target has been identified till date, might show the antimalarial effect by interacting with PfM18AAP.

     

Polymorphism of the human <Emphasis Type="Italic">MDR1</Emphasis> gene in Siberian and Central Asian populations

The multidrug resistance gene MDR1 (ABCB1) codes for a P-glycoprotein that acts as an ATP-dependent transporter and is involved in removing drugs, xenobiotics, and peptides from the cell. MDR1 is expressed in the brain, kidneys, liver, and gastrointestinal tract. The P-glycoprotein is thought to play a role in individual resistance to xenobiotics and infections. Several polymorphisms of MDR1 are associated with the level of its expression and resistance to various neurodegenerative and gastrointestinal diseases. The allele and haplotype frequencies, genetic differentiation, and linkage disequilibrium for five MDR1 single nucleotide polymorphisms (3435C/T, 2677G/T/A, 1236C/T, +139C/T, and ?1G/A) were studied in the Russian, Tuvinian, and northern and southern Kyrgyz populations. Significant genetic differences were observed between Russians and northern Kyrgyz and between Tuvinians and northern Kyrgyz. The linkage disequilibrium pattern was characterized by high population specificity.     

Novel aromatic polyketides from soil <Emphasis Type="Italic">Streptomyces</Emphasis> spp.: purification,characterization and bioactivity studies

Aromatic polyketides are important therapeutic compounds which include front line antibiotics and anticancer drugs. Since most of the aromatic polyketides are known to be produced by soil dwelling Streptomyces, 54 Streptomyces strains were isolated from the soil samples. Five isolates, R1, B1, R3, R5 and Y8 were found to be potent aromatic polyketide producers and were identified by 16S rRNA gene sequencing as Streptomyces spectabilis, Streptomyces olivaceus, Streptomyces purpurascens, Streptomyces coeruleorubidus and Streptomyces lavendofoliae respectively. Their sequences have been deposited in the GenBank under the accession numbers KF468818, KF681280, KF395224, KF527511 and KF681281 respectively. The Streptomyces strains were cultivated in the media following critically optimised culture conditions. The resulting broth extracts were fractionated on a silica gel column and preparative TLC to obtain pure compounds. The pure compounds were tested for bioactivity and the most potent compound from each isolate was identified by UV–Vis, IR and NMR spectroscopic methods. Isolated S. spectabilis (R1), yielded one potent compound identified as dihydrodaunomycin with an MIC of 4 µg/ml against Bacillus cereus and an IC₅₀ value of 24 µM against HeLa. S. olivaceus (B1), yielded a comparatively less potent compound, elloramycin. S. purpurascens (R3) yielded three compounds, rhodomycin, epelmycin and obelmycin. The most potent compound was rhodomycin with an MIC of 2 µg/ml against B. cereus and IC₅₀ of 15 µM against HeLa. S. coeruleorubidus (R5), yielded daunomycin showing an IC₅₀ of 10 µM and also exhibiting antimetastatic properties against HeLa. S. lavendofoliae (Y8), yielded a novel aclacinomycin analogue with IC₅₀ value of 2.9 µM and potent antimetastatic properties at 1 µM concentration against HeLa. The study focuses on the characterization of aromatic polyketides from soil Streptomyces spp., which can serve as potential candidates for development of chemotherapeutic drugs in future.     

Transmission of MDR and XDR Tuberculosis in Shanghai,China

Background

Multidrug-resistant (MDR) and extensively drug-resistant (XDR) tuberculosis (TB) are global health problems. We sought to determine the characteristics, prevalence, and relative frequency of transmission of MDR and XDR TB in Shanghai, one of the largest cities in Asia.

Methods

TB is diagnosed in district TB hospitals in Shanghai, China. Drug susceptibility testing for first-line drugs was performed for all culture positive TB cases, and tests for second-line drugs were performed for MDR cases. VNTR-7 and VNTR-16 were used to genotype the strains, and prior treatment history and treatment outcomes were determined for each patient.

Results

There were 4,379 culture positive TB cases diagnosed with drug susceptibility test results available during March 2004 through November 2007. 247 (5.6%) were infected with a MDR strain of M. tuberculosis and 11 (6.3%) of the 175 MDR patients whose isolate was tested for susceptibility to second-line drugs, were XDR. More than half of the patients with MDR and XDR were newly diagnosed and had no prior history of TB treatment. Nearly 57% of the patients with MDR were successfully treated.

Discussion

Transmission of MDR and XDR strains is a serious problem in Shanghai. While a history of prior anti-TB treatment indicates which individuals may have acquired MDR or XDR TB, it does not accurately predict which TB patients have disease caused by transmission of MDR and XDR strains. Therefore, universal drug susceptibility testing is recommended for new and retreatment TB cases.     

Antimicrobial activity,cytotoxicity and chemical analysis of lemongrass essential oil (<Emphasis Type="Italic">Cymbopogon flexuosus</Emphasis>) and pure citral

The aim of this study was to determine the antimicrobial effects of lemongrass essential oil (C. flexuosus) and to determine cytotoxic effects of both test compounds on human dermal fibroblasts. Antimicrobial susceptibility screening was carried out using the disk diffusion method. Antimicrobial resistance was observed in four of five Acinetobacter baumannii strains with two strains confirmed as multi-drug-resistant (MDR). All the strains tested were susceptible to both lemongrass and citral with zones of inhibition varying between 17 to 80 mm. The mean minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of citral (mic—0.14 % and mbc—0.3 % v/v) was lower than that of Lemongrass (mic—0.65 % and mbc—1.1 % v/v) determined using the microtitre plate method. Cell viability using human dermal fibroblasts (HDF; 106-05a) was determined following exposure to both compounds and a control (Grapeseed oil) using the XTT assay and the IC₅₀ determined at 0.095 % (v/v) for citral and 0.126 % (v/v) for lemongrass. Grapeseed oil had no effect on cell viability. Live cell imaging was performed using the LumaScope 500 imaging equipment and changes in HDF cell morphology such as necrotic features and shrinkage were observed. The ability of lemongrass essential oil (EO) and citral to inhibit and kill MDR A. baumannii highlights its potential for use in the management of drug-resistant infections; however, in vitro cytotoxicity does suggest further tests are needed before in vivo or ex vivo human exposure.     

Importance of differential identification of <Emphasis Type="Italic">Mycobacterium tuberculosis</Emphasis> strains for understanding differences in their prevalence,treatment efficacy,and vaccine development

Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb), remains a serious global health problem in the 21^st century because of its high mortality. Mtb is an extremely successful human-adapted pathogen that displays a multifactorial ability to control the host immune response and to evade killing by drugs, resulting in the breakdown of BCG vaccine-conferred anti-TB immunity and development of multidrug-resistant (MDR) and extensively drug-resistant (XDR) Mtb. Although genetic components of the genomes of the Mtb complex strains are highly conserved, showing over 99% similarity to other bacterial genera, recently accumulated evidence suggests that the genetic diversity of the Mtb complex strains has implications for treatment outcomes, development of MDR/XDR Mtb, BCG vaccine efficacy, transmissibility, and epidemiological outbreaks. Thus, new insights into the pathophysiological features of the Mtb complex strains are required for development of novel vaccines and for control of MDR/XDR Mtb infection, eventually leading to refinement of treatment regimens and the health care system. Many studies have focused on the differential identification of Mtb complex strains belonging to different lineages because of differences in their virulence and geographical dominance. In this review, we discuss the impact of differing genetic characteristics among Mtb complex strains on vaccine efficacy, treatment outcome, development of MDR/XDR Mtb strains, and epidemiological outbreaks by focusing on the best-adapted human Mtb lineages. We further explore the rationale for differential identification of Mtb strains for more effective control of TB in clinical and laboratory settings by scrutinizing current diagnostic methods.     

Synthesis of functionalized benzo[<Emphasis Type="Italic">f</Emphasis>]2<Emphasis Type="Italic">H</Emphasis>-chromenes and evaluation of their antimicrobial activities

Knoevenagel cyclocondensations of α-hydroxy naphthaldehyde with β-oxodithioesters and ketene dithioacetals yielded 2H-benzo[f]chromene-2-thiones and 2H-benzo[f]chromen-2-ones, respectively, in high yields. The newly synthesized compounds were evaluated for antifungal and antibacterial activities. Among them, compounds (2-furyl)(3-thioxo-3H-benzo[f]chromen-2-yl)methanone and phenyl(3-oxo-3H-benzo[f]chromen-2-yl)methanone exhibited excellent antifungal activity against tested fungi Curvularia lunata and Fusarium moniliforme. The highest antibacterial activity against the tested bacteria Escherichia coli and Staphylococcus aureus was observed for (4-chlorophenyl)(3-oxo-3H-benzo[f]chromen-2-yl)methanone. The results of antimicrobial screening demonstrate that (2-furyl)(3-thioxo-3H-benzo[f]chromen-2-yl)methanone, phenyl(3-oxo-3H-benzo[f]chromen-2-yl)methanone, and (4-chlorophenyl)(3-oxo-3H-benzo[f]chromen-2-yl)methanone are promising as antimicrobial drugs.     

Resistance Mechanism in a Terbinafine-Resistant Strain of <Emphasis Type="Italic">Microsporum canis</Emphasis>

To clarify the terbinafine (TRF) resistance mechanism in a TRF-resistant strain of Microsporum canis, the expression of the pleiotropic drug resistance (PDR1), multidrug resistance (MDR1), MDR2 and MDR4 genes were investigated by real-time quantitative PCR (RT-qPCR) analysis, given the known interaction of the corresponding proteins with antifungals and with the efflux blocker FK506. The expression of the PDR1, MDR1, MDR2 and MDR4 genes was 2–4 times higher in the TRF-resistant strain grown in the presence of 0.14 µg/mL of TRF than in TRF-susceptible strains cultured in the absence of TRF. The TRF-resistant strain exhibited MICs of > 32 µg/mL for TRF alone; this resistance was attenuated to an MIC of 8 µg/mL in the presence of FK506, indicating that the TRF inhibitory concentration index value was < 0.75. The additive effect of the efflux blocker FK506 on TRF resistance was detected in the TRF-resistant strain. These results indicated that the TRF resistance in this strain reflects overexpression of genes encoding ABC transporter proteins.     

Palaearctic species of the <Emphasis Type="Italic">Microchelonus retusus</Emphasis> group (Hymenoptera,Braconidae, Cheloninae)

Microchelonus species of the M. retusus group differ from the other members of the subgenus Microchelonus s. str. (characterized primarily by the 16-segmented female antennae and deepened apical abdominal opening of the male) in their elongate carapace of female abdomen more strongly narrowed apically than toward base. The first key to 45 species of this group, including 7 new species, is given: M. alexeevi Tobias, 1986 (apicalis Alexeev, 1971); M. angustiventris Tobias, 1986; M. apicalis Papp, 1971; M. arnoldii (Tobias, 1964); M. artus Tobias, 1986; M. cisapicalis Tobias, 1989; M. crassitarsus Tobias, 1989; M. dolosus Tobias, 1989; M. elenae Tobias, 1995; M. erosus Herrich-Schaeffer, 1838 (analipennis Fahringer, 1934; hungaricus Szépligeti, 1896; frivalaldszkyi Shenefelt, 1973); M. heraticus Tobias, 1985; M. hofferi Tobias et Lozan, 2006; M. jonaitisi Tobias, 2000; M. justus Tobias, 1989; M. kievorum sp. n. (Ukraine); M. kiritshenkoi (Tobias, 1976); M. klugei Tobias, 2001; M. kopetdagicus (Tobias, 1966) (caucasicus Abdinbekova, 1967, syn. n.); M. korinthiacus sp. n. (Greece); M. kozlovi (Tobias, 1961); M. longirimosus Tobias, 1995; M. madridi sp. n. (Spain); M. marshakovi Tobias, 1986; M. mediterraneus sp. n. (Greece); M. microphthalmus (Wesmael, 1838) (dilatus Papp, 1971); M. mikhaili Tobias, 1989; M. mirabilis (Tobias, 1972); M. morrocanus sp. n. (Morocco); M. nachitshevanicus (Abdinbekova, 1971); M. ononicus Tobias, 2000; M. pamiricus (Voinovskaya-Kriger, 1928); M. retrusus Tobias, 1989; M. retusus (Nees, 1813) (caudatus Thomson, 1874); M. stenogaster Tobias, 1995; M. sternaus (Tobias, 1964); M. subcaudatus (Tobias, 1971); M. subjustus sp. n. (Spain); M. sulcatus Jurine, 1908 (rimulosus Thomson, 1874; rimatus Szépligeti, 1896); M. tersakkanicus Tobias, 2001; M. tjanshanicus Tobias, 1995; M. turcius sp. n. (Turkey); M. volgensis Tobias, 1986; M. xenia Tobias, 2000; M. zorkuli Tobias, 1991.     

Phylogenetic relationship and time of divergence of <Emphasis Type="Italic">Mus terricolor</Emphasis> with reference to other <Emphasis Type="Italic">Mus</Emphasis> species

Mitochondrial DNA control region of Mus terricolor, three aboriginal species M. spretus, M. macedonicus, M. spicilegus; the Asian lineage M. caroli, M. cervicolor, M. cookii; and the two house mice, M. musculus domesticus and M. m. castaneus were analysed to estimate the substitution rate, phylogenetic relationship and the probable time of divergence. Results showed that M. spretus, M. caroli and M. terricolor are highly diverged from each other (caroli/terricolor = 0.146, caroli/spretus = 0.147 and terricolor/spretus = 0.122), whereas M. spretus showed less divergence with two house mice species (0.070 and 0.071). Sequence divergence between M. terricolor and the Palearctic group were found to be ranging from 0.121 to 0.134. Phylogenetic analysis by minimum evolution, neighbour-joining, unweighed pair group method with arithmetic mean and maximum parsimony showed almost similar topology. Two major clusters were found, one included the Asian lineage, M. caroli, M. cookii and M. cervicolor and the other included the house mice M. m. domesticus, M. m. castaneus and the aboriginal mice M. macedonicus and M. spicilegus along with M. spretus, forming the Palearctic clade. M. terricolor was positioned between the Palearctic and Asian clades. Results showed that Palearctic-terricolor and the Asian lineages diverged 5.47 million years ago (Mya), while M. terricolor had split around 4.63 Mya from their ancestor. M. cervicolor, M. cookii and M. caroli diverged between 4.70 and 3.36 Mya, which indicates that M. terricolor and the Asian lineages evolved simultaneously. M. spretus is expected to have diverged nearly 2.9 Mya from their most recent common ancestor.     

Clavicipitaceous entomopathogens: new species in <Emphasis Type="Italic">Metarhizium</Emphasis> and a new genus <Emphasis Type="Italic">Nigelia</Emphasis>

In several surveys in the tropical forests in Thailand, specimens that looked morphologically similar to Metarhizium martiale and Cordyceps variegata, as well as other Metarhizium species were collected and cultured in vitro. A combined phylogeny of several genes including the small (18S) and large (28S) subunits of the ribosomal DNA, elongation factor 1-α (TEF), RNA polymerase II subunits 1 and 2 (RPB1, RPB2) genes has shown these to be new taxa in the Clavicipitaceae. Nigelia is described as a new genus closely related to Metarhizium, to the scale insect pathogens Aschersonia (Hypocrella), Samuelsia and Moelleriella, and to plant pathogens in Claviceps and Balansia, and other relatives. Nigelia comprises M. martiale and a new species Nigelia aurantiaca, which has been found infecting lepidopteran larvae and which produces pseudoimmersed, obliquely arranged, obpyriform perithecia with curved or bent ostioles and with whole (non-separating) cylindric ascospores. Metarhizium chaiyaphumense, M. kalasinense, M. prachinense, M. samlanense, and M. takense are described as new species of Metarhizium. Metarhizium martiale is transferred to Nigelia, and Paecilomyces reniformis is transferred to Metarhizium.     

Programmed cell death in the cyanobacterium <Emphasis Type="Italic">Microcystis aeruginosa</Emphasis> induced by allelopathic effect of submerged macrophyte <Emphasis Type="Italic">Myriophyllum spicatum</Emphasis> in co-culture system

This investigation demonstrates that programmed cell death (PCD) in a cyanobacterium, Microcystis aeruginosa, resulting from allelopathic stress induced by a submerged macrophyte, Myriophyllum spicatum, in a co-culture system. The hallmarks of PCD, caspase-3-like protease activity, DNA fragmentation, and destruction of cell ultrastructure, as well as intracellular PCD signaling radicals, reactive oxygen species (ROS), and nitric oxide (NO), were measured in M. aeruginosa cells co-cultured with M. spicatum for 7 days. The results showed a dose–response relationship between M. spicatum biomass and M. aeruginosa mortality. A caspase-3-like protease was activated and elevated from day 3. Thylakoid disintegration, cytoplasmic vacuolation, and fuzzy nuclear zone were observed by transmission electron microscopy, and distinct DNA fragmentation was detected in M. aeruginosa cells at a M. spicatum biomass of 6.0 g fresh weight (FW) L^?1 during the 7 days. Allelochemicals of total phenolic compounds (TPCs) were determined in co-culture water, and the concentration increased with increasing of M. spicatum biomass and co-culture time. Compared with the level of ROS production in the control group, a significant overproduction of ROS was detected in M. aeruginosa cells in the treatment group, and this was positively correlated with TPC concentration. Furthermore, the level of intracellular NO increased with the percent mortality of M. aeruginosa. The results indicated that a PCD pathway was induced in the cyanobacterium M. aeruginosa when co-cultured with the submerged macrophyte M. spicatum.     

Revision of the carabid genus <Emphasis Type="Italic">Meroctenus</Emphasis> Gemminger et Harold,with a new status of <Emphasis Type="Italic">Xenodochus</Emphasis> Andrewes (Coleoptera,Carabidae: Harpalini)

Originally described as a monotypical genus with unclear taxonomic position from Sudan, Meroctenus Gemminger et Harold, 1868 is treated as a polytypical genus of the Selenophori genus group with two subgenera: Meroctenus s. str. and Xenodochus Andrewes, 1941, stat. n. (the latter was previously considered a distinct genus). Within Meroctenus, two species are recognized: M. (Meroctenus) crenulatus Chaudoir, 1843 (type species) and M. (M.) mediocris (Andrewes, 1936), comb, n., transferred to Meroctenus s. str. from Xenodochus. A new subspecies M. (M.) crenulatus orientalis subsp. n. is described from Pakistan. Diagnoses of the genus Meroctenus in new interpretation as well as of its two subgenera are discussed, and a taxonomic review of the subgenus Meroctenus s. str. with a key to the species and subspecies is provided. The following synonymy is proposed: Meroctenus Gemminger et Harold, 1868 = Paregaploa Müller, 1947, syn. n.; Meroctenus crenulatus (Chaudoir, 1843) = Egaploa (Paregaploa) conviva Müller, 1947, syn. n. Lectotypes are designated for Ctenomerus crenulatus Chaudoir, 1843 and Xenodus mediocris Andrewes, 1936.     

Chemical shift assignments of Ribosomal protein S1 from <Emphasis Type="Italic">Mycobacterium tuberculosis</Emphasis>

RpsA, also known as ribosomal protein S1, is an essential protein required for translation initiation of mRNAs when their Shine-Dalgarno sequence is degenerated (Sorensen et al. 1998). In addition, RpsA of Mycobacterium tuberculosis (M. tb) is involved in trans-translation, which is an effective system mediated by tmRNA-SmpB to release stalled ribosomes from mRNA in the presence of rare codons (Keiler 2008). Shi et al. found that POA binds to RpsA of Mtb and disrupts the formation of RpsA–tmRNA complex (Shi et al. 2011) and mutations at the C-terminus of RpsA confer PZA resistance. The previous work reported the pyrazinoic acid-binding domain of RpsA (Yang et al. Mol Microbiol 95:791–803, 2015). However, the HSQC spectra of the isolated S1 domain does not overlap with that of MtRpsA280-438, suggesting that substantial interactions occur between the flexible C-terminus and the S1 domain in MtRpsA .To further study the PZA resistance and how substantial interactions influence/affect protein structure, using heteronuclear NMR spectroscopy, we have completed backbone and side-chain ¹H, ¹⁵N, ¹³C chemical shift assignments of MtRpsA280-438 which contains S1 domain and the flexible C-terminus. These NMR resonance assignments provide the framework for detailed characterization of the solution-state protein structure determination, dynamic studies of this domain, as well as NMR-based drug discovery efforts.     

Assessment of three indigenous South African herbivores as potential reservoirs and vectors of antibiotic-resistant <Emphasis Type="Italic">Escherichia coli</Emphasis>

Due to limited data available on the presence of antibiotic-resistant (ABR) bacteria in faeces of wild herbivores in South Africa, this study analysed resistance patterns for Escherichia coli isolates from wildebeest, zebra and giraffe in addition to pet and farm pig faeces. Total and faecal coliforms and E. coli were quantified in faecal matter using a most probable number (MPN) guideline procedure. Antibiotic resistance profiles against 12 selected antibiotics representing seven classes were determined for 30 randomly selected E. coli isolates from each animal using the European Committee on Antimicrobial Susceptibility Testing (EUCAST) disk diffusion procedure. While log₁₀ MPN values per gram of animal faeces for total/faecal coliforms ranged from 4.51/4.11 to 5.70/5.50, the E. coli MPN values were in a range of 3.43–5.14. The proportion of ABR E. coli isolates ranged from 43% (giraffe) to 93% (zebra). About 47% of E. coli isolates from zebra faeces were categorized as multidrug-resistant (MDR), while for wildebeest and giraffe, no MDR isolates were detected. In comparison, 10% of E. coli isolates from pet pig and about 7% from farm pig faeces were categorized as MDR. Although most MDR isolates were resistant to at least one β-lactam antibiotic, only one MDR isolate from farm pig faeces was resistant to both norfloxacin and ciprofloxacin, the two fluoroquinolones tested. However, no resistance was detected to the tested carbapenems and tigecycline. The results of this study indicate that indigenous South African herbivores may serve as potential reservoirs and vectors for the dissemination of ABR E. coli strains.