Efficacy of indigenous predatory mites (Acari: Phytoseiidae) against the citrus rust mite Phyllocoptruta oleivora (Acari: Eriophyidae): augmentation and conservation biological control in Israeli citrus orchards

The citrus rust mite (CRM), Phyllocoptruta oleivora (Acari: Eriophyidae) is a cosmopolitan key pest of citrus, inflicting severe economic damage if not controlled. In Israel, CRM damages all citrus cultivars. International regulation and increasing control failures of CRM led growers to seek sustainable biological control solutions such as acarine biological control agents. Laboratory studies conducted in Israel have indicated that the indigenous predator species Amblyseius swirskii, Iphiseius degenerans, Typhlodromus athiasae and Euseius scutalis (all Acari: Phytoseiidae) can potentially control CRM. Our general objective in the present study was to bridge the gap of knowledge between laboratory studies and the lack of control efficacy of these species in commercial orchards. Predator augmentation in the field showed that although predator populations increased immediately following releases they later decreased and did not affect CRM populations. When A. swirskii augmentation was combined with a series of maize pollen applications, A. swirskii populations were enhanced substantially and continuously but again CRM populations were not affected. Growth chamber studies with CRM-infested seedlings, with or without a maize pollen supplement, indicated that pollen provisioning led to population increase of E. scutalis and A. swirskii but only E. scutalis significantly lowered CRM populations. Control with E. scutalis was confirmed in the field on CRM infested seedlings with pollen provisioned by adjacent flowering Rhodes grass. While experiments in mature citrus orchard showed that pollen supplement usually increased predator populations they also indicated that other factors such as intraguild interactions and pesticide treatments should be taken into account when devising CRM biological control programs.     

Bacterial genomes in epidemiology—present and future

Sequence data are well established in the reconstruction of the phylogenetic and demographic scenarios that have given rise to outbreaks of viral pathogens. The application of similar methods to bacteria has been hindered in the main by the lack of high-resolution nucleotide sequence data from quality samples. Developing and already available genomic methods have greatly increased the amount of data that can be used to characterize an isolate and its relationship to others. However, differences in sequencing platforms and data analysis mean that these enhanced data come with a cost in terms of portability: results from one laboratory may not be directly comparable with those from another. Moreover, genomic data for many bacteria bear the mark of a history including extensive recombination, which has the potential to greatly confound phylogenetic and coalescent analyses. Here, we discuss the exacting requirements of genomic epidemiology, and means by which the distorting signal of recombination can be minimized to permit the leverage of growing datasets of genomic data from bacterial pathogens.     

LAB-1 Targets PP1 and Restricts Aurora B Kinase upon Entrance into Meiosis to Promote Sister Chromatid Cohesion

Successful execution of the meiotic program depends on the timely establishment and removal of sister chromatid cohesion. LAB-1 has been proposed to act in the latter by preventing the premature removal of the meiosis-specific cohesin REC-8 at metaphase I in C. elegans, yet the mechanism and scope of LAB-1 function remained unknown. Here we identify an unexpected earlier role for LAB-1 in promoting the establishment of sister chromatid cohesion in prophase I. LAB-1 and REC-8 are both required for the chromosomal association of the cohesin complex subunit SMC-3. Depletion of lab-1 results in partial loss of sister chromatid cohesion in rec-8 and coh-4 coh-3 mutants and further enhanced chromatid dissociation in worms where all three kleisins are mutated. Moreover, lab-1 depletion results in increased Aurora B kinase (AIR-2) signals in early prophase I nuclei, coupled with a parallel decrease in signals for the PP1 homolog, GSP-2. Finally, LAB-1 directly interacts with GSP-1 and GSP-2. We propose that LAB-1 targets the PP1 homologs to the chromatin at the onset of meiosis I, thereby antagonizing AIR-2 and cooperating with the cohesin complex to promote sister chromatid association and normal progression of the meiotic program.     

Neuroblastoma Cell Lines Contain Pluripotent Tumor Initiating Cells That Are Susceptible to a Targeted Oncolytic Virus

Background

Although disease remission can frequently be achieved for patients with neuroblastoma, relapse is common. The cancer stem cell theory suggests that rare tumorigenic cells, resistant to conventional therapy, are responsible for relapse. If true for neuroblastoma, improved cure rates may only be achieved via identification and therapeutic targeting of the neuroblastoma tumor initiating cell. Based on cues from normal stem cells, evidence for tumor populating progenitor cells has been found in a variety of cancers.

Methodology/Principal Findings

Four of eight human neuroblastoma cell lines formed tumorspheres in neural stem cell media, and all contained some cells that expressed neurogenic stem cell markers including CD133, ABCG2, and nestin. Three lines tested could be induced into multi-lineage differentiation. LA-N-5 spheres were further studied and showed a verapamil-sensitive side population, relative resistance to doxorubicin, and CD133+ cells showed increased sphere formation and tumorigenicity. Oncolytic viruses, engineered to be clinically safe by genetic mutation, are emerging as next generation anticancer therapeutics. Because oncolytic viruses circumvent typical drug-resistance mechanisms, they may represent an effective therapy for chemotherapy-resistant tumor initiating cells. A Nestin-targeted oncolytic herpes simplex virus efficiently replicated within and killed neuroblastoma tumor initiating cells preventing their ability to form tumors in athymic nude mice.

Conclusions/Significance

These results suggest that human neuroblastoma contains tumor initiating cells that may be effectively targeted by an oncolytic virus.     

Identification of pathogenic bacteria in blood cultures: Comparison between conventional and PCR methods

Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa, Acinetobacter baumanii, and Klebsiella pneumoniae were found to be the most prevalent bacteremia-causing bacteria in a survey in a medical center. A PCR method for identification of these five most common pathogens in blood cultures was developed. A unique sequence was chosen for each pathogen and used for primer design. Sixty-one blood samples (from hospitalized patients) in which bacterial growth was detected were processed in parallel by conventional microbiological methods and by the PCR method. The results obtained by PCR were identical to those obtained by conventional methods in 93.4% of the cases. PCR failed to identify bacteria which were found conventionally in only 6.6% of the cases (mostly bacteria not included in the PCR cassette). Another group of eighty-eight blood samples from patients were processed immediately upon their arrival at the laboratory by taking aliquots for the PCR method. The blood sample bottles were processed in parallel by conventional methods. In 78.4% of the cases the results of both methods were identical. In 12.5% of the cases, PCR afforded identification of bacteria but conventional methods showed no bacteria in the sample. On the other hand, PCR afforded 9.1% negative results while conventional methods identified bacteria not included in the PCR cassette. It is concluded that the molecular method appears to be a specific and precise method for identifying pathogenic bacteria in blood samples.     

Molecular features of heterogeneous vancomycin-intermediate Staphylococcus aureus strains isolated from bacteremic patients

Background  

Heterogeneous vancomycin-intermediate Staphylococcus aureus (hVISA) bacteremia is an emerging infection. Our objective was to determine the molecular features of hVISA strains isolated from bacteremic patients and to compare them to methicillin resistant S. aureus (MRSA) and methicillin sensitive S. aureus (MSSA) blood isolates.     

Conservation of expression and sequence of metabolic genes is reflected by activity across metabolic states

Variation in gene expression levels on a genomic scale has been detected among different strains, among closely related species, and within populations of genetically identical cells. What are the driving forces that lead to expression divergence in some genes and conserved expression in others? Here we employ flux balance analysis to address this question for metabolic genes. We consider the genome-scale metabolic model of Saccharomyces cerevisiae, and its entire space of optimal and near-optimal flux distributions. We show that this space reveals underlying evolutionary constraints on expression regulation, as well as on the conservation of the underlying gene sequences. Genes that have a high range of optimal flux levels tend to display divergent expression levels among different yeast strains and species. This suggests that gene regulation has diverged in those parts of the metabolic network that are less constrained. In addition, we show that genes that are active in a large fraction of the space of optimal solutions tend to have conserved sequences. This supports the possibility that there is less selective pressure to maintain genes that are relevant for only a small number of metabolic states.     

Nucleotide binding and hydrolysis induces a disorder-order transition in the kinesin neck-linker region

Kinesin translocation is thought to occur by a conformational change in a region of the motor domain called the neck linker. However, most evidence supporting this hypothesis comes from monomeric constructs unable to move processively. To address this issue, we investigated the neck-linker configuration on microtubule-bound monomeric and dimeric kinesin constructs using single-molecule fluorescence polarization microscopy. We found that the neck-linker region (i) is very mobile in the absence of nucleotides and during steady walking, (ii) decreases mobility and aligns along the microtubule axis in the presence of AMPPNP or ADP + AlF4(-), (iii) is mostly ordered in the monomeric constructs in the presence of ADP + AlF4(-), and (iv) is closer to parallel to the microtubule axis in the dimeric constructs. These results support the proposed role of the neck linker and suggest a coordination mechanism between the two motor domains in the dimer.