The enterotoxin gene (cpe) of Clostridium perfringens can be chromosomal or plasmid-borne

The location of the cpe gene, encoding the enterotoxin responsible for food poisoning in humans, has been studied in a series of enterotoxigenic Ciostridium perfringens strains by means of pulsed field gel electrophoresis of genomic DNA. The cpe gene was found at the same chromosomal locus in strains associated with food poisoning in humans and was shown to be linked to a repetitive sequence, the Hin dlll repeat, and an open reading frame, ORF3, that may be part of an insertion sequence. In contrast, when the strains originated from domesticated livestock cpe was located on a large episome where it was often close to a copy of the transposable element IS 1151. In these cases, the Hin dlll repeat was not linked to the cpe gene although this was generally preceded by ORF3.     

Ants impact the composition of the aquatic macroinvertebrate communities of a myrmecophytic tank bromeliad

In an inundated Mexican forest, 89 out of 92 myrmecophytic tank bromeliads (Aechmea bracteata) housed an associated ant colony: 13 sheltered Azteca serica, 43 Dolichoderus bispinosus, and 33 Neoponera villosa. Ant presence has a positive impact on the diversity of the aquatic macroinvertebrate communities (n = 30 bromeliads studied). A Principal Component Analysis (PCA) showed that the presence and the species of ant are not correlated to bromeliad size, quantity of water, number of wells, filtered organic matter or incident radiation. The PCA and a generalized linear model showed that the presence of Azteca serica differed from the presence of the other two ant species or no ants in its effects on the aquatic invertebrate community (more predators). Therefore, both ant presence and species of ant affect the composition of the aquatic macroinvertebrate communities in the tanks of A. bracteata, likely due to ant deposition of feces and other waste in these tanks.     

Cell motility measurements with an automated microscope system

The motility of 3T3 cells has been studied using a newly developed automated microscope system which is capable of recognizing live unstained cells growing in tissue culture. A large number of individual cells can be rapidly identified and characterized and their precise positions recorded. All cells can be revisited automatically every few minutes, and the new cell positions can be determined. Quantitative data from up to 1 000 cells can then be obtained, and cell movement parameters like cell speed, distance travelled, direction of movement, etc., can be measured for individual cells and for the whole cell population. In addition, for any number of chosen cells, high-resolution digitized images can be taken for further morphological studies, including acquisition of images of individual cells.     

Esa1, an Arabidopsis mutant with enhanced susceptibility to a range of necrotrophic fungal pathogens, shows a distorted induction of defense responses by reactive oxygen generating compounds

An Arabidopsis thaliana mutant, esa1, that shows enhanced susceptibility to the necrotrophic pathogens Alternaria brassicicola, Botrytis cinerea and Plectosphaerella cucumerina, but has wild-type levels of resistance to the biotrophic pathogens Pseudomonas syringae pv. tomato and Peronospora parasitica. The enhanced susceptibility towards necrotrophic pathogens correlated with a delayed induction of phytoalexin accumulation and delayed induction of the plant defensin gene PDF1.2 upon inoculation with pathogens. Two reactive oxygen generating compounds, paraquat and acifluorfen, were found to cause induction of both phytoalexin accumulation and PDF1.2 expression in wild-type plants, but this induction was almost completely abolished in esa1. This finding suggests that esa1 may somehow be involved in transduction of signals generated by reactive oxygen species.     

Paleobot.org: establishing open-access online reference collections for archaeobotanical research

Difficulty in accessing high quality reference materials has been a limiting factor in the advancement of archaeobotanical research. However, new developments in online open source content management technology and faster downloading capabilities make high quality and low cost dynamic online curation of archaeobotanical reference images increasingly feasible. We describe the establishment of Paleobot.org, an open access online reference collection database for macrobotanical, microbotanical and isotopic data to help standardize and improve the identification of archaeobotanical remains.     

Host suitability, respiration rate and the outcome of larval competition in strains of the cowpea weevil, Callosobruchus maculatus

Abstract.  Variation between strains of Callosobruchus maculatus in several life-history traits is well known. Differences in functional anatomy of egg pores and larval respiration rates have also been reported in strains from Brazil and Yemen. The response of five strains of C. maculatus to seeds of two host species, cowpea ( Vigna unguiculata ) and mung bean ( Vigna radiata ), was measured along with the larval respiration rates of the same strains on both hosts. There was significant variability of response to the two hosts. Strains with higher larval respiration rate (µL O₂/insect/day) showed higher seed consumption, which significantly affected adult emergence per seed on both hosts. This finding provides support for the hypothesis that differential feeding rate is an important mechanistic component of the larval competition outcome observed in strains of C. maculatus .     

3D nuclear organization of telomeres in the Hodgkin cell lines U-HO1 and U-HO1-PTPN1: PTPN1 expression prevents the formation of very short telomeres including "t-stumps"

Background  

In cancer cells the three-dimensional (3D) telomere organization of interphase nuclei into a telomeric disk is heavily distorted and aggregates are found. In Hodgkin's lymphoma quantitative FISH (3D Q-FISH) reveals a major impact of nuclear telomere dynamics during the transition form mononuclear Hodgkin (H) to diagnostic multinuclear Reed-Sternberg (RS) cells. In vitro and in vivo formation of RS-cells is associated with the increase of very short telomeres including "t-stumps", telomere loss, telomeric aggregate formation and the generation of "ghost nuclei".