Ida K. Hegna

Bio: Ida K. Hegna is an academic researcher from University of Oslo. The author has contributed to research in topics: Bacillus cereus & Cereus. The author has an hindex of 11, co-authored 25 publications receiving 1643 citations.

Bacillus anthracis, Bacillus cereus, and Bacillus thuringiensis—One Species on the Basis of Genetic Evidence

Abstract: Bacillus anthracis, Bacillus cereus, and Bacillus thuringiensis are members of the Bacillus cereus group of bacteria, demonstrating widely different phenotypes and pathological effects. B. anthracis causes the acute fatal disease anthrax and is a potential biological weapon due to its high toxicity. B. thuringiensis produces intracellular protein crystals toxic to a wide number of insect larvae and is the most commonly used biological pesticide worldwide. B. cereus is a probably ubiquitous soil bacterium and an opportunistic pathogen that is a common cause of food poisoning. In contrast to the differences in phenotypes, we show by multilocus enzyme electrophoresis and by sequence analysis of nine chromosomal genes that B. anthracis should be considered a lineage of B. cereus. This determination is not only a formal matter of taxonomy but may also have consequences with respect to virulence and the potential of horizontal gene transfer within the B. cereus group.

The Bacillus cereus group: novel aspects of population structure and genome dynamics.

Abstract: Aims: To provide new insights into the population and genomic structure of the Bacillus cereus group of bacteria. Methods and Results: The genetic relatedness among B. cereus group strains was assessed by multilocus sequence typing (MLST) using an optimized scheme based on seven chromosomal housekeeping genes. A set of 48 strains from different clinical sources was included, and six clonal complexes containing several genetically similar isolates from unrelated patients were identified. Interestingly, several clonal groups contained strains that were isolated from similar human sources. Furthermore, comparative whole genome sequence analysis of 16 strains led to the discovery of novel ubiquitous genome features of the B. cereus group, such as atypical group II introns, IStrons, and hitherto uncharacterized repeated elements. Conclusions: The B. cereus group constitutes a coherent population unified by the presence of ubiquitous and specific genetic elements which do not show any pattern, either in their sequences or genomic locations, which allows to differentiate between the member species of the group. Nevertheless, the population is very dynamic, as particular lineages of clinical origin can evolve to form clonal complexes. At the genome level, the dynamic behaviour is indicated by the presence of numerous mobile and repeated elements. Significance and Impact of the Study: The B. cereus group of bacteria comprises species that are of medical and economic importance. The MLST data, along with the primers and protocols used, will be available in a public, web-accessible database (http://mlstoslo.uio.no).

Genetic diversity of Bacillus cereus B-thuringiensis isolates from natural sources

Abstract: The genetic diversity and relationships among 154 Bacillus cereus/B. thuringiensis isolates recovered from soil samples from five geographic areas in Norway were investigated with multilocus enzyme electrophoresis (MEE). Cluster analysis revealed two major groups (designated cluster I and cluster II) separated at genetic distance greater than 0.55. Cluster I included 62 electrophoretic types (ETs) originating from all five locations, whereas, in cluster II, all but one isolate were from the same location. The isolates were also serotyped with B. thuringiensis flagellar antisera, and 28 distinct serotypes were identified. In general, serotyping did not show correlation to the genetic diversity of the isolates. The presence of IS231- and IS240-like transposable elements was detected in 14% of the strains of cluster II only. Parasporal crystals were observed in three strains; ten other strains were toxic to Trichoplusia ni. We conclude that B. cereus/B. thuringiensis from soil exhibit a high degree of recombination.

Characterization of a broad range antimicrobial substance from Bacillus cereus

Abstract: Aims: The aim of this research was to isolate and characterize an antimicrobial substance from the Bacillus cereus type strain ATCC 14579. Methods and Results: A substance with antimicrobial activity was isolated from B. cereus ATCC 14579. The substance was produced during late exponential growth and well into the stationary phase with a maximum 9 h after inoculation. The inhibitory substance was purified by reverse-phase HPLC and shown to be highly active against closely related Bacillus spp. Clinically relevant species such as Staphylococcus aureus and Micrococcus luteus were also inhibited. The substance was characterized as a bacteriocin-like inhibitory substance (BLIS) with a molecular mass of ca 3·4 kDa. The BLIS was very heat stable, and sensitive only to pronase E and proteinase K. Antimicrobial activity was stable and high in the pH range of 2·0–9·0, and relatively unaffected by organic chemicals. Conclusions: An antimicrobial substance produced by the B. cereus type strain ATCC 14579 was characterized, with a wide spectrum of activity and the potential to be applied as a control agent against pathogenic bacteria. Significance and Impact of the Study: The present study is the first report of a substance with antimicrobial activity from the B. cereus type strain.

Genome organization is not conserved between Bacillus cereus and Bacillus subtilis.

Abstract: The opportunistic pathogen Bacillus cereus is the genetically stable member of a group of closely related bacteria including the insect pathogen Bacillus thuringiensis and the mammalian pathogen Bacillus anthracis. Physical maps of B. cereus and B. thuringiensis strains show considerable variations in discrete parts of the chromosome, suggesting that certain genome regions are more prone to rearrangements. B. cereus belongs to the same subgroup of Bacillus species as Bacillus subtilis, by both phenotypic and rRNA sequence classification. The analysis of 80 kb of genome sequence sampled from different regions of the B. cereus ATCC 10987 chromosome is reported. Analysis of the sequence and comparison of the localization of the putative genes with that of B. subtilis orthologues show the following: (1) gene organization is not conserved between B. cereus and B. subtilis; (2) several putative genes are more closely related to genes from other bacteria and archaea than to B. subtilis, or may be absent in B. subtilis 168; (3) B. cereus contains a 155 bp repetitive sequence that is not present in B. subtilis. By hybridization, this repeat is present in all B. cereus and B. thuringiensis strains so far investigated.

Isolation and characterization

Abstract: Isolation and Maintenance.- Isolation and Differentiation of Medaka Embryonic Stem Cells.- Maintenance of Chicken Embryonic Stem Cells In Vitro.- Derivation and Culture of Mouse Trophoblast Stem Cells In Vitro.- Derivation, Maintenance, and Characterization of Rat Embryonic Stem Cells In Vitro.- Derivation, Maintenance, and Induction of the Differentiation In Vitro of Equine Embryonic Stem Cells.- Generation and Characterization of Monkey Embryonic Stem Cells.- Derivation and Propagation of Embryonic Stem Cells in Serum- and Feeder-Free Culture.- Signaling in Embryonic Stem Cell Differentiation.- Internal Standards in Differentiating Embryonic Stem Cells In Vitro.- Matrix Assembly, Cell Polarization, and Cell Survival.- Phosphoinositides, Inositol Phosphates, and Phospholipase C in Embryonic Stem Cells.- Cripto Signaling in Differentiating Embryonic Stem Cells.- The Use of Embryonic Stem Cells to Study Hedgehog Signaling.- Transfection and Promoter Analysis in Embryonic Stem Cells.- SAGE Analysis to Identify Embryonic Stem Cell-Predominant Transcripts.- Utilization of Digital Differential Display to Identify Novel Targets of Oct3/4.- Gene Silencing Using RNA Interference in Embryonic Stem Cells.- Genetic Manipulation of Embryonic Stem Cells.- Efficient Transfer of HSV-1 Amplicon Vectors Into Embryonic Stem Cells and Their Derivatives.- Lentiviral Vector-Mediated Gene Transfer in Embryonic Stem Cells.- Use of the Cytomegalovirus Promoter for Transient and Stable Transgene Expression in Mouse Embryonic Stem Cells.- Use of Simian Immunodeficiency Virus Vectors for Simian Embryonic Stem Cells.- Generation of Green Fluorescent Protein-Expressing Monkey Embryonic Stem Cells.- DNA Damage Response and Mutagenesis in Mouse Embryonic Stem Cells.- Ultraviolet-Induced Apoptosis in Embryonic Stem Cells In Vitro.- Use of Embryonic Stem Cells in Pharmacological and Toxicological Screens.- Use of Differentiating Embryonic Stem Cells in Pharmacological Studies.- Embryonic Stem Cells as a Source of Differentiated Neural Cells for Pharmacological Screens.- Use of Murine Embryonic Stem Cells in Embryotoxicity Assays.- Use of Chemical Mutagenesis in Mouse Embryonic Stem Cells.- Epigenetic Analysis of Embryonic Stem Cells.- Nuclear Reprogramming of Somatic Nucleus Hybridized With Embryonic Stem Cells by Electrofusion.- Methylation in Embryonic Stem Cells In Vitro.- Tumor-Like Properties.- Identification of Genes Involved in Tumor-Like Properties of Embryonic Stem Cells.- In Vivo Tumor Formation From Primate Embryonic Stem Cells.- Animal Models and Therapy.- Directed Differentiation and Characterization of Genetically Modified Embryonic Stem Cells for Therapy.- Use of Differentiating Embryonic Stem Cells in the Parkinsonian Mouse Model.

Improved metagenomic analysis with Kraken 2.

Abstract: Although Kraken’s k-mer-based approach provides a fast taxonomic classification of metagenomic sequence data, its large memory requirements can be limiting for some applications. Kraken 2 improves upon Kraken 1 by reducing memory usage by 85%, allowing greater amounts of reference genomic data to be used, while maintaining high accuracy and increasing speed fivefold. Kraken 2 also introduces a translated search mode, providing increased sensitivity in viral metagenomics analysis.

Image Processing

Abstract: MUCKE aims to mine a large volume of images, to structure them conceptually and to use this conceptual structuring in order to improve large-scale image retrieval. The last decade witnessed important progress concerning low-level image representations. However, there are a number problems which need to be solved in order to unleash the full potential of image mining in applications. The central problem with low-level representations is the mismatch between them and the human interpretation of image content. This problem can be instantiated, for instance, by the incapability of existing descriptors to capture spatial relationships between the concepts represented or by their incapability to convey an explanation of why two images are similar in a content-based image retrieval framework. We start by assessing existing local descriptors for image classification and by proposing to use co-occurrence matrices to better capture spatial relationships in images. The main focus in MUCKE is on cleaning large scale Web image corpora and on proposing image representations which are closer to the human interpretation of images. Consequently, we introduce methods which tackle these two problems and compare results to state of the art methods. Note: some aspects of this deliverable are withheld at this time as they are pending review. Please contact the authors for a preview.

Bacillus anthracis, Bacillus cereus, and Bacillus thuringiensis—One Species on the Basis of Genetic Evidence

Abstract: Bacillus anthracis, Bacillus cereus, and Bacillus thuringiensis are members of the Bacillus cereus group of bacteria, demonstrating widely different phenotypes and pathological effects. B. anthracis causes the acute fatal disease anthrax and is a potential biological weapon due to its high toxicity. B. thuringiensis produces intracellular protein crystals toxic to a wide number of insect larvae and is the most commonly used biological pesticide worldwide. B. cereus is a probably ubiquitous soil bacterium and an opportunistic pathogen that is a common cause of food poisoning. In contrast to the differences in phenotypes, we show by multilocus enzyme electrophoresis and by sequence analysis of nine chromosomal genes that B. anthracis should be considered a lineage of B. cereus. This determination is not only a formal matter of taxonomy but may also have consequences with respect to virulence and the potential of horizontal gene transfer within the B. cereus group.

From soil to gut: Bacillus cereus and its food poisoning toxins

Abstract: Bacillus cereus is widespread in nature and frequently isolated from soil and growing plants, but it is also well adapted for growth in the intestinal tract of insects and mammals. From these habitats it is easily spread to foods, where it may cause an emetic or a diarrhoeal type of food-associated illness that is becoming increasingly important in the industrialized world. The emetic disease is a food intoxication caused by cereulide, a small ring-formed dodecadepsipeptide. Similar to the virulence determinants that distinguish Bacillus thuringiensis and Bacillus anthracis from B. cereus, the genetic determinants of cereulide are plasmid-borne. The diarrhoeal syndrome of B. cereus is an infection caused by vegetative cells, ingested as viable cells or spores, thought to produce protein enterotoxins in the small intestine. Three pore-forming cytotoxins have been associated with diarrhoeal disease: haemolysin BL (Hbl), nonhaemolytic enterotoxin (Nhe) and cytotoxin K. Hbl and Nhe are homologous three-component toxins, which appear to be related to the monooligomeric toxin cytolysin A found in Escherichia coli. This review will focus on the toxins associated with foodborne diseases frequently caused by B. cereus. The disease characteristics are described, and recent findings regarding the associated toxins are discussed, as well as the present knowledge on virulence regulation.