The bcr1 DNA repeat element is specific to the Bacillus cereus group and exhibits mobile element characteristics

Bacillus cereus strains ATCC 10987 and ATCC 14579 harbor an approximately 155-bp repeated element, bcr1, which is conserved in B. cereus, B. anthracis, B. thuringiensis, and B. mycoides but not in B. subtilis and B. licheniformis. In this study, we show by Southern blot hybridizations that bcr1 is present in all 54 B. cereus group strains tested but absent in 11 Bacillus strains outside the group, suggesting that bcr1 may be specific and ubiquitous to the B. cereus group. By comparative analysis of the complete genome sequences of B. cereus ATCC 10987, B. cereus ATCC 14579, and B. anthracis Ames, we show that bcr1 is exclusively present in the chromosome but absent from large plasmids carried by these strains and that the numbers of full-length bcr1 repeats for these strains are 79, 54, and 12, respectively. Numerous copies of partial bcr1 elements are also present in the three genomes (91, 128, and 53, respectively). Furthermore, the genomic localization of bcr1 is not conserved between strains with respect to chromosomal position or organization of gene neighbors, as only six full-length bcr1 loci are common to at least two of the three strains. However, the intergenic sequence surrounding a specific bcr1 repeat in one of the three strains is generally strongly conserved in the other two, even in loci where bcr1 is found exclusively in one strain. This finding indicates that bcr1 either has evolved by differential deletion from a very high number of repeats in a common ancestor to the B. cereus group or is moving around the chromosome. The identification of bcr1 repeats interrupting genes in B. cereus ATCC 10987 and ATCC 14579 and the presence of a flanking TTTAT motif in each end show that bcr1 exhibits features characteristic of a mobile element.     

Characterization of a prokaryotic haemerythrin from the methanotrophic bacterium Methylococcus capsulatus (Bath)

For a long time, the haemerythrin family of proteins was considered to be restricted to only a few phyla of marine invertebrates. When analysing differential protein expression in the methane-oxidizing bacterium, Methylococcus capsulatus (Bath), grown at a high and low copper-to-biomass ratio, respectively, we identified a putative prokaryotic haemerythrin expressed in high-copper cultures. Haemerythrins are recognized by a conserved sequence motif that provides five histidines and two carboxylate ligands which coordinate two iron atoms. The diiron site is located in a hydrophobic pocket and is capable of binding O(2). We cloned the M. capsulatus haemerythrin gene and expressed it in Escherichia coli as a fusion protein with NusA. The haemerythrin protein was purified to homogeneity cleaved from its fusion partner. Recombinant M. capsulatus haemerythrin (McHr) was found to fold into a stable protein. Sequence similarity analysis identified all the candidate residues involved in the binding of diiron (His22, His58, Glu62, His77, His81, His117, Asp122) and the amino acids forming the hydrophobic pocket in which O(2) may bind (Ile25, Phe59, Trp113, Leu114, Ile118). We were also able to model a three-dimensional structure of McHr maintaining the correct positioning of these residues. Furthermore, UV/vis spectrophotometric analysis demonstrated the presence of conjugated diiron atoms in McHr. A comprehensive genomic database search revealed 21 different prokaryotes containing the haemerythrin signature (PROSITE 00550), indicating that these putative haemerythrins may be a conserved prokaryotic subfamily.     

High resolution DNA flow cytometry of boar sperm cells in identification of boars carrying cytogenetic aberrations

The cytogenetic quality of boars used for breeding determines the litter outcome and thus has large economical consequences. Traditionally, quality controls based on the examination of simple karyograms are time consuming and sometimes give uncertain results. As an alternative, the use of high-resolution DNA flow cytometry on DAPI-stained sperm cell nuclei (CV 相似文献   

Effects of Rhizoctonia infection and drought on peroxidase and chitinase activity in Norway spruce (Picea abies)

Seedlings of Norway spruce were exposed to fungal infection and drought in order to investigate differences in their stress responses on the enzymatic level. Six-week-old seedlings were infected with the root rot fungus Rhizoctonia , or subjected to drought, respectively. Changes at the enzymatic level were more rapid and significantly higher in infected plants in comparison with drought-stressed spruce plants. Rhizoctonia infection resulted in early local and systemic increase in peroxidase and chitinase activity. The most prominent isoforms responding were highly basic peroxidases and chitinases (pI 9–9.5) and several acidic chitinases (pI3–4). An increased intensity of similar peroxidase isoforms was found in drought-affected plants. Two peroxidase isoforms (with pI < 9) accumulated exclusively in response to drought. These results suggest that at an early stage of infection and drought stress, the two stresses can be distinguished by the temporal appearance and isoform profile of peroxidases and chitinases. Changes in enzyme activity appeared before changes in physiological parameters, thus these isoform profiles could be used as early markers of stress conditions in spruce.     

Novel insights into the use of Glowing LNA as nucleic acid detection probes--influence of labeling density and nucleobases

Appropriately designed 2'-N-(pyren-1-yl)carbonyl-2'-amino-LNA (locked nucleic acid) display large increases in fluorescence intensity and remarkably high quantum yields upon hybridization with nucleic acid targets. Thermal denaturation and fluorescence spectroscopy studies on ONs modified with known thymine monomer X and novel 5-methylcytosine monomer Y provide new insights into the design principles and mechanism of these Glowing LNA nucleic acid detection probes.     

Missing saiga on the taiga

Conservation biologists understand that linking demographic histories of species at risk with causal biotic and abiotic events should help us predict the effects of ongoing biotic and abiotic change. In parallel, researchers have started to use ancient genetic information (aDNA) to explore the demographic histories of a number of species present in the Pleistocene fossil record (see, e.g. Shapiro et al. 2004). However, aDNA studies have primarily focused on identifying long-term population trends, linked to climate variability and the role of early human activity. Population trends over more recent time, e.g. during the Holocene, have been poorly explored, partly owing to analytical limitations. In this issue, Campos et al. (2010a) highlight the potential of aDNA to investigate demographic patterns over such recent time periods for the compelling and endangered saiga antelope Saiga tatarica (Fig. 1). The time may come when past and current demography can be combined to produce a seamless record. [Figure: see text].