Structure and regulation of the anthranilate synthase genes in Pseudomonas aeruginosa: II. Cloning and expression in Escherichia coli

The genes for the large and small subunits of anthranilate synthase (trpE and trpG, respectively) have been cloned from Pseudomonas aeruginosa PAC174 into E. coli by R-prime formation with the broad-host- range plasmid R68.44. Sequential subcloning into plasmid vectors reduced the active Pseudomonas DNA fragment to a length of 3.1 kb. We obtained evidence that this region contains the promoter for its own expression and retains a vestigial regulatory response to tryptophan scarcity or excess.      

Genetic evidence of intercontinental movement of avian influenza in a migratory bird: the northern pintail (Anas acuta)

The role of migratory birds in the movement of the highly pathogenic (HP) avian influenza H5N1 remains a subject of debate. Testing hypotheses regarding intercontinental movement of low pathogenic avian influenza (LPAI) viruses will help evaluate the potential that wild birds could carry Asian-origin strains of HP avian influenza to North America during migration. Previous North American assessments of LPAI genetic variation have found few Asian reassortment events. Here, we present results from whole-genome analyses of LPAI isolates collected in Alaska from the northern pintail (Anas acuta), a species that migrates between North America and Asia. Phylogenetic analyses confirmed the genetic divergence between Asian and North American strains of LPAI, but also suggested inter-continental virus exchange and at a higher frequency than previously documented. In 38 isolates from Alaska, nearly half (44.7%) had at least one gene segment more closely related to Asian than to North American strains of LPAI. Additionally, sequences of several Asian LPAI isolates from GenBank clustered more closely with North American northern pintail isolates than with other Asian origin viruses. Our data support the role of wild birds in the intercontinental transfer of influenza viruses, and reveal a higher degree of transfer in Alaska than elsewhere in North America.     

Compositional difference of the exopolysaccharides produced by the virulent and virulence-deficient strains of Xanthomonas oryzae pv. oryzae

Xanthomonas oryzae pv. oryzae, the bacterial blight pathogen of rice, is known to produce phytotoxic polysaccharides. The extracellular polysaccharide (EPS) was isolated from virulent (BXO1) and virulence-deficient gum G mutant (BXO1002) strains of X. oryzae pv. oryzae and characterized using fourier transform infrared (FT-IR) and nuclear magnetic resonance (NMR). Data from the FT-IR suggested that the aldehyde (R-CHO) group and C=O of acid anhydride are present in BXO1 but absent in BXO1002. The (1)H-NMR spectra showed the presence of an acetyl amine of hexose or pentose, free amines of glucose, an beta-anomeric carbon of hexose and pentose, hydrogen next to hydroxyl group, an acetyl amine of hexose and pentose in the polysaccharides of both BXO1 and BXO1002, and the absence of alpha-anomeric carbon of hexose or pentose and the glucuronic acid in the polysaccharides produced by BXO1002. The test for glucuronic acid also confirmed the absence of glucuronic acid in the polysaccharides of BXO1002 and the presence glucuronic acid (32 microg/mg) in the polysaccharides produced by BXO1.     

Genome relationships in the genus Dasypyrum: evidence from molecular phylogenetic analysis and in situ hybridization

The genus Dasypyrum (or Haynaldia) consists of two species, D. villosum and D. breviaristatum. However, the genomic relationships between these two species remain unclear. The objective of this study was to provide molecular phylogenic and cytological evidence on the evolutionary relationships of the genus Dasypyrum. Sequences of Chloroplast DNA (cpDNA) and α-gliadin genes both support the hypothesis that diploid D. breviaristatum is the progenitor of tetraploid D. breviaristatum, and the diploid D. villosum and D. breviaristatum evolved parallel from an ancestral species. Genomic and fluorescence in situ hybridization using ribosomal DNA and rye repetitive DNA sequence as probes also indicated that tetraploid D. breviaristatum originated from diploid D. breviaristatum.     

Impact of single dose of diethylcarbamazine and other antifilarial drug combinations on bancroftian filarial infection variables: assessment after 2 years

The impact of single dose mass drug administration of diethylcarbamazine (DEC), DEC with albendazole (ALB), and ivermectin (IVR) with albendazole, was examined on the human bancroftian filarial infections in village scale trials in south India, from a follow-up study after 2 years. The treatment arms administered with DEC alone and DEC+ALB demonstrated long-term benefits in reducing microfilaraemia significantly (P<0.05), while antigenaemia reduction was negligible. The arm with ALB+IVR did not show such reductions. Among the antigenaemic and microfilaraemic individuals, 87% became amicrofilaraemic in DEC+ALB arm, which were higher than that observed in the other 2 treatment arms. Among amicrofilaraemics (but Ag+), nearly 35% cleared of infection in DEC+ALB, while 26% and 6% in DEC alone and IVR+ALB arms, respectively. The drug combination DEC+ALB was observed to demonstrate a significant impact in reducing filarial infection even after 2 years post treatment.     

A Cell Cycle and Nutritional Checkpoint Controlling Bacterial Surface Adhesion

In natural environments, bacteria often adhere to surfaces where they form complex multicellular communities. Surface adherence is determined by the biochemical composition of the cell envelope. We describe a novel regulatory mechanism by which the bacterium, Caulobacter crescentus, integrates cell cycle and nutritional signals to control development of an adhesive envelope structure known as the holdfast. Specifically, we have discovered a 68-residue protein inhibitor of holdfast development (HfiA) that directly targets a conserved glycolipid glycosyltransferase required for holdfast production (HfsJ). Multiple cell cycle regulators associate with the hfiA and hfsJ promoters and control their expression, temporally constraining holdfast development to the late stages of G1. HfiA further functions as part of a ‘nutritional override’ system that decouples holdfast development from the cell cycle in response to nutritional cues. This control mechanism can limit surface adhesion in nutritionally sub-optimal environments without affecting cell cycle progression. We conclude that post-translational regulation of cell envelope enzymes by small proteins like HfiA may provide a general means to modulate the surface properties of bacterial cells.     

Structure and Stability of Telocentric Chromosomes in Wheat

In most eukaryotes, centromeres assemble at a single location per chromosome. Naturally occurring telocentric chromosomes (telosomes) with a terminal centromere are rare but do exist. Telosomes arise through misdivision of centromeres in normal chromosomes, and their cytological stability depends on the structure of their kinetochores. The instability of telosomes may be attributed to the relative centromere size and the degree of completeness of their kinetochore. Here we test this hypothesis by analyzing the cytogenetic structure of wheat telosomes. We used a population of 80 telosomes arising from the misdivision of the 21 chromosomes of wheat that have shown stable inheritance over many generations. We analyzed centromere size by probing with the centromere-specific histone H3 variant, CENH3. Comparing the signal intensity for CENH3 between the intact chromosome and derived telosomes showed that the telosomes had approximately half the signal intensity compared to that of normal chromosomes. Immunofluorescence of CENH3 in a wheat stock with 28 telosomes revealed that none of the telosomes received a complete CENH3 domain. Some of the telosomes lacked centromere specific retrotransposons of wheat in the CENH3 domain, indicating that the stability of telosomes depends on the presence of CENH3 chromatin and not on the presence of CRW repeats. In addition to providing evidence for centromere shift, we also observed chromosomal aberrations including inversions and deletions in the short arm telosomes of double ditelosomic 1D and 6D stocks. The role of centromere-flanking, pericentromeric heterochromatin in mitosis is discussed with respect to genome/chromosome integrity.