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Genomic Diversity of Burkholderia pseudomallei Clinical Isolates: Subtractive Hybridization Reveals a Burkholderia mallei-Specific Prophage in B . pseudomallei 1026b. David DeShazer, 2004.Burkholderia pseudomallei is the etiologic agent of the disease melioidosis and is a category B biological threat agent . The genomic sequence of B . pseudomallei K96243 was recently determined, but little is known about the overall genetic diversity of this species . Suppression subtractive hybridization was employed to assess the genetic variability between two distinct clinical isolates of B . pseudomallei, 1026b and K96243 . Numerous mobile genetic elements, including a temperate bacteriophage designated  1026b,
were identified among the 1026b-specific suppression subtractive
hybridization products . Bacteriophage
1026b
was spontaneously produced by 1026b, and it had a restricted host
range, infecting only Burkholderia mallei . It possessed a
noncontractile tail, an isometric head, and a linear 54,865-bp
genome . The mosaic nature of the
1026b
genome was revealed by comparison with bacteriophage
E125,
a B . mallei-specific bacteriophage produced by Burkholderia
thailandensis . The
1026b
genes for DNA packaging, tail morphogenesis, host lysis, integration,
and DNA replication were nearly identical to the corresponding
genes in
E125 .
On the other hand,
1026b
genes involved in head morphogenesis were similar to head
morphogenesis genes encoded by Pseudomonas putida and
Pseudomonas aeruginosa bacteriophages . Consistent with this
observation, immunogold electron microscopy demonstrated that
polyclonal antiserum against
E125
reacted with the tail of
1026b
but not with the head . The results presented here suggest that B .
pseudomallei strains are genetically heterogeneous and that
bacteriophages are major contributors to the genomic diversity of
this species . The bacteriophage characterized in this study may be a
useful diagnostic tool for differentiating B . pseudomallei and
B . mallei, two closely related biological threat agents .
veA Is Required for Toxin and Sclerotial Production in Aspergillus parasiticus. Ana M. Calvo, 2004.It was long been noted that secondary metabolism is associated with fungal development . In Aspergillus nidulans, conidiation and mycotoxin production are linked by a G protein signaling pathway . Also in A . nidulans, cleistothecial development and mycotoxin production are controlled by a gene called veA . Here we report the characterization of a veA ortholog in the aflatoxin-producing fungus A . parasiticus . Cleistothecia are not produced by Aspergillus parasiticus; instead, this fungus produces spherical structures called sclerotia that allow for survival under adverse conditions . Deletion of veA from A . parasiticus resulted in the blockage of sclerotial formation as well as a blockage in the production of aflatoxin intermediates . Our results indicate that A . parasiticus veA is required for the expression of aflR and aflJ, which regulate the activation of the aflatoxin gene cluster . In addition to these findings, we observed that deletion of veA reduced conidiation both on the culture medium and on peanut seed . The fact that veA is necessary for conidiation, production of resistant structures, and aflatoxin biosynthesis makes veA a good candidate gene to control aflatoxin biosynthesis or fungal development and in this way to greatly decrease its devastating impact on health and the economy . Structural and Genetic Analysis of the BldB Protein of Streptomyces coelicolor. Marcus Eccleston, 2002.We have demonstrated that the bldB gene of Streptomyces coelicolor is required for the formation of aerial hyphae and the synthesis of antibiotics . We also found that BldB forms a higher-order complex (most likely a dimer) and that amino acid residues 20 to 78 are important for this interaction . This region is conserved in the BldB family, suggesting that dimer formation may be a common feature of these proteins . RmpA2, an Activator of Capsule Biosynthesis in Klebsiella pneumoniae CG43, Regulates K2 cps Gene Expression at the Transcriptional Level. Yi-Chyi Lai, 2003.The rmpA2 gene, which encodes an activator for capsular polysaccharide (CPS) synthesis, was isolated from a 200-kb virulence plasmid of Klebsiella pneumoniae CG43 . Based on the sequence homology with LuxR at the carboxyl-terminal DNA-binding motif, we hypothesized that RmpA2 exerts its effect by activating the expression of cps genes that are responsible for CPS biosynthesis . Two luxAB transcriptional fusions, each containing a putative promoter region of the K . pneumoniae K2 cps genes, were constructed and were found to be activated in the presence of multicopy rmpA2 . The activation is likely due to direct binding of RmpA2 to the cps gene promoter through its C-terminal DNA binding motif . Moreover, the loss of colony mucoidy in a K . pneumoniae strain deficient in RcsB, a regulator for cps gene expression, could be recovered by complementing the strain with a multicopy plasmid carrying rmpA2 . The CPS production in Lon protease-deficient K . pneumoniae significantly increased, and the effect was accompanied by an increase of RmpA2 stability . The expression of the rmpA2 gene was negatively autoregulated and could be activated when the organism was grown in M9 minimal medium . An IS3 element located upstream of the rmpA2 was required for the full activation of the rmpA2 promoter . In summary, our results suggest that the enhancement of K2 CPS synthesis in K . pneumoniae CG43 by RmpA2 can be attributed to its transcriptional activation of K2 cps genes, and the expression level of rmpA2 is autoregulated and under the control of Lon protease . Enumeration of Bifidobacteria in Gastrointestinal Samples from Piglets. Lene Lind Mikkelsen, 2003.The population of Bifidobacterium spp . in fecal samples from suckling piglets was investigated, and Beerens, raffinose-bifidobacterium (RB), and modified Wilkins-Chalgren (MW) agar media were evaluated with regard to the enumeration of bifidobacteria in porcine intestinal samples . The results demonstrated that the population of bifidobacteria in the feces of suckling piglets is numerically low, and a phylogenetic analysis of the 16S rRNA gene from bifidobacterial isolates suggested that a possibly new Bifidobacterium species was isolated . Beerens, RB, and MW agar media were not selective for bifidobacteria in the fecal samples . The highest recovery and diversity of bifidobacteria were obtained for MW agar . Nonbifidobacterial isolates from the three agar media were identified and may contribute to the future formulation of improved selective media for the enumeration of bifidobacteria . Petroleum Pollution Bioremediation Using Water-Insoluble Uric Acid as the Nitrogen Source. Omry Koren, 2003.The biodegradation of hydrocarbon pollutants in open systems is limited by the availability of a utilizable nitrogen source . This limitation can be overcome by using uric acid . Enrichment cultures grown on crude oil-uric acid media yielded mixed and pure cultures that degraded petroleum . In a simulated open system, uric acid bound to crude oil and was available for bacterial growth and petroleum biodegradation .
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