Antilipopolysaccharide II: an antibody protective against fatal melioidosis.
(33/1391)
This was a study of IgG antibody responses to two S-type lipopolysaccharides (LPS I and LPS II) and flagellin of Burkholderia pseudomallei in patients with melioidosis. The specificity of these antibodies was 91.7%, 90.3%, and 93.8%, respectively, when compared to responses in a population where the organism is not endemic. Only the level of antibody to LPS II (anti-LPS II) was significantly higher in patients who survived than in those who died, as well as in patients with nonsepticemic vs. septicemic melioidosis. Results of logistic regression analysis, controlled for confounding factors such as duration of illness before treatment and bacteremic status, confirmed that a high level of anti-LPS II was a significant factor protective against fatal melioidosis. Thus, LPS II of B. pseudomallei would be a potentially useful component of a vaccine developed against fatal melioidosis. Further studies are in progress to determine the level of this antibody among those with asymptomatic infection in areas where melioidosis is endemic. (+info)
Multiple control of flagellum biosynthesis in Escherichia coli: role of H-NS protein and the cyclic AMP-catabolite activator protein complex in transcription of the flhDC master operon.
(34/1391)
Little is known about the molecular mechanism by which histone-like nucleoid-structuring (H-NS) protein and cyclic AMP-catabolite activator protein (CAP) complex control bacterial motility. In the present paper, we show that crp and hns mutants are nonmotile due to a complete lack of flagellin accumulation. This results from a reduced expression in vivo of fliA and fliC, which encode the specific flagellar sigma factor and flagellin, respectively. Overexpression of the flhDC master operon restored, at least in part, motility in crp and hns mutant strains, suggesting that this operon is the main target for both regulators. Binding of H-NS and CAP to the regulatory region of the master operon was demonstrated by gel retardation experiments, and their DNA binding sites were identified by DNase I footprinting assays. In vitro transcription experiments showed that CAP activates flhDC expression while H-NS represses it. In agreement with this observation, the activity of a transcriptional fusion carrying the flhDC promoter was decreased in the crp strain and increased in the hns mutant. In contrast, the activity of a transcriptional fusion encompassing the entire flhDC regulatory region extending to the ATG translational start codon was strongly reduced in both hns and crp mutants. These results suggest that the region downstream of the +1 transcriptional start site plays a crucial role in the positive control by H-NS of flagellum biosynthesis in vivo. Finally, the lack of complementation of the nonmotile phenotype in a crp mutant by activation-deficient CAP mutated proteins and characterization of cfs, a mutation resulting in a CAP-independent motility behavior, demonstrate that CAP activates flhDC transcription by binding to its promoter and interacting with RNA polymerase. (+info)
Localized reversible frameshift mutation in the flhA gene confers phase variability to flagellin gene expression in Campylobacter coli.
(35/1391)
Phase variation of flagellin gene expression in Campylobacter coli UA585 was correlated with high-frequency, reversible insertion and deletion frameshift mutations in a short homopolymeric tract of thymine residues located in the N-terminal coding region of the flhA gene. Mutation-based phase variation in flhA may generate functional diversity in the host and environment. (+info)
Rac1 and Cdc42 are required for phagocytosis, but not NF-kappaB-dependent gene expression, in macrophages challenged with Pseudomonas aeruginosa.
(36/1391)
Macrophages respond to Gram-negative bacterial pathogens by phagocytosis and pro-inflammatory gene expression. These responses may require GTPases that have been implicated in cytoskeletal alterations and activation of NF-kappaB. To determine the role of Rac1 and Cdc42 in signal transduction events triggered by Pseudomonas aeruginosa, we expressed GTP binding-deficient alleles of Rac1 or Cdc42, or Chim-GAP, a Rac1/Cdc42-specific GTPase-activating protein domain, in a subline of RAW 264.7 cells, and challenged the transfected cells with a laboratory strain of P. aeruginosa, PAO1. Expression of Rac1 N17, Cdc42 N17, or Chim-GAP led to a marked reduction of phagocytosis. In contrast, nuclear translocation of p65 NF-kappaB was unaffected by expression of the same constructs. Incubation of macrophages with PAO1 led to NF-kappaB-dependent expression of inducible nitric-oxide synthase, COX-2, and tumor necrosis factor-alpha, which was unaffected by inhibition of Rac1 or Cdc42 function. Isogenic strains of PAO1 that lacked surface adhesins were poorly ingested; however, they induced pro-inflammatory gene expression with an efficiency equal to that of PAO1. These results indicate that the signal transduction events leading to phagocytosis and pro-inflammatory protein expression are distinct. Rac1 and Cdc42 serve as effectors of phagocytosis, but not NF-kappaB-dependent gene expression, in the macrophage response to P. aeruginosa. (+info)
Isolation and characterization of Campylobacter jejuni subsp. jejuni from macaroni penguins (Eudyptes chrysolophus) in the subantarctic region.
(37/1391)
On Bird Island, South Georgia, albatrosses (n = 140), penguins (n = 100), and fur seals (n = 206) were sampled for Campylobacter jejuni. C. jejuni subsp. jejuni was recovered from three macaroni penguins (Eudyptes chrysolophus). These isolates, the first reported for the subantarctic region, showed low genetic diversity and high similarity to Northern Hemisphere C. jejuni isolates, possibly suggesting recent introduction to the area. (+info)
Characterization of CD4+ T cell responses during natural infection with Salmonella typhimurium.
(38/1391)
CD4+ T cells are important for resistance to infection with Salmonella typhimurium. However, the Ag specificity of this T cell response is unknown. Here, we demonstrate that a significant fraction of Salmonella-specific CD4+ T cells respond to the flagellar filament protein, FliC, and that this Ag has the capacity to protect naive mice from lethal Salmonella infection. To characterize this Ag-specific response further, we generated FliC-specific CD4+ T cell clones from mice that had resolved infection with an attenuated strain of Salmonella. These clones were found to respond to an epitope from a constant region of FliC, enabling them to cross-react with flagellar proteins expressed by a number of distinct Salmonella serovars. (+info)
Posttranslational processing of Methanococcus voltae preflagellin by preflagellin peptidases of M. voltae and other methanogens.
(39/1391)
Methanococcus voltae is a mesophilic archaeon with flagella composed of flagellins that are initially made with 11- or 12-amino-acid leader peptides that are cleaved prior to incorporation of the flagellin into the growing filament. Preflagellin peptidase activity was demonstrated in immunoblotting experiments with flagellin antibody to detect unprocessed and processed flagellin subunits. Escherichia coli membranes containing the expressed M. voltae preflagellin (as the substrate) were combined in vitro with methanogen membranes (as the enzyme source). Correct processing of the preflagellin to the mature flagellin was also shown directly by comparison of the N-terminal sequences of the two flagellin species. M. voltae preflagellin peptidase activity was optimal at 37 degrees C and pH 8.5 and in the presence of 0.4 M KCl with 0.25% (vol/vol) Triton X-100. (+info)
Effect of flagella on initial attachment of Listeria monocytogenes to stainless steel.
(40/1391)
At 22 degrees C a flagellin mutant of Listeria monocytogenes was found to attach to stainless steel at levels 10-fold lower than wild-type cells, even under conditions preventing active motility. At 37 degrees C, when flagella are not produced, attachment of both strains was identical. Therefore, flagella per se facilitate the early stage of attachment. (+info)