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Rickettsia heilongjiangensis , the causative agent of far eastern spotted fever, is an obligate intracellular gram-negative bacterium that belongs to the spotted fever group rickettsiae. To understand the evolution and pathogenesis of R. heilongjiangensis , we analyzed its genome and compared it with other rickettsial genomes available in GenBank. The R. heilongjiangensis chromosome contains 1333 genes, including 1297 protein coding genes and 36 RNA coding genes. The genome also contains 121 pseudogenes, 54 insertion sequences, and 39 tandem repeats. Sixteen genes encoding the major components of the type IV secretion systems were identified in the R. heilongjiangensis genome. In total, 37 β-barrel outer membrane proteins were predicted in the genome, eight of which have been previously confirmed to be outer membrane proteins. In addition, 266 potential virulence factor genes, seven partially deleted antibiotic resistance genes, and a genomic island were identified in the genome. The codon usage in the genome is compatible with its low GC content, and the amino acid usage shows apparent bias. A comparative genomic analysis showed that R. heilongjiangensis and R. japonica share one unique fragment that may be a target sequence for a diagnostic assay. The orthologs of 37 genes of R. heilongjiangensis were found in pathogenic R. rickettsii str. Sheila Smith but not in non-pathogenic R. rickettsii str. Iowa, which may explain why R. heilongjiangensis is pathogenic. Pan-genome analysis showed that R. heilongjiangensis and 42 other rickettsiae strains share 693 core genes with a pan-genome size of 4837 genes. The pan-genome-based phylogeny showed that R. heilongjiangensis was closely related to R. japonica . [ABSTRACT FROM AUTHOR]

Pantoea agglomerans YS19 is a diazotrophic endophyte isolated from rice ( Oryza sativa cv. Yuefu) grown in a temperate-climatic region in west Beijing (China). The colonization of YS19 on host rice was studied in this paper. It was revealed that YS19 colonizes in all the tissues of rice seedlings, including roots (dominantly at elongation regions, lateral root junctions, root hairs and root caps), stems and leaves. More YS19 colonizes in stem and leaves (1.40 × 105 CFU mg−1 fresh weight) than that in roots (3.60 × 104 CFU mg−1). Symplasmata, a kind of adaptive structure of the strain for its endophytic living, were repeatedly observed to form inside root or stem cortex parenchyma tissues, as well as on leaf surfaces and also rhizoplanes. A novel matrix protein (SPM43.1) with its expression paralleling to the formation of symplasmata was captured, whose meaning in structural construction of symplasmata was also discussed. [ABSTRACT FROM AUTHOR]

Background: Coxiella burnetii is an obligate intracellular Gram-negative bacterium that causes a zoonotic disease commonly called Q fever globally. In this study, an up-converting phosphor technology-based lateral flow (UPT-LF) assay was established for the rapid and specific detection of phase I strains of C. burnetii. Results: Specific monoclonal antibodies (10B5 and 10G7) against C. burnetii phase I strains were prepared and selected for use in the UPT-LF assay by the double-antibody-sandwich method. The detection sensitivity of the Coxiella-UPT-LF was 5 × 104 GE/ml for a purified C. burnetii phase I strain and 10 ng/ml for LPS of C. burnetii Nine Mile phase I (NMI). Good linearity was observed for C. burnetii phase I and NMI LPS quantification (R2 ≥ 0.989). The UPT-LF assay also exhibited a high specificity to C. burnetii, without false-positive results even at 108 GE/ml of non-specific bacteria, and good inclusivity for detecting different phase I strains of C. burnetii. Moreover, the performance of the Coxiella-UPT-LF assay was further confirmed using experimentally and naturally infected samples. Conclusions: Our results indicate that Coxiella-UPT-LF is a sensitive and reliable method for rapid screening of C. burnetii, suitable for on-site detection in the field. [ABSTRACT FROM AUTHOR]

Coxiella burnetii is a gram-negative bacterium that causes acute and chronic Q fever. Because of the severe adverse effect of whole-cell vaccination, identification of immunodominant antigens of C. burnetii has become a major focus of Q fever vaccine development. We hypothesized that secreted C. burnetii type IV secretion system (T4SS) effectors may represent a major class of CD8+ T-cell antigens, owing to their cytosolic localization. Twenty-nine peptides were identified that elicited robust CD8+ T-cell interferon γ (IFN-γ) recall responses from mice infected with C. burnetii. Interestingly, 22 of 29 epitopes were derived from 17 T4SS-related proteins, none of which were identified as immunodominant antigens by using previous antibody-guided approaches. These epitopes were expressed in an attenuated Listeria monocytogenes vaccine strain. Immunization with recombinant L. monocytogenes vaccines induced a robust CD8+ T-cell response and conferred measurable protection against C. burnetii infection in mice. These data suggested that T4SS effectors represent an important class of C. burnetii antigens that can induce CD8+ T-cell responses. We also showed that attenuated L. monocytogenes vaccine vectors are an efficient antigen-delivery platform that can be used to induce robust protective CD8+ T-cell immune responses against C. burnetii infection. [ABSTRACT FROM AUTHOR]