1,358,471 research outputs found
Bartonella henselae adhesin A (BadA), a novel non-fimbrial adhesin mediating a proangiogenic host cell response
No full textBartonella henselae causes vasculoproliferative disorders in humans. We identified a novel non-fimbrial adhesin of B. henselae designated as B. henselae adhesin A (BadA). BadA is a 340 kD protein encoded by the 9.3 kb badA gene and located in the outer membrane of B. henselae. BadA has a modular structure and contains domains homologous to Yersinia enterocolitica YadA. Expression of BadA was restored in a BadA-deficient transposon mutant by complementation in trans as shown by electronmicroscopy. BadA mediates the binding of B. henselae to extracellular matrix proteins and to endothelial cells. Expression of BadA is crucial for activation of hypoxia-inducible factor-1 (HIF-1) in host cells by B. henselae and secretion of proangiogenic cytokines (e.g., vascular endothelial growth factor). BadA is immunodominant in B. henselae-infected patients and rodents indicating that it is expressed during Bartonella infections. Our results suggest that BadA, the largest so far characterized bacterial protein, is a major pathogenicity factor of B. henselae with a role in the induction of vasculoproliferative disorders
Functional analysis of Bartonella henselae BadA domains
No full textBartonella henselae causes cat scratch disease and the vasculoproliferative disorders bacillary angiomatosis and peliosis hepatis in humans. One of the best characterized pathogenicity factors of B. henselae is Bartonella adhesin A (BadA). BadA belongs to the class of trimeric autotransporter adhesins and is constructed modularly, consisting of a head domain, 21 neck-stalk repeats and a membrane anchor. It is important for, e.g., the adhesion of B. henselae to extracellular matrix proteins and endothelial cells and for the induction of a proangiogenic host cell response. As the biological functions of certain BadA domains are not known so far, we want to elucidate the role of these domains in B. henselae-infections. For this purpose, in-frame deletion mutagenesis of badA was performed followed by a functional analysis of the respective mutants. First, 21 neck-stalk repeats were deleted leading to the expression of a truncated BadA. The mutant strain B. henselae BadA? /Hn23 was analyzed (i) for surface exposure of truncated BadA, (ii) for autoagglutination, (iii) for adhesion to fibronectin (Fn) and collagen and (iv) for adhesion to endothelial cells. In contrast to B. henselae wildtype, B. henselae BadA? /Hn23 did not bind to Fn indicating a crucial role of the neck-stalk domain in this process. In all other functional assays, B. henselae BadA- /Hn23 showed a similar phenotype as wildtype bacteria. These results suggest that mainly the head domain is important for the adhesin function of BadA. Further mutants carrying different deletions in the head- and neck-stalk domains will be analyzed in future
(A) Structures of BadA, Hia and YadA heads with the three domains colored according to the domain annotation from the alignment
No full textThe superimpositions of the individual domains from all three proteins are shown in the left panel. Note the different order of domains between Hia and BadA. In the BadA Trp-ring domain, 43 of 45 residues could be superimposed to the equivalent Hia domain with an r.m.s.d. of 2.02 Å, and in the GIN domain, 26 of 30 residues could be superimposed with an r.m.s.d. of 1.58 Å. In the BadA neck region, 19 residues could be superimposed to the YadA neck with an r.m.s.d. of 0.28 Å and to the Hia neck with an r.m.s.d. of 1.32 Å. All r.m.s.d. values refer to the C atoms. (B) Sequence alignment of the BadA head with other TAAs. The sequences of Hia and YadA are taken from the published structures; alignments based on these structures were used for homology modeling of the BadA head. The conserved residues that were used to name the domains are marked in bold. Abbreviations used: BhBadA – BadA g
Reply to Bada: Acidity and fluid composition on the Tagish Lake parent body
No full textA comment from Bada (1) attempts to flag multiple issues with our recent study (2). We appreciate the opportunity to respond, as Bada raises some interesting points, but many of his comments appear to overinterpret our results in a manner well beyond the scope of our original study. We believe Bada’s comments (1) can be broadly grouped into two key points for discussion: 1) the calculation used to yield the racemization timeline and 2) issues with our final conclusion
Long-read sequencing reveals genetic adaptation of Bartonella adhesin A among different Bartonella henselae isolates
No full textBartonella henselae is the causative agent of cat scratch disease and other clinical entities such as endocarditis and bacillary angiomatosis. The life cycle of this pathogen, with alternating host conditions, drives evolutionary and host-specific adaptations. Human, feline, and laboratory adapted B. henselae isolates often display genomic and phenotypic differences that are related to the expression of outer membrane proteins, for example the Bartonella adhesin A (BadA). This modularly-structured trimeric autotransporter adhesin is a major virulence factor of B. henselae and is crucial for the initial binding to the host via the extracellular matrix proteins fibronectin and collagen. By using next-generation long-read sequencing we demonstrate a conserved genome among eight B. henselae isolates and identify a variable genomic badA island with a diversified and highly repetitive badA gene flanked by badA pseudogenes. Two of the eight tested B. henselae strains lack BadA expression because of frameshift mutations. We suggest that active recombination mechanisms, possibly via phase variation (i.e., slipped-strand mispairing and site-specific recombination) within the repetitive badA island facilitate reshuffling of homologous domain arrays. The resulting variations among the different BadA proteins might contribute to host immune evasion and enhance long-term and efficient colonisation in the differing host environments. Considering the role of BadA as a key virulence factor, it remains important to check consistently and regularly for BadA surface expression during experimental infection procedures
Use of Bartonella adhesin A (BadA) immunoblotting in the serodiagnosis of Bartonella henselae infections
No full textBartonella henselae causes a variety of human diseases (e.g., cat scratch disease, and the vasculoproliferative disorders bacillary angiomatosis and peliosis hepatis). The laboratory diagnosis of B. henselae infections is usually based on the detection of anti- B. henselae antibodies by an indirect immunofluorescence assay (IFA) which, unfortunately, suffers a significant amount of cross-reactivity and hence is prone to deliver false positive results. In this pilot study, we evaluated the use of a potential two-step serodiagnosis of B. henselae infections by combining IFA and anti-Bartonella adhesin A (BadA) immunoblotting. Our data revealed that ~75% of the IFA positive sera of patients, with a suspected B. henselae-infection, reacted specifically with BadA and only ~20% of the IFA negative sera of healthy blood donors. Although Yersinia adhesin A (YadA) is structurally closely related to BadA, no cross-reactivity of sera from patients suffering from a Yersinia enterocolitica- or Y. pseudotuberculosis-infection with BadA was detected in immunoblotting. Unfortunately, recombinantly expressed BadA- domains (head, connector, stalk fragment) were not suitable for immunoblotting. Finally, the best resolution for full-length BadA immunoblotting was obtained when whole cell lysates of B. henselae were separated using continuous 4-15% sodium dodecyl sulfate polyacrylamide gels. In summary, our results show that BadA-antibodies are reliably detectable in the sera of B. henselae-infected patients and, therefore, this pilot study suggests to include BadA-immunoblotting in the laboratory diagnosis of B. henselae infections
Optimum energy partition between data and midamble for channel estimation in TD-CDMA
No full textChannel estimation in the uplink of a TD-CDTMA system can be accomplished by inserting 11 known sequence of symbols at the chip rate, usually in the middle of the burst, and therefore called midamble. In this paper we found the analytical solution to the problem of optimum energy partition, given the total energy per burst, between the midamble and data fields, in joint detected TD-CDMA systems. We show that, given the lengths of the data and midamble, in general the optimal solution requires different amplitude levels. We also show the burst structure in order to reach the optimum energy partition with equal amplitude symbols, and the performance degradation with traditional choices. The analysis is validated, for different channels, by comparison with simulation results of the TD-CDMA radio interlace specified for third generation cellular systems, where gains in terms of signal-to-noise ratio of 0.5-0.9 dB are achieveable
The Thursday Murder Club: Launching a megabrand author - a publishing case study
No full textIn 2020, the Christmas book charts in the UK made headlines: Barack Obama’s eagerly awaited autobiography, The Promised Land, was beaten to the top spot by The Thursday Murder Club by Richard Osman, a debut cosy crime novel set in a retirement village. Not only did Osman’s book beat the former US president’s expected bestseller, it also broke records, becoming the fastest-selling debut crime novel of all time. Although Osman has a certain level of fame in the UK from his TV appearances on shows such as Pointless, his celebrity status does not entirely explain the novel’s huge sales. This article tracks the acquisition, publication, and promotion journey of The Thursday Murder Club in order to understand the industry and cultural context of its success and to interrogate the role of celebrity in the creation of author brands. The findings suggest that the unexpected scale of the success of the book owed to a number of factors, including in-depth editing by the novel’s agent, editor, and author to tighten up the plot, an extensive and strategic promotional campaign, the pandemic (which drove interest in the book’s genre and themes), and the quality of the writing. We find that the book’s success was accentuated by Osman’s celebrity status rather than being entirely reliant on it. This research adds to the growing scholarship on celebrity authorship by means of an in-depth case study and provides insight into the processes behind publishing a ‘celebrity’ book and launching a megabrand author
Use of Bartonella adhesin A (BadA) immunoblotting in the serodiagnosis of Bartonella henselae infections
No full textBartonella henselae causes a variety of human diseases (e.g. cat scratch disease and the vasculoproliferative disorders, bacillary angiomatosis and peliosis hepatis). The laboratory diagnosis of B. henselae infections is usually based on the detection of anti-B. henselae antibodies by an indirect immunofluorescence assay (IFA) which, unfortunately, suffers from a significant amount of cross-reactivity and hence is prone to deliver false-positive results. In this pilot study, we evaluated the use of a potential two-step serodiagnosis of B. henselae infections by combining IFA and anti-Bartonella adhesin A (BadA) immunoblotting. Our data revealed that approximately 75% of the IFA-positive sera of patients with a suspected B. henselae infection reacted specifically with BadA but only approximately 25% of the IFA-negative sera of healthy blood donors. Although Yersinia adhesin A (YadA) is structurally closely related to BadA, no cross-reactivity of sera from patients suffering from a Yersinia enterocolitica or Y. pseudotuberculosis infection with BadA was detected in immunoblotting. Unfortunately, recombinantly expressed BadA domains (head, connector, stalk fragment) were not suitable for immunoblotting. Finally, the best resolution for full-length BadA immunoblotting was obtained when whole cell lysates of B. henselae were separated using continuous 4-15% sodium dodecyl sulfate polyacrylamide gels. In summary, our results show that BadA antibodies are detectable in the sera of B. henselae-infected patients and, therefore, this pilot study suggests to include BadA immunoblotting in the laboratory diagnosis of B. henselae infections
Polystyrene nanoplastics as an ecotoxicological hazard: cellular and transcriptomic evidences on marine and freshwater in vitro teleost models
No full textThe contamination of marine and freshwater environments by nanoplastics is considered a global threat for aquatic biota. Taking into account the most recent concentration range estimates reported globally and recognizing a knowledge gap in polystyrene nanoplastics (PS-NPs) ecotoxicology, the present work investigated the harmful effects of 20 nm and 80 nm PS-NPs, at increasing biological complexity, on the rainbow trout Oncorhynchus mykiss RTG-2 and gilthead seabream Sparus aurata SAF-1 cell lines. Twenty nm PS-NPs exerted a greater cytotoxicity than 80 nm ones and SAF-1 were approximately 4-fold more vulnerable to PS-NPs than RTG-2. The engagement of PS-NPs with plasma membranes was accompanied by discernible uptake patterns and morphological alterations along with a nuclear translocation already within a 30-min exposure. Cells were structurally damaged only by the 20 nm PS-NPs in a time-dependent manner as indicated by distinctive features of the execution phase of the apoptotic cell death mechanism such as cell shrinkage, plasma membrane blebbing, translocation of phosphatidylserine to the outer leaflet of the cell membrane and DNA fragmentation. At last, functional analyses unveiled marked transcriptional impairment at both sublethal and lethal doses of 20 nm PS-NPs, with the latter impacting the “Steroid biosynthesis”, “TGF-beta signaling pathway”, “ECM-receptor interaction”, “Focal adhesion”, “Regulation of actin cytoskeleton” and “Protein processing in endoplasmic reticulum” pathways. Overall, a distinct ecotoxicological hazard of PS-NPs at environmentally relevant concentrations was thoroughly characterized on two piscine cell lines. The effects were demonstrated to depend on size, exposure time and model, emphasizing the need for a comparative evaluation of endpoints between freshwater and marine ecosystems
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