Brucella Molecular And Cellular Biology Pdf Notes
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- Analyzing the molecular mechanism of lipoprotein localization in Brucella.
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- Human brucellosis: recent advances and future challenges
Keywords : Brucella , endoplasmic reticulum , macrophage , replication , virulence factors.
Analyzing the molecular mechanism of lipoprotein localization in Brucella.
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We characterised the crosstalk that exists between Brucella abortus , the causative agent of brucellosis, and the mitochondria of infected cells. Brucella replicates in a compartment derived from the endoplasmic reticulum ER and modulates ER functionality by activating the unfolded protein response.
However, the impact of Brucella on the mitochondrial population of infected cells still requires a systematic study. We observed physical contacts between Brucella containing vacuoles and mitochondria. We also found that B. We demonstrated that B. This fragmentation is DRP1-independent and might be caused by a deficit of mitochondrial fusion.
Despite their subsequent evolution, mitochondria still share many similarities with prokaryotic cells, such as a double membrane, the capacity to produce ATP through oxidative phosphorylation OXPHOS and the presence of their own genome and bacterial-type ribosomes 2.
Mitochondria are highly dynamic organelles that continuously adapt their morphology and move to specific cellular sub-compartments, using different components of the cytoskeleton, to respond to cellular needs 3.
The mitochondrial morphology is controlled by the balance between mitochondrial fission and fusion and is mediated by large GTPases related to the dynamin superfamily. On the other hand, fission requires the recruitment of dynamin-related protein 1 DRP1 to the OMM, where it assembles to form a constriction ring that leads to fission.
Fission occurs where the endoplasmic reticulum ER marks the localization of DRP1 recruitment in collaboration with elements of the actin cytoskeleton 3.
Mitochondrial dynamics and the various functions and roles of this organelle are interconnected 4. Indeed, according to the cell type and functional status, the organelle structure will vary from an interconnected and branched network that promotes exchanges between the mitochondrial fragments, to individual rounded entities that facilitate the movement, segregation and degradation of impaired mitochondria, thereby preventing the accumulation and propagation of mitochondrial dysfunction 5 , 6.
In addition to being the main ATP producers of the cell, through OXPHOS, mitochondria also fulfil many other functions, such as contributing to lipid, amino acid and nucleotide syntheses and catabolism, integration of pro- and anti-apoptotic signals, control of calcium homeostasis and redox signalling. Mitochondria are also a cell signalling hub through sensing of Pathogen-Associated Molecular Patterns PAMPs and by initiating signalling pathways such as apoptosis and innate immune responses 7 , 8 , 9.
The concentration of these various functions in one single organelle makes mitochondria a target of choice for intracellular pathogens. Several bacteria e. Listeria monocytogenes and Vibrio cholera and viruses e. Hepatitis C and Epstein-Barr are reported to manipulate mitochondria during infection 10 , 11 , In the present study, we analysed the effect of Brucella abortus on the biology of mitochondria of myeloid RAW Brucella spp. Brucellosis leads to abortion and sterility in animals, whereas Brucella infection in humans causes undulating fever and articular, cardiac and neurological complications during the chronic phase of the infection Once inside the infected cell, Brucella is contained in vacuoles BCV, for Brucella- containing vacuoles that interact with and acquire the markers of different components of the endosomal pathway In most cell types, the BCV transiently interact with the lysosomes to reach, in fine , an ER-derived compartment where bacteria replicate massively Considering the massive replication of Brucella in the ER, different groups have shown that the unfolded protein response UPR , an ER stress response, is activated in Brucella -infected cells 15 , 16 , These observations suggest that the ER is under stress and that its functions are affected during Brucella infection.
The ER and mitochondria are two organelles that interact both physically and functionally, and ER stress is known to modify mitochondrial functions 18 , It thus makes sense to analyse the impact of Brucella infection on the mitochondrial population of infected cells. A very recent study demonstrated that B. Furthermore, additional evidences suggest that other mitochondrial functions might be affected during Brucella infection.
One transcriptomic study revealed the down-regulation of several nuclear genes encoding mitochondrial proteins in B. In addition, BCV fractions obtained by subcellular fractionation of B. In the present study, we highlighted the presence of intimate contacts between BCV and mitochondria, suggesting that these structures might physically interact.
We show that B. However, we demonstrate that Brucella infection induces a strong fragmentation of the mitochondrial network in infected cells in a process that does not involve DRP1. This mitochondrial fragmentation might be caused by a deficit of fusion. First, we studied the potential interactions between Brucella and mitochondria by performing a transmission electron microscopy analysis of the ultrastructure of the infected cells. We observed, in many cases, close contacts between BCVs and mitochondria, both in vitro , in B.
These observations suggest that BCV might physically interact with mitochondria. Mitochondria and BCV seem to interact physically during Brucella abortus infection a. Electron microscopy analyses of B. Electron microscopy analyses of trophoblasts from B. Given the possible interaction between BCVs and mitochondria, we addressed the question of the role of mitochondrial bioenergetics during Brucella infection by comparing the infection efficiency in two models of mitochondrial respiration dysfunction.
The first model consists of RAW RAW Cells were then infected with B. Under the same conditions, we also used confocal microscopy to assess the percentages of cells infected by B. Mitochondrial dysfunction does not modulate Brucella abortus replication a. As shown in Supp. S1c , rho 0 cells are completely depleted of mitochondrial genome-encoded mitochondrial proteins such as the subunit I of the Cytochrome c Oxidase, COX I but not of nuclear genome-encoded mitochondrial proteins such as COX IV.
In this experiment, the number of CFU was normalised for protein content to account for the differences in the doubling time observed between these two cell lines As shown in Fig. The mtROS are also crucial for elicitation of the immune response, by taking part in cell signalling and by a direct bactericidal effect We therefore analysed the putative impact of the mtROS content on B.
Our analysis of the superoxide anion radicals content in RAW To support this conclusion, the effect of Mito-TEMPO, a specific mitochondrial-targeted superoxide scavenger 27 , was tested on bacterial replication Fig.
Taken together, these results suggest that mtROS do not participate in the control of Brucella infection, as neither an increase nor a decrease in the mtROS content affects Brucella replication. While the inhibition of the mitochondrial respiration did not affect Brucella replication, we wondered whether the intracellular bacteria could affect the mitochondrial network.
To do so, we immunostained the infected cells with an antibody targeting the Translocase of the Outer Membrane 20 TOM20 , a protein located in the mitochondrial outer membrane that acts as a receptor for mitochondrial protein import We first analysed, by confocal microscopy, the mitochondrial morphology in HeLa cells infected with B. S2c and d.
This fragmentation was exclusively observed in cells that contained bacteria. Statistical analysis: Rank sum test Mann-Whitney. The numbers indicated in the columns represent the number of cells analysed for each condition. The same analysis was performed in B. However, in the latter, there was no statistically significant difference in the aspect ratio between the control and infected cells. We further confirmed that the Brucella -induced mitochondrial fragmentation also occurred in other cell types, such as RAW S3a and BeWo trophoblasts Supp.
S3b , two additional cell models relevant to the study of Brucella infection We also determined whether mitochondrial fragmentation is specific to B. We found that B. Taken together, these results demonstrate that Brucella spp. Given the mitochondrial fragmentation induced by Brucella infection, we sought to delineate the mechanisms involved, by studying different cell components known to regulate mitochondrial morphology; namely, the cytoskeleton organisation, mitochondrial calcium uptake and the ER stress response.
Mitochondria organisation and distribution in the cell depend on the interactions of the mitochondria with the cytoskeleton Cytoskeleton elements also actively participate in the mitochondria fission process, as microtubules are involved in the mitochondrial recruitment of DRP1 31 , most likely through the promotion of ER—mitochondria interactions In addition, microfilaments take part in mitochondrial fission by recruiting DRP1 at the fission site, in collaboration with the ER Recently, a requirement for F-actin has also been postulated for the DRP1-independent mitochondrial fragmentation that occurs during Listeria monocytogenes infection Interestingly, the cytoskeleton is known to be affected during Brucella infection.
Actin polymerisation is involved in Brucella uptake in both macrophages and epithelial cells 35 , 36 , 37 , Brucella also secretes TIR domain-containing protein TcpB , an effector that modulates microtubule dynamics by acting as a stabilisation factor, although this activity has only been studied in vitro S5a and b.
We did not observe any major modification in the organisation of microfilaments or microtubules in the infected cells when compared to the organisation found in control non-infected cells. Infection with B. Therefore, we analysed the effect of inhibiting the mitochondrial calcium influx on Brucella -induced mitochondrial fragmentation. The cells were then infected or not with B. Under these conditions, we did not observe any effect of RuRed on Brucella -induced mitochondrial fragmentation, suggesting that mitochondrial calcium uptake might not be responsible for the mitochondrial morphology alteration observed during Brucella infection.
Search for potential mechanisms involved in Brucella abortus -induced mitochondrial fragmentation a. P value for interaction: 0. Actin abundance was assessed on the same blot as a loading control. These full-length blots are presented in Supp. S10a and b. The replication of Brucella has been shown to lead to the activation of one or several UPR pathways in infected macrophages and epithelial cells 15 , 16 ,
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Not a MyNAP member yet? Register for a free account to start saving and receiving special member only perks. Critical knowledge gaps remain that limit understanding, detecting, and preventing the transmission of Brucella abortus in the Greater Yellowstone Area GYA. Research to fill those knowledge gaps is needed in disease ecology, economics, immunology, vaccines and their delivery mechanisms, animal and pathogen genomics, and diagnostics. Research funding and expertise will need to be expanded to include other disciplines such as disease ecology and epidemiology for addressing gaps in the immediate term while also examining immunology, vaccines, and genomics for applications that would address gaps over the longer term.
Brucella is a genus of Gram-negative bacteria ,   named after David Bruce — They are small 0. Brucella spp. Transmission from human to human, for example through sexual intercourse or from mother to child, is exceedingly rare, but possible. The different species of Brucella are genetically very similar, although each has a slightly different host specificity. Sir David Bruce isolated B. Human brucellosis is usually not transmitted from human to human; people become infected by contact with fluids from infected animals sheep, cattle, or pigs or derived food products, such as unpasteurized milk and cheese.
Brucella abortus and B. Thus, characterizing the circulating strains is a critical first step in understanding brucellosis in the country. Sixteen Brucella strains isolated in Zimbabwe at the Central Veterinary laboratory from various hosts were characterized using all or some of these assays. The strains were identified as B. Zimbabwean strains identified as B.
Keywords: brucellosis; cattle; human; serological and molecular methods. 1. of standard serological tests is usually prepared from whole-cell Kit (MO BIO Laboratories Inc., Carlsbad, CA, USA) are Notes , 4,
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The search for ideal brucellosis vaccines remains active today. Currently, no licensed human or canine anti-brucellosis vaccines are available. In bovines, the most successful vaccine S19 is only used in calves, as adult vaccination results in orchitis in male, prolonged infection, and possible abortion complications in pregnant female cattle. Another widely deployed vaccine RB51 has a low protective efficacy. An ideal vaccine should exhibit a safe profile as well as enhance protective efficacy.
Human brucellosis: recent advances and future challenges
Of the 26 proteins identified, one is a novel, highly immunogenic protein that elicits improved protection in the mouse model. This has significance for the development of Brucella subunit vaccine. Brucellosis is a worldwide zoonotic disease. No Brucella vaccine is available for use in humans, and existing animal vaccines have limitations. Outer membrane protein 25, d -galactose periplasmic-binding protein, oligopeptide ABC transporter protein and isopropylmalate synthase were found to be the most abundant proteins. Outer membrane protein 25, Omp2b porin and one hypothetical protein were predicted as outer membrane proteins. In addition, Omp28, Omp31 and one ribosomal protein L9 were also identified.
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Recent advances in Brucella research View all 7 Articles. Brucella is a Gram-negative, facultative intracellular bacterium that causes zoonotic brucellosis in humans and various animals. Out of 10 classified Brucella species, B. In the past decade, the mechanisms of Brucella pathogenesis and host immunity have been extensively investigated using the cutting edge systems biology and bioinformatics approaches. This article provides a comprehensive review of the applications of Omics including genomics, transcriptomics, and proteomics and bioinformatics technologies for the analysis of Brucella pathogenesis, host immune responses, and vaccine targets. Based on more than 30 sequenced Brucella genomes, comparative genomics is able to identify gene variations among Brucella strains that help to explain host specificity and virulence differences among Brucella species. Diverse transcriptomics and proteomics gene expression studies have been conducted to analyze gene expression profiles of wild type Brucella strains and mutants under different laboratory conditions.
Metrics details. It is a disease of poverty; infections of livestock have a huge socioeconomic cost while human brucellosis starts as a debilitating acute infection that can be come chronic with many complications. Considering the importance of the disease, the international brucellosis research community is small; we cover a wide range of research interests ranging from veterinary and human medicine to molecular genetics, cell biology and immunology.