微生物学


分类

现刊
0 Q&A 47 Views Jun 20, 2024

Human babesiosis is a tick-borne disease caused by Babesia pathogens. The disease, which presents with malaria-like symptoms, can be life-threatening, especially in individuals with weakened immune systems and the elderly. The worldwide prevalence of human babesiosis has been gradually rising, prompting alarm among public health experts. In other pathogens, genetic techniques have proven to be valuable tools for conducting functional studies to understand the importance of specific genes in development and pathogenesis as well as to validate novel cellular targets for drug discovery. Genetic manipulation methods have been established for several non-human Babesia and Theileria species and, more recently, have begun to be developed for human Babesia parasites. We have previously reported the development of a method for genetic manipulation of the human pathogen Babesia duncani. This method is based on positive selection using the hDHFR gene as a selectable marker, whose expression is regulated by the ef-1aB promoter, along with homology regions that facilitate integration into the gene of interest through homologous recombination. Herein, we provide a detailed description of the steps needed to implement this strategy in B. duncani to study gene function. It is anticipated that the implementation of this method will significantly improve our understanding of babesiosis and facilitate the development of novel and more effective therapeutic strategies for the treatment of human babesiosis.

0 Q&A 36 Views Jun 20, 2024

Foot-and-mouth disease (FMD) is a severe and extremely contagious viral disease of cloven-hoofed domestic and wild animals, which leads to serious economic losses to the livestock industry globally. FMD is caused by the FMD virus (FMDV), a positive-strand RNA virus that belongs to the genus Aphthovirus, within the family Picornaviridae. Early detection and characterization of FMDV strains are key factors to control new outbreaks and prevent the spread of the disease. Here, we describe a direct RNA sequencing method using Oxford Nanopore Technology (ONT) Flongle flow cells on MinION Mk1C (or GridION) to characterize FMDV. This is a rapid, low cost, and easily deployed point of care (POC) method for a near real-time characterization of FMDV in endemic areas or outbreak investigation sites.

0 Q&A 37 Views Jun 20, 2024

The Auxin-inducible degron (AID) system is a genetic tool that induces rapid target protein depletion in an auxin-dependent manner. Recently, two advanced AID systems—the super-sensitive AID and AID 2—were developed using an improved pair of synthetic auxins and mutated TIR1 proteins. In these AID systems, a nanomolar concentration of synthetic auxins is sufficient as a degradation inducer for target proteins. However, despite these advancements, AID systems still require the fusion of an AID tag to the target protein for degradation, potentially affecting its function and stability. To address this limitation, we developed an affinity linker–based super-sensitive AID (AlissAID) system using a single peptide antibody known as a nanobody. In this system, the degradation of GFP- or mCherry-tagged target proteins is induced in a synthetic auxin (5-Ad-IAA)–dependent manner. Here, we introduce a simple method for generating AlissAID strains targeting GFP or mCherry fusion proteins in budding yeasts.

往期刊物
0 Q&A 179 Views Jun 5, 2024

Leishmaniasis, a neglected tropical disease, is caused by the intracellular protozoan parasite Leishmania. Upon its transmission through a sandfly bite, Leishmania binds and enters host phagocytic cells, ultimately resulting in a cutaneous or visceral form of the disease. The limited therapeutics available for leishmaniasis, in combination with this parasite’s techniques to evade the host immune system, call for exploring various methods to target this infection. To this end, our laboratory has been characterizing how Leishmania is internalized by phagocytic cells through the activation of multiple host cell signaling pathways. This protocol, which we use routinely for our experiments, delineates how to infect mammalian macrophages with either promastigote or amastigote forms of the Leishmania parasite. Subsequently, the number of intracellular parasites, external parasites, and macrophages can be quantified using immunofluorescence microscopy and semi-automated analysis protocols. Studying the pathways that underlie Leishmania uptake by phagocytes will not only improve our understanding of these host–pathogen interactions but may also provide a foundation for discovering additional treatments for leishmaniasis.

0 Q&A 503 Views Apr 20, 2024

Clustered regularly interspaced short palindromic repeats/CRISPR-associated protein 9 (CRISPR/Cas9) has become the state of the art for mutagenesis in filamentous fungi. Here, we describe a ribonucleoprotein complex (RNP)-mediated CRISPR/Cas9 for mutagenesis in Sporisorium reilianum. The efficiency of the method was tested in vitro with a cleavage assay as well as in vivo with a GFP-expressing S. reilianum strain. We applied this method to generate frameshift- and knock-out mutants in S. reilianum without a resistance marker by using an auto-replicating plasmid for selection. The RNP-mediated CRISPR/Cas9 increased the mutagenesis efficiency, can be applied for all kinds of mutations, and enables a marker-free genome editing in S. reilianum.

0 Q&A 289 Views Apr 5, 2024

Periodontal disease is characterized by the destruction of the hard and soft tissues comprising the periodontium. This destruction translates to a degradation of the extracellular matrices (ECM), mediated by bacterial proteases, host-derived matrix metalloproteinases (MMPs), and other proteases released by host tissues and immune cells. Bacterial pathogens interact with host tissue, triggering adverse cellular functions, including a heightened immune response, tissue destruction, and tissue migration. The oral spirochete Treponema denticola is highly associated with periodontal disease. Dentilisin, a T. denticola outer membrane protein complex, contributes to the chronic activation of pro-MMP-2 in periodontal ligament (PDL) cells and triggers increased expression levels of activators and effectors of active MMP-2 in PDL cells. Despite these advances, no mechanism for dentilisin-induced MMP-2 activation or PDL cytopathic behaviors leading to disease is known. Here, we describe a method for purification of large amounts of the dentilisin protease complex from T. denticola and demonstrate its ability to activate MMP-2, a key regulator of periodontal tissue homeostasis. The T. denticola dentilisin and MMP-2 activation model presented here may provide new insights into the dentilisin protein and identify potential therapeutic targets for further research.

0 Q&A 416 Views Apr 5, 2024

Contractile injection systems (CISs), one of the most important bacterial secretion systems that transport substrates across the membrane, are a collection of diverse but evolutionarily related macromolecular devices. Numerous effector proteins can be loaded and injected by this secretion complex to their specific destinations. One group of CISs called extracellular CIS (eCIS) has been proposed as secretory molecules that can be released from the bacterial cytoplasm and attack neighboring target cells from the extracellular environment. This makes them a potential delivery vector for the transportation of various cargos without the inclusion of bacterial cells, which might elicit certain immunological responses from hosts. We have demonstrated that the Photorhabdus virulence cassette (PVC), which is a typical eCIS, could be applied as an ideal vector for the translocation of proteinaceous cargos with different physical or chemical properties. Here, we describe the in-depth purification protocol of this mega complex from Escherichia coli. The protocol provided is a simpler, faster, and more productive way of generating the eCIS complexes than available methodologies reported previously, which can facilitate the subsequent applications of these nanodevices and other eCIS in different backgrounds.

0 Q&A 2215 Views Mar 20, 2024

Nanobodies are recombinant antigen-specific single domain antibodies (VHHs) derived from the heavy chain–only subset of camelid immunoglobulins. Their small molecular size, facile expression, high affinity, and stability have combined to make them unique targeting reagents with numerous applications in the biomedical sciences. From our work in producing nanobodies to over sixty different proteins, we present a standardised workflow for nanobody discovery from llama immunisation, library building, panning, and small-scale expression for prioritisation of binding clones. In addition, we introduce our suites of mammalian and bacterial vectors, which can be used to functionalise selected nanobodies for various applications such as in imaging and purification.


Key features

• Standardise the process of building nanobody libraries and finding nanobody binders so that it can be repeated in any lab with reasonable equipment.

• Introduce two suites of vectors to functionalise nanobodies for production in either bacterial or mammalian cells.


Graphical overview


0 Q&A 272 Views Mar 20, 2024

Candida glabrata is an opportunistic pathogen that may cause serious infections in an immunocompromised host. C. glabrata cell wall proteases directly interact with host cells and affect yeast virulence and host immune responses. This protocol describes methods to purify β-1,3-glucan-bonded cell wall proteases from C. glabrata. These cell wall proteases are detached from the cell wall glucan network by lyticase treatment, which hydrolyzes β-1,3-glucan bonds specifically without rupturing cells. The cell wall supernatant is further fractioned by centrifugal devices with cut-offs of 10 and 50 kDa, ion-exchange filtration(charge), and gel filtration (size exclusion). The enzymatic activity of C. glabrata proteases is verified with MDPF-gelatin zymography and the degradation of gelatin is visualized by loss of gelatin fluorescence. With this procedure, the enzymatic activities of the fractions are kept intact, differing from methods used in previous studies with trypsin digestion of the yeast cell wall. The protein bands may be eventually located from a parallel silver-stained gel and identified with LC–MS/MS spectrometry. The advantage of this methodology is that it allows further host protein degradation assays; the protocol is also suitable for studying other Candida yeast species.


Key features

• Uses basic materials and laboratory equipment, enabling low-cost studies.

• Facilitates the selection and identification of proteases with certain molecular weights.

• Enables further functional studies with host proteins, such as structural or immune response–related, or enzymes and candidate protease inhibitors(e.g., from natural substances).

• This protocol has been optimized for C. glabrata but may be applied with modifications to other Candida species.


Graphical overview


0 Q&A 397 Views Mar 20, 2024

Erwinia persicina is a gram-negative bacterium that causes diseases in plants. Recently, E. persicina BST187 was shown to exhibit broad-spectrum antibacterial activity due to its inhibitory effects on bacterial acetyl-CoA carboxylase, demonstrating promising potential as a biological control agent. However, the lack of suitable genetic manipulation techniques limits its exploitation and industrial application. Here, we developed an efficient transformation system for E. persicina. Using pET28a as the starting vector, the expression cassette of the red fluorescent protein–encoding gene with the strong promoter J23119 was constructed and transformed into BST187 competent cells to verify the overexpression system. Moreover, suicide plasmid–mediated genome editing systems was developed, and lacZ was knocked out of BST187 genome by parental conjugation transfer using the recombinant suicide vector pKNOCK-sacB-km-lacZ. Therefore, both the transformation and suicide plasmid–mediated genome editing system will greatly facilitate genetic manipulations in E. persicina and promote its development and application.


Key features

• Our studies establish a genetic manipulation system for Erwinia persicina, providing a versatile tool for studying the gene function of non-model microorganisms.

• Requires approximately 6–10 days to complete modification of a chromosome locus.


Graphical overview


0 Q&A 341 Views Mar 5, 2024

The Plasmodium parasites that cause malaria undergo an obligate, asymptomatic developmental stage in the host liver before initiating the symptomatic blood-stage infection. The parasite liver stage is a key intervention point for antimalarial chemoprophylaxis: successful targeting of liver-stage parasites prevents disease development in individuals and can help to reduce parasite transmission in populations, as the gametocyte forms that transmit infection to mosquitos are exclusively found in the blood stage. Antimalarial drugs that can target multiple parasite stages are thus highly desirable, and one emerging cellular target for such multistage active compounds is the process of protein synthesis or translation. Quantitative study of liver stage translation, and thus mechanistic evaluation of translation inhibitors against liver stage parasites, is not amenable to the methods allowing quantification of asexual blood stage translation, such as radiolabeled amino acid incorporation or lysate-based translation of reporter transcripts. Here, we present a method using o-propargyl puromycin (OPP) labeling of host and parasite nascent proteomes in the P. berghei-HepG2 infection model, followed by automated confocal image acquisition and computational separation of P. berghei vs. H. sapiens nascent proteome signals to allow simultaneous readout of the effects of translation inhibitors on both host and parasite. This protocol details our HepG2 cell culture and infected monolayer handling optimized for microscopy, our OPP labeling workflow, and our approach to automated confocal imaging, image processing, and data analysis.


Key features

• Uses the o-propargyl puromycin labeling technique developed by Liu et al. to quantitatively analyze protein synthesis in Plasmodium berghei liver-stage parasites in actively translating hepatoma cells.

• This quantitative approach should be adaptable for other puromycin-sensitive intracellular pathogens residing in actively translating host cells.

• The P. berghei–infected HepG2 recovery and reseeding protocol presented here is of use in applications beyond nascent proteome labeling and quantification.


Graphical overview


0 Q&A 303 Views Mar 5, 2024

Intracellular bacterial pathogens have evolved to be adept at manipulating host cellular function for the benefit of the pathogen, often by means of secreted virulence factors that target host pathways for modulation. The lysosomal pathway is an essential cellular response pathway to intracellular pathogens and, as such, represents a common target for bacterial-mediated evasion. Here, we describe a method to quantitatively assess bacterial pathogen–mediated suppression of host cell trafficking to lysosomes, using Salmonella enterica serovar Typhimurium infection of epithelial cells as a model. This live-cell imaging assay involves the use of a BODIPY TR-X conjugate of BSA (DQ-Red BSA) that traffics to and fluoresces in functional lysosomes. This method can be adapted to study infection with a broad array of pathogens in diverse host cell types. It is capable of being applied to identify secreted virulence factors responsible for a phenotype of interest as well as domains within the bacterial protein that are important for mediating the phenotype. Collectively, these tools can provide invaluable insight into the mechanisms of pathogenesis of a diverse array of pathogenic bacteria, with the potential to uncover virulence factors that may be suitable targets for therapeutic intervention.


Key features

• Infection-based analysis of bacterial-mediated suppression of host trafficking to lysosomes, using Salmonella enterica serovar Typhimurium infection of human epithelial cells as a model.

• Live microscopy–based analysis allows for the visualization of individually infected host cells and is amenable to phenotype quantification.

• Assay can be adapted to a broad array of pathogens and diverse host cell types.

• Assay can identify virulence factors mediating a phenotype and protein domains that mediate a phenotype.

0 Q&A 312 Views Mar 5, 2024

The genome of the dengue virus codes for a single polypeptide that yields three structural and seven non-structural (NS) proteins upon post-translational modifications. Among them, NS protein-3 (NS3) possesses protease activity, involved in the processing of the self-polypeptide and in the cleavage of host proteins. Identification and analysis of such host proteins as substrates of this protease facilitate the development of specific drugs. In vitro cleavage analysis has been applied, which requires homogeneously purified components. However, the expression and purification of both S3 and erythroid differentiation regulatory factor 1 (EDRF1) are difficult and unsuccessful on many occasions. EDRF1 was identified as an interacting protein of dengue virus protease (NS3). The amino acid sequence analysis indicates the presence of NS3 cleavage sites in this protein. As EDRF1 is a high-molecular-weight (~138 kDa) protein, it is difficult to express and purify the complete protein. In this protocol, we clone the domain of the EDRF1 protein (C-terminal end) containing the cleavage site and the NS3 into two different eukaryotic expression vectors containing different tags. These recombinant vectors are co-transfected into mammalian cells. The cell lysate is subjected to SDS-PAGE followed by western blotting with anti-tag antibodies. Data suggest the disappearance of the EDRF1 band in the lane co-transfected along with NS3 protease but present in the lane transfected with only EDRF1, suggesting EDRF1 as a novel substrate of NS3 protease. This protocol is useful in identifying the substrates of viral-encoded proteases using ex vivo conditions. Further, this protocol can be used to screen anti-protease molecules.


Key features

• This protocol requires the cloning of protease and substrate into two different eukaryotic expression vectors with different tags.

• Involves the transfection and co-transfection of both the above recombinant vectors individually and together.

• Involves western blotting of the same PVDF membrane containing total proteins of the cell lysate with two different antibodies.

• Does not require purified proteins for the analysis of cleavage of any suspected substrate by the protease.


Graphical overview