Cyclic beta-1,2-glucan is a Brucella virulence factor required for intracellular survival

Transcriptome analysis of macrophages during Brucella abortus infection clarifies the survival mechanisms of the bacteria

Brucellosis is a critical zoonotic disease impacting humans and animals globally, causing symptoms like fever and arthritis in humans and reproductive issues in animals. The disease stems from the Brucella genus, adept at evading the immune system and proliferating within host cells. This study explores how Brucella abortus manipulates host cellular mechanisms to sustain infection, focusing on the interaction with murine macrophages over 24 h. Initial host defenses involve innate immune responses, while Brucella's survival strategies include evading lysosomal degradation and modulating host cell functions through various pathways. The research identified significant transcriptional changes in macrophages post-infection, highlighting pathways such as cytokine storm, pyroptosis signaling, Toll-like receptor pathways, and LXRs/RXRs signaling. The findings shed light on Brucella's complex mechanisms to undermine host defenses and underscore the need for further investigation into therapeutic targets to combat brucellosis.

Bottom-Up Synthesized Glucan Materials: Opportunities from Applied Biocatalysis

Linear d-glucans are natural polysaccharides of simple chemical structure. They are comprised of d-glucosyl units linked by a single type of glycosidic bond. Noncovalent interactions within, and between, the d-glucan chains give rise to a broad variety of macromolecular nanostructures that can assemble into crystalline-organized materials of tunable morphology. Structure design and functionalization of d-glucans for diverse material applications largely relies on top-down processing and chemical derivatization of naturally derived starting materials. The top-down approach encounters critical limitations in efficiency, selectivity, and flexibility. Bottom-up approaches of d-glucan synthesis offer different, and often more precise, ways of polymer structure control and provide means of functional diversification widely inaccessible to top-down routes of polysaccharide material processing. Here the natural and engineered enzymes (glycosyltransferases, glycoside hydrolases and phosphorylases, glycosynthases) for d-glucan polymerization are described and the use of applied biocatalysis for the bottom-up assembly of specific d-glucan structures is shown. Advanced material applications of the resulting polymeric products are further shown and their important role in the development of sustainable macromolecular materials in a bio-based circular economy is discussed.

Increased Brucella abortus asRNA_0067 expression under intraphagocytic stressors is associated with enhanced virB2 transcription

Intracellular pathogens like Brucella face challenges during the intraphagocytic adaptation phase, where the modulation of gene expression plays an essential role in taking advantage of stressors to persist inside the host cell. This study aims to explore the expression of antisense virB2 RNA strand and related genes under intracellular simulation media. Sense and antisense virB2 RNA strands increased expression when nutrient deprivation and acidification were higher, being starvation more determinative. Meanwhile, bspB, one of the T4SS effector genes, exhibited the highest expression during the exposition to pH 4.5 and nutrient abundance. Based on RNA-seq analysis and RACE data, we constructed a regional map depicting the 5' and 3' ends of virB2 and the cis-encoded asRNA_0067. Without affecting the CDS or a possible autonomous RBS, we generate the deletion mutant ΔasRNA_0067, significantly reducing virB2 mRNA expression and survival rate. These results suggest that the antisense asRNA_0067 expression is promoted under exposure to the intraphagocytic adaptation phase stressors, and its deletion is associated with a lower transcription of the virB2 gene. Our findings illuminate the significance of these RNA strands in modulating the survival strategy of Brucella within the host and emphasize the role of nutrient deprivation in gene expression.

Development of a scalable recombinant system for cyclic beta-1,2-glucans production

BACKGROUND

Cyclic β-1,2-glucans (CβG) are bacterial cyclic homopolysaccharides with interesting biotechnological applications. These ring-shaped molecules have a hydrophilic surface that confers high solubility and a hydrophobic cavity able to include poorly soluble molecules. Several studies demonstrate that CβG and many derivatives can be applied in drug solubilization and stabilization, enantiomer separation, catalysis, synthesis of nanomaterials and even as immunomodulators, suggesting these molecules have great potential for their industrial and commercial exploitation. Nowadays, there is no method to produce CβG by chemical synthesis and bacteria that synthesize them are slow-growing or even pathogenic, which makes the scaling up of the process difficult and expensive. Therefore, scalable production and purification methods are needed to afford the demand and expand the repertoire of applications of CβG.

RESULTS

We present the production of CβG in specially designed E. coli strains by means of the deletion of intrinsic polysaccharide biosynthetic genes and the heterologous expression of enzymes involved in CβG synthesis, transport and succinilation. These strains produce different types of CβG: unsubstituted CβG, anionic CβG and CβG of high size. Unsubstituted CβG with a degree of polymerization of 17 to 24 glucoses were produced and secreted to the culture medium by one of the strains. Through high cell density culture (HCDC) of that strain we were able to produce 4,5 g of pure unsubstituted CβG /L in culture medium within 48 h culture.

CONCLUSIONS

We have developed a new recombinant bacterial system for the synthesis of cyclic β-1,2-glucans, expanding the use of bacteria as a platform for the production of new polysaccharides with biotechnological applications. This new approach allowed us to produce CβG in E. coli with high yields and the highest volumetric productivity reported to date. We expect this new highly scalable system facilitates CβG availability for further research and the widespread use of these promising molecules across many application fields.

Detection of Virulence-Associated Genes among Brucella melitensis and Brucella abortus Clinical Isolates in Greece, 2001-2022

Brucellosis remains an important zoonotic disease in several parts of the world; in Greece, although it is declining, it is still endemic, affecting both the financial and public health sectors. The current study was undertaken to investigate the presence and distribution of virulence-associated genes among Brucella spp. clinical strains isolated during 2001-2022. Species identification was performed using conventional methodology and Bruce-ladder PCR. The presence of the virulence genes mviN, manA, wbkA, perA, omp19, ure, cbg and virB was investigated using PCR. During the study period, a total of 334 Brucella isolates were identified, of which 328 (98.2%) were detected from positive blood cultures; 315 (94.3%) of the isolates were identified as B. melitensis, whilst the remaining 16 (4.8%) and 3 (0.9%) were identified as B. abortus and B. suis, respectively. Notably, two of the B. melitensis were assigned to the REV-1 vaccine strain type. The presence of the omp19, manA, mviN and perA genes was confirmed in all 315 B. melitensis isolates, while ure, wbkA, cbg and virB genes were detected in all but 9, 2, 1 and 1 of the isolates, respectively. All eight virulence genes were amplified in all B. abortus and B. suis isolates. The detection rate of virulence genes did not differ significantly among species. In conclusion, brucellosis is still considered a prevailing zoonotic disease in Greece, with the majority of the isolates identified as B. melitensis. The eight pathogenicity-associated genes were present in almost all Brucella isolates, although the ure gene was absent from a limited number of B. melitensis isolates.

Immunomodulatory Effect and Biological Significance of β-Glucans

β-glucan, one of the homopolysaccharides composed of D-glucose, exists widely in cereals and microorganisms and possesses various biological activities, including anti-inflammatory, antioxidant, and anti-tumor properties. More recently, there has been mounting proof that β-glucan functions as a physiologically active "biological response modulator (BRM)", promoting dendritic cell maturation, cytokine secretion, and regulating adaptive immune responses-all of which are directly connected with β-glucan-regulated glucan receptors. This review focuses on the sources, structures, immune regulation, and receptor recognition mechanisms of β-glucan.

New two-stage pH combined with dissolved oxygen control strategy for cyclic β-1,2 glucans synthesis

On the basis of a novel two-stage pH combined with dissolved oxygen (DO) control strategy in fed-batch fermentation, this research addresses the influence of pH on cyclic β-1,2-glucans (CβGs) biosynthesis and melanin accumulation during the production of CβGs by Rhizobium radiobacter ATCC 13,333. Under these optimal fermentation conditions, the maximum cell concentration and CβGs concentration in a 7-L stirred-tank fermenter were 7.94 g L^-1 and 3.12 g L^-1, which were the maximum production reported for R. radiobacter. The melanin concentration of the fermentation broth was maintained at a low level, which was beneficial to the subsequent separation and purification of the CβGs. In addition, a neutral extracellular oligosaccharide (COGs-1) purified by the two-stage pH combined with DO control strategy fermentation medium was structurally characterized. Structural analyses indicated that COGs-1 was a family of unbranched cyclic oligosaccharides composed of only β-1,2-linked D-glucopyranose residues with degree of polymerization between 17 and 23, namely CβGs. This research provides a reliable source of CβGs and structural basis for further studies of biological activity and function. KEY POINTS: • A two-stage pH combined with DO control strategy was proposed for CβGs production and melanin biosynthesis by Rhizobium radiobacter. • The final extracellular CβGs production reached 3.12 g L^-1, which was the highest achieved by Rhizobium radiobacter. • The existence of CβGs could be detected by TLC quickly and accurately.

The mechanism of chronic intracellular infection with Brucella spp

Globally, brucellosis is a widespread zoonotic disease. It is prevalent in more than 170 countries and regions. It mostly damages an animal's reproductive system and causes extreme economic losses to the animal husbandry industry. Once inside cells, Brucella resides in a vacuole, designated the BCV, which interacts with components of the endocytic and secretory pathways to ensure bacterial survival. Numerous studies conducted recently have revealed that Brucella's ability to cause a chronic infection depends on how it interacts with the host. This paper describes the immune system, apoptosis, and metabolic control of host cells as part of the mechanism of Brucella survival in host cells. Brucella contributes to both the body's non-specific and specific immunity during chronic infection, and it can aid in its survival by causing the body's immune system to become suppressed. In addition, Brucella regulates apoptosis to avoid being detected by the host immune system. The BvrR/BvrS, VjbR, BlxR, and BPE123 proteins enable Brucella to fine-tune its metabolism while also ensuring its survival and replication and improving its ability to adapt to the intracellular environment.

Seroprevalence of Specific Antibodies to Toxoplasma gondii, Neospora caninum, and Brucella spp. in Sheep and Goats in Egypt

Toxoplasmosis, neosporosis, and brucellosis are devastating diseases causing infectious abortion and, therefore, substantial economic losses in farm animals. Toxoplasmosis and neosporosis are caused by the intracellular protozoan parasites Toxoplasma gondii (T. gondii) and Neospora caninum (N. caninum), respectively. Brucellosis is a bacterial disease caused by numerous Brucella species in multiple hosts. Toxoplasmosis and brucellosis are also considered foodborne zoonotic diseases. In the current study, specific antibodies to T. gondii and N. caninum, in addition to those to Brucella spp., were detected to gain a better understanding of the epidemiological situation for these three pathogens. Sheep and goat sera from Egypt (n = 360) of animals with and without a history of abortion were tested using commercial ELISAs. Seropositivity rates of 46.1%, 11.9%, and 8.6% for T. gondii, N. caninum, and Brucella spp., respectively, were revealed. Mixed infections with T. gondii and Brucella spp. (4.4%), T. gondii and N. caninum (4.2%), N. caninum and Brucella spp. (1.4%), and even some triple infections (0.6%) have been observed. Animals with a history of abortion had a significantly higher seroprevalence for Brucella spp. infection than those without abortion (12.6%; 28/222 vs. 2.2%; 3/138) (p = 0.0005; Odds ratio = 1.9-21.8), while none of the other pathogens showed a similar effect. This result suggests brucellosis as a possible cause of abortion in the study population. However, the high seroprevalence for T. gondii and N. caninum revealed in our study warrants further investigations.

Brucella ceti and Brucella pinnipedialis genome characterization unveils genetic features that highlight their zoonotic potential

The Gram-negative bacteria Brucella ceti and Brucella pinnipedialis circulate in marine environments primarily infecting marine mammals, where they cause an often-fatal disease named brucellosis. The increase of brucellosis among several species of cetaceans and pinnipeds, together with the report of sporadic human infections, raises concerns about the zoonotic potential of these pathogens on a large scale and may pose a threat to coastal communities worldwide. Therefore, the characterization of the B. ceti and B. pinnipedialis genetic features is a priority to better understand the pathological factors that may impact global health. Moreover, an in-depth functional analysis of the B. ceti and B. pinnipedialis genome in the context of virulence and pathogenesis was not undertaken so far. Within this picture, here we present the comparative whole-genome characterization of all B. ceti and B. pinnipedialis genomes available in public resources, uncovering a collection of genetic tools possessed by these aquatic bacterial species compared to their zoonotic terrestrial relatives. We show that B. ceti and B. pinnipedialis genomes display a wide host-range infection capability and a polyphyletic phylogeny within the genus, showing a genomic structure that fits the canonical definition of closeness. Functional genome annotation led to identifying genes related to several pathways involved in mechanisms of infection, others conferring pan-susceptibility to antimicrobials and a set of virulence genes that highlight the similarity of B. ceti and B. pinnipedialis genotypes to those of Brucella spp. displaying human-infecting phenotypes.

Molecular identification of intracellular survival related Brucella melitensis virulence factors

Introduction and Aim: Brucellosis is an important zoonotic disease caused by Brucella spp. which is an intracellular gram-negative bacterium. Brucella melitensis lacks the "traditional" virulence factors such as exotoxins or cytolysins, but is capable of persisting intracellularly and evading the immune system. This study aims to identify B. melitensis using PCR and discover genes associated with its severity for early detection and therapy.  Materials and Methods: Ten ml of unclotted blood sample was collected from each patient (n=100) suspected to be infected with brucellosis. The Castaneda technique was used to inoculate blood samples onto Brucella Basel agar with a selective supplement and tryptone soy broth in a diphasic flask. Biochemical tests were used in identifying the isolated colonies. B. melitensis isolates were further confirmed by the polymerase chain reaction (PCR) technique using, primers targeting a specific region (IS711 gene) of the genome. Multiplex PCR was used to determine the four virulence related genes (lps B, mgtA, omp25, CBG) in all positive samples. Results: Brucella melitensis was detected in 9% (9/100) of the blood samples. Among the virulence factors, LpsB and mgtA, were detected in all the isolates while, the genes omp25 and CBG were detected in 66.6% and 55.5% of the isolates, respectively. Conclusion: Brucellosis could be diagnosed rapidly using molecular techniques. PCR technique could also be used in identifying the Brucella virulence related genes lpsB, mgtA, CBG, and omp25 that are crucial to the bacterium's pathogenicity in the intracellular environment.

Brucella melitensis Wzm/Wzt System: Changes in the Bacterial Envelope Lead to Improved Rev1Δwzm Vaccine Properties

The lipopolysaccharide (LPS) O-polysaccharide (O-PS) is the main virulence factor in Brucella. After synthesis in the cytoplasmic membrane, O-PS is exported to the periplasm by the Wzm/Wzt system, where it is assembled into a LPS. This translocation also engages a bactoprenol carrier required for further biosynthesis pathways, such as cell wall biogenesis. Targeting O-PS export by blockage holds great potential for vaccine development, but little is known about the biological implications of each Wzm/Wzt moiety. To improve this knowledge and to elucidate its potential application as a vaccine, we constructed and studied wzm/wzt single- and double-deletion mutants, using the attenuated strain Brucella melitensis Rev1 as the parental strain. This allowed us to describe the composition of Brucella peptidoglycan for the first time. We observed that these mutants lack external O-PS yet trigger changes in genetic transcription and in phenotypic properties associated with the outer membrane and cell wall. The three mutants are highly attenuated; unexpectedly, Rev1Δwzm also excels as an immunogenic and effective vaccine against B. melitensis and Brucella ovis in mice, revealing that low persistence is not at odds with efficacy. Rev1Δwzm is attenuated in BeWo trophoblasts, does not infect mouse placentas, and is safe in pregnant ewes. Overall, these attributes and the minimal serological interference induced in sheep make Rev1Δwzm a highly promising vaccine candidate.

Immunosuppressive Mechanisms in Brucellosis in Light of Chronic Bacterial Diseases

Brucellosis is considered one of the major zoonoses worldwide, constituting a critical livestock and human health concern with a huge socio-economic burden. Brucella genus, its etiologic agent, is composed of intracellular bacteria that have evolved a prodigious ability to elude and shape host immunity to establish chronic infection. Brucella's intracellular lifestyle and pathogen-associated molecular patterns, such as its specific lipopolysaccharide (LPS), are key factors for hiding and hampering recognition by the immune system. Here, we will review the current knowledge of evading and immunosuppressive mechanisms elicited by Brucella species to persist stealthily in their hosts, such as those triggered by their LPS and cyclic β-1,2-d-glucan or involved in neutrophil and monocyte avoidance, antigen presentation impairment, the modulation of T cell responses and immunometabolism. Attractive strategies exploited by other successful chronic pathogenic bacteria, including Mycobacteria, Salmonella, and Chlamydia, will be also discussed, with a special emphasis on the mechanisms operating in brucellosis, such as granuloma formation, pyroptosis, and manipulation of type I and III IFNs, B cells, innate lymphoid cells, and host lipids. A better understanding of these stratagems is essential to fighting bacterial chronic infections and designing innovative treatments and vaccines.

Comparative Review of Brucellosis in Small Domestic Ruminants

Brucella melitensis and Brucella ovis are the primary etiological agents of brucellosis in small domestic ruminants. B. melitensis was first isolated in 1887 by David Bruce in Malta Island from spleens of four soldiers, while B. ovis was originally isolated in Australia and New Zealand in early 1950's from ovine abortion and rams epididymitis. Today, both agents are distributed worldwide: B. melitensis remains endemic and associated with an extensive negative impact on the productivity of flocks in -some regions, and B. ovis is still present in most sheep-raising regions in the world. Despite being species of the same bacterial genus, B. melitensis and B. ovis have extensive differences in their cultural and biochemical characteristics (smooth vs. rough colonial phases, serum and CO2 dependence for in vitro growth, carbohydrate metabolism), host preference (female goat and sheep vs. rams), the outcome of infection (abortion vs. epididymitis), and their zoonotic potential. Some of these differences can be explained at the bacterial genomic level, but the role of the host genome in promoting or preventing interaction with pathogens is largely unknown. Diagnostic techniques and measures to prevent and control brucellosis in small ruminants vary, with B. melitensis having more available tools for detection and prevention than B. ovis. This review summarizes and analyzes current available information on: (1) the similarities and differences between these two etiological agents of brucellosis in small ruminants, (2) the outcomes after their interaction with different preferred hosts and current diagnostic methodologies, (3) the prevention and control measures, and (4) alerting animal producers about the disease and raise awareness in the research community for future innovative activities.

Evaluation of Th2 and Th17 Immunity-Related Factors as Indicators of Brucellosis

Objective

Brucellosis is a common bacterial zoonotic infection, and greater than half a million new cases are diagnosed annually. This study investigates the expression of Th2 and Th17 immunity-related factors (Th2-LCR lncRNA, IL-25, TRAF3IP2, and IL-17RB) in different stages of Brucella infections.

Material and Methods

In total, 99 brucellosis patients were divided into three groups (acute = first infection before treatment, relapse = before treatment, and treated = after treatment for 6–8 weeks with doxycycline and rifampin). Thirty-three healthy volunteers represented the control group. Gene expression levels were assessed by quantitative amplification in reference to the 18S rRNA gene and statistically evaluated.

Results

No significant differences in the expression of these genes were observed between the control group and patients after completion of antibiotic treatment. Compared to these two groups, only Th2-LCR lncRNA and TRAF3IP2 were significantly more highly expressed in the acute group. Th2-LCR lncRNA was also significantly elevated in the relapse group. TRAF3IP2 expression was additionally significantly increased in the acute group compared to the relapse group.

Conclusion

IL-25 and IL-17RB failed to differentiate between the infected and noninfected groups. TRAF3IP2 and Th2-LCR lncRNA might be good indicators of brucellosis during the acute phase, but the expression levels varied strongly among patients. To verify the suitability of these factors as an indicator for brucellosis, acute infection or relapse should be investigated in further studies on larger cohorts with well-defined inclusion criteria.

Comparative Genomic Analysis of Labrenzia aggregata (Alphaproteobacteria) Strains Isolated From the Mariana Trench: Insights Into the Metabolic Potentials and Biogeochemical Functions

Hadal zones are marine environments deeper than 6,000 m, most of which comprise oceanic trenches. Microbes thriving at such depth experience high hydrostatic pressure and low temperature. The genomic potentials of these microbes to such extreme environments are largely unknown. Here, we compare five complete genomes of bacterial strains belonging to Labrenzia aggregata (Alphaproteobacteria), including four from the Mariana Trench at depths up to 9,600 m and one reference from surface seawater of the East China Sea, to uncover the genomic potentials of this species. Genomic investigation suggests all the five strains of L. aggregata as participants in nitrogen and sulfur cycles, including denitrification, dissimilatory nitrate reduction to ammonium (DNRA), thiosulfate oxidation, and dimethylsulfoniopropionate (DMSP) biosynthesis and degradation. Further comparisons show that, among the five strains, 85% gene functions are similar with 96.7% of them encoded on the chromosomes, whereas the numbers of functional specific genes related to osmoregulation, antibiotic resistance, viral infection, and secondary metabolite biosynthesis are majorly contributed by the differential plasmids. A following analysis suggests the plasmidic gene numbers increase along with isolation depth and most plasmids are dissimilar among the five strains. These findings provide a better understanding of genomic potentials in the same species throughout a deep-sea water column and address the importance of externally originated plasmidic genes putatively shaped by deep-sea environment.

Idiosyncratic Biogenesis of Intracellular Pathogens-Containing Vacuoles

While most bacterial species taken up by macrophages are degraded through processing of the bacteria-containing vacuole through the endosomal-lysosomal degradation pathway, intravacuolar pathogens have evolved to evade degradation through the endosomal-lysosomal pathway. All intra-vacuolar pathogens possess specialized secretion systems (T3SS-T7SS) that inject effector proteins into the host cell cytosol to modulate myriad of host cell processes and remodel their vacuoles into proliferative niches. Although intravacuolar pathogens utilize similar secretion systems to interfere with their vacuole biogenesis, each pathogen has evolved a unique toolbox of protein effectors injected into the host cell to interact with, and modulate, distinct host cell targets. Thus, intravacuolar pathogens have evolved clear idiosyncrasies in their interference with their vacuole biogenesis to generate a unique intravacuolar niche suitable for their own proliferation. While there has been a quantum leap in our knowledge of modulation of phagosome biogenesis by intravacuolar pathogens, the detailed biochemical and cellular processes affected remain to be deciphered. Here we discuss how the intravacuolar bacterial pathogens Salmonella, Chlamydia, Mycobacteria, Legionella, Brucella, Coxiella, and Anaplasma utilize their unique set of effectors injected into the host cell to interfere with endocytic, exocytic, and ER-to-Golgi vesicle traffic. However, Coxiella is the main exception for a bacterial pathogen that proliferates within the hydrolytic lysosomal compartment, but its T4SS is essential for adaptation and proliferation within the lysosomal-like vacuole.

High Genomic Identity between Clinical and Environmental Strains of Herbaspirillum frisingense Suggests Pre-Adaptation to Different Hosts and Intrinsic Resistance to Multiple Drugs

The genus Herbaspirillum is widely studied for its ability to associate with grasses and to perform biological nitrogen fixation. However, the bacteria of the Herbaspirillum genus have frequently been isolated from clinical samples. Understanding the genomic characteristics that allow these bacteria to switch environments and become able to colonize human hosts is essential for monitoring emerging pathogens and predicting outbreaks. In this work, we describe the sequencing, assembly, and annotation of the genome of H. frisingense AU14559 isolated from the sputum of patients with cystic fibrosis, and its comparison with the genomes of the uropathogenic strain VT-16-41 and the environmental strains GSF30, BH-1, IAC152, and SG826. The genes responsible for biological nitrogen fixation were absent from all strains except for GSF30. On the other hand, genes encoding virulence and host interaction factors were mostly shared with environmental strains. We also identified a large set of intrinsic antibiotic resistance genes that were shared across all strains. Unlike other strains, in addition to unique genomic islands, AU14559 has a mutation that renders the biosynthesis of rhamnose and its incorporation into the exopolysaccharide unfeasible. These data suggest that H. frisingense has characteristics that provide it with the metabolic diversity needed to infect and colonize human hosts.

Pathogenesis of Brucella epididymoorchitis-game of Brucella death

Brucellosis is a worldwide zoonotic disease caused by Brucella spp. Human infection often results from direct contact with tissues from infected animals or by consumption of undercooked meat and unpasteurised dairy products, causing serious economic losses and public health problems. The male genitourinary system is a common involved system in patients with brucellosis. Among them, unilateral orchitis and epididymitis are the most common. Although the clinical and imaging aspect of orchi-epididymitis caused by brucellosis have been widely described, the cellular and molecular mechanisms involved in the damage and the immune response in testis and epididymis have not been fully elucidated. In this review, we first summarised the clinical characteristics of Brucella epididymo-orchitis and the composition of testicular and epididymal immune system. Secondly, with regard to the mechanism of Brucella epididymoorchitis, we mainly discussed the process of Brucella invading testis and epididymis in temporal and spatial order, including i) Brucella evades innate immune recognition of testicular PRRs；ii) Brucella overcomes the immune storm triggered by the invasion of testis through bacterial lipoproteins and virulence factors, and changes the secretion mode of cytokines; iii) Brucella breaks through the blood-testis barrier with the help of macrophages, and inflammatory cytokines promote the oxidative stress of Sertoli cells, damaging the integrity of BTB; iv) Brucella inhibits apoptosis of testicular phagocytes. Finally, we revealed the structure and sequence of testis invaded by Brucella at the tissue level. This review will enable us to better understand the pathogenesis of orchi-epididymitis caused by brucellosis and shed light on the development of new treatment strategies for the treatment of brucellosis and the prevention of transition to chronic form. Facing the testicle with immunity privilege, Brucella is like Bruce Lee in the movie Game of Death, winning is survival while losing is death.HIGHLIGHTSWe summarized the clinical features and pathological changes of Brucellaepididymoorchitis.Our research reveals the pathogenesis of Brucella epididymoorchitis, which mainly includes the subversion of testicular immune privilege by Brucella and a series of destructive reactions derived from it.As a basic framework and valuable resource, this study can promote the exploration of the pathogenesis of Brucella and provide reference for determining new therapeutic targets for brucellosis in the future.

Donnan Potential across the Outer Membrane of Gram-Negative Bacteria and Its Effect on the Permeability of Antibiotics

The cell envelope structure of Gram-negative bacteria is unique, composed of two lipid bilayer membranes and an aqueous periplasmic space sandwiched in between. The outer membrane constitutes an extra barrier to limit the exchange of molecules between the cells and the exterior environment. Donnan potential is a membrane potential across the outer membrane, resulted from the selective permeability of the membrane, which plays a pivotal role in the permeability of many antibiotics. In this review, we discussed factors that affect the intensity of the Donnan potential, including the osmotic strength and pH of the external media, the osmoregulated periplasmic glucans trapped in the periplasmic space, and the displacement of cell surface charges. The focus of our discussion is the impact of Donnan potential on the cellular permeability of selected antibiotics including fluoroquinolones, tetracyclines, β-lactams, and trimethoprim.

Environmental and clinical isolates of Herbaspirillum induce pulmonary infection in mice and its secretome is cytotoxic to human lung cells

Introduction. In recent years, the Herbaspirillum genus has emerged as a pathogen in healthcare-related infections and has became stablished as an opportunistic pathogen.Hypothesis/Gap Statement. Little is known about the pathogenesis induced by Herbaspirillum genus.Aim. To evaluate the cytotoxic effects of genus Herbaspirillum, its ability to adhere to lung human cells and the ability of environmental and clinical strains of Herbaspirillum to induce pneumonia in mice.Methodology. Environmental and clinical isolates of Herbaspirillum were examined for their cytotoxic effects on the Calu-3 cell lineage. Cytotoxic activity of secretome was tested using MTT/neutral red assays and cell morphology analysis. Herbaspirillum adhesion on Calu-3 cells was assessed using bright-field microscopy and cell-associated bacteria were counted. A mouse model of acute lung infection was done using a clinical and an environmental strain. Adult male mice were used, and the pneumonia was inducted by intra-tracheal inoculation of 10⁸ or 10⁹ bacteria. Mice weight variations were evaluated at the end of the experiment. Bronchoalveolar lavage was collected and evaluated for total and differential cytology. A histological examination of lungs was performed giving a histological score.Results. The secretomes of all the strains induced morphological alterations in cells, but only H. seropedicae SmR1 were cytotoxic in MTT and neutral red assays. Clinical strains of H. frisingense AU14459 and H. hutttiense subsp. huttiense AU11883 exhibited low adherence to lung cells, while SmR1 was non-adhesive. Following intratracheal inoculation, mice treated with 10⁹ c.f.u. of the SmR1 and AU11883 strains lost 18 and 6% of their weight over 7 days, respectively, and presented moderate clinical signs. Infected mice showed inflammatory cell infiltration in the perivascular and peribroncheal/peribronchiolar spaces. Bronchoalveolar fluid of mice inoculated with SmR1 10⁹ c.f.u. presented an increase in total leucocyte cells and in neutrophils population.Conclusion. These in vivo and in vitro results provide insights into how some Herbaspirillum strains cause infection in humans, providing a basis for the characterization of pathogenesis studies on this emerging infectious agent.

Uncovering the Hidden Credentials of Brucella Virulence

Bacteria in the genus Brucella are important human and veterinary pathogens. The abortion and infertility they cause in food animals produce economic hardships in areas where the disease has not been controlled, and human brucellosis is one of the world's most common zoonoses. Brucella strains have also been isolated from wildlife, but we know much less about the pathobiology and epidemiology of these infections than we do about brucellosis in domestic animals. The brucellae maintain predominantly an intracellular lifestyle in their mammalian hosts, and their ability to subvert the host immune response and survive and replicate in macrophages and placental trophoblasts underlies their success as pathogens. We are just beginning to understand how these bacteria evolved from a progenitor alphaproteobacterium with an environmental niche and diverged to become highly host-adapted and host-specific pathogens. Two important virulence determinants played critical roles in this evolution: (i) a type IV secretion system that secretes effector molecules into the host cell cytoplasm that direct the intracellular trafficking of the brucellae and modulate host immune responses and (ii) a lipopolysaccharide moiety which poorly stimulates host inflammatory responses. This review highlights what we presently know about how these and other virulence determinants contribute to Brucella pathogenesis. Gaining a better understanding of how the brucellae produce disease will provide us with information that can be used to design better strategies for preventing brucellosis in animals and for preventing and treating this disease in humans.

Brucella: Reservoirs and Niches in Animals and Humans

Brucella is an intracellular bacterium that causes abortion, reproduction failure in livestock and leads to a debilitating flu-like illness with serious chronic complications if untreated in humans. As a successful intracellular pathogen, Brucella has developed strategies to avoid recognition by the immune system of the host and promote its survival and replication. In vivo, Brucellae reside mostly within phagocytes and other cells including trophoblasts, where they establish a preferred replicative niche inside the endoplasmic reticulum. This process is central as it gives Brucella the ability to maintain replicating-surviving cycles for long periods of time, even at low bacterial numbers, in its cellular niches. In this review, we propose that Brucella takes advantage of the environment provided by the cellular niches in which it resides to generate reservoirs and disseminate to other organs. We will discuss how the favored cellular niches for Brucella infection in the host give rise to anatomical reservoirs that may lead to chronic infections or persistence in asymptomatic subjects, and which may be considered as a threat for further contamination. A special emphasis will be put on bone marrow, lymph nodes, reproductive and for the first time adipose tissues, as well as wildlife reservoirs.

Integrative Bioinformatics Indentification of the Autophagic Pathway-Associated miRNA-mRNA Networks in RAW264.7 Macrophage Cells Infected with ∆Omp25 Brucella melitensis

Brucellosis is a zoonotic infectious disease caused by Brucella infection. Outer membrane protein 25 (Omp25) is closely related to the virulence and immunogenicity of Brucella. However, the molecular mechanism of Omp25 affecting Brucella-mediated macrophage autophagy remains unclear. Our previous study reported that four miRNAs (the upregulation of mmu-miR-146a-5p and mmu-miR-155-5p and downregulation of mmu-miR-149-3p and mmu-miR-5126) were confirmed and revealed the differentially expressed genes (DEGs) profile in RAW264.7 macrophage cells infected with Brucella melitensis Omp25 deletion mutant (∆Omp25 B. melitensis). Here, we predicted the target genes of the four miRNAs by TargetScan, miRanda, and PicTar. GO and KEGG were used for functional enrichment analysis of DEGs profile to reveal the autophagic pathway-associated genes. The overlapped genes, which drawn the autophagic pathway-associated miRNA-mRNA networks by cytoscape software, were identified by intersecting with the predicted target genes and autophagic pathway-associated DEGs. qRT-PCR was performed to validate the mRNAs of networks. The results showed that the autophagic pathway-associated networks of mmu-miR-149-3p-Ptpn5, mmu-miR-149-3p-Ppp2r3c, and mmu-miR-146a-5p-Dusp16 were identified in RAW264.7 macrophage cells infected with ∆Omp25 B. melitensis. Our findings are of great significance in elucidating the function of Omp25, revealing the infection mechanism of Brucella and prophylaxising and treating brucellosis.

Scenario of pathogenesis and socioeconomic burden of human brucellosis in Saudi Arabia

Brucellosis is considered a prevailing endemic infectious disease in the Kingdom of Saudi Arabia and represents a health problem with socio-economic burden. There are two main Brucella species that cause human brucellosis; Brucella abortus, and Brucella melitensis. The clinical features range from asymptomatic to the acute symptoms of fever, joint pain, muscle pain, headache, nausea/vomiting, anorexia and malaise in addition to the subsequent complications that might occur. The endemicity of brucellosis might be explained due to obstacles in controlling the importation of animals for slaughtering during Hajj periods and for several other predisposing factors. The distribution of the disease is all over the country and the most prevalent part is the south followed by north and then the east and central parts. However, in the complexity of brucellosis control measures, there are several activities which have been implemented to tackle the disease such as mass vaccination of animals, regulating importation of slaughter animals, and improving public awareness. This review provides a detailed description of the status of brucellosis in Saudi Arabia, which includes epidemiology, clinical characteristics, virulence and pathophysiology, and prevention of the disease.

Genomic insights into Brucella

Brucellosis is a zoonotic disease caused by certain species of Brucella. Each species has its preferred host animal, though it can infect other animals too. For a longer period, only six classical species were recognized in the genus Brucella. No vaccine is available for human brucellosis. Therefore, human brucellosis can be controlled only by controlling brucellosis in animals. The genus is now expanding with the newly isolated atypical strains from various animals, including marine mammals. Presently, 12 species of Brucella have been recognized. The first genome of Brucella was released in 2002, and today, we have more than 1500 genomes of Brucella spp. isolated worldwide. Multiple genome sequences are available for the major zoonotic species, B. abortus, B. melitensis, and B. suis. The Brucella genome has two chromosomes with the approximate sizes of 2.1 and 1.2 Mbp. The genome of Brucella is highly conserved across all the species at the nucleotide level. One of the unanswered questions is what makes host preference in different species of Brucella. Here, I summarize the recent advancements in the Brucella genomics research.

The Role of Neutrophils in Brucellosis

Brucellosis is a bacterial disease of domestic animals and humans. The pathogenic ability of Brucella organisms relies on their stealthy strategy and their capacity to replicate within host cells and to induce long-lasting infections. Brucella organisms barely induce neutrophil activation and survive within these leukocytes by resisting microbicidal mechanisms. Very few Brucella-infected neutrophils are found in the target organs, except for the bone marrow, early in infection. Still, Brucella induces a mild reactive oxygen species formation and, through its lipopolysaccharide, promotes the premature death of neutrophils, which release chemokines and express "eat me" signals. This effect drives the phagocytosis of infected neutrophils by mononuclear cells that become thoroughly susceptible to Brucella replication and vehicles for bacterial dispersion. The premature death of the infected neutrophils proceeds without NETosis, necrosis/oncosis, or classical apoptosis morphology. In the absence of neutrophils, the Th1 response exacerbates and promotes bacterial removal, indicating that Brucella-infected neutrophils dampen adaptive immunity. This modulatory effect opens a window for bacterial dispersion in host tissues before adaptive immunity becomes fully activated. However, the hyperactivation of immunity is not without a price, since neutropenic Brucella-infected animals develop cachexia in the early phases of the disease. The delay in the immunological response seems a sine qua non requirement for the development of long-lasting brucellosis. This property may be shared with other pathogenic alphaproteobacteria closely related to Brucella We propose a model in which Brucella-infected polymorphonuclear neutrophils (PMNs) function as "Trojan horse" vehicles for bacterial dispersal and as modulators of the Th1 adaptive immunity in infection.

Mycobacterium Lipids Modulate Host Cell Membrane Mechanics, Lipid Diffusivity, and Cytoskeleton in a Virulence-Selective Manner

Microbial lipids play a critical role in the pathogenesis of infectious diseases by modulating the host cell membrane properties, including lipid/protein diffusion and membrane organization. Mycobacterium tuberculosis (Mtb) synthesizes various chemically distinct lipids that are exposed on its outer membrane and interact with host cell membranes. However, the effects of the structurally diverse Mtb lipids on the host cell membrane properties to fine-tune the host cellular response remain unknown. In this study, we employed membrane biophysics and cell biology to assess the effects of different Mtb lipids on cell membrane mechanics, lipid diffusion, and the cytoskeleton of THP-1 macrophages. We found that Mtb lipids modulate macrophage membrane properties, actin cytoskeleton, and biochemical processes, such as protein phosphorylation and lipid peroxidation, in a virulence lipid-selective manner. These results emphasize that Mtb can fine-tune its interactions with the host cells governed by modulating the lipid profile on its surface. These observations provide a novel lipid-centric paradigm of Mtb pathogenesis that is amenable to pharmacological inhibition and could promote the development of robust biomarkers of Mtb infection and pathogenesis.

Virulence Factors in the Phytopathogen-Host Interactions: An Overview

Phytopathogens are responsible for great losses in agriculture, once they are able to subvert or elude the host defense mechanisms through virulence factors secretion for their dissemination. Herein, it is reviewed phytotoxins that act as virulence factors and are produced by bacterial phytopathogens (Candidatus Liberibacter spp., Erwinia amylovora, Pseudomonas syringae pvs and Xanthomonas spp.) and fungi (Alternaria alternata, Botrytis cinerea, Cochliobolus spp., Fusarium spp., Magnaporthe spp., and Penicillium spp.), which were selected in accordance to their worldwide importance due to the biochemical and economical aspects. In the current review, it is sought to understand the role of virulence factors in the pathogen-host interactions that result in plant diseases.

A Zinc-Dependent Metalloproteinase of Brucella abortus Is Required in the Intracellular Adaptation of Macrophages

Brucella abortus is a pathogen that survives in macrophages. Several virulence factors participate in this process, including the open reading frame (ORF) BAB1_0270 codifying for a zinc-dependent metalloproteinase (ZnMP). Here, its contribution in the intracellular adaptation of B. abortus was analyzed by infecting RAW264.7 macrophages with the mutant B. abortus Δ270 strain. Results showed that this ZnMP did not participated in either the adherence or the initial intracellular traffic of B. abortus in macrophages. Nevertheless, its deletion significantly increased the co-localization of B. abortus Δ270 with phagolysosomal cathepsin D and reduced its co-localization with calnexin present in endoplasmic reticulum (RE)-derived vesicles. Although B. abortus Δ270 showed an upregulated expression of genes involved in virulence (vjbR, hutC, bvrR, virB1), it was insufficient to reach a successful intracellular replication within macrophages. Furthermore, its attenuation favored in macrophages infected the production of high levels of cytokines (TNF-α and IL-6) and co-stimulatory proteins (CD80 and CD86), signals required in T cell activation. Finally, its deletion significantly reduced the ability of B. abortus Δ270 to adapt, grow and express several virulence factors under acidic conditions. Based on these results, and considering that this ZnMP has homology with ImmA/IrrE proteases, we discuss its role in the virulence of this pathogen, concluding that ZnMP is required in the intracellular adaptation of B. abortus 2308 during the infection of macrophages.

Chemistry and microbial sources of curdlan with potential application and safety regulations as prebiotic in food and health

Curdlan - a homopolysaccharide is comprised of glucose using β-1,3-glycosidic bond and produced by different types of microorganisms as exopolysaccharide. Curdlan gel is stable during freezing and thawing processes which find several applications in food and pharmaceutical industries. It acts as a prebiotic, stabilizer and water-holding, viscosifying and texturing agent. Additionally, curdlan gel is used as a food factor to develop the new products e.g. milk fat substitute, non-fat whipped cream, retorting (freeze-drying) process of Tofu, low-fat sausage, and low-fat hamburger. However, a great variation exists among different countries regarding the regulatory aspects of curdlan as food additives, dietary components or prebiotic substances. Therefore, the present review paper aims to discuss safety issues and the establishment of common guidelines and legislation globally, focusing on the use the applications of curdlan in the food sector including the development of noodles, meat-based products, and fat-free dairy products. This review analyzes and describes in detail the potential of curdlan as a sustainable alternative additive in health and food industries, emphasizing on the chemical composition, production, properties, and potential applications.

Brucella abortus Depends on l-Serine Biosynthesis for Intracellular Proliferation

l-Serine is a nonessential amino acid and a key intermediate in several relevant metabolic pathways. In bacteria, the major source of l-serine is the phosphorylated pathway, which comprises three enzymes: d-3-phosphoglycerate dehydrogenase (PGDH; SerA), phosphoserine amino transferase (PSAT; SerC), and l-phosphoserine phosphatase (PSP; SerB). The Brucella abortus genome encodes two PGDHs (SerA-1 and SerA-2), involved in the first step in l-serine biosynthesis, and one PSAT and one PSP, responsible for the second and third steps, respectively. In this study, we demonstrate that the serA1 serA2 double mutant and the serC and serB single mutants are auxotrophic for l-serine. These auxotrophic mutants can be internalized but are unable to replicate in HeLa cells and in J774A.1 macrophage-like cells. Replication defects of auxotrophic mutants can be reverted by cell medium supplementation with l-serine at early times postinfection. In addition, the serB mutant is attenuated in the murine intraperitoneal infection model and has an altered lipid composition, since the lack of l-serine abrogates phosphatidylethanolamine synthesis in this strain. Taken together, these results reveal that limited availability of l-serine within the host cell impairs proliferation of the auxotrophic strains, highlighting the relevance of this biosynthetic pathway in Brucella pathogenicity.

Research Progress on Brucellosis

Brucellosis is a debilitating febrile illness caused by an intracellular Brucella. The disease is distributed in humans and animals widely, especially in developing countries. Ten species are included in the genus Brucella nowadays; four species of them are pathogenic to humans, which make brucellosis a zoonosis with more than 500,000 new cases reported annually. For human brucellosis, the most pathogenic species is B. melitensis followed by B. suis, while B. abortus is the mildest type of brucellosis. The infection mechanism of Brucella is complicated and mostly relies on its virulence factors. The therapy of the disease contains vaccination and antibiotic. However, there are some defects in currently available vaccines such as the lower protective level and safety. Thus, safe and efficient vaccines for brucellosis are still awaited. The dual therapy of antibacterial is effective in the treatment of brucellosis if a rapid and exact detection method is found.

Immune Response to Mucosal Brucella Infection

Brucellosis is one of the most prevalent bacterial zoonosis of worldwide distribution. The disease is caused by Brucella spp., facultative intracellular pathogens. Brucellosis in animals results in abortion of fetuses, while in humans, it frequently manifests flu-like symptoms and a typical undulant fever, being osteoarthritis a common complication of the chronic infection. The two most common ways to acquire the infection in humans are through the ingestion of contaminated dairy products or by inhalation of contaminated aerosols. Brucella spp. enter the body mainly through the gastrointestinal and respiratory mucosa; however, most studies of immune response to Brucella spp. are performed analyzing models of systemic immunity. It is necessary to better understand the mucosal immune response induced by Brucella infection since this is the main entry site for the bacterium. In this review, some virulence factors and the mechanisms needed for pathogen invasion and persistence are discussed. Furthermore, some aspects of local immune responses induced during Brucella infection will be reviewed. With this knowledge, better vaccines can be designed focused on inducing protective mucosal immune response.

Evaluation of human trophoblasts and ovine testis cell lines for the study of the intracellular pathogen Brucella ovis

Since pathogenic Brucella survive and replicate inside phagocytes, cellular models of infection constitute important tools in brucellosis research. We describe the behavior of B. ovis PA (which causes a type of ovine brucellosis mainly affecting the male reproductive tract) and representative attenuated mutants in two commercially available cell lines of non-professional phagocytes related to Brucella tissue preference: OA3.Ts ovine testis cells and JEG-3 human trophoblasts. In comparison with J774.A1 macrophages and HeLa cells, intracellular bacteria were enumerated at several post-infection time points and visualized by confocal microscopy. Replication of B. ovis in OA3.Ts and JEG-3 cells was equivalent to that observed in J774.A1 macrophages-despite the more efficient internalization in the latter-and better than in HeLa cells. Multiplication and/or survival in all phagocytes was dependent on virB2 and vjbR but independent of cgs, despite the attenuation in mice of the Δcgs mutant. However, Omp25c was required for B. ovis internalization only in HeLa cells, and removal of Omp31 increased bacterial internalization in human HeLa and JEG-3 cells. The results presented here demonstrate variability in the interaction of B. ovis with different host cells and provide advantageous models of non-professional phagocytes to study the intracellular behavior of B. ovis.

Genome comparison between clinical and environmental strains of Herbaspirillum seropedicae reveals a potential new emerging bacterium adapted to human hosts

BACKGROUND

Herbaspirillum seropedicae is an environmental β-proteobacterium that is capable of promoting the growth of economically relevant plants through biological nitrogen fixation and phytohormone production. However, strains of H. seropedicae have been isolated from immunocompromised patients and associated with human infections and deaths. In this work, we sequenced the genomes of two clinical strains of H. seropedicae, AU14040 and AU13965, and compared them with the genomes of strains described as having an environmental origin.

RESULTS

Both genomes were closed, indicating a single circular chromosome; however, strain AU13965 also carried a plasmid of 42,977 bp, the first described in the genus Herbaspirillum. Genome comparison revealed that the clinical strains lost the gene sets related to biological nitrogen fixation (nif) and the type 3 secretion system (T3SS), which has been described to be essential for interactions with plants. Comparison of the pan-genomes of clinical and environmental strains revealed different sets of accessorial genes. However, antimicrobial resistance genes were found in the same proportion in all analyzed genomes. The clinical strains also acquired new genes and genomic islands that may be related to host interactions. Among the acquired islands was a cluster of genes related to lipopolysaccharide (LPS) biosynthesis. Although highly conserved in environmental strains, the LPS biosynthesis genes in the two clinical strains presented unique and non-orthologous genes within the genus Herbaspirillum. Furthermore, the AU14040 strain cluster contained the neuABC genes, which are responsible for sialic acid (Neu5Ac) biosynthesis, indicating that this bacterium could add it to its lipopolysaccharide. The Neu5Ac-linked LPS could increase the bacterial resilience in the host aiding in the evasion of the immune system.

CONCLUSIONS

Our findings suggest that the lifestyle transition from environment to opportunist led to the loss and acquisition of specific genes allowing adaptations to colonize and survive in new hosts. It is possible that these substitutions may be the starting point for interactions with new hosts.

Topological Glycopolymers as Agglutinator and Inhibitor: Cyclic versus Linear

Carbohydrates play an important role in biological processes for their specific interactions with proteins. Cyclic glycopolymers are promising to mimic the topology of natural macrocycle-biomacromolecules due to their unique architecture of lacking chain ends. To systematically study the effect of glycopolymer architecture on the interactions with protein, the cyclic glycopolymers bearing galactose side-chain (cyclic PMAG_n ) with three degrees of polymerization (n = 14, 24, 47) are prepared for the first time. The cyclic PMAG_n exhibits unique properties in agglutinating and inhibiting proteins in subsequent studies by comparison with the linear precursor with the same molecular weights. More impressively, the cyclic PMAG_n highlight the improved performance of cyclic architecture. For example, the cyclic PMAG_n shows superior inhibition abilities to suppress amyloid formation from amyloid β protein fragment 1-42 aggregation and block the specific interaction between bacteria and galactose-modified surface compared to that of respective linear counterpart. This interesting finding suggests that the architecture of cyclic glycopolymers may be capable of optimizing the ability to bind or inhibit proteins in biological processes.

A Role for the VPS Retromer in Brucella Intracellular Replication Revealed by Genomewide siRNA Screening

Brucella, the agent causing brucellosis, is a major zoonotic pathogen with worldwide distribution. Brucella resides and replicates inside infected host cells in membrane-bound compartments called Brucella-containing vacuoles (BCVs). Following uptake, Brucella resides in endosomal BCVs (eBCVs) that gradually mature from early to late endosomal features. Through a poorly understood process that is key to the intracellular lifestyle of Brucella, the eBCV escapes fusion with lysosomes by transitioning to the replicative BCV (rBCV), a replicative niche directly connected to the endoplasmic reticulum (ER). Despite the notion that this complex intracellular lifestyle must depend on a multitude of host factors, a holistic view on which of these components control Brucella cell entry, trafficking, and replication is still missing. Here we used a systematic cell-based small interfering RNA (siRNA) knockdown screen in HeLa cells infected with Brucella abortus and identified 425 components of the human infectome for Brucella infection. These include multiple components of pathways involved in central processes such as the cell cycle, actin cytoskeleton dynamics, or vesicular trafficking. Using assays for pathogen entry, knockdown complementation, and colocalization at single-cell resolution, we identified the requirement of the VPS retromer for Brucella to escape the lysosomal degradative pathway and to establish its intracellular replicative niche. We thus validated the VPS retromer as a novel host factor critical for Brucella intracellular trafficking. Further, our genomewide data shed light on the interplay between central host processes and the biogenesis of the Brucella replicative niche.IMPORTANCE With >300,000 new cases of human brucellosis annually, Brucella is regarded as one of the most important zoonotic bacterial pathogens worldwide. The agent causing brucellosis resides inside host cells within vacuoles termed Brucella-containing vacuoles (BCVs). Although a few host components required to escape the degradative lysosomal pathway and to establish the ER-derived replicative BCV (rBCV) have already been identified, the global understanding of this highly coordinated process is still partial, and many factors remain unknown. To gain deeper insight into these fundamental questions, we performed a genomewide RNA interference (RNAi) screen aiming at discovering novel host factors involved in the Brucella intracellular cycle. We identified 425 host proteins that contribute to Brucella cellular entry, intracellular trafficking, and replication. Together, this study sheds light on previously unknown host pathways required for the Brucella infection cycle and highlights the VPS retromer components as critical factors for the establishment of the Brucella intracellular replicative niche.

Brucella - Virulence Factors, Pathogenesis and Treatment

Brucellae are Gram-negative, small rods infecting mammals and capable of causing disease called brucellosis. The infection results in abortion and sterility in domestic animals (sheeps, pigs, rams etc). Especially dangerous for humans are: Brucella melitensis, Brucella suis, Brucella abortus, and Brucella canis that trigger unspecific symptoms (flu-like manifestation). Brucella rods are introduced via host cells, by inhalation, skin abrasions, ingestion or mucosal membranes. The most important feature of Brucella is the ability to survive and multiply within both phagocytic and non-phagocytic cells. Brucella does not produce classical virulence factors: exotoxin, cytolisins, exoenzymes, plasmids, fimbria, and drug resistant forms. Major virulence factors are: lipopolysaccharide (LPS), T4SS secretion system and BvrR/BvrS system, which allow interaction with host cell surface, formation of an early, late BCV (Brucella Containing Vacuole) and interaction with endoplasmic reticulum (ER) when the bacteria multiply. The treatment of brucellosis is based on two-drug therapy, the most common combinations of antibiotics are: doxycycline with rifampicin or fluoroquinolones with rifampicin. Currently, also other methods are used to disrupt Brucella intracellular replication (tauroursodeoxycholic acid or ginseng saponin fraction A).

Large-scale preparation of β-1,2-glucan using quite a small amount of sophorose

A large amount of β-1,2-glucan was produced enzymatically from quite a small amount of sophorose as an acceptor material through three synthesis steps using a sucrose phosphorylase and a 1,2-β-oligoglucan phosphorylase. The first synthesis step was performed in a 200 μL of a reaction solution containing 5 mM sophorose and 1.0 M sucrose. β-1,2-Glucan in a part of the resultant solution was hydrolyzed to β-1,2-glucooligosaccharides by a β-1,2-glucanase. The second synthesis was performed in 25 times the volume for the first synthesis. The hydrolysate solution (1% volume of the reaction solution) was used as an acceptor. After treatment with the β-1,2-glucanase again, the third synthesis was performed 200 times the volume for the second synthesis (1 L). The reaction yield of β-1,2-glucan at each synthesis was 93%, 76% and 91%. Finally, more than 140 g of β-1,2-glucan was synthesized using approximately 20 μg of sophorose as the starting acceptor material. Abbreviations: DPs: degrees of polymerization; SOGP: 1,2-β-oligoglucan phosphorylase; Sop_ns: β-1,2-glucooligosaccharides with DP of n; Glc1P: α-glucose 1-phosphate; SucP: sucrose phosphorylase from Bifidobacterium longum subsp. longum; SGL: β-1,2-glucanase; CaSGL: Chy400_4174 protein; TLC: thin layer chromatography; GOPOD: glucose oxidase/peroxidase; PGM: phosphoglucomutase; G6PDH: glucose 6-phosphate dehydrogenase.

The role and mechanism of icmF in Aeromonas hydrophila survival in fish macrophages

Survival in host macrophages is an effective strategy for pathogenic bacteria to spread. Aeromonas hydrophila has been found to survive in fish macrophages, but the mechanisms remain unknown. In this paper, the roles and possible mechanisms of IcmF in bacterial survival in fish macrophages were investigated. First, a stable silencing strain icmF-RNAi was constructed by shRNA and RT-qPCR confirmed the expression of icmF was down-regulated by 94.42%. The expression of Hcp, DotU and VgrG was also decreased in icmF-RNAi. The intracellular survival rate of the wild-type strain was 92.3%, while the survival rate of icmF-RNAi was only 20.58%. The escape rate of the wild-type strain was 20%, while that of the icmF-RNAi was only 7.5%. Further studies indicated that the expression of icmF can significantly affect the adhesion, biofilm formation, motility and acid resistance of A. hydrophila, but has no significant effect on the growth of A. hydrophila even under the stress of H₂ O₂ . The results indicated that IcmF of A. hydrophila not only acts as a structural protein which participates in virulence-related characteristics such as bacterial motility, adhesion and biofilm formation, but also acts as a key functional protein which participates in the interaction between bacteria and host macrophages.

Infection by Anaplasma phagocytophilum Requires Recruitment of Low-Density Lipoprotein Cholesterol by Flotillins

Anaplasma phagocytophilum is an obligatory intracellular bacterium that proliferates in membrane-bound inclusions. A. phagocytophilum is dependent on cholesterol and acquire cholesterol from low-density lipoprotein (LDL) endocytosed by mammalian host cells. The mechanism of cholesterol transport to Anaplasma inclusions, however, is not fully understood. Flotillin-1 (FLOT1) and FLOT2 are cholesterol-associated membrane proteins that form a heterodimer and/or oligomer complex. Here, we found that Anaplasma infection was significantly reduced by small interfering RNA (siRNA) knockdown of FLOT1 or FLOT2. Anaplasma inclusions were encircled with small vesicles containing endogenous FLOT1 or FLOT2 or with ectopically expressed FLOT1-mCherry and FLOT2-green fluorescent protein (FLOT2-GFP). FLOT1- and FLOT2-containing vesicles were enriched with unesterified cholesterol, as indicated by labeling with filipin and aminomethyl coumarin acetic acid-conjugated theonellamide. Localization of FLOT2 to Anaplasma inclusions was dependent on cholesterol, as FLOT2-GFP bearing two mutations in the cholesterol recognition/interaction motif could not target the inclusions. The cholesterol-sequestering agent methyl-β-cyclodextrin abrogated FLOT1 localization to Anaplasma inclusions and cleared infection. FLOT2-GFP also localized to fluorescent 3,3'-dioctadecylindocarbocyanine (DiI)-LDL-containing vesicles, including those surrounding Anaplasma inclusions. FLOT2 siRNA knockdown blocked DiI-LDL trafficking to Anaplasma inclusions and reduced bacteria-associated cholesterol amount, and therefore inhibiting Anaplasma infection. Vesicles containing acid lipase, which hydrolyzes LDL cholesterol esters to free cholesterol, colocalized with FLOT2 and encircled Anaplasma inclusions, while the acid lipase inhibitor orlistat significantly inhibited Anaplasma replication. Together, the data revealed that FLOTs are crucial for Anaplasma replication in host cells, likely by aiding vesicular traffic of LDL-derived free cholesterol to Anaplasma inclusions, and suggest a new way of inhibiting Anaplasma infection.IMPORTANCE Cholesterol is essential for animal cells, but most bacteria do not depend on cholesterol and instead lack cholesterol. However, the intracellular Gram-negative bacterium Anaplasma phagocytophilum that causes human granulocytic anaplasmosis (HGA) is unusual, as it contains significant amount of cholesterol and depends on cholesterol for survival and infection. A. phagocytophilum lacks genes for cholesterol biosynthesis or modification but acquire cholesterol from host cells exclusively from the LDL uptake pathway by a yet-to-be defined mechanism. Here, we uncovered a role of cholesterol-binding proteins FLOT1 and FLOT2 in LDL-derived cholesterol trafficking to Anaplasma inclusions and cholesterol acquisition by Anaplasma species. Importantly, we found that FLOTs localize to A. phagocytophilum-containing inclusions and the compartments containing LDL, and the acid lipase inhibitor orlistat significantly inhibits Anaplasma replication. Our data suggest a fundamental role of FLOTs in intracellular vesicular transport of LDL-derived free cholesterol and may provide insight regarding a new therapeutic target for HGA treatment.

Deletion of the Type IV Secretion System Effector VceA Promotes Autophagy and Inhibits Apoptosis in Brucella-Infected Human Trophoblast Cells

Brucellosis is the most common zoonotic disease that caused by intracellular parasitic bacteria Brucella. The survival and replication of Brucella in the host depend on the type IV secretion system (T4SS). The T4SS system of Brucella has many components and secreted proteins. But the mechanism helped Brucella to evade the host defense is still not clear. The objective of the present study was to investigate the effects of VceA on autophagy and apoptosis in Brucella-infected embryonic trophoblast cells. We constructed the VceA mutant strain (2308ΔVceA) and complementary strain (2308ΔVceA-C) of Brucella abortus 2308 (S2308). The human trophoblast cells (HPT-8 cells) and mice were infected by S2308, 2308ΔVceA and 2308ΔVceA-C. The cell autophagy and apoptosis were detected. The Atg5, LC3-II and Bcl-2 mRNA expression were significantly increased in 2308ΔVceA group than the S2308 group, and mRNA expression of P62 and Caspase-3 were significantly decreased than the S2308 group. Western blotting, qPCR and flow cytometry analysis showed that 2308ΔVceA promoted autophagy and inhibited apoptosis. Mouse immunohistochemistry experiments showed that P62 protein was scattered coloring and Cytochrome C protein was scarcely in 2308ΔVceA group at the myometrium. These results indicated that 2308ΔVceA promoted autophagy and inhibited apoptosis in HPT-8 cells during Brucella infection.

A review of the immunopathogenesis of Brucellosis

Brucellosis, caused by the intracellular pathogens Brucella, is one of the major zoonotic infections. Considering the economic burden, its prevalence has been a health concern especially in endemic regions. Brucella is able to survive and replicate within host cells by expressing different virulence factors and using various strategies to avoid the host's immune response. This leads to progression of the disease from an acute phase to chronic brucellosis. Exploration of genetic variations has confirmed the expected influence of gene polymorphisms on susceptibility and resistance to brucellosis of humans. Since there is no approved human vaccine and treatment is uncertain with risk of relapse, it is important to increase knowledge about pathogenesis, diagnosis and treatment of brucellosis in order to manage and control this infection, especially in endemic regions.

Harnessing Macrophages for Controlled-Release Drug Delivery: Lessons From Microbes

With the effectiveness of therapeutic agents ever decreasing and the increased incidence of multi-drug resistant pathogens, there is a clear need for administration of more potent, potentially more toxic, drugs. Alternatively, biopharmaceuticals may hold potential but require specialized protection from premature in vivo degradation. Thus, a paralleled need for specialized drug delivery systems has arisen. Although cell-mediated drug delivery is not a completely novel concept, the few applications described to date are not yet ready for in vivo application, for various reasons such as drug-induced carrier cell death, limited control over the site and timing of drug release and/or drug degradation by the host immune system. Here, we present our hypothesis for a new drug delivery system, which aims to negate these limitations. We propose transport of nanoparticle-encapsulated drugs inside autologous macrophages polarized to M1 phenotype for high mobility and treated to induce transient phagosome maturation arrest. In addition, we propose a significant shift of existing paradigms in the study of host-microbe interactions, in order to study microbial host immune evasion and dissemination patterns for their therapeutic utilization in the context of drug delivery. We describe a system in which microbial strategies may be adopted to facilitate absolute control over drug delivery, and without sacrificing the host carrier cells. We provide a comprehensive summary of the lessons we can learn from microbes in the context of drug delivery and discuss their feasibility for in vivo therapeutic application. We then describe our proposed "synthetic microbe drug delivery system" in detail. In our opinion, this multidisciplinary approach may hold the solution to effective, controlled drug delivery.

A genome-wide association analysis reveals a potential role for recombination in the evolution of antimicrobial resistance in Burkholderia multivorans

Cystic fibrosis (CF) lung infections caused by members of the Burkholderia cepacia complex, such as Burkholderia multivorans, are associated with high rates of mortality and morbidity. We performed a population genomics study of 111 B. multivorans sputum isolates from one CF patient through three stages of infection including an early incident isolate, deep sampling of a one-year period of chronic infection occurring weeks before a lung transplant, and deep sampling of a post-transplant infection. We reconstructed the evolutionary history of the population and used a lineage-controlled genome-wide association study (GWAS) approach to identify genetic variants associated with antibiotic resistance. We found the incident isolate was basally related to the rest of the strains and more susceptible to antibiotics from three classes (β-lactams, aminoglycosides, quinolones). The chronic infection isolates diversified into multiple, distinct genetic lineages and showed reduced antimicrobial susceptibility to the same antibiotics. The post-transplant reinfection isolates derived from the same source as the incident isolate and were genetically distinct from the chronic isolates. They also had a level of susceptibility in between that of the incident and chronic isolates. We identified numerous examples of potential parallel pathoadaptation, in which multiple mutations were found in the same locus or even codon. The set of parallel pathoadaptive loci was enriched for functions associated with virulence and resistance. Our GWAS analysis identified statistical associations between a polymorphism in the ampD locus with resistance to β-lactams, and polymorphisms in an araC transcriptional regulator and an outer membrane porin with resistance to both aminoglycosides and quinolones. Additionally, these three loci were independently mutated four, three and two times, respectively, providing further support for parallel pathoadaptation. Finally, we identified a minimum of 14 recombination events, and observed that loci carrying putative parallel pathoadaptations and polymorphisms statistically associated with β-lactam resistance were over-represented in these recombinogenic regions.

Cystic fibrosis (CF) is the most common lethal genetic disorder affecting individuals of European descent. Most CF patients die at a young age due to chronic lung infections. Among the organisms involved in these infections are bacteria from the Burkholderia cepacia complex (BCC), which are strongly associated with poor clinical prognosis. This study examines how the most prevalent BCC species among CF patients, B. multivorans, evolves within a single CF patient by studying the first B. multivorans isolate recovered from the patient, one hundred isolates recovered over a one year period during the chronic infection phase, and an additional ten isolates recovered after the reinfection of the transplanted lungs. We found that B. multivorans diversify phenotypically and genetically within the CF lung over the course of the infection, and evolves into a complex population during the chronic infection phase. We found that isolates collected from the post-transplant reinfection were more closely related to descendants of the original isolate rather than those recovered in the chronic infection. We identify genetic variants statistically associated with resistance to the antibiotics, and showed that some of these variants were found in regions that show patterns of recombination (genetic exchange) between strains. We also found that genes which were mutated multiple times during overall infection were more likely to be found in regions showing signals consistent with recombination. The presence of multiple independent mutations in a gene is a very strong signal that the gene helps bacteria adapt to their environment. Overall, this study provides insight into how pathogens adapt to the host during long-term infections, specific genes associated with antibiotic resistance, and the origin of new and recurrent infections.