Non-encapsulated Bacteria Research Articles

Bio-encapsulation of Microbial Biostimulant for Drought Resilience in Groundnut (Arachis hypogaea L.)

ABSTRACT Plant growth promoting rhizobacteria (PGPR) as microbial biostimulant promotes growth and productivity of crops under drought. However, their commercial utility is constrained by their instability and low viability in field trials. Immobilization or encapsulation of PGPR biostimulant aims to provide physical protection from stressful environment and ensure a high rate of rhizospheric colonization. In this work, we immobilized Acinetobacter calcoaceticus AC01 in 2% alginate by ionic gelation process, and evaluated for in vitro and in vivo studies. The rhizobacteria was characterized for osmotic stress, indole, phosphate solubilization, siderophore, gibberellic acid, salicylic acid, alginate and Exopolysaccharide (EPS). The encapsulated PGPR AC01 exhibited optimal moisture content of 3.57%, expansion rate of 80.62%, 95% embedding efficiency and diameter of 1.2–1.4 mm. The viability of AC01 in microcapsules remained 107CFU/g during 90 days of storage. The encapsulated PGPR biostimulant were also evaluated in Arachis hypogaea L. for drought mitigation. The inclusion of rhizobacterial microcapsules considerably induced maximum growth with significantly increased plant height, biomass, nodule count, relative water content, membrane stability index and osmolyte accumulation under drought conditions compared to non-encapsulated bacteria. Our results demonstrate that bio-encapsulation of Acinetobacter sp. AC01 in alginate matrix is a potential alternative for alleviating drought and a promising delivery system for agricultural applications.

Assessment of Encapsulated Probiotic Lactococcus lactis A12 Viability Using an In Vitro Digestion Model for Tilapia.

Probiotics face harsh conditions during their transit through the gastrointestinal tract (GIT) of fish because of low-pH environments and intestine fluid. Therefore, the evaluation of probiotic viability under simulated gastrointestinal conditions is an important step to consider for probiotic supplementation in fish feed prior to in vivo trials. Therefore, this study aimed to evaluate the effect of stomach and intestinal simulated conditions on the viability of encapsulated Lactococcus lactis A12 using an in vitro digestion model for tilapia. A Box Behnken design was used to evaluate the potential effect of three factors, namely stomach pH, residence time in the stomach, and enzyme quantity, on the viability of encapsulated Lactococcus lactis A12. As the main results, low pH (4.00), long residence time (4 h), and enzyme quantity (2.68 U of total protease activity) led to lower final cell counts after the phases of the stomach and intestine. Encapsulated probiotic bacteria showed higher viability (p < 0.05) and antibacterial activity (p < 0.05) against the pathogen Streptococcus agalactiae than non-encapsulated bacteria. The results suggest that L. lactis A12 survives in GIT conditions and that the proposed in vitro model could be used to explore the viability of probiotic bacteria intended for fish feed supplementation.

Platelet factor 4 improves survival in a murine model of antibiotic-susceptible and methicillin-resistant Staphylococcus aureus peritonitis.

The complement receptor CR3, also known as integrin Mac-1 (CD11b/CD18), is one of the major phagocytic receptors on the surface of neutrophils and macrophages. We previously demonstrated that in its protein ligands, Mac-1 binds sequences enriched in basic and hydrophobic residues and strongly disfavors negatively charged sequences. The avoidance by Mac-1 of negatively charged surfaces suggests that the bacterial wall and bacterial capsule possessing net negative electrostatic charge may repel Mac-1 and that the cationic Mac-1 ligands can overcome this evasion by acting as opsonins. Indeed, we previously showed that opsonization of Gram-negative Escherichia coli with several cationic peptides, including PF4 (Platelet Factor 4), strongly augmented phagocytosis by macrophages. Here, we investigated the effect of recombinant PF4 (rPF4) on phagocytosis of Gram-positive Staphylococcus aureus in vitro and examined its impact in a mouse model of S. aureus peritonitis. Characterization of the interaction of rPF4 with nonencapsulated and encapsulated S. aureus showed that rPF4 localizes on the bacterial surface, thus making it available for Mac-1. Furthermore, rPF4 did not have direct bactericidal and bacteriostatic activity and was not toxic to host cells. rPF4 enhanced phagocytosis of S. aureus bioparticles by various primary and cultured Mac-1-expressing leukocytes by several folds. It also increased phagocytosis of live nonencapsulated and encapsulated bacteria. Notably, the augmentation of phagocytosis by rPF4 did not compromise the intracellular killing of S. aureus by macrophages. Using a murine S. aureus peritonitis model, we showed that treatment of infected mice with rPF4 caused a significant increase in the clearance of antibiotic-susceptible S. aureus and its methicillin-resistant (MRSA) variant and markedly improved survival. These findings indicate that rPF4 binding to the bacterial surface circumvents its antiphagocytic properties, improving host defense against antibiotic-susceptible and antibiotic-resistant bacteria.

Development and characterization of fermented soy beverages containing encapsulated or non-encapsulated vaginal probiotics

Human microbial niches such as the healthy vagina, are recently emerging as “unconventional” sources of candidate probiotics capable of preventing from different vaginal diseases. These microorganisms could be provided as oral preparations since they can reach the vaginal niche passing through the gastrointestinal tract. However, their use in food would be challenging. The aim of this work was to develop and characterize fermented soy beverages with encapsulated and non-encapsulated vaginal lactobacilli, namely Lactobacillus crispatus BC4 and Lactobacillus gasseri BC9, as future dietary strategies for vaginal dysbiosis. The viability of vaginal strains remained stable at 7 log CFU/mL of product during the entire 28 days of storage, despite the use of encapsulated or non-encapsulated bacteria. Samples containing encapsulated bacteria, especially E-BC4+BC9, showed higher Water Holding Capacity (62.29%), lactic acid content (1.43%), and a remarkable antagonistic activity against enteropathogens. Moreover, encapsulation protected the strains from simulated GIT conditions (>1 Log) but reduced the acceptability of the final products. Overall, strain BC4 and BC9, alone or in mix, demonstrated to be promising co-starter cultures providing a characteristic flavor (pleasant smell and taste) and aroma (lower hexanal, benzaldehyde and higher diacetyl, and 2,3-pentanedione, compared to control) to the fermented soy beverages.

Microencapsulation of Bacillus smithii XY1 by spray drying and evaluation for treatment of inflammatory bowel disease

Microencapsulation is a promising and feasible method to help probiotics against adverse situation and overcome storage instability. In this study, we prepared Bacillus smithii XY1 microcapsules by spray drying. Firstly, wall materials of the microcapsules were screened and the ratio between wall materials and protective agent was optimized. The results showed that 9% gum arabic and 5% soluble starch along with 4% skim milk powder were the best condition for spray drying through response surface method. Through scanning electron microscope (SEM), bacteria were successfully encapsuled in the wall materials and microcapsules presented complete structure without cracks. Compared to non-encapsulated bacteria, encapsulation increased tolerance of B. smithii XY1 in gastrointestinal environment, improved shelf time and showed a better effect on alleviating intestine inflammation of zebrafish induced by dextran dulfate sodium (DSS). Thus, this encapsulation approach may have the potential application for improving efficacy of B. smithii XY1 and other probiotics.

Microencapsulation and in situ incubation methodology for the cultivation of marine bacteria.

Environmental microorganisms are important sources of biotechnology innovations; however, the discovery process is hampered by the inability to culture the overwhelming majority of microbes. To drive the discovery of new biotechnology products from previously unculturable microbes, several methods such as modification of media composition, incubation conditions, single-cell isolation, and in situ incubation, have been employed to improve microbial recovery from environmental samples. To improve microbial recovery, we examined the effect of microencapsulation followed by in situ incubation on the abundance, viability, and diversity of bacteria recovered from marine sediment. Bacteria from marine sediment samples were resuspended or encapsulated in agarose and half of each sample was directly plated on agar and the other half inserted into modified Slyde-A-Lyzer™ dialysis cassettes. The cassettes were incubated in their natural environment (in situ) for a week, after which they were retrieved, and the contents plated. Colony counts indicated that bacterial abundance increased during in situ incubation and that cell density was significantly higher in cassettes containing non-encapsulated sediment bacteria. Assessment of viability indicated that a higher proportion of cells in encapsulated samples were viable at the end of the incubation period, suggesting that agarose encapsulation promoted higher cell viability during in situ incubation. One hundred and 46 isolates were purified from the study (32–38 from each treatment) to assess the effect of the four treatments on cultivable bacterial diversity. In total, 58 operational taxonomic units (OTUs) were identified using a 99% 16S rRNA gene sequence identity threshold. The results indicated that encapsulation recovered greater bacterial diversity from the sediment than simple resuspension (41 vs. 31 OTUs, respectively). While the cultivable bacterial diversity decreased by 43%–48% after in situ incubation, difficult-to-culture (Verrucomicrobia) and obligate marine (Pseudoalteromonas) taxa were only recovered after in situ incubation. These results suggest that agarose encapsulation coupled with in situ incubation in commercially available, low-cost, diffusion chambers facilitates the cultivation and improved recovery of bacteria from marine sediments. This study provides another tool that microbiologists can use to access microbial dark matter for environmental, biotechnology bioprospecting.

Alginate microencapsulation of an attenuated O-antigen mutant of Francisella tularensis LVS as a model for a vaccine delivery vehicle.

Francisella tularensis is the etiologic agent of tularemia and a Tier I Select Agent. Subspecies tularensis (Type A) is the most virulent of the four subspecies and inhalation of as few as 10 cells can cause severe disease in humans. Due to its niche as a facultative intracellular pathogen, a successful tularemia vaccine must induce a robust cellular immune response, which is best achieved by a live, attenuated strain. F. tularensis strains lacking lipopolysaccharide (LPS) O-antigen are highly attenuated, but do not persist in the host long enough to induce protective immunity. Increasing the persistence of an O-antigen mutant may help stimulate protective immunity. Alginate encapsulation is frequently used with probiotics to increase persistence of bacteria within the gastrointestinal system, and was used to encapsulate the highly attenuated LVS O-antigen mutant WbtIG191V. Encapsulation with alginate followed by a poly-L-lysine/alginate coating increased survival of WbtIG191V in complement-active serum. In addition, BALB/c mice immunized intraperitoneally with encapsulated WbtIG191V combined with purified LPS survived longer than mock-immunized mice following intranasal challenge. Alginate encapsulation of the bacteria also increased antibody titers compared to non-encapsulated bacteria. These data suggest that alginate encapsulation provides a slow-release vehicle for bacterial deposits, as evidenced by the increased antibody titer and increased persistence in serum compared to freely suspended cells. Survival of mice against high-dose intranasal challenge with the LVS wildtype was similar between mice immunized within alginate capsules or with LVS, possibly due to the low number of animals used, but bacterial loads in the liver and spleen were the lowest in mice immunized with WbtIG191V and LPS in beads. However, an analysis of the immune response of surviving mice indicated that those vaccinated with the alginate vehicle upregulated cell-mediated immune pathways to a lesser extent than LVS-vaccinated mice. In summary, this vehicle, as formulated, may be more effective for pathogens that require predominately antibody-mediated immunity.

Bacillus anthracis Poly-γ-D-Glutamate Capsule Inhibits Opsonic Phagocytosis by Impeding Complement Activation.

Bacillus anthracis poly-γ-D-glutamic acid (PGA) capsule is an essential virulent factor that helps the bacterial pathogen to escape host immunity. Like other encapsulated bacterial species, the B. anthracis capsule may also inhibit complement-mediated clearance and ensure bacterial survival in the host. Previous reports suggest that B. anthracis spore proteins inhibit complement activation. However, the mechanism through which the B. anthracis capsule imparts a survival advantage to the active bacteria has not been demonstrated till date. Thus, to evaluate the role of the PGA capsule in evading host immunity, we have undertaken the present head-to-head comparative study of the phagocytosis and complement activation of non-encapsulated and encapsulated B. anthracis strains. The encapsulated virulent strain exhibited resistance toward complement-dependent and complement-independent bacterial phagocytosis by human macrophages. The non-encapsulated Sterne strain was highly susceptible to phagocytosis by THP-1 macrophages, after incubation with normal human serum (NHS), heat-inactivated serum, and serum-free media, thus indicating that the capsule inhibited both complement-dependent and complement-independent opsonic phagocytosis. An increased binding of C3b and its subsequent activation to C3c and C3dg, which functionally act as potent opsonins, were observed with the non-encapsulated Sterne strain compared with the encapsulated strain. Other known mediators of complement fixation, IgG, C-reactive protein (CRP), and serum amyloid P component (SAP), also bound more prominently with the non-encapsulated Sterne strain. Studies with complement pathway-specific, component-deficient serum demonstrated that the classical pathway was primarily involved in mediating C3b binding on the non-encapsulated bacteria. Both strains equally bound the complement regulatory proteins C4BP and factor H. Importantly, we demonstrated that the negative charge of the PGA capsule was responsible for the differential binding of the complement proteins between the non-encapsulated and encapsulated strains. At lower pH closer to the isoelectric point of PGA, the neutralization of the negative charge was associated with an increased binding of C3b and IgG with the encapsulated B. anthracis strain. Overall, our data have demonstrated that the B. anthracis capsule inhibits complement fixation and opsonization resulting in reduced phagocytosis by macrophages, thus allowing the bacterial pathogen to evade host immunity.

Survival and stability of free and encapsulated probiotic bacteria under simulated gastrointestinal and thermal conditions

ABSTRACT The core objective of the current study was to assess the effect of encapsulation on the viability and stability of probiotic bacteria under simulated gastrointestinal digestion and thermal conditions. Purposely, probiotics were encapsulated with hydrogel matrices (sodium alginate and carrageenan) using encapsulator. Furthermore, developed microbeads were characterized by X-ray diffraction (XRD) and Fourier Transform Infrared (FTIR) spectroscopy to elucidate the interaction between hydrogel matrices and probiotics. The viability of probiotics assessed by subjecting to simulated GIT and thermal conditions. Encapsulation exhibited a significant (p< .05) effect on the survival and stability of probiotics. Overall, a decreasing trend in viability of probiotics was observed in all treatments. A rapid log reduction was observed when free probiotic cells were stored at refrigeration temperature compared to encapsulated probiotic bacteria. Likewise, in vitro gastrointestinal assay, only 3 log while in case of non-encapsulated bacteria 6 log reduction was recorded. In short, the results of the viable count in the case of encapsulated cells were above recommended level (106 cfu/g) under thermal as well as in GIT conditions.

Dietary encapsulated probiotic effect on broiler serum biochemical parameters.

Aim:The study aimed to evaluate the effect of encapsulated probiotic bacteria (Lactobacillus lactis and Bifidobacterium bifidum) on broiler serum biochemical parameters.Materials and Methods:Encapsulation protects the probiotics and increases their livability on exposure to unfavorable processing and storage temperatures and gastrointestinal pH. Hence, an in vitro study was undertaken to encapsulate the probiotic bacteria L. lactis and B. bifidum with sodium alginate and chitosan and evaluate the encapsulation efficiency. This experiment was conducted with 288-day-old broiler chicken; they were distributed randomly into eight treatments and six replicates in each treatment (six birds in each replicate) and given with standard feed.Results:Supplementation of the encapsulated bacteria either alone or in combination (T4, T6, and T8) significantly (p<0.05) increased mean total serum protein, albumin, and globulin as compared to the birds that were not supplemented with any probiotic (T1 and T2) or supplemented with non-encapsulated bacteria (T3, T5, and T7). Supplementation of the encapsulated bacteria either alone or in combination (T4, T6, and T8) significantly (p<0.05) lowered mean total serum cholesterol, serum low-density lipoprotein (LDL) cholesterol, and serum triglycerides, as compared to the birds that were not supplemented with any probiotic (T1 and T2) or supplemented with non-encapsulated bacteria (T3, T5, and T7).Conclusion:It may be concluded that supplementation of the encapsulated probiotic bacteria either alone or in combination significantly increased total serum protein, albumin, and globulin and significantly lowered mean total serum cholesterol, serum LDL cholesterol, and serum triglycerides as compared to the birds that were not supplemented with any probiotic or supplemented with non-encapsulated bacteria.

Co-encapsulation of lactic acid bacteria and prebiotic with alginate-fenugreek gum-locust bean gum matrix: Viability of encapsulated bacteria under simulated gastrointestinal condition and during storage time

The aim of this study was to enhance the viability of probiotic strains Pediococcus pentosaceus KID7, Lactobacillus plantarum KII2, Lactobacillus fermentum KLAB6 and Lactobacillus helveticus KII13 in gastrointestinal transit, freeze-drying condition and during storage time by microencapsulation using a combination of alginate, fenugreek gum and locust bean gum. The microcapsules were prepared using various ratio of alginate to fenugreek gum to locust bean gum and tested for its dissolution in colonic fluid. The combination that efficiently dissolved in colonic fluid was selected for co-encapsulation of the probiotic strains and prebiotics to produce synbiotic microcapsules. Further, we observed that the bacteria encapsulated with alginate-fenugreek gum-locust bean gum (AFL) matrix tolerated gastrointestinal condition efficiently compared to non-encapsulated bacteria. The encapsulated bacterial cells retained higher viability than non-encapsulated cells during freeze-drying condition and subsequent storage for 3 months at 4°C. These results show the utility of AFL matrix in microencapsulation of probiotics for use in food industry.

Microencapsulation of Lactobacillus salivarious Li01 for enhanced storage viability and targeted delivery to gut microbiota

Probiotics are used in food products, dietary supplements and pharmaceutical products because they may provide health-promoting effects in humans. To be efficacious, probiotics need to be viable at sufficient abundance within the large intestine. However, many commercial products containing probiotics suffer from a substantial loss of bacterial viability during shelf storage and during gastrointestinal transit. In this study, a probiotic (Lactobacillus salivarious Li01) was incorporated into either alginate or alginate-gelatin microgels. The morphology of the microgels was characterized by scanning electron microscopy, which indicated that they had a spherical shape and that almost all of the bacterial cells were encapsulated inside them. Probiotic viability was determined under aerobic conditions, heat treatment, and simulated gastrointestinal conditions. Encapsulation significantly enhanced the viability of the probiotic during aerobic storage. The microgels maintained their structures under simulated gastric conditions, but either eroded or swelled under simulated small intestine conditions. The alginate-gelatin microgels were the most effective at protecting the bacteria under simulated gastrointestinal conditions when compared to the alginate microgels and non-encapsulated bacteria. In conclusion, alginate-gelatin microgels have great potential for the protection and delivery of probiotics in food, supplement, and pharmaceutical products.

Survival of probiotics in pea protein-alginate microcapsules with or without chitosan coating during storage and in a simulated gastrointestinal environment.

Pea protein-alginate microcapsules with or without a chitosan coating and containing Lactobacillus rhamnosus R0011 and L. helveticus R0052 were produced by extrusion and tested for survivability during storage and in an in vitro gastrointestinal environment. Both microcapsule formulations provided significant protection for cells incubated in synthetic stomach juice at 37°C for 2 h, followed by 3 h in simulated intestinal fluid, relative to non-encapsulated bacteria. However, evaluation of cell viability during 9 weeks of storage at room temperature revealed that chitosan coating significantly improved microcapsule performance compared to non-coated microcapsules. Refrigerated storage had no negative impact on the microcapsule protection ability of both types of microcapsules. Notably, chitosan-containing microcapsules showed much higher bacterial survival counts during challenge tests even after storage. Moreover, the addition of chitosan to the microcapsule formulation did not increase the microcapsule size.

Correction: Microencapsulation of probiotics in hydrogel particles: enhancing Lactococcus lactis subsp. cremoris LM0230 viability using calcium alginate beads.

Correction for 'Microencapsulation of probiotics in hydrogel particles: enhancing Lactococcus lactis subsp. cremoris LM0230 viability using calcium alginate beads' by Timothy W. Yeung et al., Food Funct., 2016, 7, 1797-1804.

Evaluation of pea protein–polysaccharide matrices for encapsulation of acid-sensitive bacteria

Protein–polysaccharide capsules containing Bifidobacterium adolescentis were produced and tested in a series of in vitro survival experiments to evaluate capsule protection of the bacterium to simulated stomach conditions, as well as their ability to release the encapsulated bacteria under conditions similar to those found in the lower gut. A protein fraction isolated from peas (pea protein isolate: PPI; 2.0%; w/v) was mixed with each of three different polysaccharides (0.5% (w/v) of either sodium alginate, iota-carrageenan and gellan gum) to produce capsules ranging in size from 2 to 3mm diameter. All capsule formulations provided significant protection for cells exposed to synthetic stomach juice at 37°C relative to non-encapsulated bacteria. In addition, PPI-alginate and PPI-iota-carrageenan capsules were found to dissolve in simulated intestinal fluid at 37°C, releasing 70–79% of their bacteria “payload” within 3h, with higher cell numbers being released from the freeze-dried capsules. PPI-gellan gum capsules did not dissolve to the same extent and the number of released cells was ~26–30% lower. Following a temporal rat feeding study with the test bacterium encapsulated in PPI-alginate, B. adolescentis-specific PCR and qPCR analyses confirmed the presence of DNA from this species in rat feces, but only during the period of capsule intake.

Evaluation of Gram-negative bacterial infection by a stable and conjugative bioluminescence plasmid in a mouse model.

BackgroundThe green fluorescence protein (GFP)-associated fluorescence method and the luciferase-associated bioluminescence method are the two major methods for IVIS imaging system to investigate the bacterial infection in animal models. The aim of this study was to evaluate the infection route of Gram-negative bacteria carrying a stable and broad range of conjugative bioluminescence plasmid pSE-Lux1 in a mouse model.ResultsBoth encapsulated and non-encapsulated Gram-negative bacteria were used as hosts to evaluate conjugation efficiency and plasmid stability of pSE-Lux1, a recombinant of pSE34 and luxABCDE operon. The plasmid conjugation efficiencies of pSE-Lux1 ranged from 10−3 to 10−7 in various Gram-negative bacteria. Plasmid pSE-Lux1 maintained in Escherichia coli, Klebsiella pneumoniae, and Salmonella enterica serovars Choleraesues (abbreviated S. Choleraesuis) and Typhimurium (S. Typhimurium), than in Acinetobacter baumannii and Serratia marcescens, was shown to be of better stability for at least four days. To investigate systemic bacterial infections, K. pneumoniae strain CG354 was intravenously injected, and then was clearly observed to be non-pathogenic to Balb/c mice for a long-term bioluminescence monitoring for 6 days. For examining dynamic distributions of gastrointestinal tract infection, the invasion protein SipB-deficient mutant OU5045△sipB and OU5046△sipB of S. serovar Typhimurium constructed in this study, compared to wild-type strain OU5045 and its virulence plasmid-less strain OU5046, were of less virulence to mice.ConclusionsThis is the first study to evaluate the conjugative and stable bioluminescence vehicle system of pSE-Lux1 in a wide range of Gram-negative bacteria, a system that can provide a useful reporter approach to trace systemic and gastrointestinal bacterial infections in a mouse model.

English

The effects of wall materials and encapsulation by lyophilization on the viability of Weissella confusa were evaluated. Aloe vera gel, sodium casein at 5 and 15% p/v, sodium alginate at 2% p/v, buffer phosphate, and a mixture (Aloe vera gel, sodium casein, and sodium alginate) as wall materials, were used. Bacteria without encapsulation ( W. confusa ) as control were used. Encapsulated bacteria were freeze dried for 48 h, in order to determine their viability in the freezing and sublimation-drying stages. Results indicate that bacteria without encapsulation, showed greater loss of viability in the sublimation-drying stage. All the wall materials evaluated, may be used for encapsulation of bacteria, because, at the end of the freeze-drying process, the encapsulated bacteria showed higher viability percentages than non-encapsulated bacteria, with significant statistical difference (p<0.05). The protective effect of wall materials was higher in the sublimation-drying stage, compared to freezing stage. Keywords: Aloe, Weissella , probiotic, encapsulation. African Journal of Biotechbiology , Vol 13(26) 2661-2667

Microencapsulation of Lactobacillus acidophilus in zein–alginate core–shell microcapsules via electrospraying

Survival of probiotic bacteria, namely, Lactobacillus acidophilus, in gastric fluid was enhanced by embedding the bacterial cells in alginate microcapsules, which were formed by electrospraying; the resultant microcapsules were then coated with citric acid-modified zein and dried at ambient temperature. The effects of citric acid concentration (0.10–0.15%, w/v) as well as electrospraying condition (applied voltage) on morphology of the obtained core–shell microcapsules, encapsulated cell count and survival cell number after incubating in simulated gastric fluid (SGF) were investigated. The results showed that an increase in the citric acid concentration did not affect the microcapsules size; nevertheless, the survival cell number significantly decreased due to an increase in the zein solution acidity. The size of the microcapsules was significantly reduced from 543±88 to 312±69 and 259±62μm when being produced at 4, 6 and 10kV, respectively. Microcapsule surface wrinkles were significantly reduced as the applied voltage increased. After 2h-incubation in SGF at pH 1.2 with pepsin, the encapsulated L. acidophilus suffered only 1-log reduction, whilst the number of the non-encapsulated bacteria was reduced by about 5-log cycles.

A Multivalent Adsorption Apparatus Explains the Broad Host Range of Phage phi92: a Comprehensive Genomic and Structural Analysis

Bacteriophage phi92 is a large, lytic myovirus isolated in 1983 from pathogenic Escherichia coli strains that carry a polysialic acid capsule. Here we report the genome organization of phi92, the cryoelectron microscopy reconstruction of its virion, and the reinvestigation of its host specificity. The genome consists of a linear, double-stranded 148,612-bp DNA sequence containing 248 potential open reading frames and 11 putative tRNA genes. Orthologs were found for 130 of the predicted proteins. Most of the virion proteins showed significant sequence similarities to proteins of myoviruses rv5 and PVP-SE1, indicating that phi92 is a new member of the novel genus of rv5-like phages. Reinvestigation of phi92 host specificity showed that the host range is not limited to polysialic acid-encapsulated Escherichia coli but includes most laboratory strains of Escherichia coli and many Salmonella strains. Structure analysis of the phi92 virion demonstrated the presence of four different types of tail fibers and/or tailspikes, which enable the phage to use attachment sites on encapsulated and nonencapsulated bacteria. With this report, we provide the first detailed description of a multivalent, multispecies phage armed with a host cell adsorption apparatus resembling a nanosized Swiss army knife. The genome, structure, and, in particular, the organization of the baseplate of phi92 demonstrate how a bacteriophage can evolve into a multi-pathogen-killing agent.

Encapsulated group BStreptococcusmodulates dendritic cell functions via lipid rafts and clathrin-mediated endocytosis

Group B Streptococcus (GBS) capsular type III is an important agent of life-threatening invasive infections. It has been previously shown that encapsulated GBS is easily internalized by dendritic cells (DCs) and can persist inside these immune cells. The mechanisms underlying these processes are unknown. Here, colocalization studies and the use of endocytosis inhibitors and caveolin(-/-) mice, demonstrated that GBS uses multiple endocytosis mechanisms to enter mouse DCs. The capsular polysaccharide (CPS) selectively drives GBS internalization via caveolae-independent but lipid raft-dependent pathways. Non-encapsulated bacteria failed to engage lipid rafts. GBS internalization by DCs also occurs via clathrin-mediated endocytosis in a process independent of bacterial CPS. Albeit caveolae are not required for GBS internalization, signalling events through caveolin-1 are involved in production of the inflammatory chemokine CCL2 by DCs infected with encapsulated GBS only. This study addresses for the first time endocytosis pathways implicated in DC internalization of encapsulated GBS and suggests a complex interplay between GBS and DCs, which was selectively modulated by the presence of CPS.