Complete Genome Sequence of the Podoviral Bacteriophage YMC/09/02/B1251 ABA BP,Which Causes the Lysis of an OXA-23-Producing Carbapenem-Resistant Acinetobacter baumannii Isolate from a Septic Patient

The emergence of carbapenem-resistant Acinetobacter baumannii, responsible for causing nosocomial infections, has been becoming a significant global health issue. In this article, we report the complete genome sequence of bacteriophage Bϕ-B1251 (YMC/09/02/B1251 ABA BP), which causes lysis of a carbapenem-resistant A. baumannii strain. The bacteriophage belongs to the family Podoviridae and has a double-stranded circular DNA genome with a length of 45,364 bp and a 39.05% G+C content. Genome analysis showed that it had no similarity to other previously reported bacteriophages capable of infecting A. baumannii.     

Characterization and Genome Sequencing of Phage Abp1, a New phiKMV-Like Virus Infecting Multidrug-Resistant Acinetobacter baumannii

While screening for alternative antibiotics against multidrug-resistant Acinetobacter baumannii, we isolated a virulent A. baumannii bacteriophage Abp1. Transmission electron microscopy revealed that the phage had an icosahedral head with a short tail and should be classified as a member of the Podoviridae family. SDS-PAGE showed that Abp1 contained at least one major and nine minor proteins. In a single-step growth test, we demonstrated that Abp1 had a latent period of 10 min and a burst size of 350. Abp1 also had a relatively narrow host range. The entire genome was sequenced, and the final assembly yielded a 42,185 bp, linear, double-stranded DNA molecule with a G+C content of 39.15 % and containing 54 putative genes. Among these genes, 26 were functionally known, leaving 28 unknown putative genes. Abp1 is a new member of the phiKMV-like virus subgroup of the T7 group; its genome sequence is very similar to that of the A. baumannii phage phiAB1.     

Responses to booster hepatitis B vaccination are significantly correlated with genotypes of human leukocyte antigen (HLA)-DPB1 in neonatally vaccinated adolescents

Genome-wide association studies have identified single nucleotide polymorphisms (SNPs) near the human leukocyte antigen (HLA)-DP loci that were significantly correlated with outcomes of hepatitis B virus (HBV) infection. We performed a case–control study nested in a well-characterized cohort of booster recipients to assess whether genetic variants of HLA-DPB1 are also associated with response to hepatitis B (HB) vaccination. The cases and controls were 171 and 510 booster recipients whose post-booster titers of antibodies against HBV surface antigen (anti-HBs) were undetectable and detectable, respectively. The HLA-DPB1 genotype was determined using sequence-based techniques. The frequencies of HLA-DPB1 alleles were significantly different between cases and controls (p = 1.7 × 10^?8). The HLA-DPB1 05:01 and 09:01 alleles were significantly more frequent in the cases, and 02:01:02, 02:02, 03:01:01, 04:01:01, and 14:01, were significantly more frequent in the controls. The adjusted odds ratio (OR) of undetectable post-booster anti-HBs titers was significantly correlated with the number of risk alleles (p for trend = 3.8 × 10^?5). For the number of protective alleles, the trend was significantly inversed (p for trend = 1.3 × 10^?5). As compared with subjects with two risk alleles, adjusted OR were 0.34 (95 % confidence interval [CI] 0.21–0.55) and 0.20 (95 % CI 0.08–0.48) for subjects with 1 and 2 protective alleles, respectively. The HLA-DPB1 02:02, 04:01:01, 05:01 and 09:01 alleles were also significantly correlated with the likelihoods of undetectable pre-booster anti-HBs titers. Our results indicated that HLA-DPB1 is significantly correlated with response to booster HB vaccination in adolescent who had received postnatal active HB vaccination. HLA-DBP1 may also determine the long-term persistence of response to HB vaccination.     

Isolation and Partial Characterization of a Virulent Bacteriophage IHQ1 Specific for Aeromonas punctata from Stream Water

Aeromonas punctata is the causative agent of septicemia, diarrhea, wound infections, meningitis, peritonitis, and infections of the joints, bones and eyes. Bacteriophages are often considered alternative agents for controlling bacterial infection and contamination. In this study, we described the isolation and preliminary characterization of bacteriophage IHQ1 (family Myoviridae) active against the Gram-negative bacterial strain A. punctata. This virulent bacteriophage was isolated from stream water sample. Genome analysis indicated that phage IHQ1 was a double-stranded DNA virus with an approximate genome size of 25–28 kb. The initial characterization of this newly isolated phage showed that it has a narrow host range and infects only A. punctata as it failed to infect seven other clinically isolated pathogenic strains, i.e., methicillin-resistant Staphylococcus aureus 6403, MRSA 17644, Acinetobacter 33408, Acinetobacter 1172, Pseudomonas aeruginosa 22250, P. aeruginosa 11219, and Escherichia coli. Proteomic pattern of phage IHQ1, generated by SDS-PAGE using purified phage particles, showed three major and three minor protein bands with molecular weights ranging from 25 to 70 kDa. The adsorption rate of phage IHQ1 to the host bacterium was also determined, which was significantly enhanced by the addition of 10 mM CaCl₂. From the single-step growth experiment, it was inferred that the latent time period of phage IHQ1 was 24 min and a burst size of 626 phages per cell. Moreover, the pH and thermal stability of phage IHQ1 were also investigated. The maximum stability of the phage was observed at optimal pH 7.0, and it was totally unstable at extreme acidic pH 3; however, it was comparatively stable at alkaline pH 11.0. At 37°C the phage showed maximum number of plaques, and the viability was almost 100%. The existence of Aeromonas bacteriophage is very promising for the eradication of this opportunistic pathogen and also for future applications such as the design of new detection and phage typing (diagnosis) methods. The specificity of the bacteriophage for A. punctata makes it an attractive candidate for phage therapy of A. punctata infections.     

Efficacy of Mastoparan-AF alone and in combination with clinically used antibiotics on nosocomial multidrug-resistant Acinetobacter baumannii

Emergence of multidrug-resistant Acinetobacter baumannii (MDRAB) has become a critical clinical problem worldwide and limited therapeutic options for infectious diseases caused by MDRAB. Therefore, there is an urgent need for the development of new antimicrobial agents or alternative therapy to combat MDRAB infection. The aim of this study was to investigate effects of Mastoparan-AF (MP-AF), an amphipathic peptide isolated from the hornet venom of Vespa affinis with broad-spectrum antimicrobial activity, on MDRAB. As compared with clinical used antibiotics, MP-AF exhibited potent antimicrobial activity at 2–16 μg/ml against the reference strain A. baumannii ATCC 15151 and seven MDRAB clinical isolates, especially the colistin-resistant MDRAB, E0158. The synergistic antimicrobial combination study revealed that MP-AF acted synergistically with specific antibiotics, e.g., ciprofloxacin, trimethoprim/sulfamethoxazole (SXT) or colistin against some isolates of the MDRAB. It was noteworthy when MP-AF combined with SXT exhibited synergistic activity against all SXT-resistant MDRAB isolates. The synergistic combination of MP-AF and antibiotics could reduce the dosage recommended of each antimicrobial agent and improve the safety of medications with ignorable adverse effects, such as colistin with nephrotoxicity in therapeutic dose. Furthermore, MP-AF combined with antibiotics with different antimicrobial mechanisms could reduce selective pressure of antibiotics on bacteria and prevent the emergence of antimicrobial-resistant strains. Importantly, we are the first finding that MP-AF could make MDRAB from the original non-susceptibility to SXT become sensitivity. In conclusion, MP-AF alone or in combination with other antibiotics, especially SXT, is a potential candidate against MDRAB infection in clinical medicine.     

HLA alleles associated with the adaptive immune response to smallpox vaccine: a replication study

We previously reported HLA allelic associations with vaccinia virus (VACV)-induced adaptive immune responses in a cohort of healthy individuals (n = 1,071 subjects) after a single dose of the licensed smallpox (Dryvax) vaccine. This study demonstrated that specific HLA alleles were significantly associated with VACV-induced neutralizing antibody (NA) titers (HLA-B*13:02, *38:02, *44:03, *48:01, and HLA-DQB1*03:02, *06:04) and cytokine (HLA-DRB1*01:03, *03:01, *10:01, *13:01, *15:01) immune responses. We undertook an independent study of 1,053 healthy individuals and examined associations between HLA alleles and measures of adaptive immunity after a single dose of Dryvax-derived ACAM2000 vaccine to evaluate previously discovered HLA allelic associations from the Dryvax study and determine if these associations are replicated with ACAM2000. Females had significantly higher NA titers than male subjects in both study cohorts [median ID50 discovery cohort 159 (93, 256) vs. 125 (75, 186), p < 0.001; replication cohort 144 (82, 204) vs. 110 (61, 189), p = 0.024]. The association between the DQB1*03:02 allele (median ID₅₀ discovery cohort 152, p = 0.015; replication cohort 134, p = 0.010) and higher NA titers was replicated. Two HLA associations of comparable magnitudes were consistently found between DRB1*04:03 and DRB1*08:01 alleles and IFN-γ ELISPOT responses. The association between the DRB1*15:01 allele with IFN-γ secretion was also replicated (median pg/mL discovery cohort 182, p = 0.052; replication cohort 203, p = 0.014). Our results suggest that smallpox vaccine-induced adaptive immune responses are significantly influenced by HLA gene polymorphisms. These data provide information for functional studies and design of novel candidate smallpox vaccines.     

Cloning of a Family 11 Xylanase Gene from Bacillus amyloliquefaciens CH51 Isolated from Cheonggukjang

Bacillus amyloliquefaciens CH51, an isolate from cheonggukjang, Korean fermented soyfood, secretes several enzymes into culture medium. A gene encoding 19 kDa xylanase was cloned by PCR. Sequencing showed that the gene encoded a glycohydrolase family 11 xylanase and named xynA. xynAHis, xynA with additional codons for his-tag, was overexpressed in Escherichia coli BL21(DE3) using pET-26b(+). XynAHis was purified using HisTrap affinity column. K_m and V_max of XynAHis were 0.363 mg/ml and 701.1 μmol/min/mg, respectively with birchwood xylan as a substrate. The optimum pH and temperature were pH 4 and 25 °C, respectively. When xynA was introduced into Bacillus subtilis WB600, active XynA was secreted into culture medium.     

A comparative study of class 1 integrons in Acinetobacter baumannii

Multidrug resistance (MDR) in Acinetobacter baumannii is increasingly reported and has become a significant public concern. The method responsible for the acquisition of resistance genes via integrons from the environment or intra-species in A. baumannii remains to be understood. This study was performed to investigate the transmission route of these integrons using a comparative analysis of published A. baumannii complete genomes. The phylogenetic analysis of A. baumannii type 1 integrases (IntI1) showed that the integrons could be transferred across the two evolutionary lineages, the international clone I (IC I) and clone II (IC II) strains. In addition, the integrons in A. baumannii strains were mainly responsible for the transfer of resistance genes for two types of long-term usage antibiotics and antiseptics, such as aminoglycosides, chloramphenicol and the quaternary-ammonium-compound family. The in silico comparative analysis of known integron integrases revealed that the intI genes were phylogenetically related among A. baumannii strains and some microorganisms living in a sediment community, implicating that the integrons of A. baumannii might have originated from those microorganisms belonging to the β-preoteobacterial class in the sediment environment. The data suggest that the gain of class 1 integrons in A. baumannii strains may have started before the antibiotic era. This report shows that the origins of A. baumannii class 1 integrons may be the soil environment and that the resistance genes included in integrons are horizontally transferred across all the A. baumannii genomes, including IC I and IC II.     

Cloning and Characterizing the Thermophilic and Detergent Stable Cellulase CelMytB from Saccharophagus sp. Myt-1

We previously isolated and reported a second species of the Saccharophagus genus, Saccharophagus sp. strain Myt-1. In the present study, a cellulase gene (celMytB) from the genomic DNA of Myt-1 was cloned and characterized. The DNA sequence fragment contained an open reading frame of 1,893 bp that encoded a protein of 631 amino acids with an estimated molecular mass of 66.8 kDa. The deduced protein, CelMytB, had a catalytic domain that contained a conserved signature sequence (VIYEIYNEPL) of glycosyl hydrolase family 5 and a CBM6 cellulose binding module. CelMytB showed optimal activity at 55 °C and pH 6.5, which is similar to the optimal temperature and pH profile of cel5H, an endoglucanase from the closely related S. degradans 2-40. However, the cellulase (degradation of soluble cellulose) and avicelase (degradation of crystalline cellulose) activities of CelMytB were about 3-fold and 100-fold higher, respectively, than the equivalent activities of cel5H. Moreover, CelMytB could degrade xylan. From the zymogram results, we speculated that the catalytic domain of CelMytB had high activity even without the cellulose binding module. The presence of some detergents stimulated the cellulase activity of CelMytB.     

Characterization of Newly Isolated Lytic Bacteriophages Active against Acinetobacter baumannii

Based on genotyping and host range, two newly isolated lytic bacteriophages, myovirus vB_AbaM_Acibel004 and podovirus vB_AbaP_Acibel007, active against Acinetobacter baumannii clinical strains, were selected from a new phage library for further characterization. The complete genomes of the two phages were analyzed. Both phages are characterized by broad host range and essential features of potential therapeutic phages, such as short latent period (27 and 21 min, respectively), high burst size (125 and 145, respectively), stability of activity in liquid culture and low frequency of occurrence of phage-resistant mutant bacterial cells. Genomic analysis showed that while Acibel004 represents a novel bacteriophage with resemblance to some unclassified Pseudomonas aeruginosa phages, Acibel007 belongs to the well-characterized genus of the Phikmvlikevirus. The newly isolated phages can serve as potential candidates for phage cocktails to control A. baumannii infections.     

Genomic analysis of bacteriophage ϕAB1, a ϕKMV-like virus infecting multidrug-resistant Acinetobacter baumannii

We present the complete genomic sequence of a lytic bacteriophage ?AB1 which can infect many clinical isolates of multidrug-resistant Acinetobacter baumannii. The recently isolated bacteriophage displays morphology resembling Podoviridae family. The ?AB1 genome is a linear double-stranded DNA of 41,526 bp containing 46 possible open reading frames (ORFs). The majority of the predicted structural proteins were identified as part of the phage particle by mass spectrometry analysis. According to the virion morphology, overall genomic structure, and the phylogenetic tree of RNA polymerase, we propose that ?AB1 is a new member of the ?KMV-like phages. Additionally, we identified four ORFs encoding putative HNH endonucleases, one of which is presumed to integrate and create a genes-in-pieces DNA polymerase. Also, a potential lysis cassette was identified in the late genome. The lytic power of this bacteriophage combined with its specificity for A. baumannii makes ?AB1 an attractive agent for therapeutic or disinfection applications.     

The ABP-120 C-end region from Entamoeba histolytica interacts with sulfatide, a new lipid target

EhABP-120 is the first filamin identified in the parasitic protozoan Entamoeba histolytica. Filamins are a family of cross-linking actin-binding proteins that promote a dynamic orthogonal web. They have been reported to interact directly with more than 30 cellular proteins and some phosphoinositides. The biochemical consequences of these interactions may have either positive or negative effects on the cross-linking function and also form a link between the cytoskeleton and plasma membrane. In this study, the EhABP-120 carboxy-terminal domain (END) was biochemically characterized. This domain was able to associate to 3-sulfate galactosyl ceramide, a new lipid target for a member of the filamin family. Also, the END domain was able to dimerize “in vitro.” Molecular modeling analysis showed that the dimeric region is stabilized by a disulfide bond. Electrostatic and docking studies suggest that an electropositive concave pocket at the dimeric END domain interacts simultaneously with several sulfogalactose moieties of the sulfatide.     

Dongia rigui sp. nov., isolated from freshwater of a large wetland in Korea

A motile, curved to twisted rod-shaped aerobic bacterium, designated strain 04SU4-P^T, was isolated from freshwater collected from the Woopo wetland (Republic of Korea). Cells were observed to be Gram-stain negative, catalase negative and oxidase positive. The major fatty acids (>10 % of the total) were identified as C_19:0 ω8c cyclo (24.6 %), C_16:0 (24.3 %) and C_18:1 ω7c (13.1 %). The DNA G+C content was determined to be 71.5 mol%. The major polar lipids were identified as phosphatidylglycerol, phosphatidylethanolamine, one unknown phospholipid and one unknown aminolipid. The major ubiquinone was determined to be Q-10. A phylogenetic tree based on 16S rRNA gene sequences showed that strain 04SU4-P^T forms an evolutionary lineage within the genus Dongia and its nearest neighbour is Dongia mobilis LM22^T (98.0 % sequence similarity). Genomic DNA–DNA hybridization of stain 04SU4-P^T with D. mobilis LM22^T showed relatedness of only 34.2 %. The phenotypic characteristics indicate the strain 04SU4-P^T can be distinguished from the sole member of the genus Dongia. On the basis of the data presented in this study, strain 04SU4-P^T represents a novel species, for which the name Dongia rigui is proposed. The type strain is 04SU4-P^T (KCTC 23341^T = JCM 17521^T).     

Alternative bacteriophage life cycles: the carrier state of Campylobacter jejuni

Members of the genus Campylobacter are frequently responsible for human enteric disease, often through consumption of contaminated poultry products. Bacteriophages are viruses that have the potential to control pathogenic bacteria, but understanding their complex life cycles is key to their successful exploitation. Treatment of Campylobacter jejuni biofilms with bacteriophages led to the discovery that phages had established a relationship with their hosts typical of the carrier state life cycle (CSLC), where bacteria and bacteriophages remain associated in equilibrium. Significant phenotypic changes include improved aerotolerance under nutrient-limited conditions that would confer an advantage to survive in extra-intestinal environments, but a lack in motility eliminated their ability to colonize chickens. Under these circumstances, phages can remain associated with a compatible host and continue to produce free virions to prospect for new hosts. Moreover, we demonstrate that CSLC host bacteria can act as expendable vehicles for the delivery of bacteriophages to new host bacteria within pre-colonized chickens. The CSLC represents an important phase in the ecology of Campylobacter bacteriophage.     

Study of yeast populations and their enological properties in Guijoso Appellation of Origin (Spain)

The aim of the present study was to select strains of yeast with good enological qualities which were adapted to the ecological surroundings of Guijoso Appellation of Origin (A.O). For this, 11 white and red vats from different grape varieties and stages of fermentation were studied, making a total of 28 samples, with a selection of 370 isolated yeasts. Yeast cells of the Saccharomyces genus were analysed by DNA mitochondrial restriction for discrimination at the strain level, obtaining a total of 23 different molecular patterns. The pattern most frequently found was of G04, with 56 % of the isolated yeasts, followed by G02 with 15 % and G07 with 9 %. Other patterns found showed percentages close to 3 %, such as G01, G03, G05 and G06, while the remaining patterns were limited one or two isolated yeasts. Microfermentations at 25 and 15 °C were performed using a synthetic must, and the rate of fermentation, SH₂ and foam production and the capacity to consume sugars from the medium were studied. Furthermore, the killer phenotype, flocculation capacity and phenolic off-flavour (POF) characteristics were also analysed. Natural musts from Chardonnay and Cabernet Sauvignon varieties were fermented using preselected strains and the wines obtained were analysed and tasted. Two strains were selected (G01 and G04) to be used as starters in Guijoso A.O.     

HLA-DPB1*04:01 allele is associated with non-obstructive azoospermia in Japanese patients

Azoospermia is defined by absence of sperm in the semen and can either be caused by obstruction of the seminal tract (obstructive azoospermia) or by defects in spermatogenesis (non-obstructive azoospermia, NOA). Previous studies reported that specific alleles and single nucleotide polymorphisms (SNPs) in the human leukocyte antigen (HLA) region were associated with NOA in East Asians. We attempt to expand upon previous findings by genotyping more HLA genes and to replicate SNP associations by focusing on Japanese NOA patients. HLA typing of six genes (HLA-A, -B, -C, -DRB1, -DQB1, and -DPB1) was done on 355 NOA patients using SSO-Luminex assay while genotyping of two previously reported SNPs (rs498422 and rs3129878) was done on 443 patients and 544 fertile males using TaqMan assay. Association between the HLA alleles and SNP with NOA was assessed with Chi squared and logistic regression tests. We found that HLA-DPB1*04:01 [corrected p value, P _c 7.13 × 10^?6; odds ratio (OR) 2.52], DRB1*13:02 (P _c 4.93 × 10^?4, OR 1.97), DQB1*06:04 (P _c 8.94 × 10^?4, OR 1.91) and rs3129878 (p value 3.98 × 10^?4; OR 1.32) showed significant association with NOA, however, these loci are in linkage disequilibrium with each other. The conditional logistic regression tests showed that DPB1*04:01 is independently associated with NOA, confirming the involvement of the HLA region in the etiology of NOA in Japanese patients.     

Comparative genomic analysis of Acinetobacter baumannii clinical isolates reveals extensive genomic variation and diverse antibiotic resistance determinants

Background

Acinetobacter baumannii is an important nosocomial pathogen that poses a serious health threat to immune-compromised patients. Due to its rapid ability to develop multidrug resistance (MDR), A. baumannii has increasingly become a focus of attention worldwide. To better understand the genetic variation and antibiotic resistance mechanisms of this bacterium at the genomic level, we reported high-quality draft genome sequences of 8 clinical isolates with various sequence types and drug susceptibility profiles.

Results

We sequenced 7 MDR and 1 drug-sensitive clinical A. baumannii isolates and performed comparative genomic analysis of these draft genomes with 16 A. baumannii complete genomes from GenBank. We found a high degree of variation in A. baumannii, including single nucleotide polymorphisms (SNPs) and large DNA fragment variations in the AbaR-like resistance island (RI) regions, the prophage and the type VI secretion system (T6SS). In addition, we found several new AbaR-like RI regions with highly variable structures in our MDR strains. Interestingly, we found a novel genomic island (designated as GI_BJ4) in the drug-sensitive strain BJ4 carrying metal resistance genes instead of antibiotic resistance genes inserted into the position where AbaR-like RIs commonly reside in other A. baumannii strains. Furthermore, we showed that diverse antibiotic resistance determinants are present outside the RIs in A. baumannii, including antibiotic resistance-gene bearing integrons, the bla_OXA-23-containing transposon Tn2009, and chromosomal intrinsic antibiotic resistance genes.

Conclusions

Our comparative genomic analysis revealed that extensive genomic variation exists in the A. baumannii genome. Transposons, genomic islands and point mutations are the main contributors to the plasticity of the A. baumannii genome and play critical roles in facilitating the development of antibiotic resistance in the clinical isolates.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2164-15-1163) contains supplementary material, which is available to authorized users.     

Atomic Force Microscopy Analysis of the Acinetobacter baumannii Bacteriophage AP22 Lytic Cycle

Background

Acinetobacter baumannii is known for its ability to develop resistance to the major groups of antibiotics, form biofilms, and survive for long periods in hospital environments. The prevalence of infections caused by multidrug-resistant A. baumannii is a significant problem for the modern health care system, and application of lytic bacteriophages for controlling this pathogen may become a solution.

Methodology/Principal Findings

In this study, using atomic force microscopy (AFM) and microbiological assessment we have investigated A. baumannii bacteriophage AP22, which has been recently described. AFM has revealed the morphology of bacteriophage AP22, adsorbed on the surfaces of mica, graphite and host bacterial cells. Besides, morphological changes of bacteriophage AP22-infected A. baumannii cells were characterized at different stages of the lytic cycle, from phage adsorption to the cell lysis. The phage latent period, estimated from AFM was in good agreement with that obtained by microbiological methods (40 min). Bacteriophage AP22, whose head diameter is 62±1 nm and tail length is 88±9 nm, was shown to disperse A. baumannii aggregates and adsorb to the bacterial surface right from the first minute of their mutual incubation at 37°C.

Conclusions/Significance

High rate of bacteriophage AP22 specific adsorption and its ability to disperse bacterial aggregates make this phage very promising for biomedical antimicrobial applications. Complementing microbiological results with AFM data, we demonstrate an effective approach, which allows not only comparing independently obtained characteristics of the lytic cycle but also visualizing the infection process.     

Bacteriophage T5 DNA ejection under pressure

The transfer of the bacteriophage genome from the capsid into the host cell is a key step of the infectious process. In bacteriophage T5, DNA ejection can be triggered in vitro by simple binding of the phage to its purified Escherichia coli receptor FhuA. Using electrophoresis and cryo-electron microscopy, we measure the extent of DNA ejection as a function of the external osmotic pressure. In the high pressure range (7-16 atm), the amount of DNA ejected decreases with increasing pressure, as theoretically predicted and observed for λ and SPP1 bacteriophages. In the low and moderate pressure range (2-7 atm), T5 exhibits an unexpected behavior. Instead of a unique ejected length, multiple populations coexist. Some phages eject their complete genome, whereas others stop at some nonrandom states that do not depend on the applied pressure. We show that contrarily to what is observed for the phages SPP1 and λ, T5 ejection cannot be explained as resulting from a simple pressure equilibrium between the inside and outside of the capsid. Kinetics parameters and/or structural characteristics of the ejection machinery could play a determinant role in T5 DNA ejection.     

Bacteriophage immobilized graphene electrodes for impedimetric sensing of bacteria (Staphylococcus arlettae)

Bacteriophages are a class of viruses that specifically infect and replicate within a bacterium. They possess inherent affinity and specificity to the particular bacterial cells. This property of bacteriophages makes them an attractive biorecognition element in the field of biosensor development. In this work, we report the use of an immobilized bacteriophage for the development of a highly sensitive electrochemical sensor for Staphylococcus arlettae, bacteria from the pathogenic family of coagulase-negative staphylococci (CNS). The specific bacteriophages were covalently immobilized on the screen-printed graphene electrodes. Thus, the fabricated bacteriophage biosensor displayed quantitative response for the target bacteria (S. arlettae) for a broad detection range (2.0–2.0 × 10⁶ cfu). A fast response time (2 min), low limit of detection (2 cfu), specificity, and stability over a prolonged period (3 months) are some of the important highlights of the proposed sensor. The practical utility of the developed sensor has been demonstrated by the analysis of S. arlettae in spiked water and apple juice samples.