Bacillus phage phi18-2 is a novel temperate virus with an unintegrated genome present in the cytoplasm of lysogenic cells as a linear phage-plasmid.

Bacillus subtilis is a Gram-positive bacterium that is widely used in fermentation and in the pharmaceutical industry. Phage contamination occasionally occurs in various fermentation processes and causes significant economic loss. Here, we report the isolation and characterization of a temperate B. subtilis phage, termed phi18-2, from spore powder manufactured in a fermentation plant. Transmission electron microscopy showed that phi18-2 has a symmetrical polyhedral head and a long noncontractile tail. Receptor analysis showed that phi18-2 recognizes wall teichoic acid (WTA) for infection. The phage virions have a linear double-stranded DNA genome of 64,467 bp with identical direct repeat sequences of 309 bp at each end of the genome. In lysogenic cells, the phage genome was found to be present in the cytoplasm without integration into the host cell chromosome, and possibly as a linear phage-plasmid with unmodified ends. Our data may provide some insight into the molecular basis of the unique lysogenic cycle of phage phi18-2.

Surgical treatment of osteogenesis imperfecta: a summary of the incidence of femoral implant-related complications in children with Sillence type I, III and IV.

PURPOSE: This study explored the incidence of IRCs used in the procedures of the femur in children with osteogenesis imperfecta (OI) and investigated the independent risk factors of IRCs. METHODS: Three hundred eight-eight cases of surgical data about children with OI were included, who were treated with plate, elastic nail, Kirschner wire and telescopic rod. The choice of different procedures depended on the age of children, the status of femur and the availability of devices. Patient demographics and major IRCs were recorded to compare the outcomes of the four procedures. Then, Cox proportional hazard regression was used to analyse the independent risk factors of IRC, and subgroup analysis was applied to further verify the above results. RESULTS: The total incidence of IRC in the four groups was 90.1% (191/212) for plate, 96.8% (30/31) for Kirschner wire, 87.7% (57/65) for elastic nail and 30.0% (24/80) for telescopic rod. The incidence of IRC in the telescopic rod was lower than that in plate, elastic nail and Kirschner wire (P < 0.001). Cox proportional hazard regression analysis confirmed that procedure was the independent risk factor of IRC (HR, 0.191; 95% CI, 0.126-0.288; P < 0.001), fracture (HR, 0.193; 95% CI, 0.109-0.344; P < 0.001) and deformity (HR, 0.086; 95% CI, 0.027-0.272; P < 0.001). In addition, age of surgery was the independent risk factor of fracture (HR, 0.916; 95% CI, 0.882-0.952; P < 0.001) and deformity (HR, 1.052; 95% CI, 1.008-1.098; P = 0.019). Subgroup analysis confirmed that age of surgery, gender, classification, preoperative state and angle did not affect the effect of telescopic rod on reducing the risk of IRCs. CONCLUSIONS: In our cohort, lower incidence of IRCs was observed in telescopic rod group compared with plate, Kirschner wire and elastic nail. Procedure and age of surgery were independent risk factors of fracture. Likewise, procedure and age of surgery were independent risk factors of deformity, and procedure was independent risk factors of IRC.

Psychrophilic phage phiGM22-3 efficiently controls Pseudomonas fluorescens contamination in cold-stored milk.

Pseudomonas fluorescens is a common spoilage causing microbe found in milk. Antibiotic preservatives may cause emergence of multidrug resistance, posing food safety related risks to public health. Phage treatment may be used as an alternative to antibiotics in controlling P. fluorescens contaminations. Here we reported that P. fluorescens phage phiGM22-3 reproduced rapidly over a broad temperature range of 4 through 30°C, and the optimum growth of phiGM22-3 occurred at 10°C, indicating that it was a psychrophilic virus. Genome analysis revealed that phiGM22-3 has a genome of 42,662 bp with an identical terminal direct repeat sequence of 328 bp and encodes 58 predicted proteins. Evidence revealed that phiGM22-3 recognized lipopolysaccharides (LPS) as receptor for infection. Additionally, two phage mutants phiMX2 and phiMX8 with different host ranges were identified in the phiGM22-3 population. Phage killing efficiency of P. fluorescens cells artificially inoculated in milk was evaluated. Phage phiGM22-3 and the cocktails containing phiMX2 and phiMX8 can lyse almost 100% bacterial cells at 4°C within 24 h. Taken together, our data indicated that the psychrophilic virus phiGM22-3 and its two mutants can efficiently inhibit bacteria growth at 4°C, showing a great potential to be used as alternatives to conventional antibiotics against P. fluorescens in refrigerated foods.

Genome-wide transcription landscape of citric acid producing Aspergillus niger in response to glucose gradient.

Aspergillus niger is the main industrial workhorse for global citric acid production. This fungus has complex sensing and signaling pathways to respond to environmental nutrient fluctuations. As the preferred primary carbon source, glucose also acts as a critical signal to trigger intracellular bioprocesses. Currently, however, there is still a knowledge gap in systems-level understanding of metabolic and cellular responses to this vital carbon source. In this study, we determined genome-wide transcriptional changes of citric acid-producing Aspergillus niger in response to external glucose gradient. It demonstrated that external glucose fluctuation led to transcriptional reprogramming of many genes encoding proteins involved in fundamental cellular process, including ribosomal biogenesis, carbon transport and catabolism, glucose sensing and signaling. The major glucose catabolism repressor creA maintained a stable expression independent of external glucose, while creB and creD showed significant downregulation and upregulation by the glucose increase. Notably, several high-affinity glucose transporters encoding genes, including mstA, were greatly upregulated when glucose was depleted, while the expression of low-affinity glucose transporter mstC was glucose-independent, which showed clear concordance with their protein levels detected by in situ fluorescence labeling assay. In addition, we also observed that the citric acid exporter cexA was observed to be transcriptionally regulated by glucose availability, which was correlated with extracellular citric acid secretion. These discoveries not only deepen our understanding of the transcriptional regulation of glucose but also shed new light on the adaptive evolutionary mechanism of citric acid production of A. niger.

Alternating current stimulation promotes neurite outgrowth and plasticity in neurons through activation of the PI3K/AKT signaling pathway.

As a commonly used physical intervention, electrical stimulation (ES) has been demonstrated to be effective in the treatment of central nervous system disorders. Currently, researchers are studying the effects of electrical stimulation on individual neurons and neural networks, which are dependent on factors such as stimulation intensity, duration, location, and neuronal properties. However, the exact mechanism of action of electrical stimulation remains unclear. In some cases, repeated or prolonged electrical stimulation can lead to changes in the morphology or function of the neuron. In this study, immunofluorescence staining and Sholl analysis are used to assess changes in the neurite number and axon length to determine the optimal pattern and stimulation parameters of ES for neurons. Neuronal death and plasticity are detected by TUNEL staining and microelectrode array assays, respectively. mRNA sequencing and bioinformatics analysis are applied to predict the key targets of the action of ES on neurons, and the identified targets are validated by western blot analysis and qRT-PCR. The effects of alternating current stimulation (ACS) on neurons are more significant than those of direct current stimulation (DCS), and the optimal parameters are 3 µA and 20 min. ACS stimulation significantly increases the number of neurites, the length of axons and the spontaneous electrical activity of neurons, significantly elevates the expression of growth-associated protein-43 (GAP-43) without significant changes in the expression of neurotrophic factors. Furthermore, application of PI3K/AKT-specific inhibitors significantly abolishes the beneficial effects of ACS on neurons, confirming that the PI3K/AKT pathway is an important potential signaling pathway in the action of ACS.

The patient-related factors in revision procedures on tibia of patients with osteogenesis imperfecta treated with the Peter-Williams nail.

OBJECTIVE: To investigate the patient-related factors that affect the revision rate for the tibia in patients with osteogenesis imperfecta treated with the Peter-Williams nail, and to explore the relationship between the risk factors and complications postsurgery. METHODS: We retrospectively analysed the data of 211 patients (93 females (44.08%) and 118 males (55.92%)) with osteogenesis imperfecta treated with Peter-Williams. The factors affecting surgical revision were analysed by performing binary logistic regression. Then, a total of 211 patients with type III, type I or type IV OI were divided into five groups according to the results of regression. Statistical comparison of these groups was performed to further investigate the relationship between patient-related factors and revision procedures. Statistical comparison was also performed to analyse the relationship between the classification and postoperative complications. RESULTS: Among the 211 patients who underwent surgery, 40 had type I OI, 109 had type IV OI, and 62 had type III OI. Binary logistic regression revealed that the classification (OR = 3.32, 95% CI 1.06-10.39, P = 0.039) and initial operation age (OR = 0.83, 95% CI 0.76-0.92, P < 0.001) were significantly correlated with revision procedures. In type III patients, the initial operation age was significantly correlated with revision procedures (P < 0.001), and the revision rate was lower in patients aged 9 to12 years (P = 0.001). In type I and IV patients, the initial operation age was not significantly correlated with revision procedures (P = 0.281). Classification had a significant effect on postoperative deformity (P = 0.003). CONCLUSIONS: The study reported that the age of initial surgery and classification were the influencing factors affecting the revision procedures of tibia in patients with osteogenesis imperfecta treated with the Peter-Williams nail. In patients with type III disease, the revision rate was lower individuals aged 9-12 years old, and a higher incidence of postoperative deformity was observed.

Which is the best femoral implant in children with osteogenesis imperfecta? a retrospective cohort study of 783 procedures.

BACKGROUND: Osteogenesis imperfecta (OI) is a hereditary genetic disorder characterized by bone fragility and extremity deformities. The surgical management for long-bone fractures and deformities in OI remains a challenge. We aimed to compare clinical outcomes after femoral surgery splinted with the telescopic rod, the plate and screws, the elastic nail and the non-elongating rod in setting of OI. METHODS:  A retrospective cohort study included 783 femoral procedures (mean age 6.00 (interquartile range (IQR) 5.00) years, 335 (42.8%) females) was conducted, and individuals were categorized into four groups according to implants. After verifying comparability among the groups, revision rate and implant survival period were compared among the Sillence types and the same comparison were made among four groups within each Sillence type. The incidence of refractures, deformities, and implant-related complications were also compared among the four groups. RESULTS: There were no significant differences in demographic information among the four groups in terms of sex (p = 0.101), laterality (p = 0.587), Sillence type (p = 0.122), and postoperative follow-up period (p = 0.214). In total, children with Sillence type III had the highest revision rate and the shortest implant survival period; children with Sillence type I had the lowest revision rate and the longest implant survival period; and children with Sillence type IV had the revision rate and the implant survival period between those observed in Sillence types I and III. In Sillence types III and IV, the telescopic rod had lower revision rate (III 24.8%; IV 20.9%) compared to the plate (III 97.2%, p<0.001; IV 80.3%, p<0.001), the elastic nail (III 100.0%, p=0.019; IV 73.9%, p<0.001) and the non-elongating rod (III 65.0%, p<0.001; IV46.9%, p<0.001); the median implant survival period of the telescopic rod (III 48.00 (IQR 28.50) months; IV 43.00 (33.00) months) is longer than the plate (III 11.00 (9.00) months, p<0.001; IV 19.00 (20.00) months, p<0.001), the elastic nail (III 45.00 (37.75) months, p=1.000; IV 19.00 (35.00) months, p=0.028) and the non-elongating rod (III 39.00 (31.75) months, p=0.473; IV 38.50 (29.75) months, p=1.000).A similar trend was observed in Sillence type I (p = 0.063, p = 0.003; respectively). In addition, the incidence of refracture (15.5%), deformity (2.8%) and implant-related complications (23.1%) were also statistically lower in the telescopic rod group. CONCLUSION: In our cohort, lower revision rate and longer implant survival period were observed in telescopic rod group. This was mainly due to the significant lower incidence of refracture, deformity and implant-related complications with the use of telescopic rod.

Variants of a putative baseplate wedge protein extend the host range of Pseudomonas phage K8.

BACKGROUND: Narrow host range is a major limitation for phage applications, but phages can evolve expanded host range through adaptations in the receptor-binding proteins. RESULTS: Here, we report that Pseudomonas phage K8 can evolve broader host range and higher killing efficiency at the cost of virion stability. Phage K8 host range mutant K8-T239A carries a mutant version of the putative baseplate wedge protein GP075, termed GP075m. While phage K8 adsorbs to hosts via the O-specific antigen of bacterial LPS, phage K8-T239A uses GP075m to also bind the bacterial core oligosaccharide, enabling infection of bacterial strains resistant to K8 infection due to modified O-specific antigens. This mutation in GP075 also alters inter-protein interactions among phage proteins, and reduces the stability of phage particles to environmental stressors like heat, acidity, and alkalinity. We find that a variety of mutations in gp075 are widespread in K8 populations, and that the gp075-like genes are widely distributed among the domains of life. CONCLUSION: Our data show that a typical life history tradeoff occurs between the stability and the host range in the evolution of phage K8. Reservoirs of viral gene variants may be widely present in phage communities, allowing phages to rapidly adapt to any emerging environmental stressors. Video Abstract.

Bacillus subtilis phage phi18: genomic analysis and receptor identification.

Bacillus subtilis strains play a pivotal role in the fermentation industry. B. subtilis phages can cause severe damage by infecting bacterial cells used in industrial fermentation processes. In this work, we isolated and characterized a Bacillus subtilis-infecting phage, termed phi18. Transmission electron microscopy revealed that phage phi18 particles have typical myovirus morphology, with an icosahedral head connected to a contractile tail. Genomic analysis revealed that the phage genome is a linear double-stranded DNA molecule of 147,298 bp with terminal redundancy of 14,434 bp, and 226 protein coding genes and four tRNA genes were predicted in the genome. Phage-resistant mutants were selected from a mariner transposon-insertion library of B. subtilis 168 in which two bacterial genes, tagE and pgcA, which are required for the glycosylation of wall teichoic acid (WTA), were found to be disrupted, suggesting that WTA is the receptor for phage phi18. Comparative genomic analysis showed that phage phi18 is a new member of the genus Okubovirus of the family Herelleviridae. Finally, general characteristics of the phage-resistant mutants, including biofilm formation, growth, and sporulation, were examined. The results showed that the phage-resistant mutants grew as rapidly as the parental strain B. subtilis 168 at 42 °C, suggesting that these phage-resistant mutants may be used as starters in fermentation processes.

Phage phiZ98: A novel tri-segmented dsRNA cystovirus for controlling Pseudomonas strains with defective lipopolysaccharides in foods.

Many Pseudomonas phages recognize lipopolysaccharides (LPS) as the receptor for infection. LPS defective mutants are often recovered from phage treatments, possibly causing the failure of phage applications. In this work, we isolated a lytic Pseudomonas phage, phiZ98, that can specifically lyse LPS defective strains of the genus Pseudomonas. Transmission electron microscopy (TEM) showed that phiZ98 particles were enveloped in a layer of membrane-like structure. Genomic analysis revealed that the phage has a genome of tri-segmented double-stranded RNA molecules of 6627 bp, 3769 bp, and 3075 bp, respectively. The results indicated that phage phiZ98 was the nineth member of the genus Cystovirus. The phiZ98 genome encoded 12 putative proteins with predicted functions and 15 hypothetical proteins. Mass spectrum analysis further identified 11 proteins present in the virions. Antibacterial activity assays showed that phage phiZ98 significantly inhibited cell growth, reduced biofilm formation, and removed mature biofilm. Moreover, phage phiZ98 can significantly control the growth of the host bacterial cells in sterilized milk or canned corned beef. In combination with phage K8 which used LPS as the receptor, phiZ98 can significantly reduce the phage-resistant mutants generated from the K8 treatment in milk. Taken together, the dsRNA phage phiZ98 could be an effective scavenger in removing phage-resistant mutants with defective LPS in cocktail applications.

Escherichia coli phage phi2013: genomic analysis and receptor identification.

Escherichia coli is an important foodborne pathogen that can cause severe human disease. Here, we report the isolation and characterization of the lytic virus phi2013, which is specific for Escherichia coli laboratory strains. Transmission electron microscopy showed that phage phi2013 has an icosahedral head and a long, fragile, noncontractile tail, exhibiting the typical form of a siphovirus. Evidence revealed that the phi2013 genome is a linear double-stranded DNA molecule of 49,833 bp with 79 predicted genes without any known antibiotic resistance genes, virulence factor genes, or integrase genes. Moreover, the conserved outer membrane protein FhuA, which is present in members of several genera of the family Enterobacteriaceae, was identified as the receptor of phage phi2013. To evaluate the potential of phage phi2013 as a biocontrol agent for controlling E. coli contamination, it was tested in several foods, including sterilized milk, ready-to-eat beef, and crisphead lettuce. The data showed that phage phi2013 can efficiently inhibit E. coli growth in the tested foods at 4°C and 25°C. We therefore conclude that phage phi2013 or cocktails containing phi2013 may be used as an antimicrobial agent in extending the shelf-life of food products by effectively controlling the growth of E. coli.

Prolonged chronic social defeat stress promotes less resilience and higher uniformity in depression-like behaviors in adult male mice.

Chronic social defeat stress (CSDS) is widely applied to study of depression in rodents. 10-day CSDS was a most commonly employed paradigm but with high resilience ratio (∼30%), producing potential variation in depression-like behavioral symptoms. Whether prolonged period (21 days) of CSDS would promote less resilience and reduce behavioral variability remains unknown. We applied 10-day and 21-day CSDS paradigms to induce mouse model of depression and compared their resilience ratio and behavioral phenotypes. Mice under 21-day CSDS had significantly lower resilience ratio and greater changes in behavioral indicators relative to mice under 10-day CSDS. Behavioral indicators from 21-day CSDS paradigm had higher correlations and better prediction for susceptibility which indicating higher uniformity in behavioral phenotypes. Furthermore, a subset of behavioral indicators in 21-day CSDS had high prediction efficacy and should be first applied to screen susceptibility of CSDS. Thus, our study demonstrates that 21-day CSDS is a more robust paradigm inducing reliable depression-like behaviors relative to 10-day CSDS, and should be preferentially used in rodent studies of depression.

Sparse imaging and reconstruction tomography for high-speed high-resolution whole-brain imaging.

Understanding brain functions requires detailed knowledge of long-range connectivity through which different areas communicate. A key step toward illuminating the long-range structures is to image the whole brain at synaptic resolution to trace axonal arbors of individual neurons to their termini. However, high-resolution brain-wide imaging requires continuous imaging for many days to sample over 10 trillion voxels, even in the mouse brain. Here, we have developed a sparse imaging and reconstruction tomography (SMART) system that allows brain-wide imaging of cortical projection neurons at synaptic resolution in about 20 h, an order of magnitude faster than previous methods. Analyses of morphological features reveal that single cortical neurons show remarkable diversity in local and long-range projections, with prefrontal, premotor, and visual neurons having distinct distribution of dendritic and axonal features. The fast imaging system and diverse projection patterns of individual neurons highlight the importance of high-resolution brain-wide imaging in revealing full neuronal morphology.

The Effect of Streptococcus salivarius K12 on Halitosis: a Double-Blind, Randomized, Placebo-Controlled Trial.

This study was to evaluate the effect of Streptococcus salivarius K12 on tongue coating-associated halitosis. Twenty-eight subjects having tongue coating-associated halitosis were randomly divided into either a test or control group. For each of the 30 days, the test subjects sucked S. salivarius K12 tablet while the control subjects sucked placebo tablets. All the subjects did not take physical (tongue scraping) and chemical (antiseptic mouth-rinse) oral cavity pretreatment prior to use of the tablets. At baseline, and on the 1st, 7th, and 14th day after completing the course of tablets, the subjects were assessed for their organoleptic test (OLT) scores, volatile sulfur compound (VSC) levels, and tongue coating scores (TCS). During the course, all subjects kept their routine oral care habits without scraping their tongue coating. Plaque index, probing depth, and bleeding index were recorded at baseline and at the completion of the trial. On the 1st day following the end of tablet use, the OLT scores and VSC levels had significantly decreased in the test group when compared with the baseline values (P = 0.001 and P = 0.012). The TCS in the test group were also significantly decreased (P = 0.05). At days 7 and 14, the OLT scores in the test group were still significantly lower than the baseline levels (P = 0.006 and P = 0.039 respectively). However, there were no statistical differences with OLT, VSC, and TCS between the test group and the placebo group by analysis of multi-level regression model. The use of S. salivarius K12 did not have significant effect on halitosis with tongue coating cause when the tongue coating was not physically or chemically pre-treated, which implies removing tongue coating is required before Streptococcus salivarius K12 use.

A putative LysR-type transcriptional regulator inhibits biofilm synthesis in Pseudomonas aeruginosa.

Biofilm formation is an important virulence factor which is controlled by complex regulatory circuits in Pseudomonas aeruginosa. In this work, a biofilm hyper-producing strain, P2-7, was selected from a collection of transposon insertion mutants in which the PA2121 gene was disrupted. PA2121 was predicted as a putative LysR-type regulator. Analyses showed that it was involved in early biofilm formation, mature biofilm development, and colony morphology. Quantitative measurements revealed that PA2121 repressed biosynthesis of extracellular polysaccharides (alginate, psl and pel). Furthermore, it was observed that PA2121 was self-regulated, highly expressed in the early phase of biofilm development, and subject to the negative regulation by a biofilm synthesis regulator SrpA that binds directly to the PA2121 gene promoter. Collectively, this study proposes that PA2121 is a novel biofilm synthesis repressor (BsrA) in P. aeruginosa.

Characterization of a novel lytic myophage, phiA8-29, infecting Aeromonas strains.

Members of the bacterial genus Aeromonas are important aquatic pathogens that cause severe fish diseases. Here, we characterize a novel lytic phage, Aeromonas virus phiA8-29, isolated from the alimentary tract of a freshwater fish. Transmission electron microscopy showed that phiA8-29 has a long contractile tail and thus can be classified as a member of the family Myoviridae. The phage genome was identified as a double-stranded DNA molecule of 144,974 bp containing 185 open reading frames and nine tRNA-encoding genes. Comparative genomic analysis revealed that the phiA8-29 genome has little similarity to any of the currently sequenced Aeromonas phage genomes. Our data indicate that phiA8-29 is a novel lytic Myoviridae phage that does not belong to any of the known genera.

Characterization of a novel lytic podovirus O4 of Pseudomonas aeruginosa.

Phage O4 of Pseudomonas aeruginosa was previously visualized as a short-tailed virus using a transmission electron microscope. In this work, the O4 genome was characterized to be a linear dsDNA molecule comprising 50509 bp with 76 predicted genes located in five clusters. Mass spectrometry showed that the O4 virion contains 6 putative structural proteins, 2 putative enzymes, and 7 hypothetical proteins. By analyzing a Tn5G transposon mutation library, eight genes, wbpR, wbpV, wbpO, wbpT, wbpS, wbpL,  galU, and wzy, were identified and confirmed responsible for the phage-resistant phenotype; all of them are related to the synthesis of O-specific antigen (OSA) of lipopolysaccharide (LPS), indicating that OSA is the receptor for the adsorption of phage O4. Comparative genomic analysis revealed that the phage O4 genome shares little similarity to any known podovirus, indicating that phage O4 is classifiable as a novel member of the Podoviridae family.

Regulatory protein SrpA controls phage infection and core cellular processes in Pseudomonas aeruginosa.

Our understanding of the molecular mechanisms behind bacteria-phage interactions remains limited. Here we report that a small protein, SrpA, controls core cellular processes in response to phage infection and environmental signals in Pseudomonas aeruginosa. We show that SrpA is essential for efficient genome replication of phage K5, and controls transcription by binding to a palindromic sequence upstream of the phage RNA polymerase gene. We identify potential SrpA-binding sites in 66 promoter regions across the P. aeruginosa genome, and experimentally validate direct binding of SrpA to some of these sites. Using transcriptomics and further experiments, we show that SrpA, directly or indirectly, regulates many cellular processes including cell motility, chemotaxis, biofilm formation, pyocyanin synthesis and protein secretion, as well as virulence in a Caenorhabditis elegans model of infection. Further research on SrpA and similar proteins, which are widely present in many other bacteria, is warranted.

[A molecular epidemiological study of KI polyomavirus and WU polyomavirus in children with acute respiratory infection in Tianjin, China].

OBJECTIVE: To investigate the relationship of KI polyomavirus (KIPyV) and WU polyomavirus (WUPyV) with acute respiratory infection in children in Tianjin, China. METHODS: A total of 3 730 nasopharyngeal secretions were collected from hospitalized children with acute respiratory infection in Tianjin Children's Hospital from January 2011 to December 2013. Viral nucleic acid was extracted, and virus infection (KIPyV and WUPyV) was determined by PCR. Some KIPyV-positive and WUPyV-positive PCR products were subjected to sequencing. Sequencing results were aligned with the known gene sequences of KIPyV and WUPyV to construct a phylogenetic tree. Amplified VP1 fragments of KIPyV were inserted into the cloning vector (PUCm-T) transformed into E. coli competent cells. Positive clones were identified by PCR and sequencing. The nucleotide sequences were submitted to GenBank. In addition, another seven common respiratory viruses in all samples were detected by direct immunofluorescence assay. RESULTS: In the 3 730 specimens, the KIPyV-positive rate was 12.14% (453/3 730) and the WUPyV-positive rate was 1.69% (63/3 730). The mean infection rate of KIPyV was significantly higher in June and July, while the mean infection rate of WUPyV peaked in February and March. Most of the KIPyV-positive or WUPyV-positive children were <3 years. The co-infections with KIPyV, WUPyV, and other respiratory viruses were observed in the children. The co-infection rate was 2.31% (86/3 730) and there were nine cases of co-infections with WUPyV and KIPyV. Thirty-five KIPyV-positive and twelve WUPyV-positive PCR products were sequenced and the alignment analysis showed that they had high homology with the known sequences (94%-100% vs 95%-100%). The VP1 gene sequences obtained from two KIPyV strains in this study were recorded in GenBank with the accession numbers of KY465925 and KY465926. CONCLUSIONS: For some children with acute respiratory infection in Tianjin, China, the acute respiratory infection may be associated with KIPyV and WUPyV infections. KIPyV infection is common in summer, and WUPyV infection in spring. The epidemic strains in Tianjin have a high homology with those in other regions.

Quorum sensing influences phage infection efficiency via affecting cell population and physiological state.

Bacterial growth phase has been reported affecting phage infection. To underpin the related mechanism, infection efficiency of Pseudomonas aeruginosa phage K5 is characterized. When infecting the logarithmic cells, phage K5 produced significantly more infection centers than the stationary cells, well concordant with the viable cell ratio in the different growth phases. Additionally, the burst size decreased dramatically in the stationary cells, implying that the physiological state of the viable cells contributed to the productivity of phage K5, and it was consistent with the expression variation of the phage RNA polymerase. Quorum sensing inhibitor penicillic acid was applied and could significantly improve the viable cell proportion and the infection center numbers, but had less effect on the corresponding burst sizes. Moreover, the effect of penicillic acid and the quorum sensing regulator mutants on the production of phage C11 was also analyzed. Taken together, our data suggest that quorum sensing is involved in the defense of phage K5 infection by influencing the viable cell population and their physiological state, and it is an efficient and intrinsic pathway allowing bacteria to resist phage attacks in natural environment.