Novel genes associated with biofilm formation of Actinobacillus pleuropneumoniae

Actinobacillus pleuropneumoniae is a gram-negative bacterium and is the causative agent of swine pleuropneumonia, a highly contagious respiratory disease. Biofilm formation is an important ability possessed by numerous bacterial pathogens. The purpose of this study was to identify and characterize biofilm mutants of A. pleuropneumoniae serotype 1 strain S4074 created using a mini Tn-10 transposon. The transposon library was screened to identify mutants with a modified ability to form biofilms in polystyrene microtiter plates. A total of 1200 mutants were screened and the analysis identified 24 mutants that exhibited abnormal biofilm formation, at least 16 unique genes were identified. Most genes identified in the enhanced-biofilm mutants encoded proteins with unknown functions, whereas most genes identified in the biofilm-reduced mutants encoded proteins related to transport, protein synthesis and nucleic acid synthesis. Approximately 50% of genes, including hns, potD2, ptsI, tig and rpmF, identified in our screen have been previously associated with biofilm formation in A. pleuropneumoniae and other bacterial species, and thus validated the screening method. The rest of genes identified, such as APL_0049, APL_0637 and APL_1572, have not been previously associated with biofilm formation. Interestingly, gene APL_0049 was previously seen among the genes differentially expressed during a natural infection of pig lungs. Preliminary characterization of the mutants was also initiated by assessing their hydrophobicity, their biofilm matrix composition and their ability to adhere to a polystyrene surface or NPTr cells. Based on the preliminary characterization, some of the mutants identified appear to have deficiencies during the initial attachment or growth of the biofilm. In conclusion, transposon mutagenesis analysis allowed the identification of new genes associated with biofilm formation in A. pleuropneumoniae.     

Is love for green in our genes? A critical analysis of evolutionary assumptions in restorative environments research

Within the field of restorative environments research, it is commonly assumed that restorative responses, triggered by exposure to natural elements and settings, are ultimately adaptive traits originating from our species’ long evolutionary history in natural environments. The aim of this article is to critically investigate the viability of this evolutionary view on restoration. In doing so, we specifically focus on Stress Recovery Theory (SRT), as this theoretical framework has most extensively elaborated on the supposed evolutionary origins of restoration. A detailed analysis of SRT's psycho-evolutionary framework shows that neither current empirical evidence nor conceptual arguments provide any strong support for the hypothesis of restorative responses to nature as an ancient evolved adaptive trait. Based on this conclusion we put forward an alternative model for restorative responses to nature based on processing fluency, which prima facie circumvents some of the pitfalls associated with evolutionary accounts for restoration. The Discussion section reflects on the implications of our critical discussion for the theory and practice of urban forestry and urban greening.     

Genotype x environment interaction for root traits in maize,as analysed with factorial regression models

Summary The efficiency of genotopic and climatic characteristics in accounting for the interaction between genotypes and environments has been assessed in a three-year trial involving a set of genotypes presenting a range of root morphology characteristics (number and size). Climatic information on rainfall and temperature was recorded during the experiments, together with extra data on the growth and development of the genotypes. Their effects have been tested in factorial regression models.Climatic covariates were very powerful in accounting for the genotype by year interaction as well as the year main effect alone. For the number of adventitious roots on internode 7, the main effect of year could be described as a linear function of the average temperature and precipitation that occurred during the period of root initiation and growth. For internode 6, no clear conclusion was possible. For the root traits studied, 74 to 98% of the interaction could be explained by one climatic covariate. The regression coefficients can be considered as measures of genotypic stability.The genotypic covariates describing aerial development performed rather poorly, compared with environmental ones, even though the physiological and functional relationships between root and shoot are well known. Neither genotype main effect nor genotype by year interaction could be described sufficiently by factorial regression. Still, the genotypic covariates performing best clearly differed between root counts and size. Also the best genotypic covariates differed for main effect and interaction.     

Acquisition of haemoglobin-bound iron by Histophilus somni

Histophilus somni is an important pathogen of cattle and sheep. H. somni requires iron and can use ruminant transferrins as iron sources for growth. Here, we investigated the abilities of bovine (strains 649 and 2,336) and ovine (strains 9L and 3384Y) isolates of H. somni to acquire iron from haemoglobins. Using growth assays, the bovine isolates were shown to acquire iron from bovine haemoglobin, but not from ovine, porcine or human haemoglobins; the ovine isolates, however, failed to use any of these haemoglobins as iron sources for growth. In solid phase binding assays, the bovine isolates, grown under iron-restricted conditions in the presence of bovine haemoglobin, bound not only bovine but also ovine and human haemoglobins. Competition binding assays indicated that all three haemoglobins were bound by the same receptor(s) and SDS-PAGE of membrane fractions revealed that expression of haemoglobin-binding activity was associated with the production of an approximately 120-kDa outer membrane protein. PCR approaches allowed the amplification and sequencing of hgbA, and also hugX and hugZ homologues from strains 649, 9L and 3384Y. While hgbA of strain 649 was predicted to encode an HgbA precursor that is processed to yield a mature, 123.9-kDa haemoglobin-binding protein, the hgbA genes of strains 9L and 3384Y were predicted to give rise to truncated products. RT-PCR experiments revealed that in strain 649, hugX, hugZ and hgbA are co-transcribed and iron-regulated and additional sequencing suggested that in strain 2336, expression of HgbA is subject to phase variation involving a poly C tract within hgbA.     

Degradation of cyclins D in pseudorabies virus (PRV) infected proliferating cells

The pseudorabies virus code for an ICP0 protein which is half the size of the HSV1 ICP0 protein. In this work, we made the assumption that some function might have been lost in the ICP0 from PRV. One function attributed to the ICP0 from HSV1 was the stabilization of cyclins D. We then looked at the stability of these cyclins during the lytic infection with the PRV. Our results show that cyclins D are not stabilized during infection with the PRV. These results are in accord with recent data from the literature.     

Identification of apolipoprotein A‐I in the α‐globulin fraction of avian plasma

Background: Plasma protein electrophoresis is frequently used in birds as a tool for the diagnosis and monitoring of disease. Identification of proteins in individual peaks can help improve our understanding of changes in protein concentration in physiologic and pathologic conditions. Objective: The aim of this study was to verify the presence and identity the protein(s) in the prominent α‐globulin peak of orange‐winged parrots (Amazona amazonica), black kites (Milvus migrans), and rock pigeons (Columba livia). Methods: Heparinized plasma samples were obtained from 12 birds of each species. Agarose gel electrophoresis and total protein concentration were determined using standard techniques. One plasma sample from each species was then electrophoresed using high‐resolution agarose gels to isolate the α‐globulin band. Gel strips were digested in trypsin and peptides were extracted and analyzed using liquid chromatography with tandem mass spectrometry. De novo sequencing was used to identify the protein based on homology scoring against a protein database. Results: Electrophoresis verified the presence of a single prominent α‐globulin peak, usually in the α₁‐region, that had a median concentration of 9.4 g/L (range, 2.1–11.7 g/L, 21.6% of total protein) in parrots, 12.2 g/L (10.4–13.2 g/L, 35.9%) in kites, and 10.7 g/L (9.0–11.5 g/L, 40.0%) in pigeons. Mass spectrometry and sequencing analysis unequivocally identified the protein as a mature circulating form of apolipoprotein A‐I (apo A‐I) in all 3 species. Conclusions: Apo A‐I accounts for the prominent α‐globulin peak and comprises a major proportion of total protein concentration in diverse avian species. As a high‐density lipoprotein and negative acute phase protein with a pivotal role in cholesterol homeostasis, further study is warranted to determine the significance of changes in apo A‐I concentration in avian electrophoretograms.     

Atypical pneumonia associated with a Mycoplasma isolate in a kitten

An atypical case of Mycoplasma pneumonia with an unusual radiographic and computed tomographic pattern was diagnosed in a Siamese kitten. The cat showed no response to broad-spectrum antibiotic therapy including enrofloxacin. The administration of doxycycline led to a dramatic clinical and radiographic improvement.     

Canine sterile neutrophilic dermatitis (resembling Sweet's syndrome) in a Dachshund

A 6-year-old Dachshund was presented with a 2-day history of lethargy, anorexia and cutaneous erythema, edema, and multifocal erythematous papules affecting the ventral abdomen, axillae, and groin. Microscopic examination revealed a sterile neutrophilic dermatitis resembling Sweet's syndrome; however, extracutaneous lesions were not present. The condition responded rapidly to corticosteroid therapy.