The perception of a dotted line in noise: a model of good continuation and some experimental results

A formal model is proposed, describing how the perceptual interpretation of dot figures is guided by the Gestalt rule of good continuation. The algorithm will be restricted to figures with a collinear dot array (line) embedded in a background of randomly placed dots. The model, CODE-2, is an elaboration of the model, CODE-1, of grouping dots on the basis of the Gestalt rule of (relative) proximity, and consists of the introduction of non-circular symmetric gaussian distribution functions for the representation of the orientation dependent strength of interaction between collinear dots. Supra-threshold contours of the function, resulting from a superposition on each dot of the gaussian functions, are assumed to predict the perceptual grouping of the dots. A quantitative measure for the perceptual salience of dotted lines was defined as the contrast between the internal coherence of the line dots, and their interference with the noise dots. For 20 stimuli the CODE-2 grouping of the dots is reported, together with the results of a line-in-noise latency experiment. There was a significant correlation between the predicted saliences and the experimental results. The results support the usefulness of representing good continuation between collinear dots by non-circular symmetric gaussian distribution functions.     

Post-application Persistence of Entomopathogenic Nematodes

Five phases can be distinguished in the post-application persistence of entomopathogenic nematodes and each phase is associated with a specific set of mortality factors. Pre-application factors associated with production, storage and transport conditions determine the survival rate and quality of nematodes at the time of application. The phase of tank mixing and application with a sprayer, hose or other equipment does not usually cause mortality as nematode dauer juveniles are quite tolerant of shear forces. The most critical periods for survival are the first few minutes and hours directly after application. High losses, in the order of 40-80%, often occur during this phase. Ultraviolet radiation and dehydration are probably the most important mortality factors. The remaining nematodes settle in the soil and their numbers gradually decrease at levels of 5-10% per day. Predation, infection by antagonists, depletion of energy and desiccation are probably the main mortality factors during this period. In most cases, after 2-6 weeks less than 1% of the applied population is still alive. Through recycling in host insects, nematodes may then persist for years at these levels. Thus, the pattern is a rapid decline in the first few days followed by a moderate decline over the next 2-6 weeks and then a long period of recycling at a low level. Some nematode species that normally occur in warmer climatic zones can also persist in colder climates. Major side-effects of applications of entomopathogenic nematodes are not likely to occur as the population density decreases to background levels within days or weeks after application. Furthermore, there is little or no migration of the nematodes to neighbouring fields. The relatively short period of persistence of entomopathogenic nematodes and the necessity of their populations to recycle frequently in hosts in order to survive make it unlikely that they could have major effects on non-target organisms. Their selectivity and beneficial traits as biological control agents outweigh the small risks of causing unwanted environmental disturbance in non-target populations.     

Asymptomatic Middle East Respiratory Syndrome Coronavirus Infection in Rabbits

The ability of Middle East respiratory syndrome coronavirus (MERS-CoV) to infect small animal species may be restricted given the fact that mice, ferrets, and hamsters were shown to resist MERS-CoV infection. We inoculated rabbits with MERS-CoV. Although virus was detected in the lungs, neither significant histopathological changes nor clinical symptoms were observed. Infectious virus, however, was excreted from the upper respiratory tract, indicating a potential route of MERS-CoV transmission in some animal species.     

Abiotic stress protection by ecologically abundant dimethylsulfoniopropionate and its natural and synthetic derivatives: insights from Bacillus subtilis

Dimethylsulfoniopropionate (DMSP) is an abundant osmolyte and anti‐stress compound produced primarily in marine ecosystems. After its release into the environment, microorganisms can exploit DMSP as a source of sulfur and carbon, or accumulate it as an osmoprotectant. However, import systems for this ecophysiologically important compatible solute, and its stress‐protective properties for microorganisms that do not produce it are insufficiently understood. Here we address these questions using a well‐characterized set of Bacillus subtilis mutants to chemically profile the influence of DMSP import on stress resistance, the osmostress‐adaptive proline pool and on osmotically controlled gene expression. We included in this study the naturally occurring selenium analogue of DMSP, dimethylseleniopropionate (DMSeP), as well as a set of synthetic DMSP derivatives. We found that DMSP is not a nutrient for B. subtilis, but it serves as an excellent stress protectant against challenges conferred by sustained high salinity or lasting extremes in both low and high growth temperatures. DMSeP and synthetic DMSP derivatives retain part of these stress protective attributes, but DMSP is clearly the more effective stress protectant. We identified the promiscuous and widely distributed ABC transporter OpuC as a high‐affinity uptake system not only for DMSP, but also for its natural and synthetic derivatives.     

Clinical signs,diagnostics and successful treatment of a myocarditis in an adult chimpanzee (Pan troglodytes)

A chimpanzee (Pan troglodytes) was presented with lethargic behaviour. Echocardiography and abnormal cardiac and inflammatory biomarkers revealed a myocarditis. The animal fully recovered after prolonged treatment with losartan and carvedilol. This is the first report of the diagnosis and successful treatment of myocarditis in this species.     

Genomics and current genetic understanding of Erwinia amylovora and the fire blight antagonist Pantoea vagans

The bacterial plant pathogen Erwinia amylovora causes fire blight, a major disease threat to pome fruit production worldwide with further impact on a wide-range of Rosaceae species. Important factors contributing to the development of the disease were discovered in the last decades. Comparative genomics of the genera Erwinia and Pantoea is coming into focus with the recent availability of complete genome sequences. Insights from comparative genomics now position us to answer fundamental questions regarding the evolution of E. amylovora as a successful pathogen and the critical elements for biocontrol activity of Pantoea spp. This trove of new data promises to reveal novel determinants and to understand interactive pathways for virulence, host range and ecological fitness. The ultimate aim is now to apply genomics and identify the pathogen Achilles heels and antagonist mechanisms of action as targets for designing innovative control strategies for fire blight.     

Adenosine Deaminase Acts as a Natural Antagonist for Dipeptidyl Peptidase 4-Mediated Entry of the Middle East Respiratory Syndrome Coronavirus

Middle East respiratory syndrome coronavirus (MERS-CoV) replicates in cells of different species using dipeptidyl peptidase 4 (DPP4) as a functional receptor. Here we show the resistance of ferrets to MERS-CoV infection and inability of ferret DDP4 to bind MERS-CoV. Site-directed mutagenesis of amino acids variable in ferret DPP4 thus revealed the functional human DPP4 virus binding site. Adenosine deaminase (ADA), a DPP4 binding protein, competed for virus binding, acting as a natural antagonist for MERS-CoV infection.     

Mucin-derived O-glycans supplemented to diet mitigate diverse microbiota perturbations

Microbiota-accessible carbohydrates (MACs) are powerful modulators of microbiota composition and function. These substrates are often derived from diet, such as complex polysaccharides from plants or human milk oligosaccharides (HMOs) during breastfeeding. Host-derived mucus glycans on gut-secreted mucin proteins serve as a continuous endogenous source of MACs for resident microbes; here we investigate the potential role of purified, orally administered mucus glycans in maintaining a healthy microbial community. In this study, we liberated and purified O-linked glycans from porcine gastric mucin and assessed their efficacy in shaping the recovery of a perturbed microbiota in a mouse model. We found that porcine mucin glycans (PMGs) and HMOs enrich for taxonomically similar resident microbes. We demonstrate that PMGs aid recovery of the microbiota after antibiotic treatment, suppress Clostridium difficile abundance, delay the onset of diet-induced obesity, and increase the relative abundance of resident Akkermansia muciniphila. In silico analysis revealed that genes associated with mucus utilization are abundant and diverse in prevalent gut commensals and rare in enteric pathogens, consistent with these glycan-degrading capabilities being selected for during host development and throughout the evolution of the host–microbe relationship. Importantly, we identify mucus glycans as a novel class of prebiotic compounds that can be used to mitigate perturbations to the microbiota and provide benefits to host physiology.Subject terms: Microbial ecology, Diseases