Effects of Temperature and Wetness Duration on Infection by Coniella diplodiella, the Fungus Causing White Rot of Grape Berries

Grapevine white rot, caused by Coniella diplodiella, can severely damage berries during ripening. The effects of temperature and wetness duration on the infection severity of C. diplodiella were investigated by artificially inoculating grape berries through via infection pathways (uninjured and injured berries, and through pedicels). The effect of temperature on incubation was also studied, as was that of inoculum dose. Injured berries were affected sooner than uninjured berries, even though 100% of the berries inoculated with C. diplodiella conidia became rotted whether injured or not; infection through pedicels was less severe. On injured berries, the disease increased as the inoculum dose increased. Irrespective of the infection pathway, 1 h of wetness was sufficient to cause infection at any temperature tested (10–35 °C); with the optimal temperature being 23.8 °C. The length of incubation was shorter for injured berries than for uninjured ones, and was shorter at 25–35 °C than at lower temperatures; the shortest incubation period was 14 h for injured berries at 30 °C. Mathematical equations were developed that fit the data, with R2 = 0.93 for infection through any infection pathway, and R2 = 0.98 for incubation on injured berries, which could be used to predict infection period and, therefore, to schedule fungicide applications.

A Potential Benefit of Hypochlorous Acid - Facial Sanitisation: A Review

Sanitisation has become a major component of everyday life, with emphasis on the hands and surfaces. The face remains unsanitised. This is due to the lack of an acceptable sanitiser. The use of masks has been implemented in order to protect the spread of the pathogens by covering the face, however there remain issues associated with the use of PPE.. The face remains a harbour for upper respiratory tract infections, with constant deposition and replication of microbes. With SARS-CoV-2 being so prominent, it was postulated that there is an inoculum dose-dependant relationship with severity. By reducing microbial load of the face, the risk of both infection and severity of infection are reduced. HOCl has proven antimicrobial and antiinflammatory activity and was tested for efficacy against SARS-CoV-2, demonstrating a 99.99% reduction (50ppm; 1 min contact). A facial sanitiser, added to the arsenal of hand sanitisers and masks, further improves protection and prevention against SARS-CoV-2. The advantages of regular sanitising of the face and mask include a reduced level of microbial contamination, reduced risk of biofilm formation, and respiratory tract and skin infections. HOCl was reviewed as a face and face mask sanitiser, concluding that it was an ideally suited product.

If we cannot eliminate them, should we tame them? Mathematics underpinning the dose effect of virus infection and its application on covid-19 virulence evolution

There is a dose effect in the infection process, that is, different initial virus invasion loads will lead to nonlinear changes in infection probability. Experiments already proved that there was a sigmoid functional relationship between virus infection probability and inoculum dose. By means of mathematical simulation of stochastic process, we theoretically demonstrate that there is a sigmoid function relationship between them. At the same time, our model found three factors that influence the severity of infection symptoms, those are virus toxicity, virus invasion dose and host immunity respectively. Therefore, the mortality rate cannot directly reflect the change of virus toxicity, but is the result of the comprehensive action of these three factors. Protective measures such as masks can effectively reduce the severity of infection while reducing the probability of infection. Based on the sigmoid function relationship between virus infection probability and initial virus invasion dose, we deduce that for highly infectious viruses, such as SARS-COV-2, the evolution of its toxicity is closely related to the host population density, and its toxicity will first increase and then decrease with the increase of host population density. That is to say, on the basis of extremely low host population density, increasing population density is beneficial to the development of virus towards strong toxicity. However, this trend is not sustainable, and there is a turning point of population density. Beyond this turning point, increasing population density will be beneficial to the development of virus towards weak toxicity. This theory can well explain the differences of mortality in Covid-19 in different countries. Countries with high population density and extremely low population density often correspond to lower mortality, while countries with population density in the range of 20-100/km2 often have higher mortality. At the same time, we propose that social distance and masks can effectively accelerate the evolution of virus towards low toxicity, so we should not give up simple and effective protection measures while emphasizing vaccination.

Co-expression With Replicating Vector Overcoming Competitive Effects Derived by a Companion Protease Inhibitor in Plants

Plant-based expression platforms are currently gaining acceptance as a viable alternative for the production of recombinant proteins (RPs), but the degradation of RPs by proteases in cells hinders their superb potentials. Co-expression of a protease inhibitor (PI) shows promise as a strategy to prevent RP from proteolytic degradation in plants. However, competitive effects behind the PI-RP co-expression system may mask or obfuscate the in situ protective effects of a companion PI. Here, we explored the competitive effects by co-expressing reteplase (rPA) with three unrelated PIs, namely NbPR4, HsTIMP, and SlCYS8, in Nicotiana benthamiana leaves. Remarkably, the accumulation of rPA was significantly repressed by each of the three PIs, suggesting that the competitive effects may be common among the PIs. The repression can be attenuated by reducing the PI inoculum dose in the co-inoculation mixtures, showing a negative correlation between the PI abundance of the PI-RP system and competitive effects. Interestingly, when a replicating vector was used to modulate the relative abundance of PI and RP in vivo, rPA was still boosted even at the maximal testing dose of PI, indicating that the competitive effects reduced to an ignorable level by this in vivo approach. Furthermore, a 7- to 12-fold increase of rPA was achieved, proving that it is a useful way for stimulating the potentials of a companion PI by overcoming competitive effects. And, this approach can be applied to molecular farming for improving the RP yields of plant expression systems.

Evaluation of the Ecological Potential of Microorganisms for Purifying Water with High Iron Content

The ability of a number of microorganisms isolated from highly magnetic soil of the city Mednogorsk to oxidize Fe (II) under conditions of periodic cultivation in a liquid medium was studied. Among the studied microorganisms, two microbial isolates with maximum growth characteristics and iron-oxidizing activity were selected and identified: Bacillus megaterium 69.3 and B. megaterium 69.5. Individual levels of metal resistance of the isolates were determined: maximum tolerated concentration (MTC) for Fe (II) of the isolates B. megaterium 69.3 and B. megaterium 69.5 was 1200 mg L−1, minimum inhibitory concentration (MIC) was 1800 mg L−1. Both microbial isolates actively oxidized Fe (II) by reducing its high concentration in the medium (1.19 g L−1) by 33 and 39% during 14 days of culturing. Total increase in the biomass of B. megaterium 69.3 and B. megaterium 69.5 after 14 days of culturing was 15.3 and 14.7 g L−1; the active parts of the biomass increased 8.7- and 6.9-fold compared to the inoculum dose, respectively. These microbial isolates could be used in future in the biotechnological process of water purification with increased/high levels of Fe (II).

Early events in hepatitis B infection: the role of inoculum dose

The relationship between the inoculum dose and the ability of the pathogen to invade the host is poorly understood. Experimental studies in non-human primates infected with different inoculum doses of hepatitis B virus have shown a non-monotonic relationship between dose magnitude and infection outcome, with high and low doses leading to 100% liver infection and intermediate doses leading to less than 0.1% liver infection, corresponding to CD4 T-cell priming. Since hepatitis B clearance is CD8 T-cell mediated, the question of whether the inoculum dose influences CD8 T-cell dynamics arises. To help answer this question, we developed a mathematical model of virus–host interaction following hepatitis B virus infection. Our model explains the experimental data well, and predicts that the inoculum dose affects both the timing of the CD8 T-cell expansion and the quality of its response, especially the non-cytotoxic function. We find that a low-dose challenge leads to slow CD8 T-cell expansion, weak non-cytotoxic functions, and virus persistence; high- and medium-dose challenges lead to fast CD8 T-cell expansion, strong cytotoxic and non-cytotoxic function, and virus clearance; while a super-low-dose challenge leads to delayed CD8 T-cell expansion, strong cytotoxic and non-cytotoxic function, and virus clearance. These results are useful for designing immune cell-based interventions.

Zika virus dynamics: Effects of inoculum dose, the innate immune response and viral interference

Experimental Zika virus infection in non-human primates results in acute viral load dynamics that can be well-described by mathematical models. The inoculum dose that would be received in a natural infection setting is likely lower than the experimental infections and how this difference affects the viral dynamics and immune response is unclear. Here we study a dataset of experimental infection of non-human primates with a range of doses of Zika virus. We develop new models of infection incorporating both an innate immune response and viral interference with that response. We find that such a model explains the data better than models with no interaction between virus and the immune response. We also find that larger inoculum doses lead to faster dynamics of infection, but approximately the same total amount of viral production.

Refinement of the CS6-expressing enterotoxigenic Escherichia coli strain B7A human challenge model: A randomized trial

Background Human challenge models for enterotoxigenic Escherichia coli (ETEC) facilitate vaccine down-selection. The B7A (O148:H28 CS6+LT+ST+) strain is important for vaccine development. We sought to refine the B7A model by identifying a dose and fasting regimen consistently inducing moderate-severe diarrhea. Methods An initial cohort of 28 subjects was randomized (1:1:1:1) to receive B7A following an overnight fast at doses of 108 or 109 colony forming units (cfu) or a 90-minute fast at doses of 109 or 1010 cfu. A second cohort included naïve and rechallenged subjects who had moderate-severe diarrhea and were given the target regimen. Immune responses to important ETEC antigens were assessed. Results Among subjects receiving 108 cfu of B7A, overnight fast, or 109 cfu, 90-minute fast, 42.9% (3/7) had moderate-severe diarrhea. Higher attack rates (71.4%; 5/7) occurred in subjects receiving 109 cfu, overnight fast, or 1010 cfu, 90-minute fast. Upon rechallenge with 109 cfu of B7A, overnight fast, 5/11 (45.5%) had moderate-severe diarrhea; the attack rate among concurrently challenge naïve subjects was 57.9% (11/19). Anti-CS6, O148 LPS and LT responses were modest across all groups. Conclusions An overnight fast enabled a reduction in the B7A inoculum dose; however, the attack rate was inconsistent and protection upon rechallenge was minimal.

Effect of Addition of a Specific Mixture of Yeast, Lactic and Acetic Bacteria in the Fermentation Process to Improve the Quality and Flavor of Cocoa Beans in Colombia

Cocoa fermentation process is fundamental to generate flavors and aromas that are characteristics of chocolate. In Colombia, this process is carried out by microbiota that spontaneously colonizes cocoa beans, therefore the quality of the fermentation is inconsistent. Taking into account that the fermentation of cocoa beans is carried out by a consortium of microorganisms, the aim of thisresearch was to describe the effect of the addition of a specific mixture of yeasts, acetic acid bacteria, and lactic acid bacteria on the physicochemical and organolepticcharacteristics of cocoa beans (clone CCN 51). Isolates of two yeasts (Wickerhamomyces anomalus and Debaryomyces hansenii), three acetic acid bacteria (AAB), (Gluconobacter japonicus, Acetobacter tropicalis, and Acetobacter pasteurianus) and three lactic acid bacteria (LAB) (Pediococcus acidilactici, Lactobacillus brevis, and Lactobacillus plantarum) obtained fromprevious cocoa fermentations selected for their pectinases and acid production capacities in a specific mixture were used. Using the micro-fermentation technique, the effect of a biological starter was evaluated under different viable microorganismsratios (Yeasts: LAB: AAB as follows, 1: 1: 1, 1: 2: 2, 1: 2: 1, 1: 1: 2, 2: 1: 1, 2: 2: 1, 2: 1: 2, and 2: 2: 2). The concentration of each microorganism was standardized at 1x107 cfu/mL, then the biomass of 4 mL for ratio 1 and 8 mL for ratio 2 of each suspension of microorganisms was added at time zero. Different doses of inoculum were 0%, 1%, 2%, 3%, 4%, and 5% v/w mL inoculum/g cocoa beans. A beneficial effecton the sensory quality of cocoa beans was evidenced by the addition of microorganisms; the best proportion of microorganisms was 2:1:2 (yeasts:LAB:AAB) and the best inoculum dose was 3% (v/w) showing lower acidity, astringency, and bitterness, and emphasizing the cocoa flavors, fruity, nutty, and panela malt.