Topical Probiotic Formulation Promotes Rapid Healing in Dog Keratinocyte Cells: A Promising Approach for Wound Management.

The use of probiotics has gained increasing attention as a strategy for wound healing to decrease microbial resistance to disinfectants and antibiotics. This study aimed to investigate the potential of a non-medicinal topical cocktail of probiotic bacteria (CPB) in promoting wound healing in dogs using in vitro scratch assay. Canine Progenitors Epidermal Keratinocytes (CPEK) were exposed to a prototype product formulated with CPB (PPP), non-formulated CPB, and the vehicle. The viability of CPB and CPEK cells was first evaluated in the co-culture model. Then, wound closure was analyzed over time. The CPB required a minimum concentration of 75 CFU/mL for better viability with CPEK. While the CPEK preserved 100% of their viability when PPP was diluted to up to 75,000 CFU/mL. At higher concentrations, the viability of CPEK was reduced by the concomitant effect of the non-formulated CPB and the vehicle. The formulated and non-formulated CPB and the vehicle seem to lead to a dose-dependent increase in cell migration compared to the control. Importantly, at the concentration of 750,000 CFU/mL, the PPP showed a 20% increase in wound closure. Taken together, our findings suggest the potential beneficial effects of the probiotic-based topical cocktail (PPP) on wound healing. However, to confirm and validate these effects, further experiments are necessary to provide more robust evidence and allow us to confidently establish the potential beneficial effects of the probiotic bacteria (CPB) in promoting wound healing.

Receptors and Cofactors That Contribute to SARS-CoV-2 Entry: Can Skin Be an Alternative Route of Entry?

To prevent the spread of SARS-CoV-2, all routes of entry of the virus into the host must be mapped. The skin is in contact with the external environment and thus may be an alternative route of entry to transmission via the upper respiratory tract. SARS-CoV-2 cell entry is primarily dependent on ACE2 and the proteases TMPRSS2 or cathepsin L but other cofactors and attachment receptors have been identified that may play a more important role in specific tissues such as the skin. The continued emergence of new variants may also alter the tropism of the virus. In this review, we summarize current knowledge on these receptors and cofactors, their expression profile, factors modulating their expression and their role in facilitating SARS-CoV-2 infection. We discuss their expression in the skin and their possible involvement in percutaneous infection since the presence of the virus has been detected in the skin.

Characterization of antifungal compounds produced by lactobacilli in cheese-mimicking matrix: Comparison between active and inactive strains.

Biopreservation of dairy products by acid lactic bacteria appears as a promising alternative to either replace or reduce the use of chemical preservatives. This study aimed at the identification of bacteria preventing fungal spoilers growth in dairy products, and, at the understanding of their antifungal activity. First, antifungal activity of eighteen Lactobacillus strains was tested against five molds and four yeasts leading to selection of L. casei 7006 which had an activity against seven fungal targets. Then, challenge tests against C. lusistaniae 3668 in a cheese-mimicking matrix have been performed demonstrating that this strain was able to reduce strongly this yeast growth after 14 and 21 days storages at 7 °C. Antifungal compounds produced in cheese-mimicking matrix containing L. casei 7006 strain were quantified, then compared to the one prepared with an inactive strain (L. casei 6960) or without Lactobacillus strain. Three compounds were differently produced between cheeses with or without Lactobacillus strain after 21 days at 7 °C: lactic acid, benzoic acid and diacetyl. However, lactic acid concentrations were similar between the three cheeses after 14 days at 7 °C, but an antifungal activity was only associated to L. casei 7006 presence. Benzoic acid concentrations between cheese with L. casei 7006 and negative control L. casei 6960 were also the same. Among the antifungal molecules retrieved from these analyses, diacetyl was the most significantly overproduced in cheese containing L. casei 7006, thus this volatile was associated to the antifungal activity of this strain.

Availability of the Molecular Switch XylR Controls Phenotypic Heterogeneity and Lag Duration during Escherichia coli Adaptation from Glucose to Xylose.

The glucose-xylose metabolic transition is of growing interest as a model to explore cellular adaption since these molecules are the main substrates resulting from the deconstruction of lignocellulosic biomass. Here, we investigated the role of the XylR transcription factor in the length of the lag phases when the bacterium Escherichia coli needs to adapt from glucose- to xylose-based growth. First, a variety of lag times were observed when different strains of E. coli were switched from glucose to xylose. These lag times were shown to be controlled by XylR availability in the cells with no further effect on the growth rate on xylose. XylR titration provoked long lag times demonstrated to result from phenotypic heterogeneity during the switch from glucose to xylose, with a subpopulation unable to resume exponential growth, whereas the other subpopulation grew exponentially on xylose. A stochastic model was then constructed based on the assumption that XylR availability influences the probability of individual cells to switch to xylose growth. The model was used to understand how XylR behaves as a molecular switch determining the bistability set-up. This work shows that the length of lag phases in E. coli is controllable and reinforces the role of stochastic mechanism in cellular adaptation, paving the way for new strategies for the better use of sustainable carbon sources in bioeconomy.IMPORTANCE For decades, it was thought that the lags observed when microorganisms switch from one substrate to another are inherent to the time required to adapt the molecular machinery to the new substrate. Here, the lag duration was found to be the time necessary for a subpopulation of adapted cells to emerge and become the main population. By identifying the molecular mechanism controlling the subpopulation emergence, we were able to extend or reduce the duration of the lags. This work is of special importance since it demonstrates the unexpected complexity of monoclonal populations during growth on mixed substrates and provides novel mechanistic insights with regard to bacterial cellular adaptation.

Alka(e)ne synthesis in Cupriavidus necator boosted by the expression of endogenous and heterologous ferredoxin-ferredoxin reductase systems.

To boost aldehyde deformylating oxygenase (ADO) activity in a Cupriavidus necator strain expressing a synthetic alkane pathway, the expression of two ferredoxin-ferredoxin reductase systems was tested. The genes of a native fd/FNR-like system were identified in C. necator and expressed in a previously engineered alka(e)ne producing strain. The improved production of alka(e)nes in this Re2061-pMAB1 strain confirmed the activity of the native Fd/FNR system in C. necator. Concomitantly, the expression of the heterologous system from Synechococcus elongatus was investigated identically, leading to a second strain, Re2061-pMAB2. In the bioreactor, the aldehyde production was strongly reduced compared with the original alka(e)ne producer, leading to alka(e)nes production up to 0.37 and 1.48 g/L (22 and 82 mg/gCDW ), respectively. The alka(e)ne production yield of Re2061-pMAB2 accounted for 15% of the theoretical yield. We report here the highest level and yield of alka(e)nes production by an engineered bacterium to date.