RESUMEN
Bacteria can be dead, alive, or exhibit slowed or suspended life forms, making bacterial death difficult to establish. Here, agar-plating, microscopic-counting, SYTO9/propidium-iodide staining, MTT-conversion, and bioluminescence-imaging were used to determine bacterial death upon exposure to different conditions. Rank correlations between pairs of assay outcomes were low, indicating different assays measure different aspects of bacterial death. Principal-component analysis yielded two principal components, named "reproductive-ability" (PC1) and "metabolic-activity" (PC2). Plotting of these principal components in two-dimensional space revealed a dead region, with borders defined by the PC1 and PC2 values. Sensu stricto implies an unpractical reality that all assays determining PC1 and PC2 must be carried out in order to establish bacterial death. Considering this unpracticality, it is suggested that at least one assay determining reproductive activity (PC1) and one assay determining metabolic activity (PC2) should be used to establish bacterial death. Minimally, researchers should specifically describe which dimension of bacterial death is assessed, when addressing bacterial death.
Asunto(s)
Viabilidad Microbiana , Bacterias/clasificación , Bacterias/genética , Análisis de Componente Principal , Mediciones Luminiscentes/métodosRESUMEN
The adult brain is made up of anatomically and functionally distinct regions with specific neuronal compositions. At the root of this neuronal diversity are neural stem and progenitor cells (NPCs) that produce many neurons throughout embryonic development. During development, NPCs switch from initial expanding divisions to neurogenic divisions, which marks the onset of neurogenesis. Here, we aimed to understand when NPCs switch division modes to generate the first neurons in the anterior-most part of the zebrafish brain, the telencephalon. To this end, we used the deep learning-based segmentation method Cellpose and clonal analysis of individual NPCs to assess the production of neurons by NPCs in the first 24 h of zebrafish telencephalon development. Our results provide a quantitative atlas detailing the production of telencephalic neurons and NPC division modes between 14 and 24 h postfertilization. We find that within this timeframe, the switch to neurogenesis is gradual, with considerable heterogeneity in individual NPC neurogenic potential and division rates. This quantitative characterization of initial neurogenesis in the zebrafish telencephalon establishes a basis for future studies aimed at illuminating the molecular mechanisms and regulators of early neurogenesis.
Quantification of neuron production and neural progenitor division modes in zebrafish embryonic telencephalon up to 24 h postfertilization using deep learning-based segmentation and clonal analysis methods.