Spatially localized expression of glutamate decarboxylase gadB in Escherichia coli O157:H7 microcolonies in hydrogel matrix
Résumé
Functional diversity within isogenic spatially organized bacterial populations has been shown to trigger emergent community properties such as stress tolerance. Taking advantage of confocal laser scanning microscopy combined with a transcriptional fluorescent fusion reporting at single cell scale the expression of the glutamic acid decarboxylase gadB in E. coli O157:H7, it was possible to visualize for the first-time spatial patterns of bacterial gene expression in microcolonies grown in a gelled matrix. The gadB gene is involved in E. coli tolerance to acidic conditions and its strong over-expression was observed locally on the periphery of embedded microcolonies grown in acidic hydrogels. This spatialization of gadB expression did not correlate with live/dead populations that appeared randomly distributed in the colonies. While the planktonic population of the pathogens was eradicated by an exposition to a pH of 2 (HCl) for 4h, mimicking a stomachal acidic stress, bacteria grown in gel-microcolonies were poorly affected by this treatment, in particular in conditions where gadB was spatially overexpressed. Consequences of these results for food safety are further discussed.
Mots clés
E. coli O157:H7 food matrix microcolonies local gene expression gadB fluorescent transcriptional fusions confocal laser scanning microscopy (CLSM) Food safety
E. coli O157:H7
food matrix
microcolonies
local gene expression
gadB
fluorescent transcriptional fusions
confocal laser scanning microscopy (CLSM)
Food safety
Domaines
Sciences du Vivant [q-bio]Origine | Fichiers produits par l'(les) auteur(s) |
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Licence |