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Bacterial Colonies in Solid Media and Foods: A Review on Their Growth and Interactions with the Micro-Environment

Bacteria, either indigenous or added, are immobilized in solid foods where they grow as colonies. Since the 80's, relatively few research groups have explored the implications of bacteria growing as colonies and mostly focused on pathogens in large colonies on agar/gelatine media. It is only re...

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Autores principales: Jeanson, Sophie, Floury, Juliane, Gagnaire, Valérie, Lortal, Sylvie, Thierry, Anne
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Frontiers Media S.A. 2015
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4664638/
https://www.ncbi.nlm.nih.gov/pubmed/26648910
http://dx.doi.org/10.3389/fmicb.2015.01284
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author Jeanson, Sophie
Floury, Juliane
Gagnaire, Valérie
Lortal, Sylvie
Thierry, Anne
author_facet Jeanson, Sophie
Floury, Juliane
Gagnaire, Valérie
Lortal, Sylvie
Thierry, Anne
author_sort Jeanson, Sophie
collection PubMed
description Bacteria, either indigenous or added, are immobilized in solid foods where they grow as colonies. Since the 80's, relatively few research groups have explored the implications of bacteria growing as colonies and mostly focused on pathogens in large colonies on agar/gelatine media. It is only recently that high resolution imaging techniques and biophysical characterization techniques increased the understanding of the growth of bacterial colonies, for different sizes of colonies, at the microscopic level and even down to the molecular level. This review covers the studies on bacterial colony growth in agar or gelatine media mimicking the food environment and in model cheese. The following conclusions have been brought to light. Firstly, under unfavorable conditions, mimicking food conditions, the immobilization of bacteria always constrains their growth in comparison with planktonic growth and increases the sensibility of bacteria to environmental stresses. Secondly, the spatial distribution describes both the distance between colonies and the size of the colonies as a function of the initial level of population. By studying the literature, we concluded that there systematically exists a threshold that distinguishes micro-colonies (radius < 100–200 μm) from macro-colonies (radius >200 μm). Micro-colonies growth resembles planktonic growth and no pH microgradients could be observed. Macro-colonies growth is slower than planktonic growth and pH microgradients could be observed in and around them due to diffusion limitations which occur around, but also inside the macro-colonies. Diffusion limitations of milk proteins have been demonstrated in a model cheese around and in the bacterial colonies. In conclusion, the impact of immobilization is predominant for macro-colonies in comparison with micro-colonies. However, the interaction between the colonies and the food matrix itself remains to be further investigated at the microscopic scale.
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spelling pubmed-46646382015-12-08 Bacterial Colonies in Solid Media and Foods: A Review on Their Growth and Interactions with the Micro-Environment Jeanson, Sophie Floury, Juliane Gagnaire, Valérie Lortal, Sylvie Thierry, Anne Front Microbiol Microbiology Bacteria, either indigenous or added, are immobilized in solid foods where they grow as colonies. Since the 80's, relatively few research groups have explored the implications of bacteria growing as colonies and mostly focused on pathogens in large colonies on agar/gelatine media. It is only recently that high resolution imaging techniques and biophysical characterization techniques increased the understanding of the growth of bacterial colonies, for different sizes of colonies, at the microscopic level and even down to the molecular level. This review covers the studies on bacterial colony growth in agar or gelatine media mimicking the food environment and in model cheese. The following conclusions have been brought to light. Firstly, under unfavorable conditions, mimicking food conditions, the immobilization of bacteria always constrains their growth in comparison with planktonic growth and increases the sensibility of bacteria to environmental stresses. Secondly, the spatial distribution describes both the distance between colonies and the size of the colonies as a function of the initial level of population. By studying the literature, we concluded that there systematically exists a threshold that distinguishes micro-colonies (radius < 100–200 μm) from macro-colonies (radius >200 μm). Micro-colonies growth resembles planktonic growth and no pH microgradients could be observed. Macro-colonies growth is slower than planktonic growth and pH microgradients could be observed in and around them due to diffusion limitations which occur around, but also inside the macro-colonies. Diffusion limitations of milk proteins have been demonstrated in a model cheese around and in the bacterial colonies. In conclusion, the impact of immobilization is predominant for macro-colonies in comparison with micro-colonies. However, the interaction between the colonies and the food matrix itself remains to be further investigated at the microscopic scale. Frontiers Media S.A. 2015-12-01 /pmc/articles/PMC4664638/ /pubmed/26648910 http://dx.doi.org/10.3389/fmicb.2015.01284 Text en Copyright © 2015 Jeanson, Floury, Gagnaire, Lortal and Thierry. http://creativecommons.org/licenses/by/4.0/ This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
spellingShingle Microbiology
Jeanson, Sophie
Floury, Juliane
Gagnaire, Valérie
Lortal, Sylvie
Thierry, Anne
Bacterial Colonies in Solid Media and Foods: A Review on Their Growth and Interactions with the Micro-Environment
title Bacterial Colonies in Solid Media and Foods: A Review on Their Growth and Interactions with the Micro-Environment
title_full Bacterial Colonies in Solid Media and Foods: A Review on Their Growth and Interactions with the Micro-Environment
title_fullStr Bacterial Colonies in Solid Media and Foods: A Review on Their Growth and Interactions with the Micro-Environment
title_full_unstemmed Bacterial Colonies in Solid Media and Foods: A Review on Their Growth and Interactions with the Micro-Environment
title_short Bacterial Colonies in Solid Media and Foods: A Review on Their Growth and Interactions with the Micro-Environment
title_sort bacterial colonies in solid media and foods: a review on their growth and interactions with the micro-environment
topic Microbiology
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4664638/
https://www.ncbi.nlm.nih.gov/pubmed/26648910
http://dx.doi.org/10.3389/fmicb.2015.01284
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