About this Research Topic
Traditionally, bacteria and particularly pathogens are classified as extracellular that thrive independently of a host cell, obligate intracellular bacteria that require a host cell to develop within it and, in between these two behaviors, facultative intracellular bacteria that proliferate outside and within a host cell. This traditional view applies mostly to human (animal)-bacteria interactions, but the fact that it is also true with amoeba and other microorganisms softened these borders.
We are witnessing an increasing number of bacteria, previously described as extracellular, for which some strains show facultative intracellular characteristics such as Escherichia coli, Vibrio cholerae, and Acinetobacter baumannii. This novel paradigm shift is of high impact for microbiologists, because showing this behavioral change might not only affect our fundamental understanding of the biology of these microorganisms per se, but can strongly impact human health, since the microbial-related diseases and infection cycles will be better understood, with clinical consequences of this understanding being of pivotal importance.
We are thus asking the following biological questions: (i) is intracellular life style frequent in the bacteria kingdom ? (ii) Which forms does such intracellular life style take ? (iii) What are the factors and conditions promoting a facultative intracellular behavior towards human and non-human host cells with biological relevance ?
In this context, we highly encourage approaches that not only prove the intracellular resistance of new bacteria, but also whether or not it is accompanied by an intracellular growth ability.
Hence, we welcome in this Research Topic: a) Reviews about the state of the art of previously extracellular bacteria that are now facultative intracellular, b) Opinions papers (concepts, definition, impact of fundamental and applied/clinical fields and consequences), c) Methods papers on the techniques used to observe co-cultures and intracellular behaviors, with or without new technologies, and d) Original Research articles on not yet characterized facultative intracellular bacteria and/or new bacterial determinants involved in such behavior.
Keywords: Extracellular bacteria, Intracellular bacteria, Facultative intracellular bacteria, Microbial-related diseases
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