It is generally assumed that microorganisms synthesize release detect and respond to small
signaling hormone-like molecules. These molecules are used for a process termed quorum sensing
(QS) a phenomenon that enables bacteria to sense when the minimal number of cells or quorum
is achieved for a concerted response to be initiated. Words such as language and behavior are
frequently used to depict QS in the literature. More simply put language and cross-talk
between bacteria and between bacteria and animal or plant hosts determines the behavior (e.g.
beneficial or pathogenic effects) of bacteria. Currently the major concern is to understand
and decode this language. Overall bacterial cross-talk was mainly studied on environmental
plant and human pathogenic bacteria. Few studies considered food-related lactic acid bacteria.
The cross-talk between bacteria influences the behavior and in turn the environmental
adaptation and phenotypes. Therefore it is understood that bacterial cross-talk has important
applicative repercussions. The language spoken between bacteria populating the same food
ecosystem may condition the phenotypic traits of starter lactic acid bacteria and consequently
their performance. This Brief aims to define the basis of cell-to-cell signalling in food
fermentation and will highlight: (i) microbiology nutritional chemical and functional aspects
(ii) functional properties due to microbial adaptation to the gastrointestinal tract (iii)
principal phenotypes under control of QS circuitries (iv) quorum quenching. This Brief will be
the first reference on this topic and it will highlight the main results for a more productive
industrial application. Draft content 1. Signals of food related Gram-negative and
Gram-positive bacteria The chapter will describe the different signaling languages used by
Gram-negative bacteria (N-acyl-L-homoserine lactones) and Gram-positive bacteria (based on the
synthesis of post-translationally modified peptides) and the universal chemical lexicon shared
by both Gram-positive and -negative bacteria (autoinducer-2 through the activity of the LuxS
enzyme). 2. Phenotypes related to quorum sensing The chapter will describe the bacterial
phenotypes such as virulence biofilm maturation bacteriocin synthesis and secondary
metabolite production under control of QS circuitries. 3. Cell-to-cell signalling in fermented
food: sourdough The chapter will describe the language spoken between bacteria populating the
same food ecosystem (sourdough) and will provide an overview of the conditioned phenotypic
traits of starter lactic acid bacteria and consequently their performance. 4. Cell-to-cell
signalling in fermented food: yoghurt The chapter will describe the language spoken between
bacteria populating the same food ecosystem (yoghurt) and will provide an overview of the
conditioned phenotypic traits of starter lactic acid bacteria and consequently their
performance. 5. Probiotic message at the intra- inter-species and inter-kingdom level The
chapter will describe the mechanisms that regulate the interaction between microorganism and
host and the capacity of the microorganism to adapt to environment. Particular reference will
also be made to: (i) pathogen inhibition and restoration of microbial homeostasis through
microbe-microbe interactions (ii) enhancement of epithelial barrier function and (iii)
modulation of immune responses. 6. New Perspectives of quorum sensing This chapter will provide
an overview of the future perspective regarding quorum sensing showing that bacterial
cross-talk may have important applicative repercussions. It will highlight the interference on
the language of QS which is defined as quorum quenching (QQ). Increasing translation of the
bacterial cross-talk has shown that in some environmental circumstances quenching of the
language may occur.
