Ethanol stress in Oenococcus oeni : transcriptional response and complex physiological mechanisms

Abstract

SummaryOenococcus oeni is the dominant species able to cope with a hostile environment of wines, comprising cumulative effects of low pH, high ethanol and SO 2 content, nonoptimal growth temperatures and growth inhibitory compounds. Ethanol tolerance is a crucial feature for the activity of O. oeni cells in wine because ethanol acts as a disordering agent of its cell membrane and negatively affects metabolic activity; it damages the membrane integrity, decreases cell viability and, as other stress conditions, delays the start of malolactic fermentation with a consequent alteration of wine quality. The cell wall, cytoplasmic membrane and metabolic pathways are the main sites involved in physiological changes aimed to ensure an adequate adaptive response to ethanol stress and to face the oxidative damage caused by increasing production of reactive oxygen species. Improving our understanding of the cellular impact of ethanol toxicity and how the cell responds to ethanol stress can facilitate the development of strategies to enhance microbial ethanol tolerance; this allows to perform a multidisciplinary endeavour requiring not only an ecological study of the spontaneous process but also the characterization of useful technological and physiological features of the predominant strains in order to select those with the highest potential for industrial applications.

Heat Adaptation Induced Cross Protection Against Ethanol Stress in Tetragenococcus halophilus: Physiological Characteristics and Proteomic Analysis

“…In the present study, the phenotype observed by SEM (Figure 2B) demonstrated that ethanol stress resulted in the deformation of T. halophilus cells (HP-ES and ES in Figure 2B). A similar result also reported that ethanol destroyed the cell membrane and affected the industrial performance of O. oeni (Bonomo et al, 2018). In this study, the degree of cell deformation was apparently improved after preadaptation at 45 • C for 1.5 h (Figure 2B, HP-ES), which suggested that heat preadaptation contributed to ethanol resistance by maintaining the morphology of cells at a normal condition.…”

Influences of acid and ethanol stresses on Oenococcus oeniSD‐2a and its proteomic and transcriptional responses

“…Low pH and ethanol stress appeared to be the crucial factors that decrease the viability of O. oeni in wine, as they both strongly influenced cell growth 4,5 . Ethanol strongly influenced cell membrane fluidity, and low pH inhibited cell malolactic activity 4,6 . Nonetheless, O. oeni has developed a variety of ways to escape or to tolerate wine conditions.…”

Production and Antimicrobial Activity of Nisin Under Enological Conditions

“…This inhibitory effect of ethanol is in agreement with the model for biofilm formation by Gram-positive bacteria ( Vlamakis et al, 2013 ), where ethanol may exert its inhibitory activity at two levels: (1) acting as a biofilm disruptor ( Böttcher et al, 2013 ) by interacting with the exopolysaccharides produced by planktonic bacteria to form the biofilm, and thus, disrupting the required aggregation for biofilm formation; and (2) as a bactericide molecule, provoking bacterial death, and, consequently, decreasing the density of viable cells, which results in retarding or preventing the formation of biofilm. The mechanisms of ethanol stress in O. oeni , and its molecular response are well known and have been previously reported ( Bonomo et al, 2018 ), whereas to our knowledge, this is the first report describing the response of L. mesenteroides to ethanol.…”