Transcriptomic analysis of Escherichia coli MG1655 cells exposed to pulsed electric fields

Influence of general stress-response alternative sigma factors σS (RpoS) and σB (SigB) on bacterial tolerance to the essential oils from Origanum vulgare L. and Rosmarinus officinalis L. and pulsed electric fields

“…The E. coli MG1655 strain was tested because it has been used in physiological studies approaching the bacterial tolerance to antimicrobial compounds or procedures in Gram-negative cells (Minty et al, 2011;Fontenot et al, 2013;Chueca et al, 2015), as well as L. monocytogenes EDG-e has been tested representing Gram-positive cells (van der Veen and Abee, 2010;Somolinos et al, 2010a;Ait-Ouazzou et al, 2012). The rpoS mutant was constructed using P1 phage transduction and was derived from an E. coli single-gene knockout library (Baba et al, 2006).…”

“…Escherichia coli and Listeria monocytogenes are often cited as able to mount protection responses to different stressing conditions normally applied in food conservation Ryu et al, 2012). Most E. coli are harmless to humans, however some E. coli strains are pathogenic causing diarrhea or illness outside of the intestinal tract (Ryu et al, 2012;Chueca et al, 2015). L. monocytogenes is a foodborne pathogen that causes listeriosis, a life-threatening invasive disease in humans (Timmermans et al, 2014).…”

“…Because of the development of increased bacterial tolerance to classical compounds or thermal treatment applied by industry to control microbial growth in foods, essential oils (EOs) and the non-thermal technology pulsed electric fields (PEF) have been proposed as alternatives to control these organisms by food industry Timmermans et al, 2014;Chueca et al, 2015). Additionally, consumers have demanded safer, fresher and healthier foods with no or few chemical preservatives, creating a market demand for natural, non-thermal and feasible technologies for ensuring the microbial safety of foods (Sivakumar and Bautista-Baños, 2014).…”

“…The EOs from Origanum vulgare L.-oregano (OVEO) and Rosmarinus officinalis L.-rosemary (ROEO) have shown broad-spectrum antimicrobial activity against a range of food-related bacteria in synthetic media and in mimicking foodmodels (Azerêdo et al, 2011;Gomes-Neto et al, 2014;Luz et al, 2012). PEF has presented efficacy in bacterial inactivation to guarantee food safety, and in contrast to heat treatments presents minimal impact on sensory and nutritional food properties (Espina et al, 2013;Chueca et al, 2015).…”

“…Since the incorporation of high doses of EOs may adversely affect the sensory aspects of foods (Azerêdo et al, 2011), minimization of the concentrations of these substances in foods has been strongly recommended, mainly when applied in sequence or in combination with other selected physical inactivation techniques, such as PEF (Ait-Ouazzou et al, 2011;Chueca et al, 2015). Despite the fact that EOs are known as potential antimicrobials for use in emerging non-thermal food preservation procedures (Ait-Ouazzou et al, 2012;Gomes-Neto et al, 2012), the investigations about the possible induction of increased bacterial cross-tolerance to PEF by EOs at subinhibitory concentrations (as usually possible to be applied in foods) are still scarce or inexistent.…”