title: Investigating boundaries of survival, growth and expression of genes associated with stress and virulence of Listeria monocytogenes in response to acid and osmotic stress.
abstract: The objective of this study was to correlate the relative transcription of Listeria monocytogenes (strains C5, 6179) stress- (gad2, sigB) and virulence- (prfA) associated genes following habituation at twenty-five pH (4.8, 5.0, 5.2, 5.5, 6.4) and NaCl (2, 4, 6, 8, 10% w/v) combinations at 7 °C, with the survival against subsequent exposure to severe acid stress (pH 2.0 at 37 °C). Our findings pointed out the inter-strain variation governing growth inhibiting conditions (pH ≤5.0 and NaCl ≥6%), where C5 was less affected (a reduction of 2.0-3.0 log CFU/mL) than 6179 which was reduced by 4.0-6.0 log CFU/mL at the end of storage. Nevertheless, the higher the habituation at the growth permitting (pH ≥5.5; NaCl ≤4% w/v) or growth inhibiting conditions, the higher the acquired acid resistance or sensitization, respectively. At day 2, gad2 increased relative transcriptional levels are more related to elevated acid resistance, while at day 6 both gad2 transcriptional levels and upregulation of sigB were correlated to low log reductions and high DpH:2.0-values against severe acid stress. Regarding virulence, the increased transcriptional levels of prfA at day 2 were correlated to adverse pH and NaCl combinations, while prolonged stay in suboptimal conditions as well as exposure to severe acid stress resulted in general activation of the virulence regulator. Such data could definitely contribute in designing safe intervention strategies and additionally integrate -omics aspects in quantitative microbial risk assessment.
authors.affiliation: Laboratory of Food Quality Control & Hygiene, Department of Food Science & Human Nutrition, Agricultural University of Athens, Iera Odos 75, 118 55, Athens, Greece.
authors.forename: I P
authors.initials: IP
authors.lastname: Makariti
authors.affiliation: Laboratory of Food Quality Control & Hygiene, Department of Food Science & Human Nutrition, Agricultural University of Athens, Iera Odos 75, 118 55, Athens, Greece.
authors.forename: A
authors.initials: A
authors.lastname: Printezi
authors.affiliation: Laboratory of Food Quality Control & Hygiene, Department of Food Science & Human Nutrition, Agricultural University of Athens, Iera Odos 75, 118 55, Athens, Greece.
authors.forename: A E
authors.initials: AE
authors.lastname: Kapetanakou
authors.affiliation: Applied Microbiology, Department of Chemistry, Faculty of Engineering, Lund University, Lund, Sweden.
authors.forename: N
authors.initials: N
authors.lastname: Zeaki
authors.affiliation: Laboratory of Food Quality Control & Hygiene, Department of Food Science & Human Nutrition, Agricultural University of Athens, Iera Odos 75, 118 55, Athens, Greece. Electronic address: pskan@aua.gr.
authors.forename: P N
authors.initials: PN
authors.lastname: Skandamis
mesh_terms: D000143:Acids / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D008089:Listeria monocytogenes / Q000235:genetics / Q000254:growth & development* / Q000472:pathogenicity* / Q000502:physiology; D050296:Microbial Viability; D009997:Osmotic Pressure; D013312:Stress, Physiological; D014774:Virulence
chemical_list: D000143:Acids; D001426:Bacterial Proteins
keywords: Acid resistance; Habituation; Inter-strain variation; Listeria monocytogenes; Osmotic-acid stress; Relative gene transcription