scholarly journals Effect of Food Processing-Related Stresses on Acid Tolerance of Listeria monocytogenes

2003 ◽  
Vol 69 (12) ◽  
pp. 7514-7516 ◽  
Author(s):  
Konstantinos P. Koutsoumanis ◽  
Patricia A. Kendall ◽  
John N. Sofos
Keyword(s):  
Listeria Monocytogenes ◽  
Food Processing ◽  
Adaptive Response ◽  
Acid Stress ◽  
Acid Tolerance ◽  
Acid Resistance ◽  
Acidic Ph ◽  
Temperature Stresses ◽  
Subsequent Exposure ◽  
Effect Of Food

ABSTRACT Stationary-phase cells of Listeria monocytogenes grown in glucose-free or glucose-containing media were exposed for 90 min to various stresses, including acid stress (pH 4.0 to 7.0), osmotic stress (10.5 to 20.5% NaCl), and various temperatures (−5 to 50°C), and were further exposed to pH 3.5. Exposure to a mildly acidic (pH 5.0 to 6.0) environment provided protection of the pathogen against acid upon subsequent exposure. This adaptive response, however, was found to be strongly dependent on other environmental conditions during the shock, such as temperature or the simultaneous presence of a second stress factor (NaCl). Growth of L. monocytogenes in the presence of glucose resulted in enhanced survival of the pathogen at pH 3.5. Sublethal stresses other than acidic stresses, i.e., osmotic, heat, and low-temperature stresses, did not affect the acid resistance of L. monocytogenes (P > 0.5). More-severe levels of these stresses, however, resulted in sensitization of the pathogen to acid.

Induced Acid-Tolerance Response Confers Limited Nisin Resistance on Listeria monocytogenes Scott A

1996 ◽  
Vol 59 (9) ◽  
pp. 1003-1006 ◽  
Author(s):  
AMECHI OKEREKE ◽  
STERLING S. THOMPSON
Keyword(s):  
Listeria Monocytogenes ◽  
Acid Stress ◽  
Brain Heart Infusion ◽  
Acid Tolerance ◽  
Acid Resistance ◽  
Cross Protection ◽  
C Cells ◽  
Acid Tolerance Response ◽  
Tolerance Response ◽  
Resistance Trait

The presence of an inducible acid-tolerance response (ATR) in Listeria monocytogenes Scott A was established. Protection of cells with induced ATR against nisin-mediated inhibition and stress was also evaluated. ATR was induced in L. monocytogenes Scott A by culturing in brain heart infusion (BHI) broth buffered to pH 5.4. The unadapted cells were grown at pH 7.2. Both acid-adapted and unadapted cells were challenged at pH 3.3 and 4.3 at 35°C. The acid-adapted cells were 150- to 7,500-fold more resistant to acid stress at pH 3.3 than unadapted cells. Both cells were equally resistant to acid stress at pH 4.3. The acid-adapted and unadapted cells were exposed to 0, 0.3, 0.6, 1.2 and 1.5 μg of nisin per ml of buffered BHI broth at pH 6.0 for 90 min at 35°C. Cells with the induced acid-resistance trait were slightly more resistant to nisin than the unadapted cells. In the presence of 1.5 μg of nisin per ml, 47% of the acid-adapted cells survived compared to 41% of the unadapted cells. In the range of nisin concentration included in this study, there was no significant (P < 0.05) difference in the nisin resistance of adapted and unadapted cells. The data suggest that ATR induction confers very limited cross protection against nisin stress and kill.

scholarly journals D-Methionine and D-Phenylalanine Improve Lactococcus lactis F44 Acid Resistance and Nisin Yield by Governing Cell Wall Remodeling

2020 ◽  
Vol 86 (9) ◽  
Author(s):  
Hao Wu ◽  
Ershu Xue ◽  
Ning Zhi ◽  
Qianqian Song ◽  
Kairen Tian ◽  
...  
Keyword(s):  
Amino Acids ◽  
Cell Wall ◽  
Lactococcus Lactis ◽  
Acid Stress ◽  
Acid Tolerance ◽  
Acid Resistance ◽  
Cell Wall Synthesis ◽  
Nisin Production ◽  
Content Type ◽  
Nisin Yield

ABSTRACT Lactococcus lactis encounters various environmental challenges, especially acid stress, during its growth. The cell wall can maintain the integrity and shape of the cell under environmental stress, and d-amino acids play an important role in cell wall synthesis. Here, by analyzing the effects of 19 different d-amino acids on the physiology of L. lactis F44, we found that exogenously supplied d-methionine and d-phenylalanine increased the nisin yield by 93.22% and 101.29%, respectively, as well as significantly increasing the acid resistance of L. lactis F44. The composition of the cell wall in L. lactis F44 with exogenously supplied d-Met or d-Phe was further investigated via a vancomycin fluorescence experiment and a liquid chromatography-mass spectrometry assay, which demonstrated that d-Met could be incorporated into the fifth position of peptidoglycan (PG) muropeptides and d-Phe could be added to the fourth and fifth positions. Moreover, overexpression of the PG synthesis gene murF further enhanced the levels of d-Met and d-Phe involved in PG and increased the survival rate under acid stress and the nisin yield of the strain. This study reveals that the exogenous supply of d-Met or d-Phe can change the composition of the cell wall and influence acid tolerance as well as nisin yield in L. lactis. IMPORTANCE As d-amino acids play an important role in cell wall synthesis, we analyzed the effects of 19 different d-amino acids on L. lactis F44, demonstrating that d-Met and d-Phe can participate in peptidoglycan (PG) synthesis and improve the acid resistance and nisin yield of this strain. murF overexpression further increased the levels of d-Met and d-Phe incorporated into PG and contributed to the acid resistance of the strain. These findings suggest that d-Met and d-Phe can be incorporated into PG to improve the acid resistance and nisin yield of L. lactis, and this study provides new ideas for the enhancement of nisin production.

Comparative Analysis of Acid Resistance between Susceptible and Multi-Antimicrobial-Resistant Salmonella Strains Cultured under Stationary-Phase Acid Tolerance–Inducing and Noninducing Conditions

2003 ◽  
Vol 66 (5) ◽  
pp. 732-740 ◽  
Author(s):  
R. T. BACON ◽  
J. N. SOFOS ◽  
P. A. KENDALL ◽  
K. E. BELK ◽  
G. C. SMITH
Keyword(s):  
Stationary Phase ◽  
Antimicrobial Agents ◽  
Acid Stress ◽  
Acid Tolerance ◽  
Acid Resistance ◽  
Low Ph ◽  
Acid Exposure ◽  
Acid Adaptation ◽  
Acid Shock ◽  
Resistant Strains

This study compared acid resistance levels among five antimicrobial-susceptible strains of Salmonella and five strains that were simultaneously resistant to a minimum of six antimicrobial agents. The induction of a stationary-phase acid tolerance response (ATR) was attempted by both transient low-pH acid shock and acid adaptation. For acid shock induction, strains were grown for 18 h in minimal E medium containing 0.4% glucose (EG medium) and exposed to sublethal acid stress (pH 4.3) for 2 h, and subsequently, both shocked and nonshocked cultures were acid challenged (pH 3.0) for 4 h. Acid adaptation was achieved by growing strains for 18 h in tryptic soy broth containing 1.0% glucose (TSB+G), while nonadapted cultures were grown for 18 h in glucose-free tryptic soy broth (TSB−G). Acid-adapted and nonadapted inocula were acid challenged (pH 2.3) for 4 h. Initial (0 h) mean populations of nonchallenged Salmonella were 8.5 to 8.7, 8.4 to 8.8, and 8.2 to 8.3 log CFU/ml for strains grown in EG medium, TSB−G, and TSB+G, respectively. After 4 h of acid challenge, mean populations were 3.0 to 4.8 and 2.5 to 3.7 log CFU/ml for previously acid-shocked susceptible and resistant strains, respectively, while corresponding counts for nonshocked strains were 4.3 to 5.5 log CFU/ml and 3.9 to 4.9 log CFU/ml. Following 4 h of acid exposure, acid-adapted cultures of susceptible and resistant strains had mean populations of 6.1 to 6.4 log CFU/ml and 6.4 to 6.6 log CFU/ml, respectively, while corresponding counts for nonadapted cultures were 1.9 to 2.1 log CFU/ml and 1.8 to 2.0 log CFU/ml, respectively. A low-pH–inducible ATR was not achieved through transient acid shock, while an ATR was evident following acid adaptation, as adapted populations were 4.2 to 4.8 log units larger than nonadapted populations following acid exposure. Although some strain-dependent variations in acid resistance were observed, results from this study suggest no association between susceptibility to antimicrobial agents and the ability of the Salmonella strains evaluated to survive low-pH stress.

Heat and Acid Tolerance Responses of Listeria monocytogenes as Affected by Sequential Exposure to Hurdles during Growth

2009 ◽  
Vol 72 (7) ◽  
pp. 1412-1418 ◽  
Author(s):  
PANAGIOTIS N. SKANDAMIS ◽  
JARRET D. STOPFORTH ◽  
YOHAN YOON ◽  
PATRICIA A. KENDALL ◽  
JOHN N. SOFOS
Keyword(s):  
Lactic Acid ◽  
Listeria Monocytogenes ◽  
Yeast Extract ◽  
Acid Tolerance ◽  
Acid Resistance ◽  
Low Ph ◽  
Acid Ph ◽  
Applied Stresses

This study aimed to evaluate the effects of the level and sequence of hurdles, applied during growth, on the subsequent heat and acid tolerances of a 10-strain composite of Listeria monocytogenes. Individual strains were grown in glucose-free tryptic soy broth with 0.6% yeast extract (TSBYE–G). Then cultures were mixed and inoculated in fresh TSBYE–G (0.5% NaCl, pH 7.42; control), TSBYE–G that was supplemented with 3% NaCl (3.5% NaCl in total), or TSBYE–G with pH adjusted to 6.01 or 5.04 with lactic acid and incubated at 30°C for 24 h. Furthermore, the culture composite was exposed to the following five combinations of double sequential hurdles (12 h in each at 30°C): NaCl then pH 6.01, NaCl then pH 5.04, pH 7.42 then NaCl, pH 5.04 then NaCl, and pH 6.01 then NaCl. The heat and acid tolerances of the culture were assessed at 57°C (for 2 h) and at pH 3.5 (for 7 h), respectively, in TSBYE–G. No significant (P ≥ 0.05) differences in thermotolerance were observed among cultures exposed to various stresses. In contrast, the acid resistance followed the order: pH 6.01 = NaCl > NaCl then pH 5.04 > pH 6.01 then NaCl = pH 5.04 > pH 5.04 then NaCl > pH 7.42 then NaCl > control. The results suggest that exposure of L. monocytogenes to NaCl and low pH during growth may not affect its heat (57°C) tolerance, but it may increase its acid (pH 3.5) resistance, depending on the sequence and intensity of the applied stresses.

scholarly journals Nuclear Localization of Haa1, Which Is Linked to Its Phosphorylation Status, Mediates Lactic Acid Tolerance in Saccharomyces cerevisiae

2014 ◽  
Vol 80 (11) ◽  
pp. 3488-3495 ◽  
Author(s):  
Minetaka Sugiyama ◽  
Shin-Pei Akase ◽  
Ryota Nakanishi ◽  
Hitoshi Horie ◽  
Yoshinobu Kaneko ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Lactic Acid ◽  
Subcellular Localization ◽  
Target Genes ◽  
Acid Stress ◽  
Acid Tolerance ◽  
Acid Resistance ◽  
Nuclear Accumulation ◽  
Content Type ◽  
Adaptation Response

ABSTRACTImprovement of the lactic acid resistance of the yeastSaccharomyces cerevisiaeis important for the application of the yeast in industrial production of lactic acid from renewable resources. However, we still do not know the precise mechanisms of the lactic acid adaptation response in yeast and, consequently, lack effective approaches for improving its lactic acid tolerance. To enhance our understanding of the adaptation response, we screened forS. cerevisiaegenes that confer enhanced lactic acid resistance when present in multiple copies and identified the transcriptional factor Haa1 as conferring resistance to toxic levels of lactic acid when overexpressed. The enhanced tolerance probably results from increased expression of its target genes. When cells that expressed Haa1 only from the endogenous promoter were exposed to lactic acid stress, the main subcellular localization of Haa1 changed from the cytoplasm to the nucleus within 5 min. This nuclear accumulation induced upregulation of the Haa1 target genesYGP1,GPG1, andSPI1, while the degree of Haa1 phosphorylation observed under lactic acid-free conditions decreased. Disruption of the exportin geneMSN5led to accumulation of Haa1 in the nucleus even when no lactic acid was present. Since Msn5 was reported to interact with Haa1 and preferentially exports phosphorylated cargo proteins, our results suggest that regulation of the subcellular localization of Haa1, together with alteration of its phosphorylation status, mediates the adaptation to lactic acid stress in yeast.

Mutants of Mycobacterium smegmatis unable to grow at acidic pH in the presence of the protonophore carbonyl cyanide m-chlorophenylhydrazone

Microbiology ◽  
2005 ◽  
Vol 151 (3) ◽  
pp. 665-672 ◽  
Author(s):  
Sieu L. Tran ◽  
Min Rao ◽  
Cameron Simmers ◽  
Susanne Gebhard ◽  
Karen Olsson ◽  
...  
Keyword(s):  
Mycobacterium Smegmatis ◽  
Screening Method ◽  
Acid Stress ◽  
Acid Resistance ◽  
Acidic Ph ◽  
Ph Homeostasis ◽  
Carbonyl Cyanide ◽  
Genes Encoding ◽  
Phosphite Assimilation ◽  
Xenobiotic Response

Mycobacterium smegmatis is able to grow and survive at acidic pH, and exhibits intracellular pH homeostasis under these conditions. In this study, the authors have identified low proton permeability of the cytoplasmic membrane, and high cytoplasmic buffering capacity, as determinants of intrinsic acid resistance of M. smegmatis. To identify genes encoding proteins involved in protecting cells from acid stress, a screening method was developed using the electrogenic protonophore carbonyl cyanide m-chlorophenylhydrazone (CCCP). CCCP was used to suppress intrinsic acid resistance of M. smegmatis. The screen involved exposing cells to pH 5·0 in the presence of CCCP, and survivors were rescued at various time intervals on solid medium at pH 7·5. Cells capable of responding to intracellular acidification (due to CCCP-induced proton equilibration) will survive longer under these conditions than acid-sensitive cells. From a total pool of 5000 transposon (Tn611) insertion mutants screened, eight acid-sensitive M. smegmatis mutants were isolated. These acid-sensitive mutants were unable to grow at pH 5·0 in the presence of 1–5 μM CCCP, a concentration not lethal to the wild-type strain mc2155. The DNA flanking the site of Tn611 was identified using marker rescue in Escherichia coli, and DNA sequencing to identify the disrupted locus. Acid-sensitive mutants of M. smegmatis were disrupted in genes involved in phosphonate/phosphite assimilation, methionine biosynthesis, the PPE multigene family, xenobiotic-response regulation and lipid biosynthesis. Several of the acid-sensitive mutants were also defective in stationary-phase survival, suggesting that overlapping stress protection systems exist in M. smegmatis.

Growth and Stress Resistance Variation in Culture Broth among Listeria monocytogenes Strains of Various Serotypes and Origins

2006 ◽  
Vol 69 (11) ◽  
pp. 2640-2647 ◽  
Author(s):  
ALEXANDRA LIANOU ◽  
JARRET D. STOPFORTH ◽  
YOHAN YOON ◽  
MARTIN WIEDMANN ◽  
JOHN N. SOFOS
Keyword(s):  
Listeria Monocytogenes ◽  
Heat Resistance ◽  
Stress Responses ◽  
Stress Resistance ◽  
Growth Rates ◽  
Acid Stress ◽  
Acid Resistance ◽  
Culture Broth ◽  
Death Rates ◽  
Serotype 4B

Twenty-five Listeria monocytogenes strains of various serotypes and sources, including clinical and food isolates associated with the same outbreaks, were characterized and compared based on growth rates and heat and acid death rates. Growth was monitored in tryptic soy broth supplemented with 0.6% yeast extract (TSBYE) at 4 and 30°C for 32 days and 20 h, respectively. Heat and acid stress responses in TSBYE heated to 55°C or acidified to pH 3.0 with lactic acid were evaluated for 240 or 120 min, respectively. Extensive variation in growth and stress resistance was observed among the tested strains. Growth rate differences were less evident at 30 than at 4°C, where growth rates (log CFU per milliliter per day) ranged from 0.28 to 0.43. Thermal and acid death rates (log CFU per milliliter per minute) ranged from −0.023 to −0.052 and from −0.012 to −0.134, respectively. Serotype appeared to play a significant role (P < 0.05) only with respect to the heat resistance of the organism. Serotype 4b isolates as a group had lower heat resistance than did isolates representing all other serotypes combined. Although no clear origin-related (food versus clinical) trends were observed under the tested conditions, outbreak-related isolates of serotype 4b had lower acid death rates (higher acid resistance) (P < 0.05) than did the rest of the strains belonging to this serotype. Strain Scott A exhibited slow growth at 4°C and low acid resistance, behavior that was distinct among both clinical and serotype 4b isolates. The results of this study highlight the risks associated with extrapolation to other strains of findings obtained with only one strain of L. monocytogenes. This information should be useful when test strains are to be selected for the evaluation of antimicrobial alternatives in ready-to-eat meat and other food products and when risk assessments are to be conducted.

scholarly journals Comparative Analysis of Listeria monocytogenes Plasmids and Expression Levels of Plasmid-Encoded Genes during Growth under Salt and Acid Stress Conditions

Toxins ◽  
2019 ◽  
Vol 11 (7) ◽  
pp. 426 ◽  
Author(s):  
Patricia Hingston ◽  
Thomas Brenner ◽  
Lisbeth Truelstrup Hansen ◽  
Siyun Wang
Keyword(s):  
Listeria Monocytogenes ◽  
Acid Stress ◽  
Acid Tolerance ◽  
Stress Conditions ◽  
Chaperone Protein ◽  
Nadh Peroxidase ◽  
Genes Encoding ◽  
Fold Induction ◽  
N 93 ◽  
Unique Plasmid

Listeria monocytogenes strains are known to harbour plasmids that confer resistance to sanitizers, heavy metals, and antibiotics; however, very little research has been conducted into how plasmids may influence L. monocytogenes’ ability to tolerate food-related stresses. To investigate this, a library (n = 93) of L. monocytogenes plasmid sequences were compared. Plasmid sequences were divided into two groups (G1 and G2) based on a repA phylogeny. Twenty-six unique plasmid types were observed, with 13 belonging to each of the two repA-based groups. G1 plasmids were significantly (p < 0.05) smaller than G2 plasmids but contained a larger diversity of genes. The most prevalent G1 plasmid (57,083 bp) was observed in 26 strains from both Switzerland and Canada and a variety of serotypes. Quantitative PCR (qPCR) revealed a >2-fold induction of plasmid-contained genes encoding an NADH peroxidase, cadmium ATPase, multicopper oxidase, and a ClpL chaperone protein during growth under salt (6% NaCl) and acid conditions (pH 5) and ProW, an osmolyte transporter, under salt stress conditions. No differences in salt and acid tolerance were observed between plasmid-cured and wildtype strains. This work highlights the abundance of specific plasmid types among food-related L. monocytogenes strains, the unique characteristics of G1 and G2 plasmids, and the possible contributions of plasmids to L. monocytogenes tolerance to food-related stresses.

Modeling Survival of Listeria monocytogenes in the Traditional Greek Soft Cheese Katiki

2008 ◽  
Vol 71 (9) ◽  
pp. 1835-1845 ◽  
Author(s):  
MARIOS MATARAGAS ◽  
VIRGINIA STERGIOU ◽  
GEORGE-JOHN E. NYCHAS
Keyword(s):  
Listeria Monocytogenes ◽  
Survival Rate ◽  
Survival Rates ◽  
Acid Stress ◽  
Acid Tolerance ◽  
Initial Population ◽  
Bacterial Cells ◽  
Mathematical Equations ◽  
Estimation And Control ◽  
And Control

In the present work, survival of Listeria monocytogenes in the traditional Greek soft, spreadable cheese Katiki was studied throughout the shelf life of the product. Samples of finished cheese were inoculated with a cocktail of five L. monocytogenes strains (ca. 6 log CFU g−1) and stored at 5, 10, 15, and 20°C. Acid-stress adaptation or cross-protection to the same stress was also investigated by inoculation of acid-adapted cells in the product. The results showed that pathogen survival was biphasic. Various mathematical equations (Geeraerd, Cerf, Albert-Mafart, Whiting, Zwietering, and Baranyi models) were fitted to the experimental data. A thorough statistical analysis was performed to choose the best model. The Geeraerd model was finally selected, and the results revealed no acid tolerance acquisition (no significant differences, P &gt; 0.05, in the survival rates of the non–acid-adapted and acid-adapted cells). Secondary modeling (second-order polynomial with a0 = 0.8453, a1 = −0.0743, and a2 = 0.0059) of the survival rate (of sensitive population), and other parameters that were similar at all temperatures (fraction of initial population in the major population = 99.98%, survival rate of resistant population = 0.10 day−1, and initial population = 6.29 log CFU g−1), showed that survival of the pathogen was temperature dependent with bacterial cells surviving for a longer period of time at lower temperatures. Finally, the developed predictive model was successfully validated at two independent temperatures (12 and 17°C). This study underlines the usefulness of predictive modeling as a tool for realistic estimation and control of L. monocytogenes risk in food products. Such data are also useful when conducting risk assessment studies.

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