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Physiology and Genetics of Listeria Monocytogenes Survival and Growth at Cold Temperatures
Critical Reviews In Food Science and Nutrition
Abstract and Figures
Listeria monocytogenes is a foodborne pathogen that can cause serious invasive human illness in susceptible patients, notably immunocompromised, pregnant women, and adults > 65 years old. Most human listeriosis cases appear to be caused by consumption of refrigerated ready-to-eat foods that are contaminated with high levels of L. monocytogenes. While initial L. monocytogenes levels in contaminated foods are usually low, the ability of L. monocytogenes to survive and multiply at low temperatures allows it to reach levels high enough to cause human disease, particularly if contaminated foods that allow for L. monocytogenes growth are stored for prolonged times under refrigeration. In this review, relevant knowledge on the physiology and genetics of L. monocytogenes' ability to adapt to and multiply at low temperature will be summarized and discussed, including selected relevant findings on the physiology and genetics of cold adaptation in other Gram-positive bacteria. Further improvement in our understanding of the physiology and genetics of L. monocytogenes cold growth will hopefully enhance our ability to design successful intervention strategies for this foodborne pathogen.
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... Their optimum temperature is 37 °C and their maximum growth temperature is around 42 °C 46-49 . One distinctive trait of Lm is its ability to grow at 4 °C and below [50][51][52] www.nature.com/scientificreports/ In invasion assays in soil microcosms, discrete disturbances were used to promote time-dependent shifts in the stochastic/deterministic balance of processes that promote resistance to invasion. ...
Current knowledge about effects of disturbance on the fate of invaders in complex microbial ecosystems is still in its infancy. In order to investigate this issue, we compared the fate of Klebsiella pneumoniae (Kp) and Listeria monocytogenes (Lm) in soil microcosms. We then used environmental disturbances (freeze–thaw or heat cycles) to compare the fate of both invaders and manipulate soil microbial diversity. Population dynamics of the two pathogens was assessed over 50 days of invasion while microbial diversity was measured at times 0, 20 and 40 days. The outcome of invasion was strain-dependent and the response of the two invaders to disturbance differed. Resistance to Kp invasion was higher under the conditions where resident microbial diversity was the highest while a significant drop of diversity was linked to a higher persistence. In contrast, Lm faced stronger resistance to invasion in heat-treated microcosms where diversity was the lowest. Our results show that diversity is not a universal proxy of resistance to microbial invasion, indicating the need to properly assess other intrinsic properties of the invader, such as its metabolic repertoire, or the array of interactions between the invader and resident communities.
... Listeria is of peritrichous flagella and motile at 20-25 °C but is immotile or less obviously motile at 37 °C [40]. Being a psychrotroph and able to thrive at low temperatures due to transcriptional machinery is a crucial for L. monocytogenes to yield infectious dose levels on contaminated refrigerated aliments [41,42]. Uncovering the mechanisms behind this phenotypic event is essential to develop novel interventions against this pathogen in foods kept in cold milieus. ...
The present study aimed to predict the biofilm-formation ability of L. monocytogenes isolates obtained from cattle carcasses via the ARIMA model at different temperature parameters. The identification of L. monocytogenes obtained from carcass samples collected from slaughterhouses was determined by PCR. The biofilm-forming abilities of isolates were phenotypically determined by calculating the OD value and categorizing the ability via the microplate test. The presence of some virulence genes related to biofilm was revealed by QPCR to support the biofilm profile genotypically. Biofilm-formation of the isolates was evaluated at different temperature parameters (37 °C, 22 °C, 4 °C and − 20 °C). Estimated OD values were obtained with the ARIMA model by dividing them into eight different estimation groups. The prediction performance was determined by performance measurement metrics (ME, MAE, MSE, RMSE, MPE and MAPE). One week of incubation showed all isolates strongly formed biofilm at all controlled temperatures except − 20 °C. In terms of the metrics examined, the 3 days to 7 days forecast group has a reasonable prediction accuracy based on OD values occurring at 37 °C, 22 °C, and 4 °C. It was concluded that measurements at 22 °C had lower prediction accuracy compared to predictions from other temperatures. Overall, the best OD prediction accuracy belonged to the data obtained from biofilm formation at -20 °C. For all temperatures studied, especially after the 3 days to 7 days forecast group, there was a significant decrease in the error metrics and the forecast accuracy increased. When evaluating the best prediction group, the lowest RMSE at 37 °C (0.055), 22 °C (0.027) and 4 °C (0.024) belonged to the 15 days to 21 days group. For the OD predictions obtained at -20 °C, the 15 days to 21 days prediction group had also good performance (0.011) and the lowest RMSE belongs to the 7 days to 15 days group (0.007). In conclusion, this study will guide in using indicator parameters to evaluate biofilm forming ability to predict optimum temperature-time. The ARIMA models integrated with this study can be useful tools for industrial application and risk assessment studies using different parameters such as pH, NaCl concentration, and especially temperature applied during food processing and storage on the biofilm-formation ability of L. monocytogenes.
... Listeriosis has been linked to outbreaks caused by contaminated milk, sh, cheese, ready-to-eat foods, vegetables, and meat [5, 6]. L. monocytogenes survives in various stress conditions, such as low temperatures, high pressures, and acidity, challenging the food industry [3,7]. Thus, food products should be treated carefully to prevent L. monocytogenes contamination or survival. ...
Background
Listeria monocytogenes is a foodborne pathogen that can survive various stresses. To inactivate Listeria monocytogenes, food processing facilities use high energy methods, such as high-pressure processing (HPP). In this study, we explored the transcriptional units of barotolerant L. monocytogenes RO15 using Cappable-seq and direct RNA sequencing, two novel techniques.
Results
We detected 1641 transcription start sites (TSSs) in L. monocytogenes RO15, including six HPP-specific TSSs, showing that HPP influences the TSS selection. In addition, we predicted small RNAs (sRNAs) candidates and examined promoter motifs, which revealed new regulatory elements that control gene expression. By integrating short and long RNA-seq reads, we predicted the operon structure of L. monocytogenes RO15 and found 658 operons, comprising 71% of all the genes. The largest operons were mainly located in prophage regions. Moreover, we identified A-to-I RNA editing events in L. monocytogenes for the first time. HPP treatment statistically significantly (p < 0.05) increased the A-to-I editing of several genes including hpf and mdxE suggesting a role in the stress response. We predicted m6A RNA modifications in L. monocytogenes RO15 using direct RNA sequencing reads. This is the first report of m6A RNA modifications in L. monocytogenes by using direct RNA sequencing.
Conclusions
This study provides novel insights into the transcriptome complexity and diversity, stress response strategies, and post-transcriptional modifications of L. monocytogenes. Our results uncover the genomic mechanisms of adaptation of L. monocytogenes to HPP and indicate potential targets for developing new strategies to control this pathogen. However, further studies are needed to validate the functional roles of the identified sRNAs, RNA editing events, and RNA modifications in L. monocytogenes.
... In particular, fresh-cut vegetables are designed to be consumed without any additional preparation (Lianou & Sofos, 2007). The concern towards this pathogen is emphasized by its ability to grow under refrigeration conditions, at which fresh-cut vegetables are normally stored, resulting dominant over other food pathogens (Chan & Wiedmann, 2008). Several outbreaks of listeriosis have been reported in leafy vegetables in USA, such as romaine lettuce and packaged salads with 15, 1, and 3 deaths, respectively (CDC, 2016;CDC, 2022;Shrivastava, 2016;Zhu et al., 2017). ...
... This observation suggests that SigB T1 would help lineage I and lineage III isolates endure low temperatures under nutrient-poor conditions and increase their likelihood of survival and persistence in frigid natural environments. L. monocytogenes ubiquitously exist in various sources and can survive in the presence of high osmolarity, low-temperature conditions, and extreme environments (Chan and Wiedmann, 2009). Different microbial lineages have adapted to different environments and sources, and their proportions vary depending on the environment they inhabit. ...
Introduction
Listeria monocytogenes is a globally distributed bacterium that exhibits genetic diversity and trait heterogeneity. The alternative sigma factor SigB serves as a crucial transcriptional regulator essential for responding to environmental stress conditions and facilitating host infection.
Method
We employed a comprehensive genetic analysis of sigB in a dataset comprising 46,921 L. monocytogenes genomes. The functional attributes of SigB were evaluated by phenotypic experiments.
Results
Our study revealed the presence of two predominant SigB factors (SigB T1 and SigB T2 ) in L. monocytogenes , with a robust correlation between SigB T1 and lineages I and III, as well as SigB T2 and lineage II. Furthermore, SigB T1 exhibits superior performance in promoting cellular invasion, cytotoxicity and enhancing biofilm formation and cold tolerance abilities under minimally defined media conditions compared to SigB T2 .
Discussion
The functional characteristics of SigB T1 suggest a potential association with the epidemiology of lineages I and III strains in both human hosts and the natural environment. Our findings highlight the important role of distinct SigB factors in influencing the biological traits of L. monocytogenes of different lineages, thus highlighting its distinct pathogenic and adaptive attributes.
... Multicellular biofilm formation is a key feature for bacterial tolerance to adverse environmental conditions [31,32]. In L. monocytogenes, biofilms promote surface adherence [33,34] and persistence in food production environments [35][36][37][38], even enabling survival and replication in refrigeration conditions [39][40][41] and resistance to antimicrobials, including disinfectants [42][43][44][45]. This is a major public health concern since food contamination can result in fatal listeriosis outbreaks following consumption [46,47]. ...
Listeria monocytogenes is an opportunistic food-borne bacterium that is capable of infecting humans with high rates of hospitalization and mortality. Natural populations are genotypically and phenotypically variable, with some lineages being responsible for most human infections. The success of L. monocytogenes is linked to its capacity to persist on food and in the environment. Biofilms are an important feature that allow these bacteria to persist and infect humans, so understanding the genetic basis of biofilm formation is key to understanding transmission. We sought to investigate the biofilm-forming ability of L. monocytogenes by identifying genetic variation that underlies biofilm formation in natural populations using genome-wide association studies (GWAS). Changes in gene expression of specific strains during biofilm formation were then investigated using RNA sequencing (RNA-seq). Genetic variation associated with enhanced biofilm formation was identified in 273 genes by GWAS and differential expression in 220 genes by RNA-seq. Statistical analyses show that the number of overlapping genes flagged by either type of experiment is less than expected by random sampling. This novel finding is consistent with an evolutionary scenario where rapid adaptation is driven by variation in gene expression of pioneer genes, and this is followed by slower adaptation driven by nucleotide changes within the core genome.
... L. monocytogenes is remarkably tolerant to environmental stresses, being able to grow at temperatures ranging from −0.4 • C to 45 • C, a pH as low as 4.1, salt concentrations up to 13.9%, and in the presence of moderate levels of nitrite and other food preservatives [7][8][9]. The combination of this high environmental resilience with a versatile saprophytic lifestyle explains the ubiquitous occurrence of L. monocytogenes in water, soil, vegetation, and food processing environments [10][11][12][13]. ...
Hop beta acids (HBAs) are characteristic compounds from the hop plant that are of interest for their strong antimicrobial activity. In this work, we report a resistance mechanism against HBA in the foodborne pathogen Listeria monocytogenes. Using an evolution experiment, we isolated two HBA-resistant mutants with mutations in the mprF gene, which codes for the Multiple Peptide Resistance Factor, an enzyme that confers resistance to cationic peptides and antibiotics in several Gram-positive bacteria by lysinylating membrane phospholipids. Besides the deletion of mprF, the deletion of dltA, which mediates the alanylation of teichoic acids, resulted in increased HBA resistance, suggesting that resistance may be caused by a reduction in positive charges on the cell surface. Additionally, we found that this resistance is maintained at low pH, indicating that the resistance mechanism is not solely based on electrostatic interactions of HBA with the cell surface. Finally, we showed that the HBA-resistant mutants display collateral sensitivity to the cationic antimicrobials polymyxin B and nisin, which may open perspectives for combining antimicrobials to prevent resistance development.
The cold chain is an integral part of the modern food industry. Low temperatures can effectively alleviate food loss and the transmission of foodborne diseases caused by microbial reproduction. However, recent reports have highlighted shortcomings in the current cold chain technology's ability to prevent and control cold-tolerant foodborne pathogens. Furthermore, it has been observed that certain cold-chain foods have emerged as new sources of infection for foodborne disease outbreaks. Consequently, there is a pressing need to enhance control measures targeting cold-tolerant pathogens within the existing cold chain system. This paper aims to review the recent advancements in understanding the cold tolerance mechanisms of key model organisms, identify key issues in current research, and explore the potential of utilizing big data and omics technology in future studies.
The alternative transcription factor sigma B of Bacillus subtilis is activated during the stationary growth phase by a regulatory network responsive to stationary-phase signals. On the basis of the results reported here, we propose that sigma B controls a general stress regulon that is induced when cells encounter a variety of growth-limiting conditions. Expression of genes controlled by sigma B, including the ctc gene and the sigB operon that codes for sigma B and its associated regulatory proteins, was dramatically induced in both the exponential and stationary phases by environmental challenges known to elicit a general stress response. After cells were subjected to salt stress, the increased expression of lacZ transcriptional fusions to the ctc and sigB genes was entirely dependent on sigma B, and primer extension experiments confirmed that the sigma B-dependent transcriptional start site was used during salt induction of sigB operon expression. Western blotting (immunoblotting) experiments measuring the levels of sigma B protein indicated that ethanol addition and heat stress also induced sigma B activity during logarithmic growth. Salt and ethanol induction during logarithmic growth required RsbV, the positive regulator of sigma B activity that is normally necessary for activity in stationary-phase cells. However, heat induction of sigma B activity was largely independent of RsbV, indicating that there are two distinct pathways by which these environmental signals are conveyed to the transcriptional apparatus.
The antimicrobial activities of sodium lactate (SL) and sodium acetate (SA) are well documented, but there is limited information on the effect of their combination or of the combination of SL and sodium diacetate (SDA) on survival and growth of Listeria monocytogenes and salmonellae in meat. Effects of SL (1.8 and 2.5%), SDA (0.1 and 0.2%), or SA (0.2%) and their combinations on the behavior of L. monocytogenes and Salmonella enterica serovar Enteritidis were investigated in sterile comminuted beef (pH 6.3, 79% moisture) during storage at 5 and 10 degreesC. Although L. monocytogenes grew faster than Salmonella Enteritidis in control samples at 10 degreesC, numbers of both pathogens increased from 3.5 to approximately 8.0 log CFU/g after 20 days. SL (1.8%) decreased the growth rate of both L. monocytogenes and Salmonella Enteritidis. SDA (0.2%) was more effective than SL in decreasing the growth rate of L. monocytogenes, and it caused a more than 1 log CFU/g decline in initial numbers of Salmonella Enteritidis during storage for 25 days at 10 degreesC. Synergy was observed by combinations of SL and SDA. Combinations of 2.5% SL and 0.2% SDA were bacteriostatic to L. monocytogenes and bactericidal to Salmonella Enteritidis after 20 days at 10 degreesC. At 5 degreesC, a listeriostatic effect was produced by 1.8% SL + 0.1% SDA, whereas numbers of Salmonella Enteritidis were less than 10 cells/g after refrigeration for 30 days. Although SA was consistently and significantly less inhibitory than SDA, its mixtures with SL also demonstrated synergistic activity against both pathogens. Combinations of 2.5% SL and 0.2% SDA can be expected to greatly enhance the safety of refrigerated and temperature-abused ready-to-eat meats.
Branched-chain fatty acids of the iso and anteiso series occur in many bacteria as the major acyl constituents of membrane lipids. In addition, omega-cyclohexyl and omega-cycloheptyl fatty acids are present in several bacterial species. These two types of fatty acids are synthesized by the repeated condensation of malonyl coenzyme A with one of the branched-chain and cyclic primers by the same enzyme system. The pathway of de novo branched-chain fatty acid synthesis differs only in initial steps of synthesis from that of the common straight-chain fatty acid (palmitic acid) present in most organisms. The cell membranes composed largely of iso-, anteiso-, and omega-alicyclic acids support growth of bacteria, which inhabit normal as well as extreme environments. The occurrence of these types of fatty acids as major cellular fatty acids is an important criterion used to aid identification and classification of bacteria.
SMALL MOLECULES HAVE LONG BEEN ASSOCIATED with biological discoveries, but, in contrast to biochemical and genetic approaches, the small-molecule approach has lacked generality Although the advances made through the use of small molecules as probes (as distinct from medicines) are impressive, they have in general come about on a case-by-case basis. Advances in diversity-oriented organic synthesis and a focus on the underlying similarities between the small-molecule and genetic approaches have increased the generality of the small-molecule approach. Although a truly systematic way to explore any and all facets of biology with small-molecule modulators has not yet been reached, these advances are beginning to influence researchers on a much broader scale. It is becoming more common for a life scientist to ask, "Should I tackle this problem with small molecules?" or even to state, "The only way I can tackle this problem is with small molecules."1 The latter is becoming increasingly common as global views ...
The role of ς B , an alternative sigma factor of Staphylococcus aureus , has been characterized in response to environmental stress, starvation-survival and recovery, and pathogenicity. ς B was mainly expressed during the stationary phase of growth and was repressed by 1 M sodium chloride. A sigB insertionally inactivated mutant was created. In stress resistance studies, ς B was shown to be involved in recovery from heat shock at 54°C and in acid and hydrogen peroxide resistance but not in resistance to ethanol or osmotic shock. Interestingly, S. aureus acquired increased acid resistance when preincubated at a sublethal pH 4 prior to exposure to a lethal pH 2. This acid-adaptive response resulting in tolerance was mediated via sigB . However, ς B was not vital for the starvation-survival or recovery mechanisms. ς B does not have a major role in the expression of the global regulator of virulence determinant biosynthesis, staphylococcal accessory regulator ( sarA ), the production of a number of representative virulence factors, and pathogenicity in a mouse subcutaneous abscess model. However, SarA upregulates sigB expression in a growth-phase-dependent manner. Thus, ς B expression is linked to the processes controlling virulence determinant production. The role of ς B as a major regulator of the stress response, but not of starvation-survival, is discussed.
Use of adequate isolation procedures, enough time, and a little perseverance by investigators make it possible to isolate Listeria spp., including Listeria monocytogenes, from most forms of animal life. A similar situation also exists with products of plant origin. An apparent association between consumption of silage and occurrence of an illness resembling listeriosis in ruminants was observed as early as 1922; however, this link between silage consumption and listeriosis in domestic livestock was not confirmed until 1960 [54]. Although several papers published during the next 15-year period documented the presence of L. monocytogenes in vegetation grown primarily for consumption by animals [103,104,105], scientists at the time were generally unconcerned about the incidence of listeriae in produce destined for human consumption, primarily because such products had not been positively linked to human listeriosis. In fact, the only instance in which listeriae were reportedly recovered from raw retail produce before 1981 occurred in 1975, when investigators isolated three untypeable Listeria strains from lettuce marketed in Brazil [62].
Listeria monocytogenes is ubiquitous in nature. Therefore, the many aquatic creatures including finfish, oysters, shrimp, crabs, lobsters, squid, and scallops harvested from natural environments can be potential sources of Listeria in the human diet. Many of these products are also subjected to a variety of processing methods that can inactivate Listeria on the raw product. Listeria can also be introduced during processing by poor sanitation conditions or manufacturing practices or by postprocess contamination. The psychrotrophic nature of L. monocytogenes allows its survival or even multiplication during refrigerated storage or temperature abuse situations. This is of special concern for those products receiving minimal or no heat treatment before consumption. Since L. monocytogenes was first isolated from imported cooked crabmeat in 1987, at least 126 Class I recalls (where reasonable probability exists that the use of or exposure to a violative product would cause serious adverse health consequences or death) have been issued by the U.S. Food and Drug Administration (FDA) for more than 266,070 lb of ready-to-eat (RTE) domestic or imported fish and seafood; this pathogen is routinely found in 7.6% of all such products marketed in the United States. The first of several cases of listeriosis positively linked to consumption of fish or seafood was not reported until 1989, when a 54-year-old woman in Italy contracted listeric meningitis 4 days after consuming steamed fish from which L. monocytogenes was later isolated [43]. This case and the potential hazard associated with consumption of other Listeria -contaminated RTE food such as cooked crabmeat, cooked shrimp, and smoked salmon have prompted studies on determining the incidence and control of Listeria in various seafoods.