Explorative multifactor approach for investigating global survival mechanisms of Campylobacter jejuni under environmental conditions

Understanding the transition to viable but non-culturable state in Escherichia coli W3110: a comprehensive analysis of potential spectrochemical biomarkers

The viable but non-culturable (VBNC) state is considered a survival strategy employed by bacteria to endure stressful conditions, allowing them to stay alive. Bacteria in this state remain unnoticed in live cell counts as they cannot proliferate in standard culture media. VBNC cells pose a significant health risk because they retain their virulence and can revive when conditions normalize. Hence, it is crucial to develop fast, reliable, and cost-effective methods to detect bacteria in the VBNC state, particularly in the context of public health, food safety, and microbial control assessments. This research examined the biomolecular changes in Escherichia coli W3110 induced into the VBNC state in artificial seawater under three different stress conditions (temperature, metal, and antibiotic). Initially, confirmation of VBNC cells under various stresses was done using fluorescence microscopy and plate counts. Subsequently, lipid peroxidation was assessed through the TBARS assay, revealing a notable increase in peroxidation end-products in VBNC cells compared to controls. ATR-FTIR spectroscopy and chemomometrics were employed to analyze biomolecular changes, uncovering significant spectral differences in RNA, protein, and nucleic acid concentrations in VBNC cells compared to controls. Notably, RNA levels increased, while protein and nucleic acid amounts decreased. ROC analyses identified the 995 cm- 1 RNA band as a consistent marker across all studied stress conditions, suggesting its potential as a robust biomarker for detecting cells induced into the VBNC state under various stressors.

Applications of Fourier Transform-Infrared spectroscopy in microbial cell biology and environmental microbiology: advances, challenges, and future perspectives

Microorganisms play pivotal roles in shaping ecosystems and biogeochemical cycles. Their intricate interactions involve complex biochemical processes. Fourier Transform-Infrared (FT-IR) spectroscopy is a powerful tool for monitoring these interactions, revealing microorganism composition and responses to the environment. This review explores the diversity of applications of FT-IR spectroscopy within the field of microbiology, highlighting its specific utility in microbial cell biology and environmental microbiology. It emphasizes key applications such as microbial identification, process monitoring, cell wall analysis, biofilm examination, stress response assessment, and environmental interaction investigation, showcasing the crucial role of FT-IR in advancing our understanding of microbial systems. Furthermore, we address challenges including sample complexity, data interpretation nuances, and the need for integration with complementary techniques. Future prospects for FT-IR in environmental microbiology include a wide range of transformative applications and advancements. These include the development of comprehensive and standardized FT-IR libraries for precise microbial identification, the integration of advanced analytical techniques, the adoption of high-throughput and single-cell analysis, real-time environmental monitoring using portable FT-IR systems and the incorporation of FT-IR data into ecological modeling for predictive insights into microbial responses to environmental changes. These innovative avenues promise to significantly advance our understanding of microorganisms and their complex interactions within various ecosystems.

The effect of bio-electro-magnetic-energy-regulation therapy on sleep duration and sleep quality among elite players in Norwegian women's football

The current study investigated if physical loads peak on game days and if Bio-Electro-Magnetic-Energy-Regulation (BEMER) therapy is affecting sleep duration and sleep quality on nights related to game nights among elite players in Norwegian women's elite football. The sample included 21 female football players from an elite top series club with a mean age of ~24 years (± 2.8). Sleep was measured every day over a period of 273 consecutive days with a Somnofy sleep monitor based on ultra-wideband (IR-UWB) pulse radar and Doppler technology. The current study was conducted as a quasi-experiment, where each player was their own control based on a control period that lasted for 3 months, and an experimental period that lasted for 5 months. Accordantly, the time each player spent with BEMER therapy was used as a control variable. Multivariate analyses of variance using FFMANOVA and univariate ANOVA with False Discovery Rate adjusted p-values show that physical performance (total distance, distance per minute, sprint meters >22.5 kmh, accelerations and decelerations) significantly peak on game day compared with ordinary training days and days related to game days. The results also show that sleep quantity and quality are significantly reduced on game night, which indicate disturbed sleep caused by the peak in physical load. Most sleep variables significantly increased in the experiment period, where BEMER therapy was used, compared to the control period before the introduction of BEMER therapy. Further, the analyses show that players who spent BEMER therapy >440 h had the most positive effects on their sleep, and that these effects were significantly compared to the players who used BEMER therapy <440 h. The findings are discussed based on the function of sleep and the different sleep stages have on recovery.

Transcriptome Analysis of Campylobacter jejuni and Campylobacter coli during Cold Stress

Campylobacter spp. are known to cause campylobacteriosis, a bacterial disease that remains a public health threat. Campylobacter spp. are prevalent in retail meat and liver products, and the prolonged survival of Campylobacter in the low temperatures needed for storage is a challenge for food safety. In this study, RNA-seq was used for the analysis of the C. coli HC2-48 (Cc48) and C. jejuni OD2-67 (Cj67) transcriptomes at 4 °C in a nutrient-rich medium (chicken juice, CJ) and Mueller-Hinton broth (MHB) for 0 h, 0.5 h, 24 h and 48 h. Differentially expressed genes (DEGs) involved in flagellar assembly were highly impacted by low temperatures (4 °C) in C. coli HC2-48, whereas genes related to the ribosome and ribonucleoprotein complex were modulated for C. jejuni OD2-67 at 4 °C. Most of the DEGs in cells grown at 4 °C in the two medium formulations were not significantly expressed at different incubation times. Although more DEGs were observed in CJ as compared to MHB in both Campylobacter strains, the absence of common genes expressed at all incubation times indicates that the food matrix environment is not the sole determinant of differential expression in Campylobacter spp. at low temperatures.

Optimization of Mixed Inulin, Fructooligosaccharides, and Galactooligosaccharides as Prebiotics for Stimulation of Probiotics Growth and Function

Prebiotics have become an important functional food because of their potential for modulating the gut microbiota and metabolic activities. However, different prebiotics can stimulate the growth of different probiotics. The optimization of prebiotics was focused on in this study in order to stimulate the representative probiotics' growth (Lacticaseibacillus rhamnosus (previously Lactobacillus rhamnosus) and Bifidobacterium animalis subsp. lactis) and their function. The culture medium was supplemented with three prebiotics, including inulin (INU), fructooligosaccharides (FOS), and galactooligosaccharides (GOS). All prebiotics can clearly stimulate the growth of probiotic strains in both monoculture and co-culture. The specific growth rates of L. rhamnosus and B. animalis subsp. lactis were shown in GOS (0.019 h^-1) and FOS (0.023 h^-1), respectively. The prebiotic index (PI) scores of INU (1.03), FOS (0.86), and GOS (0.84) in co-culture at 48 h were significantly higher than the control (glucose). The mixture of prebiotics to achieve high quality was optimized using the Box-Behnken design. The optimum prebiotic ratios of INU, FOS, and GOS were 1.33, 2.00, and 2.67% w/v, respectively, with the highest stimulated growth of probiotic strains occurring with the highest PI score (1.03) and total short chain fatty acid concentration (85.55 µmol/mL). The suitable ratio of mixed prebiotics will function as a potential ingredient for functional foods or colonic foods.

Roles of viable but non-culturable state in the survival of Campylobacter jejuni

Despite being considered fragile and fastidious, Campylobacter jejuni is the most prevalent cause of foodborne bacterial gastroenteritis, and chicken meat is considered the main vehicle of transmission to humans. This agent can survive adverse conditions in the form of biofilms, but extreme stress (nutritional, oxidative and thermal) promotes the acquisition of a state called viable but not culturable (VBNC). The emergence of this pathogen worldwide and the recent international requirements in its control instigated us to qualitatively and quantitatively estimate the time required for the acquisition of the VBNC form in 27 strains of C. jejuni, characterize morphological aspects, determine its adaptive and invasive potential and perform comparative metabolomic evaluation. Extreme stress promoted the complete acquisition of the VBNC form in a mean time of 26 days. Starting from an average initial count of 7.8 log CFU/mL, the first four days determined the greatest average reduction of the culturable form of 3.2 log CFU/mL. The scanning and transmission image analyses showed a transition from the typical viable form (VT) to the VBNC form, with initial acquisition of the straight rod shape, followed by loss of the flagella and subdivision into two to 11 imperfect cocci arranged in a chain and rich in cellular content, until their individual release. RT-PCR identified the presence of ciaB and p19 transcripts in the 27 cultivable C. jejuni strains, a character maintained in the VBNC form only for p19 and in 59.3% (16/27) of the VBNC strains for the ciaB gene. The average inoculation of 1.8 log CFU/mL of C. jejuni VBNC into primary chicken embryo hepatocyte cells promoted the occurrence of apoptosis processes significantly after 24 hours of contact by one of the strains tested. In C. jejuni VBNC, we detected higher expression of metabolites linked to protective and adaptation mechanisms and of volatile organic precursor compounds indicative of metabolism interruption. The oscillations in the time of acquisition of the VBNC form together with the presence of transcripts for ciaB and p19, the identification of cell lysis and metabolites that ensure the maintenance of the pathogen alert to the fact that C. jejuni VBNC remains virulent and adapted to stress, which makes evident the potential danger of this latent form, which is not detectable by official methodologies.

Molecular Targets in Campylobacter Infections

Human campylobacteriosis results from foodborne infections with Campylobacter bacteria such as Campylobacter jejuni and Campylobacter coli, and represents a leading cause of bacterial gastroenteritis worldwide. After consumption of contaminated poultry meat, constituting the major source of pathogenic transfer to humans, infected patients develop abdominal pain and diarrhea. Post-infectious disorders following acute enteritis may occur and affect the nervous system, the joints or the intestines. Immunocompromising comorbidities in infected patients favor bacteremia, leading to vascular inflammation and septicemia. Prevention of human infection is achieved by hygiene measures focusing on the reduction of pathogenic food contamination. Molecular targets for the treatment and prevention of campylobacteriosis include bacterial pathogenicity and virulence factors involved in motility, adhesion, invasion, oxygen detoxification, acid resistance and biofilm formation. This repertoire of intervention measures has recently been completed by drugs dampening the pro-inflammatory immune responses induced by the Campylobacter endotoxin lipo-oligosaccharide. Novel pharmaceutical strategies will combine anti-pathogenic and anti-inflammatory effects to reduce the risk of both anti-microbial resistance and post-infectious sequelae of acute enteritis. Novel strategies and actual trends in the combat of Campylobacter infections are presented in this review, alongside molecular targets applied for prevention and treatment strategies.

Roles of Aerotolerance, Biofilm Formation, and Viable but Non-Culturable State in the Survival of Campylobacter jejuni in Poultry Processing Environments

Campylobacter jejuni is one of the most common causes of foodborne human gastroenteritis in the developed world. This bacterium colonizes in the ceca of chickens, spreads throughout the poultry production chain, and contaminates poultry products. Despite numerous on farm intervention strategies and developments in post-harvest antimicrobial treatments, C. jejuni is frequently detected on broiler meat products. This indicates that C. jejuni is evolving over time to overcome the stresses/interventions that are present throughout poultry production and processing. The development of aerotolerance has been reported to be a major survival strategy used by C. jejuni in high oxygen environments. Recent studies have indicated that C. jejuni can enter a viable but non-culturable (VBNC) state or develop biofilm in response to environmental stressors such as refrigeration and freezing stress and aerobic stress. This review provides an overview of different stressors that C. jejuni are exposed to throughout the poultry production chain and the genotypic and phenotypic survival mechanisms, with special attention to aerotolerance, biofilm formation, and development of the VBNC state.

Cerebrospinal fluid proteome shows disrupted neuronal development in multiple sclerosis

Despite intensive research, the aetiology of multiple sclerosis (MS) remains unknown. Cerebrospinal fluid proteomics has the potential to reveal mechanisms of MS pathogenesis, but analyses must account for disease heterogeneity. We previously reported explorative multivariate analysis by hierarchical clustering of proteomics data of MS patients and controls, which resulted in two groups of individuals. Grouping reflected increased levels of intrathecal inflammatory response proteins and decreased levels of proteins involved in neural development in one group relative to the other group. MS patients and controls were present in both groups. Here we reanalysed these data and we also reanalysed data from an independent cohort of patients diagnosed with clinically isolated syndrome (CIS), who have symptoms of MS without evidence of dissemination in space and/or time. Some, but not all, CIS patients had intrathecal inflammation. The analyses reported here identified a common protein signature of MS/CIS that was not linked to elevated intrathecal inflammation. The signature included low levels of complement proteins, semaphorin-7A, reelin, neural cell adhesion molecules, inter-alpha-trypsin inhibitor heavy chain H2, transforming growth factor beta 1, follistatin-related protein 1, malate dehydrogenase 1 cytoplasmic, plasma retinol-binding protein, biotinidase, and transferrin, all known to play roles in neural development. Low levels of these proteins suggest that MS/CIS patients suffer from abnormally low oxidative capacity that results in disrupted neural development from an early stage of the disease.

Changes in cell membrane properties and phospholipid fatty acids of bacillus subtilis induced by polyphenolic extract of Sanguisorba officinalis L

Sanguisorba officinalis L. (family Rosaceae, subfamily Rosoideae) is a plant found throughout Southern Europe, Northern Africa, and Eastern Asia. This study demonstrated the antibacterial activity of a purified polyphenolic extract (PPE) from S. officinalis L. against Bacillus subtilis using growth inhibitory and apoptosis assays, and investigated the antibacterial mechanism responsible for changes in cell membrane properties. Fourier transform infrared spectroscopy suggested that PPE altered the cell wall and membrane properties of B. subtilis. Further determination of cell membrane integrity and permeability revealed that B. subtilis membrane integrity was more severely damaged by PPE at the minimum inhibitory concentration (MIC) than at the minimum bactericidal concentrati on (MBC). Instead, PPE at the MBC reduced cell membrane fluidity by significantly decreasing the proportion of anteiso- and iso-branched phospholipid fatty acids (PLFAs) from 64.17 ± 0.28% and 27.23 ± 0.03% in the control to 5.57 ± 1.06% and 6.00 ± 1.40%, respectively (P < 0.001). Scanning electron microscopy revealed different effects of PPE on cell morphology, demonstrating that, at the MIC and MBC, PPE exerted antibacterial activity by disrupting the cell membrane and reducing cell membrane fluidity, respectively. Consequently, this study elucidated changes in the bacterial membrane due to exposure to PPE and its potential use as an antimicrobial agent. PRACTICAL APPLICATION: The abuse of synthetic chemical preservatives raises food safety concerns; however, plant-derived polyphenolic compounds may be a safe and effective alternative. This study demonstrated the strong antibacterial activity of a purified polyphenolic extract (PPE) of Sanguisorba officinalis L. and revealed its antibacterial mechanism against Bacillus subtilis, suggesting that it may provide a useful antimicrobial agent in food industry applications.

Sensory Assessment of Fish and Chicken Protein Hydrolysates. Evaluation of NMR Metabolomics Profiling as a New Prediction Tool

Nuclear magnetic resonance (NMR) metabolomics profiling was evaluated as a new tool in sensory assessment of protein hydrolysates. Hydrolysates were produced on the basis of different raw materials (cod, salmon, and chicken), enzymes (Food Pro PNL and Bromelain), and hydrolysis time (10 and 50 min). The influence of raw material and hydrolysis parameters on sensory attributes was determined by traditional descriptive sensory analysis and ¹H NMR spectroscopy. The raw material had a major influence on the attribute intensity and metabolite variation, followed by enzyme and hydrolysis time. However, the formation of bitter taste was not affected by the raw material. Partial least-squares regression (PLSR) on ¹H NMR and sensory data provided good models (Q² = 0.55-0.89) for 11 of the 17 evaluated attributes, including bitterness. Significant metabolite-attribute associations were identified. The study confirms the potential prediction of the sensory properties of protein hydrolysates from cod, salmon, and chicken based on ¹H NMR metabolomics profiling.

Antibacterial Activity of Bifidobacterium breve Against Clostridioides difficile

Bifidobacterium breve (YH68) is widely used in the fields of food fermentation and biomedicine. In this study, we explored the antibacterial activity of the cell free culture supernatant (CFCS) of YH68 against Clostridioides difficile ATCC 9689 (CD) by measuring multiple indexes, including the growth, spores production, toxin A/B production, and the expression levels of the tcdA and tcdB genes of CD. In addition, we examined the changes in major cellular functional groups, structures, permeability, integrity, and the proton motive force (PMF) of the cytoplasmic membrane. The results showed that double-dilution ratio of YH68-CFCS (3 × 10⁹ CFU/mL) was the MIC value. The cell density, spores production, and the toxin production of CD treated with YH68-CFCS were lower than that of the control (p < 0.05). In addition, the gene expression levels of tcdA and tcdB in CD treated with YH68-CFCS were significant downregulated (p < 0.05). Marked differences were observed in the cell membrane and cell wall by a FT-IR spectroscopy and SEM. Analysis of the cell membrane permeability and integrity of the CD cells revealed that YH68-CFCS induced the leakage of a large amount of intracellular K⁺, inorganic phosphate, ATP, nucleic acids and proteinaceous substances. Furthermore, PMF analysis indicated that there was a significant change in Δψ and ΔpH. These findings demonstrated that the antibacterial activity of YH68-CFCS against CD involved the inhibition of growth, spore production, toxin production, and virulence genes expression; a consumption of PMF in the cytoplasmic membrane, the formation of pore in the cell membrane, together with the enhanced cell membrane permeability; and, eventually, cell completely disintegration.

Kinetic Behavior of Campylobacter jejuni in Beef Tartare at Cold Temperatures and Transcriptomes Related to Its Survival

This study was conducted to examine the kinetic behavior of Campylobacter jejuni in raw beef tartare by using mathematical models and to identify genes related to C. jejuni survival at cold temperatures. C. jejuni was inoculated onto beef tartare samples, stored at 4, 10, 15, 25, and 30°C, plated on modified charcoal-cefoperazone-deoxycholate agar, and enumerated. The survival data was fitted to the Weibull model to calculate delta (δ), which is the time required for the first 1-log reduction of the cells. The Davey model was then fitted to the δ to evaluate the effect of temperature. To evaluate the performance of the developed model, the root mean square error (RMSE) was calculated by comparing the observed data with the predicted data. The mRNA was extracted from samples stored at 4 and 30°C under aerobic and anaerobic conditions, and the expression of oxidative stress response and stress response genes was evaluated. C. jejuni survived in beef tartare longer at 4°C (δ = 657.1 ± 79.6 min) than at other temperatures (9.7 ± 11.2 to 465.7 ± 139.3°C) even under aerobic conditions. The RMSE (0.475) suggested that the developed model was appropriate to describe the kinetic behavior of C. jejuni. Quantitative real-time PCR results revealed that oxidative stress and stress response genes were related to C. jejuni survival at cold temperatures, even under aerobic conditions. These results indicate that the model will be useful for describing the kinetic behavior of C. jejuni in beef tartare and that this pathogen can survive at cold temperatures because of the expression of the sodB, katA, and clpP genes.

FTIR spectroscopy of whole cells for the monitoring of yeast apoptosis mediated by p53 over-expression and its suppression by Nigella sativa extracts

p53 over expression in yeast results in cell death with typical markers of apoptosis such as DNA fragmentation and phosphatidylserine externalization. We aimed to substitute/supplement classical fluorescent techniques (TUNEL, Annexin V, ROS detection) usually used to detect biochemical changes occurring during yeast apoptosis mediated by p53 over expression and the effect of anti-apoptotic purified molecules from Nigel (Nigella sativa) extracts on these same yeasts by the label free technique of FTIR spectroscopy. The comparison of the entire IR spectra highlighted clear modifications between apoptotic p53-expressing yeasts and normal ones. More precisely, DNA damage was detected by the decrease of band intensities at 1079 and 1048 cm^-1. While phosphatidylserine exposure was followed by the increase of νsCH₂ and νasCH₂ bands of unsaturated fatty acids that were exhibited at 2855 and 2926 cm^-1, and the appearance of the C = O ester functional group band at 1740 cm^-1. In a second step, this FTIR approach was used to estimate the effect of a purified fraction of the Nigel extract. The modulation of band intensities specific to DNA and membrane status was in agreement with apoptosis supression in presence of the Nigel extracts. FTIR spectroscopy is thus proven to be a very reliable technique to monitor the apoptotic cell death in yeast and to be used as a means of evaluating the biomolecules effect on yeast survival.

The impact of environmental conditions on Campylobacter jejuni survival in broiler faeces and litter

INTRODUCTION

Campylobacter jejuni is the leading bacterial food-borne pathogen within the European Union, and poultry meat is an important vehicle for its transmission to humans. However, there is limited knowledge about how this organism persists in broiler litter and faeces. The aim of this study was to assess the impact of a number of environmental parameters, such as temperature, humidity, and oxygen, on Campylobacter survival in both broiler litter and faeces.

MATERIALS AND METHODS

Used litter was collected from a Campylobacter-negative broiler house after final depopulation and fresh faeces were collected from transport crates. Samples were confirmed as Campylobacter negative according to modified ISO methods for veterinary samples. Both sample matrices were inoculated with 9 log10 CFU/ml C. jejuni and incubated under high (≥85%) and low (≤70%) relative humidity conditions at three different temperatures (20°C, 25°C, and 30°C) under both aerobic and microaerophilic atmospheres. Inoculated litter samples were then tested for Campylobacter concentrations at time zero and every 2 hours for 12 hours, while faecal samples were examined at time zero and every 24 hours for 120 hours. A two-tailed t-test assuming unequal variance was used to compare mean Campylobacter concentrations in samples under the various temperature, humidity, and atmospheric conditions.

RESULTS AND DISCUSSION

C. jejuni survived significantly longer (P≤0.01) in faeces, with a minimum survival time of 48 hours, compared with 4 hours in used broiler litter. C. jejuni survival was significantly enhanced at 20°C in all environmental conditions in both sample matrices tested compared with survival at 25°C and 30°C. In general, survival was greater in microaerophilic compared with aerobic conditions in both sample matrices. Humidity, at the levels examined, did not appear to significantly impact C. jejuni survival in any sample matrix. The persistence of Campylobacter in broiler litter and faeces under various environmental conditions has implications for farm litter management, hygiene, and disinfection practices.

Draft Genome Sequence of Campylobacter jejuni Bf, an Atypical Strain Able To Grow under Aerobiosis

In this study, we describe the draft genome sequence of a Campylobacter jejuni clinical isolate issued from a French patient suffering from severe campylobacteriosis. This atypical strain is characterized by an unusual resistance to oxygen and the ability to grow under an aerobic atmosphere, a characteristic as-of-yet unique to this species.

Draft Genome Sequence of the Enteropathogenic Bacterium Campylobacter jejuni Strain cj255

The enteropathogen Campylobacter jejuni is a global health disaster, being one of the leading causes of bacterial gastroenteritis. Here, we present the draft genome sequence of C. jejuni strain cj255, isolated from a chicken source in Islamabad, Pakistan. The draft genome sequence will aid in epidemiological studies and quarantine of this broad-host-range pathogen.

Molecular detection identified a type six secretion system in Campylobacter jejuni from various sources but not from human cases

AIM

To determine the presence of the T6SS in Campylobacter jejuni from diverse sources.

METHODS AND RESULTS

The recently identified type VI secretion system (T6SS) is a bacterial injection machinery that plays a role in virulence, symbiosis, bacterial interactions and environmental stress responses. This system has been recently discovered in the major enteric pathogen Camp. jejuni. In this study, we used multiplex PCR (mPCR), based on conserved genetic markers of the T6SS, to screen 366 Pakistani Camp. jejuni isolates from humans, poultry, cattle, wildlife or waste-water sources. We identified the T6SS in isolates from all of these sources except humans. The overall prevalence of the T6SS among the isolates was 17/366 (4·6%) and the T6SS positive isolates clustered into four different groups. Transcription of the T6SS genes, determined using RT-PCR, was observed in bacteria cultured at 37 or 42°C but not in 37°C cultures adjusted to pH3.

CONCLUSIONS

Campylobacter jejuni isolates harbouring T6SS markers genes were identified in livestock and non-livestock sources but in this study we did not identify human diarrhoeal isolates which possessed the T6SS. We demonstrated down-regulation of T6SS in an acidic environment.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study questions the role of the T6SS in human diarrhoeal disease. Moreover this study did not identify a clear association of Camp. jejuni isolates harbouring T6SS with any of the niches tested. Our study highlights the need to establish the role of the T6SS in environmental survival or virulence.

Reduction of the temperature sensitivity of Halomonas hydrothermalis by iron starvation combined with microaerobic conditions

The limits to biological processes on Earth are determined by physicochemical parameters, such as extremes of temperature and low water availability. Research into microbial extremophiles has enhanced our understanding of the biophysical boundaries which define the biosphere. However, there remains a paucity of information on the degree to which rates of microbial multiplication within extreme environments are determined by the availability of specific chemical elements. Here, we show that iron availability and the composition of the gaseous phase (aerobic versus microaerobic) determine the susceptibility of a marine bacterium, Halomonas hydrothermalis, to suboptimal and elevated temperature and salinity by impacting rates of cell division (but not viability). In particular, iron starvation combined with microaerobic conditions (5% [vol/vol] O2, 10% [vol/vol] CO2, reduced pH) reduced sensitivity to temperature across the 13°C range tested. These data demonstrate that nutrient limitation interacts with physicochemical parameters to determine biological permissiveness for extreme environments. The interplay between resource availability and stress tolerance, therefore, may shape the distribution and ecology of microorganisms within Earth's biosphere.

FTIR spectroscopic evaluation of changes in the cellular biochemical composition of the phytopathogenic fungus Alternaria alternata induced by extracts of some Greek medicinal and aromatic plants

In this study, the biological activity of aquatic extracts of selected Greek medicinal and aromatic plants to the phytopathogenic fungus Alternaria alternata was investigated. Lamiaceae species (Hyssopus officinalis L., Melissa officinalis L., Origanum dictamnus L., Origanum vulgare L. and Salvia officinalis L.) were found to enhance significantly the mycelium growth whereas Crocus sativus appears to inhibit it slightly. M. officinalis and S. officinalis caused the highest stimulation in mycelium growth (+97%) and conidia production (+65%) respectively. In order to further investigate the bioactivity of plant extracts to A. alternata, we employed Fourier Transform Infrared Spectroscopy (FTIR). Differences of original spectra were assigned mainly to amides of proteins. The second derivative transformation of spectra revealed changes in spectral regions corresponding to absorptions of the major cellular constituents such as cell membrane and proteins. Principal component analysis of the second derivative transformed spectra confirmed that fatty acids of the cell membranes, amides of proteins and polysaccharides of the cell wall had the major contribution to data variation. FTIR band area ratios were found to correlate with fungal mycelium growth.

Investigating the responses of Cronobacter sakazakii to garlic-drived organosulfur compounds: a systematic study of pathogenic-bacterium injury by use of high-throughput whole-transcriptome sequencing and confocal micro-raman spectroscopy

We present the results of a study using high-throughput whole-transcriptome sequencing (RNA-seq) and vibrational spectroscopy to characterize and fingerprint pathogenic-bacterium injury under conditions of unfavorable stress. Two garlic-derived organosulfur compounds were found to be highly effective antimicrobial compounds against Cronobacter sakazakii, a leading pathogen associated with invasive infection of infants and causing meningitis, necrotizing entercolitis, and bacteremia. RNA-seq shows changes in gene expression patterns and transcriptomic response, while confocal micro-Raman spectroscopy characterizes macromolecular changes in the bacterial cell resulting from this chemical stress. RNA-seq analyses showed that the bacterial response to ajoene differed from the response to diallyl sulfide. Specifically, ajoene caused downregulation of motility-related genes, while diallyl sulfide treatment caused an increased expression of cell wall synthesis genes. Confocal micro-Raman spectroscopy revealed that the two compounds appear to have the same phase I antimicrobial mechanism of binding to thiol-containing proteins/enzymes in bacterial cells generating a disulfide stretching band but different phase II antimicrobial mechanisms, showing alterations in the secondary structures of proteins in two different ways. Diallyl sulfide primarily altered the α-helix and β-sheet, as reflected in changes in amide I, while ajoene altered the structures containing phenylalanine and tyrosine. Bayesian probability analysis validated the ability of principal component analysis to differentiate treated and control C. sakazakii cells. Scanning electron microscopy confirmed cell injury, showing significant morphological variations in cells following treatments by these two compounds. Findings from this study aid in the development of effective intervention strategies to reduce the risk of C. sakazakii contamination in the food production environment and on food contact surfaces, reducing the risks to susceptible consumers.

Hydrogen-producing Escherichia coli strains overexpressing lactose permease: FT-IR analysis of the lactose-induced stress

The lactose permease gene (lacY) was overexpressed in the septuple knockout mutant of Escherichia coli, previously engineered for hydrogen production from glucose. It was expected that raising the lactose transporter activity would elevate the intracellular lactose concentration, inactivate the lactose repressor, induce the lactose operon, and as a result stimulate overall lactose consumption and conversion. However, overexpression of the lactose transporter caused a considerable growth delay in the recombinant strain on lactose, resembling to some extent the "lactose killing" phenomenon. Therefore, the recombinant strain was subjected to selection on lactose-containing media. Selection on plates with 3% lactose yielded a strain with a decreased content of the recombinant plasmid but with an improved ability to grow and produce hydrogen on lactose. Macromolecular analysis of its biomass by means of Fourier transform-infrared spectroscopy demonstrated that increase of the cellular polysaccharide content might contribute to the adaptation of E. coli to lactose stress.

Examination of nanoparticle inactivation of Campylobacter jejuni biofilms using infrared and Raman spectroscopies

AIMS

To investigate inactivation effect and mechanism of zinc oxide nanoparticles (ZnO NPs) activity against Campylobacter jejuni biofilms.

METHODS AND RESULTS

ZnO NPs with concentrations of 0, 0·6, 1·2 and 6 mmol l(-1) were employed in antimicrobial tests against Camp. jejuni planktonic cells and biofilms. Campylobacter jejuni sessile cells in biofilms were more resistant to a low concentration of ZnO NPs when compared to planktonic cells. The ZnO NPs penetrated the extracellular polymeric substance (EPS) without damage to the EPS and directly interacted with the sessile bacterial cells, as determined using infrared spectroscopy and scanning electron microscopy. Raman spectroscopy shows alterations in quinone structures and damage to nucleic acids following Camp. jejuni treatment with ZnO NPs. The mechanism of DNA damage is most likely due to the generation of reactive oxygen species (ROS). Spectroscopic-based partial least squares regression (PLSR) models could predict the number of surviving sessile cell numbers within a bacterial biofilm (≥log 4 CFU, root mean square error of estimation <0·36) from Fourier transform infrared (FT-IR) spectral measurements.

CONCLUSIONS

ZnO NPs were found to have antimicrobial activity against Camp. jejuni biofilms. ZnO NPs penetrated the biofilm EPS within 1 h without damaging it and interacted directly with sessile cells in biofilms. Alterations in the DNA/RNA bases, which are owing to the generation of ROS, appear to result in Camp. jejuni cell death.

SIGNIFICANCE AND IMPACT OF THE STUDY

ZnO NPs may offer a realistic strategy to eliminate Camp. jejuni biofilms in the environment.

Antimicrobial effect of diallyl sulphide on Campylobacter jejuni biofilms

OBJECTIVES

Bacterial biofilms pose significant food safety risks because of their attachment to fomites and food surfaces, including fresh produce surfaces. The purpose of this study was to systematically investigate the activity of selected antimicrobials on Campylobacter jejuni biofilms.

METHODS

C. jejuni biofilms and planktonic cells were treated with ciprofloxacin, erythromycin and diallyl sulphide and examined using infrared and Raman spectroscopies coupled with imaging analysis.

RESULTS

Diallyl sulphide eliminated planktonic cells and sessile cells in biofilms at a concentration that was at least 100-fold less than used for either ciprofloxacin or erythromycin on the basis of molarity. Distinct cell lysis was observed in diallyl sulphide-treated planktonic cells using immunoblot analysis and was confirmed by a rapid decrease in cellular ATP. Two phases of C. jejuni biofilm recalcitrance modes against ciprofloxacin and erythromycin were validated using vibrational spectroscopies: (i) an initial hindered adsorption into biofilm extracellular polymeric substance (EPS) and delivery of antibiotics to sessile cells within biofilms; and (ii) a different interaction between sessile cells in a biofilm compared with their planktonic counterparts. Diallyl sulphide destroyed the EPS structure of the C. jejuni biofilm, after which the sessile cells were killed in a similar manner as planktonic cells. Spectroscopic models can predict the survival of sessile cells within biofilms.

CONCLUSIONS

Diallyl sulphide elicits strong antimicrobial activity against planktonic and sessile C. jejuni and may have applications for reducing the prevalence of this microbe in foods, biofilm reduction and, potentially, as an alternative chemotherapeutic agent for multidrug-resistant bacterial strains.

Fate and Survival of Campylobacter coli in Swine Manure at Various Temperatures

Campylobacter coli is the most common Campylobacter species found in pig (95%), but the ability of this bacterium to survive in swine manure as well as the potential for causing human illness are poorly understood. We present here laboratory-scale experiments to investigate the effect of temperature on the survival of C. coli in spiked swine manure samples at temperatures from 4 to 52°C. The survival of C. coli during storage for 30 days was studied by three different methods: bacterial culture (plate counting), DNA qPCR, and mRNA RT-qPCR. The results indicate that C. coli could survive in swine manure up to 24 days at 4°C. At higher temperatures, this bacterium survived only 7 days (15°C) or 6 days (22°C) of storage. The survival of C. coli was extremely short (few hours) in samples incubated at 42 and 52°C. The results from the RT-qPCR method were consistent with the data from the bacterial culture method, indicating that it detected only viable C. coli cells, thus eliminating false-positive resulting from DNA from dead C. coli cells.

Physiological characterization of Campylobacter jejuni under cold stresses conditions: its potential for public threat

Campylobacter jejuni is the major cause of human gastroenteritis worldwide. Under stress conditions, C. jejuni can enter a viable but non-culturable (VBNC) state. We found that the C. jejuni was able to enter a VBNC state by prolonged incubation at 4°C. The standard isolation methods using pre-enrichment steps in Bolton broth or Preston broth could not detect the VBNC cells in spiked chicken meat. The transcription levels of virulence-associated genes (flaA, flaB, cadF, ciaB, cdtA, cdtB and cdtC) were expressed in VBNC cells but in low levels. The VBNC cells retained the ability to invade Caco-2 human intestinal epithelial cells in vitro. In most cases, VBNC cells failed to resuscitate in Caco-2 cells, but in some experiments, they formed colonies after co-incubation with host cells. Collectively, C. jejuni enters into a VBNC state at 4°C and the VBNC C. jejuni remains virulent which may possibly lead to disease in humans. C. jejuni in VBNC state is a potential concern for food safety.

Infrared and Raman spectroscopic studies of the antimicrobial effects of garlic concentrates and diallyl constituents on foodborne pathogens

The antimicrobial effects of garlic (Allium sativum) extract (25, 50, 75, 100, and 200 μL/ml) and diallyl sulfide (5, 10, and 20 μM) on Listeria monocytogenes and Escherichia coli O157:H7 cultivated in tryptic soy broth at 4, 22, and 35 °C for up to 7 days were investigated. L. monocytogenes was more resistant to garlic extract and diallyl compounds treatment than E. coli O157:H7. Fourier transform infrared (FT-IR) spectroscopy indicated that diallyl constituents contributed more to the antimicrobial effect than phenolic compounds. This effect was verified by Raman spectroscopy and Raman mapping on single bacteria. Scanning electron microscope (SEM) and transmission electron microscope (TEM) showed cell membrane damage consistent with spectroscopic observation. The degree of bacterial cell injury could be quantified using chemometric methods.

Antimicrobial edible apple films inactivate antibiotic resistant and susceptible Campylobacter jejuni strains on chicken breast

Campylobacter jejuni is the leading cause of bacterial diarrheal illness worldwide. Many strains are now becoming multidrug resistant. Apple-based edible films containing carvacrol and cinnamaldehyde were evaluated for bactericidal activity against antibiotic resistant and susceptible C. jejuni strains on chicken. Retail chicken breast samples inoculated with D28a and H2a (resistant strains) and A24a (a sensitive strain) were wrapped in apple films containing cinnamaldehyde or carvacrol at 0.5%, 1.5%, and 3% concentrations, and then incubated at 4 or 23 °C for 72 h. Immediately after wrapping and at 72 h, samples were plated for enumeration of viable C. jejuni. The antimicrobial films exhibited dose- and temperature-dependent bactericidal activity against all strains. Films with ≥1.5% cinnamaldehyde reduced populations of all strains to below detection at 23 °C at 72 h. At 4 °C with cinnamaldehyde, reductions were variable for all strains, ranging from 0.2 to 2.5 logs and 1.8 to 6.0 logs at 1.5% and 3.0%, respectively. Films with 3% carvacrol reduced populations of A24a and H2a to below detection, and D28a by 2.4 logs at 23 °C and 72 h. A 0.5-log reduction was observed for both A24a and D28a, and 0.9 logs for H2a at 4 °C at 3% carvacrol. Reductions ranged from 1.1 to 1.9 logs and 0.4 to 1.2 logs with 1.5% and 0.5% carvacrol at 23 °C, respectively. The films with cinnamaldehyde were more effective than carvacrol films. Reductions at 23 °C were greater than those at 4 °C. Our results showed that antimicrobial apple films have the potential to reduce C. jejuni on chicken and therefore, the risk of campylobacteriosis. Possible mechanisms of antimicrobial effects are discussed.

PRACTICAL APPLICATION

  Apple antimicrobial films could potentially be used in retail food packaging to reduce C. jejuni commonly present on food.

Profound differences in the transcriptome of Campylobacter jejuni grown in two different, widely used, microaerobic atmospheres

It was noted that quantitative and qualitative differences occurred between the growth of Campylobacter in microaerobic atmospheres provided by a gas replacement jar and that in a modular atmosphere controlled system cabinet, despite the fact that oxygen levels were comparable. Hydrogen was, however, only present in the replacement mixture (3%). Investigations were therefore carried out to examine any accompanying physiological or transcriptional differences. Growth curves and motility studies using Campylobacter jejuni HPC5 showed that cultures growing in the cabinet were impaired, but only in the early stages of growth compared to growth in the jar. However, transcriptome studies highlighted profound changes in the transcript profiles of exponential cultures grown in the cabinet compared to the jar, including genes indicative of oxidative stress. Genes involved in detoxification, synthesis and modification of macromolecules, probable prophage genes and genes associated with inhibition of natural transformation showed relative increases in expression in the cabinet. Conversely, genes that function in energy metabolism, chaperones, heat shock and motility were increased in the jar, which was indicative of balanced growth. This work highlights the need to carefully annotate the different methods of atmosphere generation in the description of experiments in microarray databases; the assessment of these experimental details is crucial to overcome difficulties in comparing transcriptomic studies of campylobacter cultures between different laboratories.

Fourier transform infrared spectroscopy as a tool to characterize molecular composition and stress response in foodborne pathogenic bacteria

Vibrational spectroscopy techniques have shown capacity to provide non-destructive, rapid, relevant information on microbial systematics, useful for classification and identification. Infrared spectroscopy enables the biochemical signatures from microbiological structures to be extracted and analyzed, in conjunction with advanced chemometrics. In addition, a number of recent studies have shown that Fourier Transform Infrared (FT-IR) spectroscopy can help understand the molecular basis of events such as the adaptive tolerance responses expressed by bacteria when exposed to stress conditions in the environment (e.g. those that cells confront in food and during food processing). The current review gives an overview of the published experimental techniques, data-processing algorithms and approaches used in FT-IR spectroscopy to assess the mechanisms of bacterial inactivation by food processing technologies and antimicrobial compounds, to monitor the spore and membrane properties of foodborne pathogens in changing environments, to detect stress-injured microorganisms in food-related environments, to assess dynamic changes in bacterial populations, and to study bacterial tolerance responses.

Responses of Staphylococcus aureus exposed to HCl and organic acid stress

Staphylococcus aureus is an important food poisoning bacterium. In food preservation, acidification is a well-known method. Permeant weak organic acids, like lactic and acetic acids, are known to be more effective against bacteria than inorganic strong acids (e.g., HCl). Growth experiments and metabolic and transcriptional analyses were used to determine the responses of a food pathogenic S. aureus strain exposed to lactic acid, acetic acid, and HCl at pH 4.5. Lactic and acetic acid stress induced a slower transcriptional response and large variations in growth patterns compared with the responses induced by HCl. In cultures acidified with lactic acid, the pH of the medium gradually increased to 7.5 during growth, while no such increase was observed for bacteria exposed to acetic acid or HCl. Staphylococcus aureus increased the pH in the medium mainly through accumulation of ammonium and the removal of acid groups, resulting in increased production of diacetyl (2,3-butanedione) and pyrazines. The results showed flexible and versatile responses of S. aureus to different types of acid stress. As measured by growth inhibition, permeant organic acid stress introduced severe stress compared with the stress caused by HCl. Cells exposed to lactic acid showed specific mechanisms of action in addition to sharing many of the mechanisms induced by HCl stress.

Clinician-rated mental health in outpatient child and adolescent mental health services: associations with parent, teacher and adolescent ratings

BACKGROUND

Clinician-rated measures are used extensively in child and adolescent mental health services (CAMHS). The Health of the Nation Outcome Scales for Children and Adolescents (HoNOSCA) is a short clinician-rated measure developed for ordinary clinical practice, with increasing use internationally. Several studies have investigated its psychometric properties, but there are few data on its correspondence with other methods, rated by other informants. We compared the HoNOSCA with the well-established Achenbach System of Empirically Based Assessment (ASEBA) questionnaires: the Child Behavior Checklist (CBCL), the Teacher's Report Form (TRF), and the Youth Self-Report (YSR).

METHODS

Data on 153 patients aged 6-17 years at seven outpatient CAMHS clinics in Norway were analysed. Clinicians completed the HoNOSCA, whereas parents, teachers, and adolescents filled in the ASEBA forms. HoNOSCA total score and nine of its scales were compared with similar ASEBA scales. With a multiple regression model, we investigated how the ASEBA ratings predicted the clinician-rated HoNOSCA and whether the different informants' scores made any unique contribution to the prediction of the HoNOSCA scales.

RESULTS

We found moderate correlations between the total problems rated by the clinicians (HoNOSCA) and by the other informants (ASEBA) and good correspondence between eight of the nine HoNOSCA scales and the similar ASEBA scales. The exception was HoNOSCA scale 8 psychosomatic symptoms compared with the ASEBA somatic problems scale. In the regression analyses, the CBCL and TRF total problems scores together explained 27% of the variance in the HoNOSCA total scores (23% for the age group 11-17 years, also including the YSR). The CBCL provided unique information for the prediction of the HoNOSCA total score, HoNOSCA scale 1 aggressive behaviour, HoNOSCA scale 2 overactivity or attention problems, HoNOSCA scale 9 emotional symptoms, and HoNOSCA scale 10 peer problems; the TRF for all these except HoNOSCA scale 9 emotional symptoms; and the YSR for HoNOSCA scale 9 emotional symptoms only.

CONCLUSION

This study supports the concurrent validity of the HoNOSCA. It also demonstrates that parents, teachers and adolescents all contribute unique information in relation to the clinician-rated HoNOSCA, indicating that the HoNOSCA ratings reflect unique perspectives from multiple informants.

Different contributions of HtrA protease and chaperone activities to Campylobacter jejuni stress tolerance and physiology

The microaerophilic bacterium Campylobacter jejuni is the most common cause of bacterial food-borne infections in the developed world. Tolerance to environmental stress relies on proteases and chaperones in the cell envelope, such as HtrA and SurA. HtrA displays both chaperone and protease activities, but little is known about how each of these activities contributes to stress tolerance in bacteria. In vitro experiments showed temperature-dependent protease and chaperone activities of C. jejuni HtrA. A C. jejuni mutant lacking only the protease activity of HtrA was used to show that the HtrA chaperone activity is sufficient for growth at high temperature or under oxidative stress, whereas the HtrA protease activity is essential only under conditions close to the growth limit for C. jejuni. However, the protease activity was required to prevent induction of the cytoplasmic heat shock response even under optimal growth conditions. Interestingly, the requirement of HtrA at high temperatures was found to depend on the oxygen level, and our data suggest that HtrA may protect oxidatively damaged proteins. Finally, protease activity stimulates HtrA production and oligomer formation, suggesting that a regulatory role depends on the protease activity of HtrA. Studying a microaerophilic organism encoding only two known periplasmic chaperones (HtrA and SurA) revealed an efficient HtrA chaperone activity and proposed multiple roles of the protease activity, increasing our understanding of HtrA in bacterial physiology.

Effect of chicken meat environment on gene expression of Campylobacter jejuni and its relevance to survival in food

Poultry meat is the major food source responsible for gastrointestinal infections caused by the human pathogen Campylobacter jejuni. Even though C. jejuni does not grow below 30 °C, the bacterium survives on raw meat surfaces at refrigerated temperatures and thus poses a risk to the consumer. Previously, we have shown that chicken meat juice prolongs survival of C. jejuni at 5 °C compared to laboratory medium, suggesting that compounds present in meat juice influence adaptation to low temperatures. In the present study we have used chicken meat juice to identify C. jejuni genes that are differentially expressed in a typical chicken meat environment encountered by consumers. The analysis showed that chicken meat juice increased expression of luxS involved in quorum sensing, as well as a gene involved in O-linked flagellin glycosylation in C. jejuni, while expression of haemin uptake and the peroxide stress response genes were reduced. Furthermore, we propose that LuxS may play a key role in adaptation to the chicken meat juice environment, as lack of the luxS gene reduces the ability of C. jejuni to survive in chicken meat juice at low temperature. Finally, our data suggest that part of an ABC transport system is induced and we speculate that uptake of cryoprotectants may be important for C. jejuni to adapt to low temperature. In summary, we found that C. jejuni has a specific but limited transcriptional response to chicken meat juice and that luxS has an impact on the prolonged survival of C. jejuni in this important environment in the food chain.

Identification of proteins related to the stress response in Enterococcus faecalis V583 caused by bovine bile

BACKGROUND

Enterococcus faecalis is an opportunistic pathogen and one of the most important causes of hospital infections. Bile acids are a major stress factor bacteria have to cope with in order to colonize and survive in the gastro-intestinal tract. The aim of this study was to investigate the effects of bile acids on the intracellular proteome of E. faecalis V583.

RESULTS

The proteomes of cells challenged with 1% bile were analyzed after 20 - 120 minutes exposure, using 2D gel electrophoresis and mass spectrometry. Among the approximately 500 observed proteins, 53 unique proteins were found to be regulated in response to bile and were identified with mass spectrometry. The identified proteins belonged to nine different functional classes, including fatty acid- and phospholipid-biosynthesis, energy metabolism, and transport and binding. Proteins involved in fatty acid and phospholipid biosynthesis pathways were clearly overrepresented among the identified proteins and all were down-regulated upon exposure to bile. The proteome data correlated reasonably well with data from previous transcriptome experiments done under the same conditions, but several differences were observed.

CONCLUSION

The results provide an overview of potentially important proteins that E. faecalis V583 needs to regulate in order to survive and adapt to a bile-rich environment, among which are several proteins involved in fatty acid and phospholipid biosynthesis pathways. In addition, this study reveals several hypothetical proteins, which are both abundant and clearly regulated and thus stand out as targets for future studies on bile stress.

Survival mechanisms and culturability of Campylobacter jejuni under stress conditions

Culture-based isolation and enumeration of bacterial human pathogens from environmental and human food samples has significant limitations.Many pathogens enter a viable but non-culturable(VBNC) state in response to stress, and cannot be detected via culturing methods. Favourable growth conditions with a source of energy and an ideal stoichiometric ratio of carbon to inorganic elements can reverse this VBNC state. This review will focus on the bacterium Campylobacter jejuni which is a leading cause of food borne illness in the developed world. C. jejuni can enter a VBNC state in response to extremes in: pH, moisture content, temperature,nutrient content and salinity. Once in a VBNC state,the organism must maintain an energy balance from substrate oxidation through respiration to grow,divide and remain viable. The goal of this review isa greater understanding of how abiotic stress and thermodynamics influence the viability of C. jejuni.

Long-term survival of Campylobacter jejuni at low temperatures is dependent on polynucleotide phosphorylase activity

Campylobacter jejuni is a leading cause of bacterial gastroenteritis worldwide. Infection generally occurs after ingestion of contaminated poultry products, usually conserved at low temperatures. The mechanisms promoting survival of C. jejuni in the cold remain poorly understood despite several investigations. The present study provides insight into the survival mechanism by establishing the involvement of polynucleotide phosphorylase (PNPase), a 3'-5' exoribonuclease with multiple biological functions in cold survival. The role of PNPase was demonstrated genetically using strains with altered pnp genes (which encode PNPase) created in C. jejuni F38011 and C. jejuni 81-76 backgrounds. Survival assays carried out at low temperatures (4 and 10 degrees C) revealed a difference of 3 log CFU/ml between the wild-type and the pnp deletion (Deltapnp) strains. This did not result from a general requirement for PNPase because survival rates of the strains were similar at higher growth temperatures (37 or 42 degrees C). trans-Complementation with plasmid pNH04 carrying the pnp gene under the control of its natural promoter restored the cold survival phenotype to the pnp deletion strains (at 4 and 10 degrees C) but not to the same level as the wild type. In this study we demonstrate the role of PNPase in low-temperature survival of C. jejuni and therefore attribute a novel biological function to PNPase directly related to human health.

Global responses ofEscherichia colito adverse conditions determined by microarrays and FT-IR spectroscopy

The global gene expression and biomolecular composition in an Escherichia coli model strain exposed to 10 adverse conditions (sodium chloride, ethanol, glycerol, hydrochloric and acetic acid, sodium hydroxide, heat (46 °C), and cold (15 °C), as well as ethidium bromide and the disinfectant benzalkonium chloride) were determined using DNA microarrays and Fourier transform infrared (FT-IR) spectroscopy. In total, approximately 40% of all investigated genes (1682/4279 genes) significantly changed expression, compared with a nonstressed control. There were, however, only 3 genes (ygaW (unknown function), rmf (encoding a ribosomal modification factor), and ghrA (encoding a glyoxylate/hydroxypyruvate reductase)) that significantly changed expression under all conditions (not including benzalkonium chloride). The FT-IR analysis showed an increase in unsaturated fatty acids during ethanol and cold exposure, and a decrease during acid and heat exposure. Cold conditions induced changes in the carbohydrate composition of the cell, possibly related to the upregulation of outer membrane genes (glgAP and rcsA). Although some covariance was observed between the 2 data sets, principle component analysis and regression analyses revealed that the gene expression and the biomolecular responses are not well correlated in stressed populations of E. coli, underlining the importance of multiple strategies to begin to understand the effect on the whole cell.