Photobacterium profundum under Pressure:A MS-Based Label-Free Quantitative Proteomics Study

Photobacterium profundum SS9 is a Gram-negative bacterium, originally collected from the Sulu Sea. Its genome consists of two chromosomes and a 80 kb plasmid. Although it can grow under a wide range of pressures, P. profundum grows optimally at 28 MPa and 15°C. Its ability to grow at atmospheric pressure allows for both easy genetic manipulation and culture, making it a model organism to study piezophily. Here, we report a shotgun proteomic analysis of P. profundum grown at atmospheric compared to high pressure using label-free quantitation and mass spectrometry analysis. We have identified differentially expressed proteins involved in high pressure adaptation, which have been previously reported using other methods. Proteins involved in key metabolic pathways were also identified as being differentially expressed. Proteins involved in the glycolysis/gluconeogenesis pathway were up-regulated at high pressure. Conversely, several proteins involved in the oxidative phosphorylation pathway were up-regulated at atmospheric pressure. Some of the proteins that were differentially identified are regulated directly in response to the physical impact of pressure. The expression of some proteins involved in nutrient transport or assimilation, are likely to be directly regulated by pressure. In a natural environment, different hydrostatic pressures represent distinct ecosystems with their own particular nutrient limitations and abundances. However, the only variable considered in this study was atmospheric pressure

Genomic characterization of the most barotolerant Listeria monocytogenes RO15 strain compared to reference strains used to evaluate food high pressure processing

BackgroundHigh pressure processing (HPP; i.e. 100-600MPa pressure depending on product) is a non-thermal preservation technique adopted by the food industry to decrease significantly foodborne pathogens, including Listeria monocytogenes, from food. However, susceptibility towards pressure differs among diverse strains of L. monocytogenes and it is unclear if this is due to their intrinsic characteristics related to genomic content. Here, we tested the barotolerance of 10 different L. monocytogenes strains, from food and food processing environments and widely used reference strains including clinical isolate, to pressure treatments with 400 and 600MPa. Genome sequencing and genome comparison of the tested L. monocytogenes strains were performed to investigate the relation between genomic profile and pressure tolerance.ResultsNone of the tested strains were tolerant to 600MPa. A reduction of more than 5 log(10) was observed for all strains after 1min 600MPa pressure treatment. L. monocytogenes strain RO15 showed no significant reduction in viable cell counts after 400MPa for 1min and was therefore defined as barotolerant. Genome analysis of so far unsequenced L. monocytogenes strain RO15, 2HF33, MB5, AB199, AB120, C7, and RO4 allowed us to compare the gene content of all strains tested. This revealed that the three most pressure tolerant strains had more than one CRISPR system with self-targeting spacers. Furthermore, several anti-CRISPR genes were detected in these strains. Pan-genome analysis showed that 10 prophage genes were significantly associated with the three most barotolerant strains.ConclusionsL. monocytogenes strain RO15 was the most pressure tolerant among the selected strains. Genome comparison suggests that there might be a relationship between prophages and pressure tolerance in L. monocytogenes.Peer reviewe

NATO-SPS Pilot Study on Food Chain Security: Findings and Recommendations

The chapter reports the outcomes of an ongoing NATO-SPS Pilot Study on "Food Chain Security." These include (1) Overview of the food system in participating countries; (2) Prevention, surveillance and detection systems and (3) Response systems. A survey was carried out in order to identify the concerns of the food industries with regard to contamination of the food chain (i.e. what did the industry perceive as the main hazards associated with the food chain?); to evaluate the extent to which food safety management systems had been implemented as a safeguard against contamination incidents and to determine the feasibility and limitations of conducting such a survey within participating countries. A survey tool was prepared and sent to public and private food sector(s) by each group member. A total of 18 different countries participated in the pilot study and nine countries completed the survey. Participants' views were gathered, and the outcomes are discussed in terms of reducing possible risks and threats to the food system. The detailed analysis of the outcomes will be a key to address to the countermeasures that are necessary to be taken to minimize the adverse effect(s) on human health, society, and environment at large. The possible scenarios developed by the experts in the project duration are shared. These are believed to be useful in developing a prototype system and for sharing information related to acts of terrorism to the environment, agriculture, and water systems. The final outputs given here allow some comparison between country partners and identify common weaknesses of the food systems in general. The importance of continuing exchange of experience between participating countries in the area of legal regulations, logistical and institutional aspects of food safety is highly encouraged

High hydrostatic pressure effects on mold flora, citrinin mycotoxin, hydroxytyrosol, oleuropein phenolics and antioxidant activity of black table olives

High hydrostatic pressure (HHP) as a non-thermal technology is an effective tool for microbiologically safe and shelf-stable fruits. Mycotoxin citrinin (CIT) is a toxic secondary metabolite, especially produced from filamentous fungus Penicillium citrinum and is also produced by other species of Penicillium, Aspergillus, and Monascus that are able to develop on olive after harvest, during brine and storage of olives. Nutritional benefits of olive fruit are mainly related to phenolics such as hydroxytyrosol, oleuropein and antioxidative effects. With HHP application of olives, total mold was reduced to 90% at 25 °C whereas it was 100% at 4 °C based on Rose-Bengal Chloramphenicol Agar (RBCA). Total Aerobic-Mesofilic Bacteria load was reduced to 35-76% at 35 ± 2 °C based on the Plate Count Agar (PCA). Citrinin load was reduced to 64-100% at 35 ± 2 °C. 2.5; 10; 25; and 100 ppb of spiked citrinin in sample were degraded as %56; %37; %9; and %1.3, respectively. 2.5 ppb and less citrinin contamination in table olive were degraded more (56%). Total phenolics were increased to 2.1-2.5-fold after HHP (as mgGA/100 g). Hydroxytyrosol in olives increased on average 0.8-2.0-fold whereas oleuropein decreased on average 1-1.2-fold after HHP (as mg/kg dwt). Antioxidant activity values varied from 17.238 to 29.344 mmol Fe2+/100 g for control samples whereas 18.579-32.998 mmol Fe2+/100 g for HHP-treated samples. HHP could be used in the olive industry as non-thermal preservation. © 2009 Elsevier Ltd. All rights reserved