Bacterial Culturability Research Articles

Participation of two general stress response proteins from Xanthomonas citri subsp. citri in environmental stress adaptation and virulence.

Xanthomonas citri subsp. citri (Xcc) is the bacteria responsible for citrus canker. During its life cycle Xcc is found on leaves as epiphyte, where desiccation conditions may occur. In this work, two Xcc genes, XAC0100 and XAC4007, predicted in silico to be involved in general stress response, were studied under salt, osmotic, desiccation, oxidative and freezing stress, and during plant-pathogen interaction. Expression of XAC0100 and XAC4007 genes was induced under these stress conditions. Disruption of both genes in Xcc caused decreased bacterial culturability under desiccation, freezing, osmotic and oxidative stress. Importantly, the lack of these genes impaired Xcc epiphytic fitness. Both Xac0100 and Xac4007 recombinant proteins showed protective effects on Xanthomonas cells subjected to drought stress. Also, Escherichia coli overexpressing Xac4007 showed a better performance under standard culture, saline and osmotic stress and were more tolerant to freezing and oxidative stress than wild type E. coli. Moreover, both Xac0100 and Xac4007 recombinant proteins were able to prevent the freeze-thaw-induced inactivation of L-Lactate dehydrogenase. In conclusion, Xac0100 and Xac4007 have a relevant role as bacteria and protein protectors; and these proteins are crucial to bacterial pathogens that must face environmental stressful conditions that compromise the accomplishment of the complete virulence process.

Microbiota of bovine milk, teat skin, and teat canal: Similarity and variation due to sampling technique and milk fraction

The aim of this study was to evaluate the effect of sampling technique and milk fraction on bovine milk microbiota data and to compare the microbiota in milk to microbiota on the teat end and in the teat canal. Representative milk samples are highly important for assessment of bacteriological findings and microbiota in milk. Samples were obtained from 5 healthy lactating dairy cows at udder quarter level during 1 milking. Swab samples from the teat end and teat canal, and milk samples collected using different techniques and in different milk fractions were included. Milk was collected by hand stripping and through a teat canal cannula before and after machine milking, through a trans-teat wall needle aspirate after milking, and from udder quarter composite milk. The microbiota of the samples was analyzed with sequencing of the V1-V3 region of the 16S rRNA gene. In addition, somatic cell counts and bacterial cultivability were analyzed in the milk samples. Microbiota data were analyzed using multivariate methods, and differences between samples were tested using analysis of similarity (ANOSIM). Differences between samples were further explored via individual studies of the 10 most abundant genera. The microbiota on the teat end, in the teat canal, and in udder quarter composite milk, collected using a milking machine, differed in composition from the microbiota in milk collected directly from the udder quarter. No differences in milk microbiota composition were detected between hand-stripped milk samples, milk samples taken through a teat canal cannula, or milk samples taken as a trans-teat wall needle aspirate before or after milking. We conclude that for aseptic milk samples collected directly from the lactating udder quarter, sampling technique or milk fraction has minor effect on the microbiota composition.

The effects of varied food acid ratios and egg components on Salmonella Typhimurium culturability from raw egg-based sauces

Raw egg-based sauces, such as mayonnaise and aioli, are frequently identified as sources of Salmonella during outbreaks of human cases of foodborne gastrointestinal disease. In this study, we surveyed aioli and mayonnaise recipes from different popular food websites to identify potential risk factors that may lead to the survival of Salmonella Typhimurium. In laboratory experiments, different ratios of food acids were used to determine if lemon juice, vinegar, or a combination of both restricted Salmonella Typhimurium culturability. We found that as long as the pH was below 4.2, bacterial culturability was limited. The use of whole egg alone or in combination with egg yolk was also investigated. Sauce preparations containing whole egg exhibited higher pH and supported Salmonella Typhimurium culturability longer than those containing yolk only. Ten restaurant prepared sauces were also obtained to further characterize the effect of preparation variability. Sauce preparations with a pH ≤ 3.8 did not support bacterial culturability after 4 h incubation at any temperature. The higher the pH the longer Salmonella Typhimurium remained culturable. Based on this study, it is recommended that raw egg-based foods are acidified, then stored at room temperature for at least 4 h prior to consumption.

In vitro antimicrobial effects and mechanism of air plasma‐activated water on Staphylococcus aureus biofilm

AbstractThe deactivation effects and mechanism of plasma‐activated water (PAW) against Staphylococcus aureus biofilm and the inhibitory effect on the biofilm regrowth capacity for the surviving S. aureus post PAW treatment were investigated in vitro. Systematic measurements on bacterial cultivability, metabolic capacity, membrane integrity and intracellular reactive oxygen species (ROS) concentration under two different experimental categories were carried out after PAW treatment. Considerable deactivation effects were discovered on biofilm S. aureus on both prolonging the PAW inducement or treatment time. The rising concentration of intracellular ROS and the PAW‐contained RS might exert synergistic effects in deactivating the biofilm S. aureus. Moreover, the biomass, bacterial cultivability and metabolic capacity of the regrown S. aureus biofilm all significantly declined along with the increasing PAW inducement or treatment time. Therefore, except for the short‐term rapid inactivation effects on the biofilm, the PAW treatment could also exert long‐term inhibitory effects on the regeneration of S. aureus biofilm.

Virulence genes expression in viable but non-culturable state of Listeria monocytogenes in fish meat.

This study aimed to evaluate the fate of Listeria monocytogenes in water microcosm and rainbow trout fillet under salinity stress of 0% and 30% NaCl at refrigerator temperature (4 ± 2 ℃). Bacterial culturability was studied by standard culture and colony count method. Reverse transcription-PCR (RT-PCR) of 16 S rRNA gene was used to detect viability of non-culturable bacteria. Also, the qualitative expression of pathogenic genes (hly and inlA) was studied using RT-PCR. The results showed that bacteria in water microcosm lost their culturability at 13 days under 0% salinity (starvation or distilled water) and at 27 days under 30% salinity; however, bacteria in rainbow trout fillet remained culturable under 0% and 30% NaCl. RT-PCR of 16 S rRNA gene was positive for all treatments during the period of this study, indicating the entering of L. monocytogenes into the viable but non-culturable state in water microcosm under 0% and 30% NaCl. Also, viable but non-culturable L. monocytogenes retained the expression of hly and inlA genes. So, it could be concluded that L. monocytogenes in viable but non-culturable state can cause serious health problems and further investigation is necessary to elucidate the effects of other processing and storage conditions (light, dark, smoking, etc.) on behavior of L. monocytogenes in smoked and salted fish.

Effects of abiotic and biotic factors on Vibrio harveyi ATCC 14126T survival dynamics in seawater microcosms

AME Aquatic Microbial Ecology Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials AME 83:109-118 (2019) - DOI: https://doi.org/10.3354/ame01910 Effects of abiotic and biotic factors on Vibrio harveyi ATCC 14126T survival dynamics in seawater microcosms Maite Orruño1,2,*, Claudia Parada1, Elixabet Ogayar1, Vladimir R. Kaberdin1,2,3, Inés Arana1,2 1Department of Immunology, Microbiology and Parasitology, Faculty of Science and Technology, University of the Basque Country UPV/EHU, 48340 Leioa, Spain 2Research Centre for Experimental Marine Biology and Biotechnology (PIE-UPV/EHU), 48620 Plentzia, Spain 3IKERBASQUE, Basque Foundation for Science, 48013 Bilbao, Spain *Corresponding author: maite.orruno@ehu.es ABSTRACT: The ability of marine bacteria to adequately respond to environmental abiotic and biotic stressors ensures that they can thrive in diverse aquatic ecosystems. Here, we showed that interaction of Vibrio harveyi with natural microbiota can greatly reduce the number of vibrios, and this effect was dependent on temperature. In contrast, the impact of abiotic stress factors was less hostile, primarily affecting V. harveyi morphology and physiological state. Although exposure to an oligohaline environment (0.5‰) and nutrient limitation led to a rapid and irreversible loss of V. harveyi culturability, higher salinities (15-35.5‰) induced transition to the viable but nonculturable (VBNC) state and cell size reduction in a temperature-dependent manner. Namely, while low temperature (4°C) caused a marked loss of culturability resulting in a dominant VBNC population, higher temperatures (12, 20 and 30°C) affected bacterial culturability to a lesser extent, but resulted in shorter cells after prolonged incubation, especially at 20 and 30°C. In summary, our results define temperature as a key factor that influences V. harveyi physiology, morphology and persistence in aquatic systems. KEY WORDS: Vibrio harveyi · Temperature · Predation · Viable but nonculturable Full text in pdf format NextCite this article as: Orruño M, Parada C, Ogayar E, Kaberdin VR, Arana I (2019) Effects of abiotic and biotic factors on Vibrio harveyi ATCC 14126T survival dynamics in seawater microcosms. Aquat Microb Ecol 83:109-118. https://doi.org/10.3354/ame01910 Export citation Mail this link - Contents Mailing Lists - RSS Facebook - Tweet - linkedIn Cited by Published in AME Vol. 83, No. 2. Online publication date: July 11, 2019 Print ISSN: 0948-3055; Online ISSN: 1616-1564 Copyright © 2019 Inter-Research.

Among Live and Dead Bacteria, the Optimization of Sample Collection and Processing Remains Essential in Recovering Gut Microbiota Components.

The human gut microbiota plays an important role in human health. Accessing and culturing the gut microbes remains critical in microbiology. The culturomics approach, combined with sequencing strategies, provides new insights in the study of gut microbiota components. However, we are still far from having described all the microbes. Many factors are involved in recovering as much bacteria as possible. One of the most important factors is sample preparation and conservation. The aim of the present work was to evaluate three different types of stool sample conditioning by mainly studying the effect of atmospheric oxygen on bacterial viability and culturability. Quantitative analysis of fecal samples from eight different healthy individuals was carried out using a culture-independent method (flow cytometry) and a culture-dependent method (plating technique). We found that the cultured bacteria reached a 50% yield when the samples were exposed to oxygen for 120 min without any protectant medium, while the percentage of culturability increased to 67% in the presence of antioxidants. More importantly, when samples were exposed to oxygen for less than 2 min, combined with the work under the anaerobic chamber, no discordance was found between the two counting techniques and the culturability increased to 87%. Our study confirmed the importance of sample conditioning to preserve the bacterial viability in samples, especially for oxygen-sensitive intestinal bacteria.

Culturability, metabolic activity and composition of ambient bacterial aerosols in a surrogate lung fluid

Interactions of particulate matter (PM) and respiratory tract play a crucial role in PM-related respiratory diseases. The majority of the work focuses on the oxidative stress induced by reactions between PM-borne redox-active components and lung lining fluid (LLF). The effects of PM-borne biological components are largely unknown. Of all PM-borne biologicals, bacteria, as living microorganisms, are closely related with inflammatory immune responses. However, its inhalation risk is usually determined without considering the respiratory physiological conditions. In this study, a surrogate lung fluid (SLF) with four typical antioxidants was applied to characterize the ambient bacteria, including concentrations of total bacteria/viable bacteria/culturable bacteria, metabolic activity, bacteria-derived endotoxin, as well as the community structure. Comparing to those determined by SLF, we find that use of PBS leads to an underestimation of the bacterial culturability and metabolic activity. No effect was seen regarding the number of total bacteria and viable bacteria (with intact membrane). Population structure change was seen for bacteria cultured from SLF-collected samples, when compared to that from PBS. Spore-forming bacteria, e.g., genus Bacillus, were found to be easily recovered with SLF. This implies that use of PBS could underestimate the bacteria inhalation risk, especially those bacterial endospores. Our work highlights the necessity to consider the respiratory airway environment when evaluating microbial inhalation risk.

High proportions of bacteria are culturable across major biomes.

The paradigm that only 1% of microbes are culturable has had a profound impact on our understanding of microbial ecology and is still a major motivation for mostly using molecular tools to characterize microbial communities. However, this point is often expressed vaguely, suggesting that some scientists have different interpretations of the paradigm. In addition, there have been substantial advances in cultivation techniques suggesting that this paradigm may no longer be correct. To quantify bacterial culturability across six major biomes, I found that the median 16S rRNA similarity of bacteria to known cultured relatives was 97.3 ± 2.3% (s.d.). Furthermore, 52.0 ± 24% of sequences and 34.9 ± 23% of taxa (defined as >97% similar) had a closely related cultured relative. Thus, many cells and taxa across environments are culturable with known techniques, suggesting that the 1% paradigm is no longer correct.

Soil Bacterial Communities From the Chilean Andean Highlands: Taxonomic Composition and Culturability.

The Atacama Desert is a highly complex, extreme ecosystem which harbors microorganisms remarkable for their biotechnological potential. Here, a soil bacterial prospection was carried out in the high Altiplano region of the Atacama Desert (>3,800 m above sea level; m a.s.l.), where direct anthropogenic interference is minimal. We studied: (1) soil bacterial community composition using high-throughput sequencing of the 16S rRNA gene and (2) bacterial culturability, by using a soil extract medium (SEM) under a factorial design of three factors: temperature (15 and 30°C), nutrient content (high and low nutrient disposal) and oxygen availability (presence and absence). A total of 4,775 OTUs were identified and a total of 101 isolates were selected for 16S rRNA sequencing, 82 of them corresponded to unique or non-redundant sequences. To expand our view of the Altiplano landscape and to obtain a better representation of its microbiome, we complemented our Operational Taxonomic Units (OTUs) and isolate collection with data from other previous data from our group and obtained a merged set of OTUs and isolates that we used to perform our study. Taxonomic comparisons between culturable microbiota and metabarcoding data showed an overrepresentation of the phylum Firmicutes (44% of isolates vs. 2% of OTUs) and an underrepresentation of Proteobacteria (8% of isolates vs. 36% of OTUs). Within the Next Generation Sequencing (NGS) results, 33% of the OTUs were unknown up to genus, revealing an important proportion of putative new species in this environment. Biochemical characterization and analysis extracted from the literature indicated that an important number of our isolates had biotechnological potential. Also, by comparing our results with similar studies on other deserts, the Altiplano highland was most similar to a cold arid desert. In summary, our study contributes to expand the knowledge of soil bacterial communities in the Atacama Desert and complements the pipeline to isolate selective bacteria that could represent new potential biotechnological resources.

High throughput cultivation-based screening on porous aluminum oxide chips allows targeted isolation of antibiotic resistant human gut bacteria.

The emergence of bacterial pathogens that are resistant to clinical antibiotics poses an increasing risk to human health. An important reservoir from which bacterial pathogens can acquire resistance is the human gut microbiota. However, thus far, a substantial fraction of the gut microbiota remains uncultivated and has been little-studied with respect to its resistance reservoir-function. Here, we aimed to isolate yet uncultivated resistant gut bacteria by a targeted approach. Therefore, faecal samples from 20 intensive care patients who had received the prophylactic antibiotic treatment selective digestive decontamination (SDD), i.e. tobramycin, polymyxin E, amphotericin B and cefotaxime, were inoculated anaerobically on porous aluminium oxide chips placed on top of poor and rich agar media, including media supplemented with the SDD antibiotics. Biomass growing on the chips was analysed by 16S rRNA gene amplicon sequencing, showing large inter-individual differences in bacterial cultivability, and enrichment of a range of taxonomically diverse operational taxonomic units (OTUs). Furthermore, growth of Ruminococcaceae (2 OTUs), Enterobacteriaceae (6 OTUs) and Lachnospiraceae (4 OTUs) was significantly inhibited by the SDD antibiotics. Strains belonging to 16 OTUs were candidates for cultivation to pure culture as they shared ≤95% sequence identity with the closest type strain and had a relative abundance of ≥2%. Six of these OTUs were detected on media containing SDD antibiotics, and as such were prime candidates to be studied regarding antibiotic resistance. One of these six OTUs was obtained in pure culture using targeted isolation. This novel strain was resistant to the antibiotics metrodinazole and imipenem. It was initially classified as member of the Ruminococcaceae, though later it was found to share 99% nucleotide identity with the recently published Sellimonas intestinalis BR72T. In conclusion, we show that high-throughput cultivation-based screening of microbial communities can guide targeted isolation of bacteria that serve as reservoirs of antibiotic resistance.

Fate of bacterial indicators and Salmonella in biofilm developed on ultrafiltration membranes treating secondary effluents of domestic wastewater

The fate of representative indicator and pathogenic bacteria on ultrafiltration (UF)-membrane surfaces treating secondary wastewater effluent, as well as their reaction to common biofouling-removal techniques was investigated. Field-condition experiments showed that the number of heterotrophic bacteria, fecal coliforms, E. coli and Salmonella on membrane surface increased rapidly and continuously until the end of the experiment, reaching 9, 6.5, 6, and 2.4 logs, respectively. Similar results were obtained under controlled laboratory conditions. However, the increase in the bacterial numbers was dependent on the supply of fresh wastewater. Quantitative real-time PCR verified the behavior of attached E. coli cells, although the numbers were 1–2 logs higher compared to the standard culture-based method. The number of attached bacteria was positively correlated to increases in DNA and protein content and negatively correlated to the membrane flux. In-situ membrane cleaning using sodium hypochlorite significantly reduced the number of attached bacteria. However, the effect was temporary and affected bacterial cell cultivability rather than viability. Taken together, these findings suggest that, under the studied conditions, indicator and pathogenic bacteria can initiate rapid biofilm development, persist on UF membrane surfaces, and survive membrane cleaning with sodium hypochlorite.

Functional Genetic Diversity and Culturability of Petroleum-Degrading Bacteria Isolated From Oil-Contaminated Soils.

In this study, we compared the culturability of aerobic bacteria isolated from long-term oil-contaminated soils via enrichment and direct-plating methods; bacteria were cultured at 30°C or ambient temperatures. Two soil samples were collected from two sites in the Shengli oilfield located in Dongying, China. One sample (S0) was close to the outlet of an oil-production water treatment plant, and the other sample (S1) was located 500 m downstream of the outlet. In total, 595 bacterial isolates belonging to 56 genera were isolated, distributed in Actinobacteria, Firmicutes, Bacterioidetes, and Proteobacteria. It was interesting that Actinobacteria and Firmicutes were not detected from the 16S rRNA gene clone library. The results suggested the activation of rare species during culture. Using the enrichment method, 239 isolates (31 genera) and 96 (22 genera) isolates were obtained at ambient temperatures and 30°C, respectively, from S0 soil. Using the direct-plating method, 97 isolates (15 genera) and 163 isolates (20 genera) were obtained at ambient temperatures and 30°C, respectively, from two soils. Of the 595 isolates, 244 isolates (41.7% of total isolates) could degrade n-hexadecane. A greater number of alkane-degraders was isolated at ambient temperatures using the enrichment method, suggesting that this method could significantly improve bacterial culturability. Interestingly, the proportion of alkane degrading isolates was lower in the isolates obtained using enrichment method than that obtained using direct-plating methods. Considering the greater species diversity of isolates obtained via the enrichment method, this technique could be used to increase the diversity of the microbial consortia. Furthermore, phenol hydroxylase genes (pheN), medium-chain alkane monooxygenases genes (alkB and CYP153A), and long-chain alkane monooxygenase gene (almA) were detected in 60 isolates (11 genotypes), 91 isolates (27 genotypes) and 93 isolates (24 genotypes), and 34 isolates (14 genotypes), respectively. This study could provide new insights into microbial resources from oil fields or other environments, and this information will be beneficial for bioremediation of petroleum contamination and for other industrial applications.

Air microbial quality in certain public buildings, Egypt: A comparative study

This study aims to determine microbiological air quality in public buildings: libraries, faculties, schools, child daycare centers and hospitals and its association with microclimatic conditions, particulate matter (PM) and ventilation type. Airborne bacteria and fungi were collected using Andersen two-stage sampler, it divides particles into coarse (≥7 μm) and fine (<2.5 μm) size ranges. Bacterial and fungal concentrations ranged between 0 ‒ 105 CFU/m3 and 0–103 CFU/m3, respectively. The 95th percentile values were 3399 CFU/m3 for environmental bacteria; 2299 CFU/m3 for mesophilic bacteria and 513 CFU/m3 for fungi. The Global Index of Microbial Contamination (GIMC/m3) exceeded 2000 CFU/m3 in hospitals' admission rooms and educational buildings. Index of Mesophilic Bacterial Contamination (IMC) achieved the greatest value in the faculty of specific education (F.SE), indicating overcrowding and hypoventilation. Fine particle fraction ranged within 2–41% for bacteria and 47–94% for fungi. Bacillus subtilis and Bacillus atrophaeus were the common bacterial species. Aspergillus, Alternaria, Penicillium and Cladosporium were the common fungal types. The secondary and tertiary fungal colonizers were detected in low counts. Agreement ratios showed that, outdoor air was the main contributor of indoor fungal flora, and accumulated dust was important contributor of fungal and bacterial flora in schools and faculties. Indoor/outdoor (I/O) ratios of PM concentrations exceeded 1 in ∼37% of the public buildings. Temperature negatively affected bacterial culturability while, relative humidity and PM supported fungal culturability in indoor environment. However¸ PM positively affected bacterial culturability and temperature negatively affected bacterial and fungal curturability in outdoor environment.

Bacterial culturability and the viable but non-culturable (VBNC) state studied by a proteomic approach using an artificial soil

Gram-negative bacteria in soil rapidly adapt to various stresses, including nutrient limitation and desiccation, by adopting the viable but non-culturable (VBNC) state as a survival strategy. Due to the physico-chemical and microbiological complexity of soils, little is understood on the effects of nutrient availability and moisture level on the transition from the VBNC state to culturability in soil. We evaluated the effects of gluconate or water on the transition of the soil borne bacterium C. metallidurans strain CH34 from the VBNC state to culturability by experiments of inoculation into artificial soils and bacterial metaproteomic analysis. Incubation without water or nutrients reduced the bacterial culturability to zero in 12 d, and addition of both water or gluconate restored the bacterial culturability to high levels within 24 h. The proteomic analysis showed that under water and nutrient limitation, proteins related to the cell shape and protein synthesis were rapidly down-regulated and stress-related proteins were quickly up-regulated during the transition from culturability to VBNC state. Reversion from the VBNC state to a culturable state with water or gluconate led to highly different bacterial proteomic profiles of C. metallidurans. Gluconate availability restored main protein biosynthesis and energy metabolic pathways, whereas water addition led to up-regulation of only six proteins, one of which degrade sigma factors involved in expression of genes controlling bacterial resistance under nutrient limitation. Proteins regulated during the transition between culturable and VBNC states could also be involved in the phenotypic VBNC for other soil bacteria, and can highlight some of the microbial genetic mechanisms allowing the entering and exiting from the VBNC state. Implications of the VBNC in microbial diversity and soil functionality are discussed.

Microbial Contamination of Smartphone Touchscreens of Italian University Students.

In this study, the microbial contamination of smartphones from Italian University students was analyzed. A total of 100 smartphones classified as low, medium, and high emission were examined. Bacteria were isolated on elective and selective media and identified by biochemical tests. The mean values of cfu/cm2 were 0.79 ± 0.01; in particular, a mean of 1.21 ± 0.12, 0.77 ± 0.1 and 0.40 ± 0.10cfu/cm2 was present on smartphones at low, medium, and high emission, respectively. The vast majority of identified microorganisms came from human skin, mainly Staphylococci, together with Gram-negative and positive bacilli and yeasts. Moreover, the main isolated species and their mixture were exposed for 3h to turned on and off smartphones to evaluate the effect of the electromagnetic wave emission on the bacterial cultivability, viability, morphology, and genotypic profile in respect to the unexposed broth cultures. A reduction rate of bacterial growth of 79 and 46% was observed in Staphylococcus aureus and Staphylococcus epidermidis broth cultures, respectively, in the presence of turned on smartphone. No differences in viability were observed in all detected conditions. Small colony variants and some differences in DNA fingerprinting were detected on bacteria when the smartphones were turned on in respect to the other conditions. The colonization of smartphones was limited to human skin microorganisms that can acquire phenotype and genotypic modifications when exposed to microwave emissions.

Antimicrobial effects of pulsed electromagnetic fields from commercially available water treatment devices – controlled studies under static and flow conditions

AbstractBACKGROUNDPulsed‐electromagnetic field (PEMF) devices are marketed and utilized for the non‐chemical management of biofouling, with little scientific validation of their effectiveness. Proof‐of‐principle studies were carried out previously to systematically investigate the effect of two such commercial devices on the culturability of bacteria under controlled static (i.e. non‐flowing) conditions and anti‐microbial effects were demonstrated. However, such effects were small and an expanded investigation, using these devices and including the effect of flow, was deemed necessary.RESULTSThe effect of the electromagnetic fields generated by the same two commercial devices on the bacterial culturability ofEscherichia coliandPseudomonas fluorescensunder flow conditions has been contrasted with previous static results. It has been found that the effectiveness of PEMF exposure depends on waveform, extent of flow, type of bacteria and PEMF exposure duration.CONCLUSIONBoth stimulatory and inhibitory effects are observed that are uniquely dependent upon device type (i.e. a range of parameters including waveform), species of microorganism, presence and degree of flow and PEMF exposure time. For both devices and both microorganisms, stimulatory effects are uniformly observed for one device under static conditions and inhibitory effects are uniformly observed for the other device at low flow and for the former at high flow. © 2017 Society of Chemical Industry

Pectin-iron capsules: Novel system to stabilise and deliver lactic acid bacteria

The delivery of probiotics has been a challenge because microorganisms must overcome harmful environments both at a technological and at a physiological level. Encapsulation is one of the strategies to protect microorganisms against both problems. This work aimed at encapsulating probiotic Lactobacillus plantarum CIDCA 83114 in pectin-iron beads obtained by ionotropic gelation, enabling bacteria safe delivery and providing a source of iron and fibre.Microorganisms in the stationary phase were suspended in a 4% w/v pectin solution at pH 5, and the suspension, dripped into a 150 mM FeSO4 solution. The beads were freeze-dried and stored for 60 days at 4 °C. The morphology of the beads was observed by scanning electron microscopy. Bacterial culturability was determined after freeze-drying, and after the exposure to simulated saliva, gastric and intestinal conditions. The iron and pectin releases were also investigated in the same digestive conditions.Microorganisms were fully entrapped in smooth and spherical pectin-iron beads of ca. 1–2 mm diameter. Bacterial culturability did not decrease during storage. Encapsulation protected microorganisms against simulated digestive conditions, also enabling the complete release of iron and pectins in the gut.The results obtained support the safe delivery of both probiotic bacteria and iron to the gut. As iron deficiency still continuous to be a worldwide problem, using iron-pectin beads could be an adequate strategy to functionalise food products, contributing to attain the recommended iron intake.

Influence of the copper-induced viable but non-culturable state on the toxicity of Pseudomonas aeruginosa towards human bronchial epithelial cells in vitro

The viable but non-culturable (VBNC) state of the opportunistic bacterium Pseudomonas aeruginosa was previously shown to be induced by copper ions in concentrations relevant to those in drinking water plumbing systems. This decrease of bacterial culturability without loss of viability might have an influence on human health due to an underestimation of the actual contamination in drinking water systems. The aim of this study was to investigate the influence of culturable P. aeruginosa, viable but not culturable as well as culturable again after resuscitation from the VBNC state on human bronchial epithelial cells (BEAS-2B) in vitro. Cyto- and genotoxic effects of P. aeruginosa at different states were studied using trypan blue, MTT, xCELLigence as well as the micronucleus assay. While P. aeruginosa in the VBNC state did not have any cytotoxic or genotoxic effect on BEAS-2B cells, untreated (culturable) and resuscitated P. aeruginosa did show cell damage, including disruption of cell membranes, inhibition of mitochondrial activity and cell proliferation as well as DNA-damaging effects. We conclude from our study that P. aeruginosa after resuscitation from the VBNC state regains its viability and cyto-/genotoxicity and therefore might influence human health.

PH-Sensitive degradable polymeric micelles for bio-triggered targeted anti-tumor drug delivery

Sanitation is a critical step to reduce microbial load in many process industries. To assess and monitor the efficacy of sanitation processes, there is a need to rapidly measure microbial resistance to sanitizers and determine the critical concentration of sanitizers above which significant reduction in microbial load can be achieved in a complex environment. In this study, a rapid and label-free magnetic resonance (MR) imaging and relaxometry method was developed to measure resistance of Escherichia coli and Listeria monocytogenes to hydrogen peroxide based on the activity of intracellular catalase enzymes. Intracellular catalase activity is a measure of resistance of bacteria to hydrogen peroxide as these enzymes can degrade hydrogen peroxide to oxygen and water. Using sub-lethal and lethal concentration of hydrogen peroxide, the resistance of both the exponential and stationary growth phase E. coli suspended in PBS and in high organic content solution was characterized. The results show that in stationary growth phase E. coli, molecular oxygen, generated by the interaction of endogenous catalases with 1% H2O2, results in an 8 fold increase in MR imaging signal intensity and a 22 fold decrease in spin-lattice relaxation time (T1) compared to the controls. Furthermore, the resistance of E. coli and L. monocytogenes to H2O2, measured using the MR method, was correlated with the bacterial reduction, quantified with traditional plate counting method. The comparison between the two methods shows the MR method developed in this study can determine the critical concentration of H2O2 above which a significant reduction in bacterial culturability (at least 4 logs) was achieved. Overall, this study demonstrates the potential of MR imaging and relaxometry method to predict the efficacy of H2O2 in high organic load environment.