Microbial life abounds on surfaces in both natural and industrial environments, one of which is the food industry. A solid substrate, water and some nutrients are sufficient to allow the construction ...of a microbial fortress, a so-called biofilm. Survival strategies developed by these surface-associated ecosystems are beginning to be deciphered in the context of rudimentary laboratory biofilms. Gelatinous organic matrices consisting of complex mixtures of self-produced biopolymers ensure the cohesion of these biological structures and contribute to their resistance and persistence. Moreover, far from being just simple three-dimensional assemblies of identical cells, biofilms are composed of heterogeneous sub-populations with distinctive behaviours that contribute to their global ecological success. In the clinical field, biofilm-associated infections (BAI) are known to trigger chronic infections that require dedicated therapies. A similar belief emerging in the food industry, where biofilm tolerance to environmental stresses, including cleaning and disinfection/sanitation, can result in the persistence of bacterial pathogens and the recurrent cross-contamination of food products. The present review focuses on the principal mechanisms involved in the formation of biofilms of food-borne pathogens, where biofilm behaviour is driven by its three-dimensional heterogeneity and by species interactions within these biostructures, and we look at some emergent control strategies.
•Ability to form/join microbial biofilms impacts foodborne pathogen tolerance.•Biofilm tolerance to biocides and stress requires the development of new hygienic strategies.•Interspecific interactions influence pathogen fitness/survival in biofilms.•Spatial modelling as a tool to decipher biofilm structure/function relationships.
The 1759–1774 eruption of the Jorullo volcano in the Michoacán Guanajuato Volcanic Field (MGVF), Mexico, produced lavas that range in composition from basalt to basaltic andesite. We have conducted ...new major and trace element and isotopic studies (whole rock Sr–Nd–Pb–Hf–Os, and O isotopes in olivine separates) of the Jorullo lavas and tephras spanning the duration and compositional range of the eruption, to further constrain the potential roles of mantle source heterogeneity, subduction-related metasomatism, and crustal assimilation in the petrogenesis of the Jorullo magmas. This study presents the first Hf, high precision Pb and comprehensive oxygen isotope measurements for Jorullo volcanic rocks. All samples have arc-like trace element patterns with enrichments in large ion lithophile elements (e.g. Ba, Rb, and Pb) and depletions in fluid immobile elements (e.g. Nb, Ta). In addition, the samples show variations in 87Sr/86Sr (0.7038–0.7040), 143Nd/144Nd (0.51280–0.51285), 176Hf/177Hf (0.28297–0.28300), 206Pb/204Pb (18.62–18.66), 207Pb/204Pb (15.57–15.59) and 208Pb/204Pb (38.34–38.43). Osmium isotope signatures are, with one exception, more radiogenic than the depleted and primitive mantle (187Os/188Os=0.1231–0.1616). Oxygen isotope ratios of olivine phenocrysts (δ18.OSMOW=5.70–6.02‰) show limited variation, but are isotopically heavier than normal mantle olivine. The samples define two geochemical groups: high-MgO samples with higher 87Sr/86Sr, lower 143Nd/144Nd and 176Hf/177Hf, and a positive correlation of Sr and Pb isotopes; and low-MgO samples displaying lower 87Sr/86Sr but higher 143Nd/144Nd and 176Hf/177Hf than the former group, and a negative correlation of Sr and Pb isotopes. The high-MgO group comprises most of the early tephra and lavas, whereas the low-MgO group includes most of the late tephra and lavas. These compositional variations are inconsistent with shallow level contamination, but rather are interpreted to reflect mantle source heterogeneity. Trace element and isotopic signatures are consistent with North Mexican Extensional Province (NMEP) mantle metasomatised by subduction components composed of sediment- and oceanic crust-derived hydrous fluid. The temporal–compositional variations observed in Jorullo magmas are inferred to result from a combination of variable degrees of fractional crystallization of magmas produced by tapping a progressively less metasomatised mantle source that is vertically and/or laterally heterogeneous.
•Jorullo lavas and tephra show trace element signatures similar to subduction-related magmas.•Temporal–compositional variation is due to a complex magmatic plumbing system and changes in the mantle source over time.•The source heterogeneity was produced by a single mantle source fluxed by two subduction components.•Both subduction components are strongly dominated by terrigenous sediment-derived fluid.
Pelado volcano is a typical example of an andesitic Mexican shield with a summital scoria cone. It erupted ca. 10 ka in the central part of an elevated plateau in what is today the southern part of ...Mexico City. The volcano forms a roughly circular, 10-km wide lava shield with two summital cones, surrounded by up to 2.7-m thick tephra deposits preserved up to a distance of 3 km beyond the shield. New cartographic, stratigraphic, granulometric, and componentry data indicate that Pelado volcano was the product of a single, continuous eruption marked by three stages. In the early stage, a > 1.5-km long fissure opened and was active with mild explosive activity. Intermediate and late stages were mostly effusive and associated with the formation of a 250-m high lava shield. Nevertheless, during these stages, the emission of lava alternated and/or coexisted with highly explosive events that deposited a widespread tephra blanket. In the intermediate stage, multiple vents were active along the fissure, but activity was centered at the main cone during the late stage. The final activity was purely effusive. The volcano emitted > 0.9 km
3
dense-rock equivalent (DRE) of tephra and up to 5.6 km
3
DRE of lavas. Pelado shares various features with documented “violent Strombolian” eruptions, including a high fragmentation index, large dispersal area, occurrence of plate tephra, high eruptive column, and simultaneous explosive and effusive activity. Our results suggest that the associated hazards (mostly tephra fallout and emplacement of lava) would seriously affect areas located up to 25 km from the vent for fallout and 5 km from the vent for lava, an important issue for large cities built near or on potentially active zones, such as Mexico City.
The Laki eruption involved 10 fissure-opening episodes that produced 15·1 km3 of homogeneous quartz-tholeiite magma. This study focuses on the texture and chemistry of samples from the first five ...episodes, the most productive period of the eruption. The samples comprise pumiceous tephra clasts from early fallout deposits and lava surface samples from fire-fountaining and cone-building activity. The fluid lava core was periodically exposed at the surface upon lobe breakout, and its characteristics are preserved in glassy selvages from the lava surface. In all samples, plagioclase is the dominant mineral phase, followed by clinopyroxene and then olivine. Samples contain <7 vol. % of euhedral phenocrysts (>100 μm) with primitive cores An* = 100 × Ca/(Ca + Na) >70; Fo > 75; En* = 100 × Mg/(Mg + Fe) >78 and more evolved rims, and >10 vol. % of skeletal, densely distributed groundmass crystals (<100 μm), which are similar in composition to phenocryst rims (tephra: An*58-67, Fo72-78, En*72-81; lava: An*49-70, Fo63-78, En57-78). Tephra and lava have distinct vesicularity (tephra: >40 vol. %; lava: <40 vol. %), groundmass crystal content (tephra: <10 vol. %; lava: 20-30 vol. %), and matrix glass composition (tephra: 5·4-5·6 wt % MgO; lava: 4·3-5·0 wt % MgO). Whole-rock and matrix glass compositions define a trend consistent with liquid evolution during in situ crystallization of groundmass phases. Plagioclase-glass and olivine-glass thermometers place the formation of phenocryst cores at ∼10 km depth in a melt with ∼1 wt % H2O, at near-liquidus temperatures (∼1150°C). Phenocryst rims and groundmass crystals formed close to the surface, at 10-40°C melt undercooling and in an ∼10−20°C cooler drier magma (0-0·1 wt % H2O), causing an ∼10 mol % drop in An content in plagioclase. The shape, internal zoning and number density of groundmass crystals indicate that they formed under supersaturated conditions. Based on this information, we propose that degassing during ascent had a major role in rapidly undercooling the melt, prompting intensive shallow groundmass crystallization that affected the magma and lava rheology. Petrological and textural differences between tephra and lava reflect variations in the rates of magma ascent and the timing of surface quenching during each eruptive episode. That in turn affected the time available for crystallization and subsequent re-equilibration of the melt to surface (degassed) conditions. During the explosive phases, the rates of magma ascent were high enough to inhibit crystallization, yielding crystal-poor tephra. In contrast, pervasive groundmass crystallization occurred in the lava, increasing its yield strength and causing a thick rubbly layer to form during flow emplacement. Lava selvages collected across the flow-field have strikingly homogeneous glass compositions, demonstrating the high thermal efficiency of fluid lava transport. Cooling is estimated as 0·3°C/km, showing that rubbly surfaced flows can be as thermally efficient as tube-fed pāhoehoe lavas.
It was shown in the literature that ethanol locks have a positive effect on preventing catheter-related infections in patients with central venous catheters without causing any microbial resistance. ...However, ethanol is known to interact with polyurethanes. The consequences of this interaction on the catheter surface properties were studied as it can impact the biocompatibility of the material and the adhesion phenomena onto the surface. No physical and chemical degradation was put into evidence, but low molecular weight compounds such as additives were extracted from the catheter bulk or migrated and exudated onto its surface. Nevertheless, as far as bacterial adhesion is concerned, after the catheter was locked and the lock removed, the surface modifications promoted no adhesion.
To investigate the effect of liquid smoke on growth, survival, proteomic pattern and haemolytic potential of Listeria monocytogenes. Growth and survival curves were recorded in brain-heart infusion ...broth supplemented with three concentrations of liquid smoke. L. monocytogenes growth was inhibited in the presence of 15 μg ml⁻¹ phenol while a rapid decrease in cell viability occurred in the presence of 30 μg ml⁻¹ phenol. The proteome of L. monocytogenes cytosoluble proteins was slightly modified after 2-h incubation with 30 μg ml⁻¹ phenol but no protein already characterized in response to other known stresses was induced, except the protease ClpP. Liquid smoke inhibited the haemolytic potential without affecting hly gene expression, showing a potential inhibition of protein activity or stability. The presence of liquid smoke in a rich medium strongly affected growth and survival of L. monocytogenes. Brief smoke stress affected the metabolic pathways and inhibited the haemolytic activity of L. monocytogenes. This study is a first step in the investigation of the influence of a smoked product on L. monocytogenes strains.
Mielke et al. (2021) proposed a stepwise multiple testing procedure (MTP) based on marginal p‐values for rejecting at least k out of m null hypotheses. Briefly, the MTP cannot reject less than k ...hypotheses, but this property improves the power to reject k or more hypotheses relative to the stepdown MTP of Holm (1979). Mielke et al. discussed why such an MTP is of interest in the context of biosimilarity developments. This article describes how a slight modification of Holm's simple direct arguments can be used as an alternative to the closed‐testing arguments of Mielke et al. to show the strong control of the family‐wise error rate. This modification is based on a Holm‐type formulation of the rejection algorithm where each step involves a single ordered p‐value. With k equal to one, the stepwise MTP reduces to Holm's stepdown MTP. The MTP is valid quite generally. A version of the MTP with weights for hypotheses is also described and discussed. As in the case without weights: (a) a modification of Holm's arguments can be used; (b) with k equal to one, the MTP reduces to Holm's MTP with weights; and (c) the MTP is valid quite generally.
Different Liquid Drop Model mass formulae have been studied. They include a Coulomb diffuseness correction Z2/A term and pairing and shell energies of the Thomas-Fermi model. The influence of the ...selected charge radius, the curvature energy and different forms of the Wigner term has been investigated. Their coefficients have been determined by a least square fitting procedure to 2027 experimental atomic masses. The different fits lead to a surface energy coefficient of 17-18 MeV. A large equivalent rms radius (r0 1.22 − 1.24 fm) or a shorter central radius may be used. A rms deviation of 0.54 MeV can be reached between the experimental and theoretical masses. The remaining differences come from the determination of the shell and pairing energies. Mass predictions are given for exotic nuclei.
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