263,124 research outputs found
System-Level understanding of microbial interactions in subaerial biofilms inhabiting outdoor stone monuments
No full textBackground:
Many of the world’s most precious artworks are made of stone. Their irreversible deterioration due to biological attack is a worldwide concern. Microorganisms colonize outdoor lithic surfaces and develop into biofilms at the interface solid/air (subaerial biofilms, SABs), which, in turn might cause aesthetic, chemical and physical decay. Although it has been estimated that at least 99% of the world's microbial biomass exists in biofilms, the role and behavior of microorganisms within the biofilm matrix and their complex interactions with the external environment is still unknown. This work provides a pioneering and multidisciplinary research to investigate the behavior of microorganisms within the biofilm matrix for sorting out time-spatial relationships and to elucidate microorganism-EPS, interorganism, biofilm-atmosphere and biofilm-stone interactions.
Methods:
This work spans sophisticated molecular, chemical, physical and data modeling techniques and it is approached from two complementary angles:
1- Lab-scale study to delineate specific transcriptional responses of mono- and multi-species biofilms as well as the biofilm-stone interactions under controlled environmental conditions.
2- Real heritage case studies to investigate the shifts in the microbial community structure and function under different environmental conditions. Through comparing phylogenetic and functional diversity under different environmental scenarios, we provide evidence that any intuition gained from the lab-scale experiments is relevant to true environmental biofilms.
Results:
Experimental evidence suggests the existence of strong interactions between photoautotrophic and heterotrophic microorganisms in SABs, which involve complementation of physiological and biochemical functions, emphasizing optimal metabolic performance and enhanced productivity.
Conclusions:
The findings obtained so far will contribute to better understand the complexity of all the interactions encountered within SAB communities, and how these interactions may influence the biofilm outcome and the biodeterioration of the stone materials in a changing environment
Biofilm material properties as related to shear-induced deformation and detachment phenomena
No full textBiofilms of various Pseudomonas aeruginosa strains were grown in glass flow cells under laminar and turbulent flows. By relating the physical deformation of biofilms to variations in fluid shear, we found that the biofilms were viscoelastic fluids which behaved like elastic solids over periods of a few seconds but like linear viscous fluids over longer times. These data can be explained using concepts of associated polymeric systems, suggesting that the extracellular polymeric slime matrix determines the cohesive strength. Biofilms grown under high shear tended to form filamentous streamers while those grown under low shear formed an isotropic pattern of mound-shaped microcolonies. In some cases, sustained creep and necking in response to elevated shear resulted in a time-dependent fracture failure of the "tail" of the streamer from the attached upstream "head." In addition to structural differences, our data suggest that biofilms grown under higher shear were more strongly attached and were cohesively stronger than those grown under lower shears
Commonality of elastic relaxation times in biofilms
No full textBiofilms, sticky conglomerations of microorganisms and extracellular polymers, are among the Earth's most common life forms. One component for their survival is an ability to withstand external mechanical stress. Measurements indicate that biofilm elastic relaxation times are approximately the same (about 18 min) over a wide sample of biofilms though other material properties vary significantly. A possible survival significance of this time scale is that it is the shortest period over which a biofilm can mount a phenotypic response to transient mechanical stress
Viscoelastic fluid description of bacterial biofilm material properties
No full textA mathematical model describing the constitutive properties of biofilms is required for predicting biofilm deformation, failure, and detachment in response to mechanical forces. Laboratory observations indicate that biofilms are viscoelastic materials. Likewise, current knowledge of biofilm internal structure suggests modeling biofilms as associated polymer viscoelastic systems. Supporting experimental results and a system of viscoelastic fluid equations with a linear Jeffreys viscoelastic stress-strain law are presented here. This system of equations is based on elements of associated polymer physics and is also consistent with presented and previous experimental results. A number of predictions can be made. One particularly interesting result is the prediction of an elastic relaxation time on the order of a few minutes-biofilm disturbances on shorter time scales produce an elastic response, biofilm disturbances on longer time scales result in viscous flow, i.e., nonreversible biofilm deformation. Although not previously recognized, evidence of this phenomenon is in fact present in recent experimental results
Mathematical modeling of dispersal phenomenon in biofilms
No full textA mathematical model for dispersal phenomenon in multispecies biofilm based on a continuum approach and mass conservationprinciples is presented. The formation of dispersed cells is modeled by considering a mass balance for the bulk liquid and thebiofilm. Diffusion of these cells within the biofilm and in the bulk liquid is described using a diffusion-reaction equation. Diffusionsupposes a random character of mobility. Notably, biofilm growth is modeled by a hyperbolic partial differential equation whilethe diffusion process of dispersed cells by a parabolic partial differential equation. The two are mutually connected but governedby different equations that are coupled by two growth rate terms. Three biological processes are discussed. The first is relatedto experimental observations on starvation induced dispersal [1]. The second considers diffusion of a non-lethal antibiofilm agentwhich induces dispersal of free cells. The third example considers dispersal induced by a self-produced biocide agent
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MISAME
No full textRecording of Magdalena Klapper-Rybicka's Instrument- area 1. "Area I" was written on commission from the Polish Radio Experimental Studio in Warsaw. The piece was produced on Csound and a Sonic Solution system, with the cooperation of Ewa Guziolek-Tubelewicz. The piece is based on two groups of sounds: those of woodwinds and brass instruments, recorded in anechoic chamber, and sounds of string, generated by computer algorithms. The form of this piece is composed to resemble a "bridge'' as far as the sound pitch is concerned. Although "Area I" is an electroacoustic piece, it has an instrumental character
Los efectos de la comunicación de masas de Joseph T. Klapper
No full textIn this paper we review the Joseph T. Klapper (1960) book's The effects of mass communication. The paper begin with a context from the author and his work. Following we present the contents, on the one hand the effects of persuasive communication and the influence of certain specific types of media material, and on the other the generalizations which are capable of relating these findings. The article ends with reflection about the impact of the work in the history of the research. We suggest that the Klapper's book is the last legacy of the empirical sociology of the Columbia¿s Bureau led by Paul F. Lazarsfeld into the communication research.Ciencias de la Comunicación I
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Water activity in subaerial microbial biofilms on stone monuments
No full textStone monuments can be difficult environments for life, particularly with respect to liquid water access. Nevertheless, microbial communities are found on them with apparent ubiquity. A variety of strategies for access to liquid water have been proposed. Regardless of their water-retention mechanisms details, though, we argue that water activity (a key indicator for cell viability) is constrained by environmental conditions, largely inde-pendently of community structure, and is predicted by the local temperature and relative humidity. However, direct measurement of water activity in SABs, particularly those growing on stone surfaces, is difficult. A method for estimating water activity within SABs is presented that uses a minimally invasive combination of conservative sampling, weather data, confocal imaging, and mathematical modeling. Applying the methodology to mea-surements from the marble roofs of the Federal Hall National Memorial and of the Thomas Jefferson Memorial, estimations are made for water activity in their subaerial stone communities over the course of an approximately one year period
Advancements towards a system-level understanding of subaerial biofilms inhabiting outdoor stone materials
No full textBackground:
Many of the world’s most precious artworks are made of stone. Their irreversible deterioration due to biological attack is a worldwide concern. Microorganisms colonize outdoor lithic surfaces and develop into biofilms at the interface solid/air (subaerial biofilms, SABs), which, in turn might cause aesthetic, chemical and physical decay. Although it has been estimated that at least 99% of the world's microbial biomass exists in biofilms, the role and behavior of microorganisms within the biofilm matrix and their complex interactions with the external environment is still unknown.
Objectives:
This work provides a pioneering and multidisciplinary research to investigate the behavior of microorganisms within the biofilm matrix for sorting out time-spatial relationships and to elucidate microorganism-EPS, inter-organism, biofilm-atmosphere and biofilm-stone interactions.
Methods:
This work spans sophisticated molecular, chemical, physical and data modeling techniques and it is approached from two complementary angles:
1- Lab-scale study to delineate specific transcriptional responses of mono- and multi-species biofilms as well as the biofilm-stone interactions under controlled environmental conditions.
2- Real heritage case studies to investigate the shifts in the microbial community structure and function under different environmental conditions. Through comparing phylogenetic and functional diversity under different environmental scenarios, we provide evidence that any intuition gained from the lab-scale experiments is relevant to true environmental biofilms.
Conclusions:
The findings obtained so far will contribute to better understand the complexity of all the interactions encountered within SAB communities, and how these interactions may influence the biofilm outcome and the biodeterioration of the stone materials under different environmental conditions
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