A simple model for the early events of quorum sensing in Pseudomonas aeruginosa: modeling bacterial swarming as the movement of an "activation zone"

<p>Abstract</p> <p>Background</p> <p>Quorum sensing (QS) is a form of gene regulation based on cell-density that depends on inter-cellular communication. While there are a variety of models for bacterial colony morphology, there is little work linking QS genes to movement in an open system.</p> <p>Results</p> <p>The onset of swarming in environmental <it>P. aeruginosa </it>PUPa3 was described with a simplified computational model in which cells in random motion communicate via a diffusible signal (representing <it>N</it>-acyl homoserine lactones, AHL) as well as diffusible, secreted factors (enzymes, biosurfactans, i.e. "public goods") that regulate the intensity of movement and metabolism in a threshold-dependent manner. As a result, an "activation zone" emerges in which nutrients and other public goods are present in sufficient quantities, and swarming is the spontaneous displacement of this high cell-density zone towards nutrients and/or exogenous signals. The model correctly predicts the behaviour of genomic knockout mutants in which the QS genes responsible either for the synthesis (<it>lasI, rhlI</it>) or the sensing (<it>lasR, rhlR</it>) of AHL signals were inactivated. For wild type cells the model predicts sustained colony growth that can however be collapsed by the overconsumption of nutrients.</p> <p>Conclusion</p> <p>While in more complex models include self-orienting abilities that allow cells to follow concentration gradients of nutrients and chemotactic agents, in this model, displacement towards nutrients or environmental signals is an emergent property of the community that results from the action of a few, well-defined QS genes and their products. Still the model qualitatively describes the salient properties of QS bacteria, i.e. the density-dependent onset of swarming as well as the response to exogenous signals or cues.</p> <p>Reviewers</p> <p>This paper was reviewed by Gáspár Jékely, L. Aravind, Eugene V. Koonin and Artem Novozhilov (nominated by Eugene V. Koonin).</p

Rituais do poder nas organizações de saúde

O poder é ambicionado pelo ser humano que o deseja ter para si; já que através dele se sente equiparado a uma divindade capaz de tudo dominar. Quando mais frágil se encontra estruturada a personalidade do sujeito, mais necessita de poder para camuflar sua impotência. As organizações sempre foram lugares de exercício de poder. Nas organizações clássicas o poder se confunde com o pai-trão ou com os chefes. Nas organizações hipermodernas o poder se despersonaliza, passando as relações passionais a serem vivenciadas através das estruturas e valores nelas cultivados. Nas organizações de saúde, o poder se concentra no médico, pelo consentimento implícito da sociedade, tornando rígida a construção da sua identidade profissional. Os rituais são desenvolvidos e adotados nas instituições como forma de perpetuar o poder instituído. Há uma identificação dos trabalhadores com a imagem projetada da organização, surgindo um campo fértil para se implantar ideologias e políticas que são culturalmente introjetadas como verdadeiras

UM PROJETO, DUAS CIDADES: ESTUDO COMPARATIVO COM PESSOAS IDOSAS DE FRANCA E AVEIRO

Aumentou o tempo vivido pelas pessoas no mundo todo, mas sem melhoriasna sociedade contemporânea, nem culturais, econômicas ou físicas. Vida saudável, atualmente se reduz à perseguição dos modismos consumistas cada vez mais acelerados, incentivados pelo sistema econômico capitalista neoliberal globalizado do mundo atual. O planejamento das novas condições societárias deve possibilitar a implantação de medidas para atingir a qualidade de vida da população em geral com menores custos pessoais e sociais. A idéia da manutenção da autonomia e independência vincula-se à constatação que a saúde da pessoa idosa é a interação entre saúde física, saúde mental, independência financeira, capacidade funcional e suporte social. Tendo como objetivo comparar a percepção das pessoas idosas de Franca, Brasil, e Aveiro, Portugal, o estudo versa sobre o envelhecimento saudável e a expectativa que nutrem sobre a continuidade de suas vidas. Conclui-se que as idéias a respeito do envelhecimento ativo que culminam no Projeto Cidade Amiga da Pessoa Idosa, são fontes inesgotáveis de reflexão, que convidam à ação. Implicam numa inversão de valores das forças vivas da sociedade diante dos novosparadigmas que se apresentam

Bacterial Endophytes Contribute to Rice Seedling Establishment Under Submergence

Flooding events caused by severe rains and poor soil drainage can interfere with plant germination and seedling establishment. Rice is one of the cereal crops that has unique germination strategies under flooding. One of these strategies is based on the fast coleoptile elongation in order to reach the water surface and re-establish the contact with the air. Microorganisms can contribute to plant health via plant growth promoters and provide protection from abiotic stresses. To characterise the community composition of the microbiome in rice germination under submergence, a 16S rRNA gene profiling metagenomic analysis was performed of temperate japonica rice varieties Arborio and Lamone seedlings, which showed contrasting responses in terms of coleoptile length when submerged. This analysis showed a distinct microbiota composition of Arborio seeds under submergence, which are characterised by the development of a long coleoptile. To examine the potential function of microbial communities under submergence, culturable bacteria were isolated, identified and tested for plant growth-promoting activities. A subgroup of isolated bacteria showed the capacity to hydrolyse starch and produce indole-related compounds under hypoxia. Selected bacteria were inoculated in seeds to evaluate their effect on rice under submergence, showing a response that is dependent on the rice genotype. Our findings suggest that endophytic bacteria possess plant growth-promoting activities that can substantially contribute to rice seedling establishment under submergence

In Planta Colonization and Role of T6SS in Two Rice Kosakonia Endophytes.

Endophytes live inside plants and are often beneficial. Kosakonia is a novel bacterial genus that includes many diazotrophic plant-associated isolates. Plant–bacteria studies on two rice endophytic Kosakonia beneficial strains were performed, including comparative genomics, secretome profiling, in planta tests, and a field release trial. The strains are efficient rhizoplane and root endosphere colonizers and localized in the root cortex. Secretomics revealed 144 putative secreted proteins, including type VI secretory system (T6SS) proteins. A Kosakonia T6SS genomic knock-out mutant showed a significant decrease in rhizoplane and endosphere colonization ability. A field trial using rice seed inoculated with Kosakonia spp. showed no effect on plant growth promotion upon nitrogen stress and microbiome studies revealed that Kosakonia spp. were significantly more present in the inoculated rice. Comparative genomics indicated that several protein domains were enriched in plant-associated Kosakonia spp. This study highlights that Kosakonia is an important, recently classified genus involved in plant–bacteria interaction

Herbicide-resilient bacterial consortia in plant growth promotion

Modern agriculture relies heavily on agrochemicals that can adversely affect non-target organisms, including microorganisms. In terms of agricultural sustainability, herbicideresilient plant growth-promoting (PGP) bacteria that can improve crop yield are critical. Previously, we isolated 122 high herbicide concentration tolerant (HHCT) bacteria from soils contaminated with S-metolachlor, a widely used herbicide. Initially, in vitro experiments were conducted to screen potential candidates for further evaluation. Our goal was to identify HHCT bacteria with high PGP potential, and the ability to improve soil quality and biocontrol activity. Subsequently, the most promising candidates were grouped into three consortia and evaluated in pot for their effects on corn seed germination, early-stage plant development, and root colonization. Experiments were conducted with seeds of commercial maize hybrids under controlled conditions, with and without the presence of the herbicide S-metolachlor. The results showed that the consortia positively affected seed germination and promoted higher germination rates. The bacterial isolates showed the ability to colonize the root system of maize, with significant effects of the consortia on shoot and root biomass and shoot and root length. However, it was observed in some consortia that the presence of herbicides resulted in plant damage. Markedly, the presence of the herbicide S-metolachlor reduced or reversed the beneficial effects of bacterial consortia. This could be due to incomplete biotransformation of the herbicide leading to the formation of toxic intermediates. The selection of bacterial consortia that not only promote plant growth but also have the ability to fully biotransform herbicides is critical. In conclusion, the isolated HHCT bacteria showed promising PGP potential and formed an effective consortium to promote maize seed germination and early-stage development. However, careful consideration of the selection of bacterial consortia is required to ensure their compatibility with herbicides and to minimize negative impacts on plant health and environmental sustainability.Book of abstract: ICGEB WORKSHOP; Trends in microbial solutions for sustainable agriculture, 13 – 15 September 2023. Belgrade, Serbi

A new laser device for ultra-rapid and sustainable aerosol sterilization

The current COVID-19 pandemic has highlighted the importance of aerosol-based transmission of human pathogens; this therefore calls for novel medical devices which are able to sterilize contaminated aerosols. Here we describe a new laser device able to sterilize droplets containing either viruses or bacteria. Using engineered viral particles, we determined the 10,600 nm wavelength as the most efficient and exploitable laser source to be manufactured in a commercial device. Given the lack of existing working models to reproduce a human aerosol containing living microbial particles, we developed a new system mimicking human droplet formation and preserving bacterial and viral viability. This evidenced the efficacy of 10,600 nm laser light to kill two aerosol transmitted human pathogens, Legionella pneumophila and SARS-CoV-2. The minimal exposure time of &lt;15 ms was required for the inactivation of over 99% pathogens in the aerosol; this is a key element in the design of a device that is safe and can be used in preventing inter-individual transmission. This represents a major advantage over existing devices, which mainly aim at either purifying incoming air by filters or sterilizing solid surfaces, which are not the major transmission routes for airborne communicable diseases