Verticalization of bacterial biofilms

Biofilms are communities of bacteria adhered to surfaces. Recently, biofilms of rod-shaped bacteria were observed at single-cell resolution and shown to develop from a disordered, two-dimensional layer of founder cells into a three-dimensional structure with a vertically-aligned core. Here, we elucidate the physical mechanism underpinning this transition using a combination of agent-based and continuum modeling. We find that verticalization proceeds through a series of localized mechanical instabilities on the cellular scale. For short cells, these instabilities are primarily triggered by cell division, whereas long cells are more likely to be peeled off the surface by nearby vertical cells, creating an "inverse domino effect". The interplay between cell growth and cell verticalization gives rise to an exotic mechanical state in which the effective surface pressure becomes constant throughout the growing core of the biofilm surface layer. This dynamical isobaricity determines the expansion speed of a biofilm cluster and thereby governs how cells access the third dimension. In particular, theory predicts that a longer average cell length yields more rapidly expanding, flatter biofilms. We experimentally show that such changes in biofilm development occur by exploiting chemicals that modulate cell length.Comment: Main text 10 pages, 4 figures; Supplementary Information 35 pages, 15 figure

Exploration Behaviour Is Not Associated with Chick Provisioning in Great Tits

In biparental systems, members of the same pair can vary substantially in the amount of parental care they provide to offspring. The extent of this asymmetry should depend on the relative costs and benefits of care. Individual variation in personality is likely to influence this trade-off, and hence is a promising candidate to explain differences in care. In addition, plasticity in parental care may also be associated with personality differences. Using exploration behaviour (EB) as a measure of personality, we investigated these possibilities using both natural and experimental data from a wild population of great tits (Parus major). Contrary to predictions, we found no association between EB and natural variation in provisioning behaviour. Nor was EB linked to responsiveness to experimentally increased brood demand. These results are initially surprising given substantial data from other studies suggesting personality should influence investment in parental care. However, they are consistent with a recent study showing selection on EB is weak and highly context-specific in the focal population. This emphasises the difficulty faced by personality studies attempting to make predictions based on previous work, given that personalities often vary among populations of the same species

Potential Use of a Serpin from Arabidopsis for Pest Control

Although genetically modified (GM) plants expressing toxins from Bacillus thuringiensis (Bt) protect agricultural crops against lepidopteran and coleopteran pests, field-evolved resistance to Bt toxins has been reported for populations of several lepidopteran species. Moreover, some important agricultural pests, like phloem-feeding insects, are not susceptible to Bt crops. Complementary pest control strategies are therefore necessary to assure that the benefits provided by those insect-resistant transgenic plants are not compromised and to target those pests that are not susceptible. Experimental GM plants producing plant protease inhibitors have been shown to confer resistance against a wide range of agricultural pests. In this study we assessed the potential of AtSerpin1, a serpin from Arabidopsis thaliana (L). Heynh., for pest control. In vitro assays were conducted with a wide range of pests that rely mainly on either serine or cysteine proteases for digestion and also with three non-target organisms occurring in agricultural crops. AtSerpin1 inhibited proteases from all pest and non-target species assayed. Subsequently, the cotton leafworm Spodoptera littoralis Boisduval and the pea aphid Acyrthosiphon pisum (Harris) were fed on artificial diets containing AtSerpin1, and S. littoralis was also fed on transgenic Arabidopsis plants overproducing AtSerpin1. AtSerpin1 supplied in the artificial diet or by transgenic plants reduced the growth of S. littoralis larvae by 65% and 38%, respectively, relative to controls. Nymphs of A. pisum exposed to diets containing AtSerpin1 suffered high mortality levels (LC50 = 637 µg ml−1). The results indicate that AtSerpin1 is a good candidate for exploitation in pest control

A growing bacterial colony in two dimensions as an active nematic

Rod-shaped bacteria are an example of active matter. Here the authors find that a growing bacterial colony harbours internal cellular flows affecting orientational ordering in its interior and at the boundary. Results suggest this system may belong to a new active matter universality class

Guidelines for the use and interpretation of assays for monitoring autophagy (4th edition)1.

In 2008, we published the first set of guidelines for standardizing research in autophagy. Since then, this topic has received increasing attention, and many scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Thus, it is important to formulate on a regular basis updated guidelines for monitoring autophagy in different organisms. Despite numerous reviews, there continues to be confusion regarding acceptable methods to evaluate autophagy, especially in multicellular eukaryotes. Here, we present a set of guidelines for investigators to select and interpret methods to examine autophagy and related processes, and for reviewers to provide realistic and reasonable critiques of reports that are focused on these processes. These guidelines are not meant to be a dogmatic set of rules, because the appropriateness of any assay largely depends on the question being asked and the system being used. Moreover, no individual assay is perfect for every situation, calling for the use of multiple techniques to properly monitor autophagy in each experimental setting. Finally, several core components of the autophagy machinery have been implicated in distinct autophagic processes (canonical and noncanonical autophagy), implying that genetic approaches to block autophagy should rely on targeting two or more autophagy-related genes that ideally participate in distinct steps of the pathway. Along similar lines, because multiple proteins involved in autophagy also regulate other cellular pathways including apoptosis, not all of them can be used as a specific marker for bona fide autophagic responses. Here, we critically discuss current methods of assessing autophagy and the information they can, or cannot, provide. Our ultimate goal is to encourage intellectual and technical innovation in the field

A influência das habilidades em consciência fonológica na terapia para os desvios fonológicos The influence of phonological awareness abilities in therapy for phonological disorder

Este trabalho teve como objetivo analisar as habilidades em consciência fonológica e o progresso (inventário fonético e fonológico e as generalizações) na terapia fonológica. O grupo pesquisado foi constituído por cinco crianças com desvio fonológico, com idades entre 5:0 e 6:11, submetidas à terapia fonológica. Foram analisados os resultados obtidos na avaliação da consciência fonológica pré-tratamento, a fim de verificar o desempenho das crianças quanto ao seu conhecimento fonológico. Realizou-se a avaliação fonológica pré e pós-tratamento, em que foi possível obter os inventários fonéticos e fonológicos dos sujeitos. Após, foram analisadas as generalizações obtidas com a terapia fonológica (itens lexicais não utilizados no tratamento, outras posições na palavra, dentro de uma classe de sons, outra classe de sons). Os resultados evidenciaram que não existe relação entre o desempenho em tarefas de consciência fonológica e os progressos na terapia. Tais resultados corroboram os achados da literatura, confirmando que crianças com desvio fonológico podem ser capazes de responder adequadamente a tarefas metalinguísticas como a consciência fonológica, sem que essa condição as auxilie a corrigir os desvios de sua fala. Sugere-se que este assunto seja mais bem investigado com um número maior de sujeitos, bem como com a avaliação da consciência fonológica pré e pós-terapia, no intuito de se obter dados generalizáveis os quais serão importantes para o entendimento dos casos de desvio fonológico.<br>This study aimed to analyze the phonological awareness skills and progress (phonetic and phonological inventory and generalizations) in phonological therapy. The research group consisted of five children presenting speech disorders, aged 5:0 and 6:11, subjected to phonological therapy. The results of the phonological awareness assessment were analyzed before the treatment in order to verify the performance of children and their phonological knowledge. The evaluation was performed before and after the treatment. It was possible to obtain the phonetic and phonological inventories of the subjects and, after that, the generalizations obtained with phonological therapy were analyzed (considering lexical items that were not used during treatment, other positions in word, within one sound class or another class of sounds). The results showed that there is no relation between the performance in phonological awareness tasks and the evolution of the phonological therapy. On the other hand, the results agree with the research findings from the literature, reinforcing the idea that, children with phonological disorder can be able to react properly to metalinguistic tasks such as phonological awareness without being able to correct their speech problems. Finally, it can be conclude that this research subject should be investigated deeper and another analysis should be carried out involving a higher number of subjects, including the phonological awareness evaluation before and after therapy. By doing this, it will be possible to obtain other important data to improve the treatment of phonological disorder