Descubriendo la Luz: acercando la óptica a la sociedad

XIII Reunión Nacional de Óptica. -- Evento online, 22-24 noviembre 2021Peer reviewe

Discovering Light: Fun Experiments with Optics

Editor(s): Maria Viñas-Peña.Light is an element that draws together many areas of human knowledge: physics, chemistry, biology, astronomy, engineering, and art. Moreover, optical phenomena and the technologies based on them are widespread in our daily lives. However, it can be difficult to understand or explain these phenomena. What is light? Where are optics and photonics present in our lives and in nature? What lies behind different optical phenomena? What is an optical instrument? How does the eye resemble an optical instrument? How can we explain human vision? This book, written by a group of young scientists, answers these questions and many more to help you to get to know the exciting world of optics and photonics. It is intended for the general public, with an emphasis on students at all levels of secondary education. A variety of easy-to-follow experiments related to different optical phenomena and technologies are presented. All of them are preceded by an explanation of the concepts and accompanied by numerous illustrations and curiosities. All of it is meant for you to have fun with optics and photonics!Peer reviewe

Violacein and biofilm production in Janthinobacterium lividum

Aims: To analyse the environmental stimuli modulating violacein and biofilm production in Janthinobacterium lividum. Methods and Results: Violacein and biofilm production by J. lividum DSM1522T was assayed in different growth conditions. Our data suggest that violacein and biofilm production is controlled by the carbon source, being inhibited by glucose and enhanced by glycerol. J. lividum produced violacein also in the presence of different sub-inhibitory concentrations of ampicillin. As opposite, the production of N-acylhomoserine lactone(s), quorum sensing regulators was shown to be positively regulated by glucose. Moreover, violaceinproducing cultures of J. lividum showed higher CFU counts than violaceinnonproducing ones. Conclusions: Taken together, our results suggest that violacein and biofilm production could be regulated by a common metabolic pathway and that violacein as well as biofilm could represent a response to environmental stresses and a key factor in the survival mechanisms of J. lividum. Significance and Impact of the Study: Although several recent studies disclosed a number of interesting biological properties of violacein, few data are reported on the physiologic function of violacein in J. lividum. This paper adds new information on the complex mechanisms allowing and regulating bacterial life in hostile environments

Both lactoferrin and iron influence aggregation and biofilm formation in Streptococcus mutans

Streptococcus mutans, a gram-positive immobile bacterium, is an oral pathogen considered to be the principal etiologic agent of dental caries. Although some researches suggest that trace metals, including iron, can be associated with dental caries, the function of salivary iron and lactoferrin in the human oral cavity remains unclear. The data reported in this study indicates that iron-deprived saliva (Fe3+ 1 microM) inhibits both phenomena. Our findings are consistent with the hypothesis that S. mutans aggregation and biofilm formation are negatively iron-modulated as confirmed by the different effect of bovine lactoferrin (bLf), added to saliva at physiological concentration (20 microg/ml) in the apo- or iron-saturated form. Even if saliva itself induces bacterial aggregation, iron binding capability of apo-bLf is responsible for the noticeable increase of bacterial aggregation and biofilm development in the fluid and adherent phases. On the contrary, iron-saturated bLf decreases aggregation and biofilm development by supplying iron to S. mutans. Therefore, the iron-withholding capability of apo-Lf or native Lf is an important signal to which S. mutans counteracts by leaving the planktonic state and entering into a new lifestyle, biofilm, to colonize and persist in the human oral cavity. In addition, another function of bLf, unrelated to its iron binding capability, is responsible for the inhibition of the adhesion of S. mutans free, aggregated or biofilm on abiotic surfaces. Both these activities of lactoferrin, related and unrelated to the iron binding capability, could have a key role in protecting the human oral cavity from S. mutans pathogenicity