Lectura 25 Marzo 2015

Lifestyle of Vibrio cholerae foster gene transfers
Melanie Blokesh

Waterborne Vibrio cholerae bacteria cause cholera, a pandemic during the last 50 years across Asia, Africa, and Latin America. Although most infected individuals do not develop severe symptoms, some become violently ill with severe diarrhea, vomiting, and cramps, and the loss of body fluids, if untreated, can lead to shock and death. V. cholerae, which is primarily encountered in estuaries, rivers, and coastal waters in its environmental reservoir, is found not only in a free-living state but also associated with phytoplankton and zooplankton (Fig. 1). Because factors such as increasing temperatures, the El Niño phenomenon, and heavy rainfalls and floods can raise the abundance of phytoplankton and zooplankton, and, along with them, cholera bacteria, changing climatic conditions could well drive the re-emergence of cholera.

Lectura 23 Marzo 2015

Horizontal gene transfer in evolution: facts and challenges
Luis Boto

The contribution of horizontal gene transfer to evolution has been controversial since it was suggested to be a force driving evolution in the microbial world. In this paper, I review the current standpoint on horizontal gene transfer in evolutionary thinking and discuss how important horizontal gene transfer is in evolution in the broad sense, and particularly in prokaryotic evolution. I review recent literature, asking, first, which processes are involved in the evolutionary success of transferred genes and, secondly, about the extent of horizontal gene transfer towards different evolutionary times. Moreover, I discuss the feasibility of reconstructing ancient phylogenetic relationships in the face of horizontal gene transfer. Finally, I discuss how horizontal gene transfer fits in the current neo-Darwinian evolutionary paradigm and conclude there is a need for a new evolutionary paradigm that includes horizontal gene transfer as well as other mechanisms in the explanation of evolution.

Lectura 2 - 18 Marzo 2015

Chemical warfare between microbes promotes biodiversity
Tamás L. Czárán, Rolf F. Hoekstra and Ludo Pagie

Evolutionary processes generating biodiversity and ecological mechanisms maintaining biodiversity seem to be diverse themselves. Conventional explanations of biodiversity such as niche differentiation, density-dependent predation pressure, or habitat heterogeneity seem satisfactory to explain diversity in communities of macrobial organisms such as higher plants and animals. For a long time the often high diversity among microscopic organisms in seemingly uniform environments, the famous ‘‘paradox of the plankton,’’ has been difficult to understand. The biodiversity in bacterial communities has been shown to be sometimes orders of magnitudes higher than the diversity of known macrobial systems. Based on a spatially explicit game theoretical model with multiply cyclic dominance structures, we suggest that antibiotic interactions within microbial communities may be very effective in maintaining diversity.

Lectura 1 - 18 Marzo 2015

Evolution of species interactions in a biofilm community
Susse Kirkelund Hansen, Paul B. Rainey, Janus A. J. Haagensen & Søren Molin

Biofilms are spatially structured communities of microbes whose function is dependent on a complex web of symbiotic interactions. Localized interactions within these assemblages are predicted to affect the coexistence of the component species, community structure6 and function, but there have been few explicit empirical analyses of the evolution of interactions. Here we show, with the use of a two-species community, that selection in a spatially structured environment leads to the evolution of an exploitative interaction. Simple mutations in the genome of one species caused it to adapt to the presence of the other, forming an intimate and specialized association. The derived community was more stable and more productive than the ancestral community. Our results show that evolution in a spatially structured environment can stabilize interactions between species, provoke marked changes in their symbiotic nature and affect community function.

Lectura 11 Marzo 2015

The Social Lives of Microbes

Stuart A.West, Stephen P. Diggle, Angus Buckling, Andy Gardner and Ashleigh S. Griffin

Our understanding of the social lives of microbes has been revolutionized over the past 20 years. It used to be assumed that bacteria and other microorganisms lived relatively independent unicellular lives, without the cooperative behaviors that have provoked so much interest in mammals, birds, and insects. However, a rapidly expanding body of research has completely overturned this idea, showing that microbes indulge in a variety of social behaviors involving complex systems of cooperation, communication, and synchronization. Work in this area has already provided some elegant experimental tests of social evolutionary theory, demonstrating the importance of factors such as relatedness, kin discrimination, competition between relatives, and enforcement of cooperation. Our aim here is to review these social behaviors, emphasizing the unique opportunities they offer for testing existing evolutionary theory as well as highlighting the novel theoretical problems that they pose.

Lectura 09 Marzo 2015

The Genotypic View of Social Interactions in Microbial Communities

Sara Mitri and Kevin Richard Foster

Dense and diverse microbial communities are found in many environments. Disentangling the social interactions between strains and species is central to understanding microbes and how they respond to perturbations. However, the study of social evolution in microbes tends to focus on single species. Here, we broaden this perspective and review evolutionary and ecological theory relevant to microbial interactions across all phylogenetic scales. Despite increased complexity, we reduce the theory to a simple null model that we call the genotypic view. This states that cooperation will occur when cells are surrounded by identical genotypes at the loci that drive interactions, with genetic identity coming from recent clonal growth or horizontal gene transfer (HGT). In contrast, because cooperation is only expected to evolve between different genotypes under restrictive ecological conditions, different genotypes will typically compete. Competition between two genotypes includes mutual harm but, importantly, also many interactions that are beneficial to one of the two genotypes, such as predation. The literature offers support for the genotypic view with relatively few examples of cooperation between genotypes. However, the study of microbial interactions is still at an early stage.Weoutline the logic andmethods that help to better evaluate our perspective and move us toward rationally engineering microbial communities to our own advantage