Formation and maintenance of nitrogen-fixing cell patterns in filamentous cyanobacteria

Cyanobacteria forming one-dimensional filaments are paradigmaticmodel organisms of the transition between unicellular andmulticellular living forms. Under nitrogen-limiting conditions, infilaments of the genus Anabaena, some cells differentiate into heterocysts,which lose the possibility to divide but are able to fixenvironmental nitrogen for the colony. These heterocysts form aquasiregular pattern in the filament, representing a prototype ofpatterning and morphogenesis in prokaryotes. Recent years haveseen advances in the identification of the molecular mechanism regulatingthis pattern. We use these data to build a theory on heterocystpattern formation, for which both genetic regulation and theeffects of cell division and filament growth are key components. Thetheory is based on the interplay of three generic mechanisms: localautoactivation, early long-range inhibition, and late long-range inhibition.These mechanisms can be identified with the dynamics ofhetR, patS, and hetN expression. Our theory reproduces quantitativelythe experimental dynamics of pattern formation and maintenancefor wild type and mutants. We find that hetN alone is notenough to play the role as the late inhibitory mechanism: a secondmechanism, hypothetically the products of nitrogen fixation suppliedby heterocysts, must also play a role in late long-range inhibition.The preponderance of even intervals between heterocysts arisesnaturally as a result of the interplay between the timescales of geneticregulation and cell division.We also find that a purely stochasticinitiation of the pattern, without a two-stage process, is enoughto reproduce experimental observations.Funding from the Spanish Ministry of Economy and Competitiveness through Grant PHYSDEV (FIS2012-32349) and the Ramón y Cajal Program (to S.A.)

Modelos de superficies e intercaras : transiciones de fase, desorden y aplicaciones

En esta memoria estudiamos varios modelos formulados en una dimensión. Primero estudiamos el modelo de sine-Gordon, que es adecuado para estudiar el crecimiento de superficies sólidas, encontrando un comportamiento de tamaño finito semejante a una transición de fase termodinámica. A continuación hemos presentado dos modelos de la transición de mojado de superficies. Hemos utilizado la versión con desorden de estos modelos para caracterizar la dependencia con la secuencia genética de la temperatura de desnaturalización del ADN. Combinando uno de los modelos de mojado con el de sine-Gordon proponemos un modelo nuevo, cuya versión con desorden nos permite hacer comparaciones con el modelo de sine-Gordon en dos dimensiones. De ello hacemos la conjetura que la fase superrugosa del modelo en dos dimensiones es en realidad una fase plana dominada por el desorden. A continuación, utilizando el modelo de Dauxois-Peyrard-Bishop, estudiamos el efecto de las burbujas de desnaturalización en el ADN. Nuestros resultados coinciden con los experimentales, de lo cual deducimos importantes consecuencias sobre la dinámica de burbujas. Finalmente, proponemos un modelo nuevo para el estudio de la dinámica de horquillas de ADN que nos permite poner a prueba las interpretaciones vigentes sobre los resultados experimentales

Modelling of patA and hetF gene function in Anabaena heterocyst formation

[Póster presentado a]: XXII Congreso de Física Estadística (FisEs'18), Madrid, 18-20 de octubre de 2018.Differentiated cell types can form patterns in filamentous cyanobacteria. Specifically the genus Anabaena has received special interest because under nitrogen-limiting conditions some of the vegetative cells differentiate into a nitrogen-fixing form called heterocyst [1]. These heterocysts cannot undergo cell division or have photosynthetic activity, but share fixed nitrogen products with the whole filament. In order to efficiently distribute the fixed nitrogen, heterocysts are arranged forming quasiregular patterns in the filament..

Nitrogen-fixing cyanobacteria are tuned for evolvability

Cyanobacteria produce a significant fraction of the oxygen on the environment and, together with archaea, they fix atmospheric nitrogen used by all other organisms. One of the first forms of multicellular organisms on Earth are filamentous cyanobacteria, which constitutCyanobacteria produce a significant fraction of the oxygen on the environment and, together with archaea, they fix atmospheric nitrogen used by all other organisms. One of the first forms of multicellular organisms on Earth are filamentous cyanobacteria, which constitute a paradigmatic model organism of the transition between unicellular and multicellular living forms. The genus Anabaena forms colonies with cells arranged in one-dimensional filaments; under nitrogen-limiting conditions some cells can differentiate into a nitrogen-fixing heterocysts, forming regular patterns to effectively provide nitrogen for the colony. e a paradigmatic model organism of the transition between unicellular and multicellular living forms. The genus Anabaena forms colonies with cells arranged in one-dimensional filaments; under nitrogen-limiting conditions some cells can differentiate into a nitrogen-fixing heterocysts, forming regular patterns to effectively provide nitrogen for the colony..

White Paper 2: Origins, (Co)Evolution, Diversity & Synthesis Of Life

Publicado en Madrid, 185 p. ; 17 cm.How life appeared on Earth and how then it diversified into the different and currently existing forms of life are the unanswered questions that will be discussed this volume. These questions delve into the deep past of our planet, where biology intermingles with geology and chemistry, to explore the origin of life and understand its evolution, since “nothing makes sense in biology except in the light of evolution” (Dobzhansky, 1964). The eight challenges that compose this volume summarize our current knowledge and future research directions touching different aspects of the study of evolution, which can be considered a fundamental discipline of Life Science. The volume discusses recent theories on how the first molecules arouse, became organized and acquired their structure, enabling the first forms of life. It also attempts to explain how this life has changed over time, giving rise, from very similar molecular bases, to an immense biological diversity, and to understand what is the hylogenetic relationship among all the different life forms. The volume further analyzes human evolution, its relationship with the environment and its implications on human health and society. Closing the circle, the volume discusses the possibility of designing new biological machines, thus creating a cell prototype from its components and whether this knowledge can be applied to improve our ecosystem. With an effective coordination among its three main areas of knowledge, the CSIC can become an international benchmark for research in this field

Terminal heterocyst differentiation in the Anabaena patA mutant as a result of post-transcriptional modifications and molecular leakage

The Anabaena genus is a model organism of filamentous cyanobacteria whose vegetative cells can differentiate under nitrogen-limited conditions into a type of cell called heterocyst. These heterocysts lose the possibility to divide and are necessary for the colony because they can fix and share environmental nitrogen. In order to distribute the nitrogen efficiently, heterocysts are arranged to form a quasi-regular pattern whose features are maintained as the filament grows. Recent efforts have allowed advances in the understanding of the interactions and genetic mechanisms underlying this dynamic pattern. However, the main role of the patA and hetF genes are yet to be clarified; in particular, the patA mutant forms heterocysts almost exclusively in the terminal cells of the filament. In this work, we investigate the function of these genes and provide a theoretical model that explains how they interact within the broader genetic network, reproducing their knock-out phenotypes in several genetic backgrounds, including a nearly uniform concentration of HetR along the filament for the patA mutant. Our results suggest a role of hetF and patA in a post-transcriptional modification of HetR which is essential for its regulatory function. In addition, the existence of molecular leakage out of the filament in its boundary cells is enough to explain the preferential appearance of terminal heterocysts, without any need for a distinct regulatory pathway.This research was supported by MCIN/AEI/10.13039/501100011033/ and FEDER Una manera de hacer Europa through grant no. FIS2016-78313-P to S.A and the associated, and MCIN/AEI/10.13039/501100011033 through grant BADS, no. PID2019-109320GB-100, to S.A. and J. M-G. The Spanish MICINN has also funded the "Severo Ochoa" Centers of Excellence to CNB, SEV

Mathematical models of nitrogen-fixing cell patterns in filamentous cyanobacteria

The Anabaena genus is a model organism of filamentous cyanobacteria whose vegetative cells can differentiate under nitrogen-limited conditions into a type of cell called a heterocyst. These heterocysts lose the possibility to divide and are necessary for the filament because they can fix and share environmental nitrogen. In order to distribute the nitrogen efficiently, heterocysts are arranged to form a quasi-regular pattern whose features are maintained as the filament grows. Recent efforts have allowed advances in the understanding of the interactions and genetic mechanisms underlying this dynamic pattern. Here, we present a systematic review of the existing theoretical models of nitrogen-fixing cell differentiation in filamentous cyanobacteria. These filaments constitute one of the simplest forms of multicellular organization, and this allows for several modeling scales of this emergent pattern. The system has been approached at three different levels. From bigger to smaller scale, the system has been considered as follows: at the population level, by defining a mean-field simplified system to study the ratio of heterocysts and vegetative cells; at the filament level, with a continuous simplification as a reaction-diffusion system; and at the cellular level, by studying the genetic regulation that produces the patterning for each cell. In this review, we compare these different approaches noting both the virtues and shortcomings of each one of them.This research was supported by MCIN/AEI/10.13039/501100011033 and FEDER Una manera de hacer Europa through grant no. FIS2016-78313-P to SA, the associated FPI contract BES-2017-079755 to PC-F, and MCIN/AEI/10.13039/501100011033 through grant BADS, no. PID2019-109320GB-100, to SA and JM-G. The Spanish MICINN has also funded the “Severo Ochoa” Centers of Excellence to CNB, SEV 2017-0712. CSIC Library covers 25% of the APC

Origins, (Co)Evolution and Diversity of Life

Some of the mayor known unknowns of modern science deal with how lifeappeared on Earth and how from there it diversified into the different life forms present today. These questions delve into the deep past of our planet, where biology intermingles with geology and chemistry, to explore the origin of life. In addition, by learning how biological systems change over time, we can design novel biological machines based on this knowledge to fulfil unmet tasks.The main overarching theme addressed in this topic is evolution. Not because of much repeated is Theodosius Dobzhansky 1964’s statement less true: Nothing makes sense in biology except in the light of evolution. Understanding evolution will provide us with clues about the origin of life, and on the precise molecular mechanisms that operate in living beings and how they change in time. We will then be ready to attempt putting together these mechanisms in novel ways, paving the way for synthetic biology. Evolution is the single most overarching and one of the few, if not only, general principles in Biology.In this topic, we explore and discuss several aspects related to the study of evolution, as a fundamental and core discipline in Life Sciences, which must permeate different research areas in the coming years.Peer reviewe