Co-evolution is the primary force shaping termite gut microbial communities

Tese de Mestrado em Robótica apresentada à Faculdade de Ciências e Tecnologia da Universidade de CoimbraThis work is integrated in a project of development of a novel measurement device, the BMG-4 sensor, and its application in the calibration of industrial robots. The aim of the work is to define procedures and strategies that enable, through the BMG-4, to identify both geometric and compliance errors that are present in 6-axes serial industrial robots. The importance of accuracy and robot calibration as well as the problem of the suitability of most measurement systems to industrial environments is highlighted. Consequently, the BMG-4 is introduced as a solution that meets the demands of those conditions. A geometrical methodology is defined to determine the direction of a robot’s axis and to assess its accuracy. A protocol that allows to identify the real angular geometric parameters of the robot, as well as the offsets of some axes is presented. Then, a strategy is developed in order to be able to identify the compliances of the last five axes of the robot. All the tests are performed in an ABB IRB 6600 industrial robot. For axes 2 and 3, the maximum values obtained for inaccuracy are 0,062° and 0,229°, respectively. Also, the robot presents several considerable joints’ offsets errors. For axes 4 and 5 those values are −0,99° and 0,83°. The combined offset of axes 2 and 3 is −0,28°. The stiffness of axis 2 is determined, having an estimated value of 2,4 × 106 N.m/rad. Finally, a standard robot convention is proposed in order to correct the identified errors with a generalized compensation algorithm.Este trabalho está integrado num projeto de desenvolvimento de um novo dispositivo de medição, o sensor BMG-4, e da sua aplicação na calibração de robôs industriais. O objetivo do trabalho é a definição de procedimentos e estratégias que permitem, através do BMG-4, identificar erros provenientes tanto da geometria como da flexibilidade das articulações do robô que estão presentes em robôs industriais de 6-eixos. A importância da precisão e da calibração robótica, bem como o problema da adequação da maioria dos sistemas de medição em ambientes industriais são destacados. Consequentemente, o BMG-4 é introduzido como uma solução que satisfaz essas condições. Uma metodologia geométrica é definida para determinar a direção do eixo de um robô e para avaliar a sua precisão. Um protocolo que permite identificar os parâmetros geométricos angulares reais do robô, bem como os offsets de alguns eixos, é apresentado. Em seguida, uma estratégia é desenvolvida de maneira a identificar os valores de rigidez dos últimos cinco eixos do robô. Todos os testes são realizados no robô industrial ABB IRB 6600. Para os eixos 2 e 3, os valores máximos obtidos para a análise da imprecisão são 0,062° e 0,229°, respectivamente. Além disso, o robô apresenta erros de offset consideráveis. Para os eixos 4 e 5 esses valores são −0,99° e 0,83°. O valor combinado dos eixos 2 e 3 é −0,28°. A rigidez do eixo 2 é determinada, tendo um valor estimado de 2,4 × 106 N.m/rad. Finalmente, uma convenção standard de robôs é proposta e cuja finalidade é corrigir os erros previamente identificados através de um algoritmo de compensação global e independente do fabricante do robô considerado

The phylogenetic landscape and nosocomial spread of the multidrug-resistant opportunist Stenotrophomonas maltophilia

Recent studies portend a rising global spread and adaptation of human- or healthcare-associated pathogens. Here, we analyse an international collection of the emerging, multidrug-resistant, opportunistic pathogen Stenotrophomonas maltophilia from 22 countries to infer population structure and clonality at a global level. We show that the S. maltophilia complex is divided into 23 monophyletic lineages, most of which harbour strains of all degrees of human virulence. Lineage Sm6 comprises the highest rate of human-associated strains, linked to key virulence and resistance genes. Transmission analysis identifies potential outbreak events of genetically closely related strains isolated within days or weeks in the same hospitals

A phylogenomic analysis of the bacterial phylum fibrobacteres

The Fibrobacteres has been recognized as a bacterial phylum for over a decade, but little is known about the group beyond its environmental distribution, and characterization of its sole cultured representative genus, Fibrobacter, after which the phylum was named. Based on these incomplete data, it is thought that cellulose hydrolysis, anaerobic metabolism, and lack of motility are unifying features of the phylum. There are also contradicting views as to whether an uncultured sister lineage, candidate phylum TG3, should be included in the Fibrobacteres. Recently, chitin degrading cultured representatives of TG3 were isolated from a hypersaline soda lake, and the genome of one species, Chitinivibrio alkaliphilus, sequenced and described in detail. Here, we performed a comparative analysis of Fibrobacter succinogenes, C. alkaliphilus and eight near or substantially complete Fibrobacteres/TG3 genomes of environmental populations recovered from termite gut, anaerobic digester, and sheep rumen metagenomes. We propose that TG3 should be amalgamated with the Fibrobacteres phylum based on robust monophyly of the two lineages and shared character traits. Polymer hydrolysis, using a distinctive set of glycoside hydrolases and binding domains, appears to be a prominent feature of members of the Fibrobacteres. Not all members of this phylum are strictly anaerobic as some termite gut Fibrobacteres have respiratory chains adapted to the microaerophilic conditions found in this habitat. Contrary to expectations, flagella-based motility is predicted to be an ancestral and common trait in this phylum and has only recently been lost in F. succinogenes and its relatives based on phylogenetic distribution of flagellar genes. Our findings extend current understanding of the Fibrobacteres and provide an improved basis for further investigation of this phylum

A molecular survey of Australian and North American termite genera indicates that vertical inheritance is the primary force shaping termite gut microbiomes

Background: Termites and their microbial gut symbionts are major recyclers of lignocellulosic biomass. This important symbiosis is obligate but relatively open and more complex in comparison to other well-known insect symbioses such as the strict vertical transmission of Buchnera in aphids. The relative roles of vertical inheritance and environmental factors such as diet in shaping the termite gut microbiome are not well understood