Functional role of phenylacetic acid from metapleural gland secretions in controlling fungal pathogens in evolutionarily derived leaf-cutting ants

Fungus-farming ant colonies vary four to five orders of magnitude in size. They employ compounds from actinomycete bacteria and exocrine glands as antimicrobial agents. Atta colonies have millions of ants and are particularly relevant for understanding hygienic strategies as they have abandoned their ancestors'' prime dependence on antibiotic-based biological control in favour of using metapleural gland (MG) chemical secretions. Atta MGs are unique in synthesizing large quantities of phenylacetic acid (PAA), a known but little investigated antimicrobial agent. We show that particularly the smallest workers greatly reduce germination rates of Escovopsis and Metarhizium spores after actively applying PAA to experimental infection targets in garden fragments and transferring the spores to the ants'' infrabuccal cavities. In vitro assays further indicated that Escovopsis strains isolated from evolutionarily derived leaf-cutting ants are less sensitive to PAA than strains from phylogenetically more basal fungus-farming ants, consistent with the dynamics of an evolutionary arms race between virulence and control for Escovopsis, but not Metarhizium. Atta ants form larger colonies with more extreme caste differentiation relative to other attines, in societies characterized by an almost complete absence of reproductive conflicts. We hypothesize that these changes are associated with unique evolutionary innovations in chemical pest management that appear robust against selection pressure for resistance by specialized mycopathogens.     

Membrane-associated GTPases in bacteria

Members of the GTPase superfamily are extremely important in regulating membrane signalling pathways in all cells. This review focuses on membrane-associated GTPases that have been described in prokaryotes. In bacteria, LepA and NodQ are very similar to protein synthesis elongation factors but apparently have membrane-related functions. The amino acid sequences of FtsY and Ffh are clearly related to eukaryotic factors involved in protein secretion. Obg and Era are not closely related to any GTPase subgroup according to amino acid sequence comparisons, but they are essential for viability. In spite of similarities to well-studied eukaryotic proteins the signalling pathways of these cellular regulators, with the exception of NodQ, have not yet been elucidated.     

Translocation from the chloroplast stroma into the thylakoid lumen allows expression of recombinant epidermal growth factor in transplastomic tobacco plants

Transgenic Research - Chloroplast transformation has many potential advantages for the production of recombinant proteins in plants. However, it has been reported that chloroplast expression of...     

Shifts in bacterial communities of two caribbean reef-building coral species affected by white plague disease

Coral reefs are deteriorating at an alarming rate mainly as a consequence of the emergence of coral diseases. The white plague disease (WPD) is the most prevalent coral disease in the southwestern Caribbean, affecting dozens of coral species. However, the identification of a single causal agent has proved problematic. This suggests more complex etiological scenarios involving alterations in the dynamic interaction between environmental factors, the coral immune system and the symbiotic microbial communities. Here we compare the microbiome of healthy and WPD-affected corals from the two reef-building species Diploria strigosa and Siderastrea siderea collected at the Tayrona National Park in the Caribbean of Colombia. Microbiomes were analyzed by combining culture-dependent methods and pyrosequencing of 16S ribosomal DNA (rDNA) V5-V6 hypervariable regions. A total of 20 410 classifiable 16S rDNA sequences reads were obtained including all samples. No significant differences in operational taxonomic unit diversity were found between healthy and affected tissues; however, a significant increase of Alphaproteobacteria and a concomitant decrease in the Beta- and Gammaproteobacteria was observed in WPD-affected corals of both species. Significant shifts were also observed in the orders Rhizobiales, Caulobacteriales, Burkholderiales, Rhodobacterales, Aleteromonadales and Xanthomonadales, although they were not consistent between the two coral species. These shifts in the microbiome structure of WPD-affected corals suggest a loss of community-mediated growth control mechanisms on bacterial populations specific for each holobiont system.     

A GTP-binding protein (Era) has an essential role in growth rate and cell cycle control in Escherichia coli.

Era is a membrane-associated GTP-binding protein which is essential for cell growth in Escherichia coli. In order to examine the physiological role of Era, strains in which Era was expressed at 40 degrees C but completely repressed at 27 degrees C were constructed. The growth of these strains was inhibited at the nonpermissive temperature, and cells became elongated. Under such conditions, no constrictions or septum formation could be detected by phase-contrast microscopy, and DNA segregation was apparently normal as revealed by fluorescence staining. These data demonstrate that Era has an essential function in cell growth rate control in liquid media and that depletion of Era blocks cell division either directly or indirectly. Thus, the role of GTP-binding proteins as important regulators of cell growth and division may be ubiquitous in nature.     

A Three-Dimensional Human Atrial Model with Fiber Orientation. Electrograms and Arrhythmic Activation Patterns Relationship

The most common sustained cardiac arrhythmias in humans are atrial tachyarrhythmias, mainly atrial fibrillation. Areas of complex fractionated atrial electrograms and high dominant frequency have been proposed as critical regions for maintaining atrial fibrillation; however, there is a paucity of data on the relationship between the characteristics of electrograms and the propagation pattern underlying them. In this study, a realistic 3D computer model of the human atria has been developed to investigate this relationship. The model includes a realistic geometry with fiber orientation, anisotropic conductivity and electrophysiological heterogeneity. We simulated different tachyarrhythmic episodes applying both transient and continuous ectopic activity. Electrograms and their dominant frequency and organization index values were calculated over the entire atrial surface. Our simulations show electrograms with simple potentials, with little or no cycle length variations, narrow frequency peaks and high organization index values during stable and regular activity as the observed in atrial flutter, atrial tachycardia (except in areas of conduction block) and in areas closer to ectopic activity during focal atrial fibrillation. By contrast, cycle length variations and polymorphic electrograms with single, double and fragmented potentials were observed in areas of irregular and unstable activity during atrial fibrillation episodes. Our results also show: 1) electrograms with potentials without negative deflection related to spiral or curved wavefronts that pass over the recording point and move away, 2) potentials with a much greater proportion of positive deflection than negative in areas of wave collisions, 3) double potentials related with wave fragmentations or blocking lines and 4) fragmented electrograms associated with pivot points. Our model is the first human atrial model with realistic fiber orientation used to investigate the relationship between different atrial arrhythmic propagation patterns and the electrograms observed at more than 43000 points on the atrial surface.     

Determination of aldoses and uronic acid content of vegetable fiber.

The factors affecting the stability, hydrolysis, reduction, acetylation, quantitation, and identification of the neutral sugars from vegetable fiber preparations have been studied critically and optimized. The recommended method offers a consolidation of the recent modifications of the alditol acetate procedure for the estimation of neutral sugars. The recovery of the sugars was tested by glc and ion-exchange chromatography. Also, the modified carbazole method of Bitter and Muir was adapted to make it applicable for the estimation of uronic acid content of fiber because uronic acid cannot be estimated quantitatively by the acetylation procedure. It is emphasized that the proposed method is applicable only to highly purified fiber preparations which are free of coprecipitated intracellular compounds. Also, the levels of pentoses and hexoses in the fiber must be well defined and a suitable correction made for their interference in the assay.     

Morphological assessment of the Octopus vulgaris species complex evaluated in light of molecular‐based phylogenetic inferences

Cryptic species are common in the ocean, particularly among marine invertebrates such as octopuses. Delineating cryptic species is particularly problematic in octopus taxonomy where the plasticity recorded among taxonomic characters often results in low resolution at the species level. This study investigated the morphological relationships among seven phylogenetic clades (identified using cytochrome c oxidase subunit I) of the broadly distributed Octopus vulgaris species complex and close relatives. Morphological analyses in this study were successful in delimiting O. sinensis, Brazilian O. vulgaris and O. vulgaris sensu stricto, which was congruent with the molecular findings of this study. Analyses based on male morphology were successful in distinguishing 14 of 15 total pairwise comparisons and proved to be a more reliable indicator of species‐level relationships in comparison with female morphology. The majority of characters with the greatest discriminatory power were male sexual traits. Significant morphological differences were also recorded among sampling localities of conspecifics, with phenotype showing correlation with local environmental data. The findings of this study support the hypothesis that multiple O. vulgaris‐like species are currently being incorrectly treated under a single species name, O. vulgaris. Octopuses being exported globally under the name O. vulgaris are of extremely high fisheries market value and profile. Our findings have potentially significant implications for the naming and conservation of commercially harvested members of this species complex throughout their ranges.