The Escherichia coli twin-arginine translocation apparatus incorporates a distinct form of TatABC complex, spectrum of modular TatA complexes and minor TatAB complex

The Tat system transports folded proteins across bacterial plasma and plant thylakoid membranes. To date, three key Tat subunits have been identified and mechanistic studies indicate the presence of two types of complex: a TatBC-containing substrate-binding unit and a separate TatA complex. Here, we used blue-native gel electrophoresis and affinity purification to study the nature of these complexes in Escherichia coli. Analysis of solubilized membrane shows that the bulk of TatB and essentially all of the TatC is found in a single 370kDa TatABC complex. TatABC was purified to homogeneity using an affinity tag on TatC and this complex runs apparently as an identical band. We conclude that this is the primary core complex, predicted to contain six or seven copies of TatBC together with a similar number of TatA subunits. However, the data indicate the presence of an additional form of Tat complex containing TatA and TatB, but not TatC; we speculate that this may be an assembly or disassembly intermediate of the translocator. The vast majority of TatA is found in separate complexes that migrate in blue-native gels as a striking ladder of bands with sizes ranging from under 100 kDa to over 500 kDa. Further analysis shows that the bands differ by an average of 34 kDa, indicating that TatA complexes are built largely, but possibly not exclusively, from modules of three or four TatA molecules. The range and nature of these complexes are similar in a TatC mutant that is totally inactive, indicating that the ladder of bands does not stem from ongoing translocation activity, and we show that purified TatA can self-assemble in vitro to form similar complexes. This spectrum of TatA complexes may provide the flexibility required to generate a translocon capable of transporting substrates of varying sizes across the plasma membrane in a folded state.     

A new species of Creagrutus Günther (Teleostei: Ostariophysi: Characiformes), from the upper Rio Paraná basin, central Brazil

Creagrutus varii n. sp. is described based on material from the Rio São Marcos basin, in the upper Rio Paraná system, Goiás State, Brazil. This is the first record of Creagrutus in the upper Rio Paraná. The new species is proposed to be the sister group of the remaining species of Creagrutus . Creagrutus varii differs from congeners in the morphology of the maxilla, primordial ligament, premaxillary dentition and other features. The evolution of premaxillary tooth morphology in Piabina and Creagrutus and the biogeography of the Rio Paranaíba basin are discussed.     

Poptella fuscata,a new Stethaprionini from the upper Amazon basin,Peru (Characiformes: Characidae)

A new species of Poptella is described from the Río Putumayo, Upper Río Amazon basin, Peru. The new species is distinguished from congeners by having a dense field of dark chromatophores homogeneously spread over the posterior half of the body, posterior humeral blotch extending to three to four horizontal scale rows below the lateral line, and a higher number of branched dorsal-fin rays. The new species can be readily distinguished from P. paraguayensis by having a comparatively shorter predorsal spine.     

Moenkhausia andrica (Characiformes: Characidae): a new species from the rio Tapajós basin,Brazil, with minute fin hooklets in females

In this study, a new species of Moenkhausia is described from the upper rio Juruena, rio Tapajós basin, Brazil. It is distinguished from all congeners by the presence of minute bony hooks in all fins of both mature females and males and combination of a prepelvic region flattened, dorsal portion of the humeral blotch extending two scales horizontally and vertically, lateral line with 28–32 scales, five scale series above and below lateral line; circumpeduncular scales 13–14, anal-fin rays 16–19 and dorsal portion of eyes blue in live specimens. The new species is also supported by high divergence in the mitochondrial gene cytochrome c oxidase subunit I (COI). The presence of minute fin bony hooks in both females and males, population variations and late development of the lateral line in Moenkhausia andrica are discussed.     

Morphological and molecular evidence for two new species of Tetragonopterus (Characiformes: Characidae) from central Brazil

The combination of morphological and molecular data of Tetragonopterus species collected in the Rio Araguaia basin allows the recognition of two undescribed species that are presented in this article. These species are distinguished from their congeners (Tetragonopterus anostomus, Tetragonopterus argenteus, Tetragonopterus carvalhoi, Tetragonopterus chalceus and Tetragonopterus rarus) by characters related to the number and morphology of the teeth, the numbers of gill rakers on the upper and lower limbs of the first gill arch, the number of predorsal scales and the overall colour pattern. In addition, the analysis of mitochondrial DNA sequences identified an accentuated genetic distance between these two new species and their congeners. A discussion of the phylogenetic relationships within Tetragonopterus is provided.     

Amazon aquatic biodiversity imperiled by oil spills

Oil exploitation poses a significant threat to freshwater biodiversity, and future plans to develop petroleum leases in the Amazon Basin should be seem with caution. A series of oil spills have significantly affected biodiversity and human activities in some Amazonian basins, indicating that disturbances by petroleum activities will increase in the region, particularly in upper basins and river headwaters. Measures are needed to reduce the risk of spills and to minimize their impacts. More fundamentally, changes in decision making are needed that give proper weight to these impacts.     

Molecular phylogeny of Moenkhausia (Characidae) inferred from mitochondrial and nuclear DNA evidence

Moenkhausia is one of the most speciose genera in Characidae, currently composed of 75 nominal species of small fishes distributed across South American hydrographic basins, primarily the Amazon and Guyanas. Despite the large number of described species, studies involving a substantial number of its species designed to better understand their relationships and putative monophyly are still lacking. In this study, we analysed a large number of species of Moenkhausia to test the monophyly of the genus based on the phylogenetic analysis of DNA sequences of two mitochondrial and three nuclear genes. The in‐group included 29 species of Moenkhausia, and the out‐group was composed of representatives of Characidae and other members of Characiformes. All species of Moenkhausia belong to the same clade (Clade C); however, they appear distributed in five monophyletic groups along with other different genera, which means that Moenkhausia is polyphyletic and indicates the necessity of an extensive revision of the group.     

Phylogenetic relationships within the speciose family Characidae (Teleostei: Ostariophysi: Characiformes) based on multilocus analysis and extensive ingroup sampling

Background

With nearly 1,100 species, the fish family Characidae represents more than half of the species of Characiformes, and is a key component of Neotropical freshwater ecosystems. The composition, phylogeny, and classification of Characidae is currently uncertain, despite significant efforts based on analysis of morphological and molecular data. No consensus about the monophyly of this group or its position within the order Characiformes has been reached, challenged by the fact that many key studies to date have non-overlapping taxonomic representation and focus only on subsets of this diversity.

Results

In the present study we propose a new definition of the family Characidae and a hypothesis of relationships for the Characiformes based on phylogenetic analysis of DNA sequences of two mitochondrial and three nuclear genes (4,680 base pairs). The sequences were obtained from 211 samples representing 166 genera distributed among all 18 recognized families in the order Characiformes, all 14 recognized subfamilies in the Characidae, plus 56 of the genera so far considered incertae sedis in the Characidae. The phylogeny obtained is robust, with most lineages significantly supported by posterior probabilities in Bayesian analysis, and high bootstrap values from maximum likelihood and parsimony analyses.

Conclusion

A monophyletic assemblage strongly supported in all our phylogenetic analysis is herein defined as the Characidae and includes the characiform species lacking a supraorbital bone and with a derived position of the emergence of the hyoid artery from the anterior ceratohyal. To recognize this and several other monophyletic groups within characiforms we propose changes in the limits of several families to facilitate future studies in the Characiformes and particularly the Characidae. This work presents a new phylogenetic framework for a speciose and morphologically diverse group of freshwater fishes of significant ecological and evolutionary importance across the Neotropics and portions of Africa.     

An assessment approach for application of spermatic data in phylogenetic analyses: within the genus Moenkhausia Eigenmann, 1903 (Characiformes: Characidae)

Spermiogenesis and sperm ultrastructure from 21 species of Moenkhausia and others related genera are described. To evaluate the phylogenetic signals, 18 unordered characters were utilized in implied weighting analysis through the program TNT 1.1. Four variations of spermiogenesis were found. In the earliest spermatids, the nucleus can be positioned lateral, eccentric, strongly eccentric or nearly medial in relation to the distal centriole. The nuclear rotation can be present or absent. These spermiogenesis processes are related or intermediate to Type I and Type III. Taking into account the degrees of nuclear rotation during the spermiogenesis and other characteristics, distinct forms of spermatozoa are observed among the species analyzed. The phylogenetic analysis yielded a single most parsimonious tree with fit value 2.70000 and the topology obtained founds Moenkhausia as non‐monophyletic. However, some hypothesis of relationships previously proposed viz the clade 20, which contains the type species Moenkhausia xinguensis, is recovered herein. This clade is supported by five synapomorphies, and it allows the supposition that these species constitute a monophyletic group. The whole topology is presented and discussed.     

Molecular phylogeny of Aphyocharacinae (Characiformes, Characidae) with morphological diagnoses for the subfamily and recognized genera

The subfamily Aphyocharacinae was recently redefined to comprise eight genera: Aphyocharax, Prionobrama, Paragoniates, Phenagoniates, Leptagoniates, Xenagoniates, Rachoviscus and Inpaichthys. This new composition, however, is partially incongruent with published results of molecular studies especially concerning the positions of Rachoviscus and Inpaichthys. Our goal was to investigate the monophyly of Aphyocharacinae and its interrelationships using three distinct phylogenetic methodologies: Maximum-likelihood and Bayesian analyses of molecular data, and also Parsimony analysis of a concatenated molecular and morphological dataset. All tree topologies recovered herein suggest that Rachoviscus, Inpaichthys and Leptagoniates pi do not belong to the Aphyocharacinae. The remaining aphyocharacin taxa analyzed do form a monophyletic group, which is itself composed of two subgroups being one comprised of Paragoniates, Phenagoniates, Leptagoniates and Xenagoniates, and the other comprised of Aphyocharax and Prionobrama. Internal relationships among these genera are statistically well supported and morphological synapomorphies are presented at the generic level. All tree topologies also indicate that Aphyocharacidium is closely related to Aphyocharacinae suggesting that it should be included in this subfamily. As recognized in the present study, the Aphyocharacinae is diagnosed by a single morphological synapomorphy: two dorsal-fin rays articulating with the first dorsal pterygiophore.