Differential effects of coinoculations with Pseudomonas jessenii PS06 (a phosphate-solubilizing bacterium) and Mesorhizobium ciceri C-2/2 strains on the growth and seed yield of chickpea under greenhouse and field conditions

In the course of a project carried out in two regions of Spain, Castilla y León and Andalucía, aiming to find useful biofertilizers for staple grain-legumes, an efficient rhizobia nodulating chickpea (termed as C-2/2) and a powerful in vitro phosphate-solubilizing bacterial strain (termed as PS06) were isolated. Analyses of their 16S rDNA sequence indicated that they belong to the bacterial species Mesorhizobium ciceri and Pseudomonas jessenii, respectively. Greenhouse and field experiments were carried out in order to test the effect of single and dual inoculations on chickpea (ecotype ILC-482) growth. Under greenhouse conditions, plants inoculated with Mesorhizobium ciceri C-2/2 alone had the highest shoot dry weight. The inoculation treatment with P. jessenii PS06 yielded a shoot dry weight 14% greater than the uninoculated control treatment, but it was not correlated with shoot P contents. However, the co-inoculation of C-2/2 with PS06 resulted in a decrease in shoot dry weight with respect to the inoculation with C-2/2 alone. Under field conditions, plants inoculated with M. ciceri C-2/2, in single or dual inoculation, produced higher nodule fresh weight, nodule number and shoot N content than the other treatments. Inoculation with P. jessenii PS06 had no significant effect on plant growth. However, the co-inoculation treatment ranked the highest in seed yield (52% greater than the uninoculated control treatment) and nodule fresh weight. These data suggest that P. jessenii PS06 can act synergistically with M. ciceri C-2/2 in promoting chickpea growth. The contrasting results obtained between greenhouse and field experiments are discussed.     

Coupling between anammox and autotrophic denitrification for simultaneous removal of ammonium and sulfide by enriched marine sediments

In the present study, the capacity of enrichments derived from marine sediments collected from different sites of the Mexican littoral to perform anaerobic ammonium oxidation (anammox) coupled to sulfide-dependent denitrification for simultaneous removal of ammonium and sulfide linked to nitrite reduction was evaluated. Sulfide-dependent denitrification out-competed anammox during the simultaneous oxidation of sulfide and ammonium. Significant accumulation of elemental sulfur (ca. 14–30 % of added sulfide) occurred during the coupling between the two respiratory processes, while ammonium was partly oxidized (31–47 %) due to nitrite limitation imposed in sediment incubations. Nevertheless, mass balances revealed up to 38 % more oxidation of the electron donors available (ammonium and sulfide) than that expected from stoichiometry. Recycling of nitrite, from nitrate produced through anammox, is proposed to contribute to extra oxidation of sulfide, while additional ammonium oxidation is suggested by sulfate-reducing anammox (SR-anammox). The complex interaction between nitrogenous and sulfurous compounds occurring through the concomitant presence of autotrophic denitrification, conventional anammox and SR-anammox may significantly drive the nitrogen and sulfur fluxes in marine environments.     

Humus-reducing microorganisms and their valuable contribution in environmental processes

Humus constitutes a very abundant class of organic compounds that are chemically heterogeneous and widely distributed in terrestrial and aquatic environments. Evidence accumulated during the last decades indicating that humic substances play relevant roles on the transport, fate, and redox conversion of organic and inorganic compounds both in chemically and microbially driven reactions. The present review underlines the contribution of humus-reducing microorganisms in relevant environmental processes such as biodegradation of recalcitrant pollutants and mitigation of greenhouse gases emission in anoxic ecosystems, redox conversion of industrial contaminants in anaerobic wastewater treatment systems, and on the microbial production of nanocatalysts and alternative energy sources.     

Detection of Appearing and Disappearing Objects in Complex Acoustic Scenes

The ability to detect sudden changes in the environment is critical for survival. Hearing is hypothesized to play a major role in this process by serving as an “early warning device,” rapidly directing attention to new events. Here, we investigate listeners'' sensitivity to changes in complex acoustic scenes—what makes certain events “pop-out” and grab attention while others remain unnoticed? We use artificial “scenes” populated by multiple pure-tone components, each with a unique frequency and amplitude modulation rate. Importantly, these scenes lack semantic attributes, which may have confounded previous studies, thus allowing us to probe low-level processes involved in auditory change perception. Our results reveal a striking difference between “appear” and “disappear” events. Listeners are remarkably tuned to object appearance: change detection and identification performance are at ceiling; response times are short, with little effect of scene-size, suggesting a pop-out process. In contrast, listeners have difficulty detecting disappearing objects, even in small scenes: performance rapidly deteriorates with growing scene-size; response times are slow, and even when change is detected, the changed component is rarely successfully identified. We also measured change detection performance when a noise or silent gap was inserted at the time of change or when the scene was interrupted by a distractor that occurred at the time of change but did not mask any scene elements. Gaps adversely affected the processing of item appearance but not disappearance. However, distractors reduced both appearance and disappearance detection. Together, our results suggest a role for neural adaptation and sensitivity to transients in the process of auditory change detection, similar to what has been demonstrated for visual change detection. Importantly, listeners consistently performed better for item addition (relative to deletion) across all scene interruptions used, suggesting a robust perceptual representation of item appearance.     

A Single Argonaute Gene Participates in Exogenous and Endogenous RNAi and Controls Cellular Functions in the Basal Fungus Mucor circinelloides

The mechanism of RNAi is well described in metazoans where it plays a role in diverse cellular functions. However, although different classes of endogenous small RNAs (esRNAs) have been identified in fungi, their biological roles are poorly described due, in part, to the lack of phenotype of mutants affected in the biogenesis of these esRNAs. Argonaute proteins are one of the key components of the RNAi pathways, in which different members of this protein family participate in the biogenesis of a wide repertoire of esRNAs molecules. Here we identified three argonaute genes of the fungus Mucor circinelloides and investigated their participation in exogenous and endogenous RNAi. We found that only one of the ago genes, ago-1, is involved in RNAi during vegetative growth and is required for both transgene-induced RNA silencing and the accumulation of distinct classes of esRNAs derived from exons (ex-siRNAs). Classes I and II ex-siRNAs bind to Ago-1 to control mRNA accumulation of the target protein coding genes. Class III ex-siRNAs do not specifically bind to Ago-1, but requires this protein for their production, revealing the complexity of the biogenesis pathways of ex-siRNAs. We also show that ago-1 is involved in the response to environmental signals, since vegetative development and autolysis induced by nutritional stress are affected in ago-1 ⁻ M. circinelloides mutants. Our results demonstrate that a single Ago protein participates in the production of different classes of esRNAs that are generated through different pathways. They also highlight the role of ex-siRNAs in the regulation of endogenous genes in fungi and expand the range of biological functions modulated by RNAi.     

Novel application of magnetic nano-carbon composite as redox mediator in the reductive biodegradation of iopromide in anaerobic continuous systems

The redox-mediating capacity of magnetic reduced graphene oxide nanosacks (MNS) to promote the reductive biodegradation of the halogenated pollutant, iopromide (IOP), was tested. Experiments were performed using glucose as electron donor in an upflow anaerobic sludge blanket (UASB) reactor under methanogenic conditions. Higher removal efficiency of IOP in the UASB reactor supplied with MNS as redox mediator was observed as compared with the control reactor lacking MNS. Results showed 82% of IOP removal efficiency under steady state conditions in the UASB reactor enriched with MNS, while the reactor control showed IOP removal efficiency of 51%. The precise microbial transformation pathway of IOP was elucidated by high-performance liquid chromatography coupled to mass spectroscopy (HPLC-MS) analysis. Biotransformation by-products with lower molecular weight than IOP molecule were identified in the reactor supplied with MNS, which were not detected in the reactor control, indicating the contribution of these magnetic nano-carbon composites in the redox conversion of this halogenated pollutant. Reductive reactions of IOP favored by MNS led to complete dehalogenation of the benzene ring and partial rupture of side chains of this pollutant, which is the first step towards its complete biodegradation. Possible reductive mechanisms that took place in the biodegradation of IOP were stated. Finally, the novel and successful application of magnetic graphene composites in a continuous bioreactor to enhance the microbial transformation of IOP was demonstrated.

     

Effect of temperature on seed production in the invasive grass Glyceria maxima (Hartm.) Holmb. (Poaceae) in South Africa

Temperature is one of the main factors that determine sexual reproduction in terrestrial and emergent aquatic plant species. The effect of temperature on sexual reproduction and seed production of Glyceria maxima (Hartm.) Holmb. in the southern hemisphere is unknown. Glyceria maxima collections in February 2010 at three isolated infestations in KwaZulu-Natal failed to yield a single seed, only empty panicles. Laboratory experiments showed that vernalisation had no consistent effect on seed production. Field- and laboratory-grown plants produced seeds in the 2010/2011 season, because of having sufficient time at optimum temperatures required for seed production (1 491 and 1 585 hours, respectively), compared to a shorter period (1 352 hours) of suitable temperatures during the 2009/2010 growing season. An inadequate period of optimum temperatures (15–25°C) during seed production resulted in the lack of seeds in the field in the 2009/2010 growing season. This study showed that temperature and duration of exposure thereto during the seed-production period play vital roles in G. maxima sexual reproduction.     

Marmoset phylogenetics, conservation perspectives, and evolution of the mtDNA control region

Marmosets (genus Callithrix) are a diverse group of platyrrhine primates with 13-15 purported taxa, many of them considered endangered. Morphological analyses constitute most of the basis for recognition of these forms as distinct taxa. The purpose of this study was to provide a molecular view, based on mitochondrial control region sequences, of the evolutionary history of the marmosets, concomitant with a molecular phylogenetic perspective on species diversity within the group. An additional purpose was to provide the first comparative examination of a complete New World monkey control region sequence with those of other mammals. The phylogenetic analyses provide convincing support for a split between the Atlantic forest and Amazonian marmosets, with the inclusion of the pygmy marmoset (Cebuella pygmaea) at the base of the Amazonian clade. The earliest branch of the Atlantic forest group was C. aurita. In the Amazonian group, the analyses do not support the recognition of C. humeralifer and the recently described C mauesi as distinct taxa. They do, however, support a clear distinction between C. argentata and a strongly supported mixed clade of C. humeralifer and C. mauesi. In the Atlantic forest group, the phylogenetic tree suggests mixing between C. penicillata, C. kuhli, and possibly C. jacchus. Most of the sequence features characteristic of other mammal control regions were also evident in marmosets, with the exception that conserved sequence blocks (CSBs) 2 and 3 were not clearly identifiable. Tandem repeat units often associated with heteroplasmy in a variety of other mammals were not evident in the marmoset sequences.      

Persistent nuclear ribosomal DNA sequence polymorphism in the Amelanchier agamic complex (Rosaceae)

Individual plants of several Amelanchier taxa contain many polymorphic nucleotide sites in the internal transcribed spacers (ITS) of nuclear ribosomal DNA (nrDNA). This polymorphism is unusual because it is not recent in origin and thus has resisted homogenization by concerted evolution. Amelanchier ITS sequence polymorphism is hypothesized to be the result of gene flow between two major North American clades resolved by phylogenetic analysis of ITS sequences. Western North American species plus A. humilis and A. sanguinea of eastern North America form one clade (A), and the remaining eastern North American Amelanchier make up clade B. Five eastern North American taxa are polymorphic at many of the nucleotide sites where clades A and B have diverged and are thought to be of hybrid origin, with A. humilis or A. sanguinea as one parent and various members of clade B as the other parent. Morphological evidence suggests that A. humilis is one of the parents of one of the polymorphic taxa, a microspecies that we refer to informally as A. "erecta." Sequences of 21 cloned copies of the ITS1- 5.8S gene-ITS2 region from one A. "erecta" individual are identical to A. humilis sequence or to the clade B consensus sequence, or they are apparent recombinants of A. humilis and clade B ITS repeats. Amelanchier "erecta" and another polymorphic taxon are suspected to be relatively old because both grow several hundred kilometers beyond the range of one of their parents. ITS sequence polymorphisms have apparently persisted in these two taxa perhaps because of polyploidy and/or agamospermy (asexual seed production), which are prevalent in the genus.