A trait-based approach predicting community assembly and dominance of microbial invasive species

Understanding the mechanisms underlying community assembly helps to define success and susceptibility to biological invasions. Here, we explored phytoplankton community assembly following niche and neutral paradigms and using a trait-based approach. Under the hypothesis that the morphology-based functional groups (MBFG) clusters species with similar niche, we analysed how trait-related differences in fitness influence dominance of an invasive species. This was based on literature review, field data and model simulations. We predict that invading species can be dominant if: 1) do not belong to the local MBFG but use unexploited areas of the niche, or 2) belong to the resident MBFG but exhibit a higher fitness due to a particular combination of traits. The invasive dinoflagellate Ceratium furcoides was used as the model species to evaluate these hypotheses, its morphological (e.g. volume) and physiological (e.g. growth rates) traits were compared with species from the same (V: photosynthetic flagellates) and different (VII: colonial cyanobacteria) MBFG. Fitness was estimated using models parametrized with MBFG rates (R*, ability to draw down phosphate) under different environmental conditions (i.e. flushing). Results contributed to support both hypotheses. First, the alternation of C. furcoides and cyanobacteria dominance was explained by the use of different niches. Secondly, species from MBFG V were dominant under similar environments. Within this group V C. furcoides showed higher fitness under low flushing and high predation, advantage provided by a distinctive combination of traits. The application of trait-based approaches to represent the niche and estimate fitness along environmental gradients was useful to evaluate community assembly and can be used to predict the dominance of microbial species invasions.     

Assessment of Environmental Hazards to Public Health in Temperate Urban Argentina

EcoHealth - Human health risk in urban areas depends on multiple environmental features. We performed a year-round survey in a highly urbanized district located in temperate Argentina (General San...     

Desulfurization of dibenzothiophene using the 4S enzymatic route: Influence of operational conditions on initial reaction rates

The influence of operational conditions (pH, temperature and oxygen transfer rate) on the initial reaction rates of the four reactions involved in the 4S biodesulfurization route of dibenzothiophenes (DBT) has been studied. The bioprocess was carried out using a genetically modified organism, Pseudomonas putida CECT 5279. The rates of the four reactions were calculated from the rates of production of different compounds involved in the 4S pathway, by matrix manipulation. The initial (zero time) reaction rates showed a slight dependence on oxygen transfer rate. Temperature and pH were optimal at 30°C and 9, respectively, temperature being the most important variable. This study also identifies the last reaction as the limiting step in the pathway.     

oiwa,a Female Gametophytic Mutant Impaired in a Mitochondrial Manganese-Superoxide Dismutase,Reveals Crucial Roles for Reactive Oxygen Species during Embryo Sac Development and Fertilization in Arabidopsis

Reactive oxygen species (ROS) can function as signaling molecules, regulating key aspects of plant development, or as toxic compounds leading to oxidative damage. In this article, we show that the regulation of ROS production during megagametogenesis is largely dependent on MSD1, a mitochondrial Mn-superoxide dismutase. Wild-type mature embryo sacs show ROS exclusively in the central cell, which appears to be the main source of ROS before pollination. Accordingly, MSD1 shows a complementary expression pattern. MSD1 expression is elevated in the egg apparatus at maturity but is downregulated in the central cell. The oiwa mutants are characterized by high levels of ROS detectable in both the central cell and the micropylar cells. Remarkably, egg apparatus cells in oiwa show central cell features, indicating that high levels of ROS result in the expression of central cell characteristic genes. Notably, ROS are detected in synergid cells after pollination. This ROS burst depends on stigma pollination but precedes fertilization, suggesting that embryo sacs sense the imminent arrival of pollen tubes and respond by generating an oxidative environment. Altogether, we show that ROS play a crucial role during female gametogenesis and fertilization. MSD1 activity seems critical for maintaining ROS localization and important for embryo sac patterning.     

Comparison of Adoption Agency Breed Identification and DNA Breed Identification of Dogs

Governmental and other agencies may require dog caregivers (owners) to provide breed identification of their dogs. This study compares breed identification by adoption agencies with identification by DNA analysis in 20 dogs of unknown parentage. Of the 20 dogs who had been adopted from 17 different locations, the study identified 16 dogs as having (or probably having) 1 or 2 specific breed(s) in their ancestry. DNA analysis of these dogs indicated that 25% (4/16) did in fact contain genetic evidence of an adoption agency's identified breed as one of the predominant breeds in a dog's ancestry. DNA analysis did not detect all specified breeds in 14 of these dogs. That is, 87.5% of the dogs identified by an adoption agency as having specific breeds in their ancestry did not have all of those breeds detected by DNA analysis. The discrepancies between opinions of adoption agencies and identification by DNA analysis suggest that it would be worthwhile to reevaluate the reliability of breed identification as well as the justification of current public and private policies pertaining to specific dog breeds.     

Multiple genetic pathways regulate replicative senescence in telomerase‐deficient yeast

Most human tissues express low levels of telomerase and undergo telomere shortening and eventual senescence; the resulting limitation on tissue renewal can lead to a wide range of age‐dependent pathophysiologies. Increasing evidence indicates that the decline in cell division capacity in cells that lack telomerase can be influenced by numerous genetic factors. Here, we use telomerase‐defective strains of budding yeast to probe whether replicative senescence can be attenuated or accelerated by defects in factors previously implicated in handling of DNA termini. We show that the MRX (Mre11‐Rad50‐Xrs2) complex, as well as negative (Rif2) and positive (Tel1) regulators of this complex, comprise a single pathway that promotes replicative senescence, in a manner that recapitulates how these proteins modulate resection of DNA ends. In contrast, the Rad51 recombinase, which acts downstream of the MRX complex in double‐strand break (DSB) repair, regulates replicative senescence through a separate pathway operating in opposition to the MRX‐Tel1‐Rif2 pathway. Moreover, defects in several additional proteins implicated in DSB repair (Rif1 and Sae2) confer only transient effects during early or late stages of replicative senescence, respectively, further suggesting that a simple analogy between DSBs and eroding telomeres is incomplete. These results indicate that the replicative capacity of telomerase‐defective yeast is controlled by a network comprised of multiple pathways. It is likely that telomere shortening in telomerase‐depleted human cells is similarly under a complex pattern of genetic control; mechanistic understanding of this process should provide crucial information regarding how human tissues age in response to telomere erosion.     

Molecular identity,morphology and taxonomy of the Rhynchospio glutaea complex with a key to Rhynchospio species (Annelida,Spionidae)

Rhynchospio glutaea (Ehlers, 1897 Ehlers, E. 1897. Polychaeten. Ergebnisse der Hamburger Magalhaensischen Sammelreise 1892/93. L. Friederichsen & Co., Hamburg, Germany. [Google Scholar]), Rhynchospio arenincola Hartman, 1936 Hartman, O. 1936. New species of Spionidae (Annelida Polychaeta) from the coast of California. University of California Publications in Zoology 41, 45–52. [Google Scholar] and Rhynchospio arenincola asiatica Chlebovitsch, 1959 Chlebovitsch, V.V. 1959. Species of Polychaeta worms from the Kurile Islands, which are new or recorded for the first time in the USSR fauna. Zoologichesky Zhurnal 38, 167–181. [Google Scholar], originally described from Strait of Magellan, California, and South Kurile Islands respectively, appear similar to each other in adult morphology. These species and subspecies have been considered by some authors as subjective synonyms and are here referred to as members of the R. glutaea complex. Sequence data of four gene fragments (2465 bp in total) of the mitochondrial 16S rDNA, nuclear 18S and 28S rDNA, and Histone 3 have shown that R. glutaea complex individuals from the South West Atlantic (Argentina), North East Pacific (British Columbia and Oregon) and North West Pacific (South Korea) were genetically distant and not conspecific. These data also indicate that R. arenincola from North America and R. aff. asiatica from South Korea are more closely related to each other, and both are closer to R. glutaea from South America than to R. nhatrangi from Vietnam: nhatrangi (glutaea (arenincola-aff. asiatica)). Adults of the R. glutaea complex are hermaphrodites and the arrangement of gametes is suggested to be a crucial reproductive character for distinguishing these species. Based on this character, two species of the complex are apparent in the North West Pacific: R. asiatica Chlebovitsch, 1959 Chlebovitsch, V.V. 1959. Species of Polychaeta worms from the Kurile Islands, which are new or recorded for the first time in the USSR fauna. Zoologichesky Zhurnal 38, 167–181. [Google Scholar] stat. nov. from the Kurile Islands (not analysed here) and an unnamed species from the mainland coast of Asia (here referred to as R. aff. asiatica). Adult morphology of R. asiatica stat. nov. is briefly described and illustrated. The lectotype and the type locality of the species on Iturup Is. are established for the first time. An identification key is provided to the 10 currently recognized Rhynchospio species.     

Differences in synovial fluid cytokine levels but not in synovial tissue cell infiltrate between anti-citrullinated peptide/protein antibody-positive and –negative rheumatoid arthritis patients

Introduction

Comparative data on synovial cell infiltrate and cytokine levels in anti citrullinated peptide/protein antibody (ACPA)-positive and ACPA negative rheumatoid arthritis (RA) patients are scarce. Our aim was to analyze synovial cell infiltrate and synovial fluid (SF) levels of cytokines in patients with RA according to the presence or absence of ACPA in serum.

Methods

A cross-sectional study in a single center including consecutive RA patients was performed. Patients were defined as ''ACPA negative'' if serum was negative to two different ACPAs [second generation commercial anti-cyclic citrullinated peptide antibodies (CCP2) and chimeric fibrin/filaggrin citrullinated antibodies]. Parallel synovial tissue (ST) biopsies and SF were obtained by knee arthroscopy. Synovial cell infiltrate and endothelial cells were analyzed by immunohistochemistry and SF levels of Th1, Th2, Th17 and pro-inflammatory cytokines by Quantibody(R) Human Array.

Results

A total of 83 patients underwent arthroscopy, with a mean age of 55.9 ± 12 years, and mean disease duration of 45 months (interquartile range, IQR 10.8 to 122). 62% were female and 77% were ACPA positive. No significant differences were found in clinical variables, acute phase reactants, synovial cell infiltrate or lymphoid neogenesis (LN) between ACPA positive and negative patients. However ACPA positive patients had significantly higher levels of IL-1β, IL-10, IL-17 F and CC chemokine ligand 20 (CCL-20) than ACPA negative patients.

Conclusions

In our cohort of patients with RA no significant differences were found in synovial cell infiltrate or synovial LN according to ACPA status. However, ACPA positive patients had higher levels of T-cell derived and pro-inflammatory cytokines than ACPA negative patients. As systemic and local inflammation was similar in the two groups, these findings support a distinct synovial physiopathology.