Taxonomic differences shape the responses of freshwater aerobic anoxygenic phototrophic bacterial communities to light and predation

Aerobic anoxygenic phototrophic (AAP) bacteria are a phylogenetically diverse and ubiquitous group of prokaryotes that use organic matter but can harvest light using bacteriochlorophyll a. Although the factors regulating AAP ecology have long been investigated through field surveys, the few available experimental studies have considered AAPs as a group, thus disregarding the potential differential responses between taxonomically distinct AAP assemblages. Here, we used sequencing of the pufM gene to describe the diversity of AAPs in 10 environmentally distinct temperate lakes, and to investigate the taxonomic responses of AAP communities in these lakes when subjected to similar experimental manipulations of light and predator removal. The studied communities were clearly dominated by Limnohabitans AAP but presented a clear taxonomic segregation between lakes presumably driven by local conditions, which was maintained after experimental manipulations. Predation reduction (but not light exposure) caused significant compositional shifts across most assemblages, but the magnitude of these changes could not be clearly related to changes in bulk AAP abundances or taxonomic richness of AAP assemblages during experiments. Only a few operational taxonomic units, which differed taxonomically between lakes, were found to respond positively during experimental treatments. Our results highlight that different freshwater AAP communities respond differently to similar control mechanisms, highlighting that in‐depth knowledge on AAP diversity is essential to understand the ecology and potential role of these photoheterotrophs.     

Correction to: Population genomic structure of the black coral Antipathella subpinnata in Mediterranean Vulnerable Marine Ecosystems

Coral Reefs - A correction to this paper has been published: https://doi.org/10.1007/s00338-021-02120-y     

Osservazioni Preliminari sui Sistemi Degradanti dell'RNA nei semi di Ricino

Abstract

Preliminary observations on the enzymatic degradation of RNA in castor bean seeds. — Cocucci, Maggio, Monroy and Marrè have shown the decrease of RNA content during ripening in castor bean seeds, and its increase during germination. Furthermore, these Authors have demonstrated that in the dry ripe seeds the ribosomes are undetectable, and that they increase rapidly during germination. Two peaks of ribosomes are easily detected upon ultracentrifugal analysis in germinating seeds (Cocucci and Sturani). These observations were the basis for our investigations of the enzymes of RNA metabolism in castor bean seeds. This paper deals with our preliminary observations on RNA degrading enzymes in these tissues. We have been able to measure RNase activity, phosphodiesterase, 3′-,5′- and 2′-nucleotidases in castor bean seeds at different stages of development. RNase activity (measured in crude extracts) changes little during the ripening process, its rate corresponding to 40–50 μMoles of nucleotides liberated from RNA per hour and per gram of fresh weight. In the dry seeds, RNase activity is 30–40 μMoles of nucleotides/h.g.f.w., and it increases to about 60–70 μMoles/h/g.f.w. after 72 hours of germination.

Phosphodiesterase activity is about 4–5 μMoles/h.g.f.w.

The following rates have been found in seeds almost completely ripe seeds for 3′-, 5′- and 2′-nucleotidase activities, respectively 45–50 μMoles/h.g.f.w.; 6–7 μMoles/h.g.f.w.; 8 μMoles/h.g.f.w.; ATP-ase activity was of about 80–100 μMoles of phosphate liberated /h.g.f.w. - The high activity of 3′-nucleotidase, of the same order of that of RNase, suggests that these two enzymes are responsible for degradation of RNA to nucleosides and inorganic phosphate. Further investigations are being carried on to define the biochemical properties of castor bean RN-ase.     

Differential microRNA Profiles and Their Functional Implications in Different Immunogenetic Subsets of Chronic Lymphocytic Leukemia

Critical processes of B-cell physiology, including immune signaling through the B-cell receptor (BcR) and/or Toll-like receptors (TLRs), are targeted by microRNAs. With this in mind and also given the important role of BcR and TLR signaling and microRNAs in chronic lymphocytic leukemia (CLL), we investigated whether microRNAs could be implicated in shaping the behavior of CLL clones with distinct BcR and TLR molecular and functional profiles. To this end, we examined 79 CLL cases for the expression of 33 microRNAs, selected on the following criteria: (a) deregulated in CLL versus normal B-cells; (b) differentially expressed in CLL subgroups with distinct clinicobiological features; and, (c) if meeting (a) + (b), having predicted targets in the immune signaling pathways. Significant upregulation of miR-150, miR-29c, miR-143 and miR-223 and downregulation of miR-15a was found in mutated versus unmutated CLL, with miR-15a showing the highest fold difference. Comparison of two major subsets with distinct stereotyped BcRs and signaling signatures, namely subset 1 [IGHV1/5/7-IGKV1(D)-39, unmutated, bad prognosis] versus subset 4 [IGHV4-34/IGKV2-30, mutated, good prognosis] revealed differences in the expression of miR-150, miR-29b, miR-29c and miR-101, all down-regulated in subset 1. We were also able to link these distinct microRNA profiles with cellular phenotypes, importantly showing that, in subset 1, miR-101 downregulation is associated with overexpression of the enhancer of zeste homolog 2 (EZH2) protein, which has been associated with clinical aggressiveness in other B-cell lymphomas. In conclusion, specific miRNAs differentially expressed among CLL subgroups with distinct BcR and/or TLR signaling may modulate the biological and clinical behavior of the CLL clones.     

Driving factors of a vegetation shift from Scots pine to pubescent oak in dry Alpine forests

An increasing number of studies have reported on forest declines and vegetation shifts triggered by drought. In the Swiss Rhone valley (Valais), one of the driest inner‐Alpine regions, the species composition in low elevation forests is changing: The sub‐boreal Scots pine (Pinus sylvestris L.) dominating the dry forests is showing high mortality rates. Concurrently the sub‐Mediterranean pubescent oak (Quercus pubescens Willd.) has locally increased in abundance. However, it remains unclear whether this local change in species composition is part of a larger‐scale vegetation shift. To study variability in mortality and regeneration in these dry forests we analysed data from the Swiss national forest inventory (NFI) on a regular grid between 1983 and 2003, and combined it with annual mortality data from a monitoring site. Pine mortality was found to be highest at low elevation (below 1000 m a.s.l.). Annual variation in pine mortality was correlated with a drought index computed for the summer months prior to observed tree death. A generalized linear mixed‐effects model indicated for the NFI data increased pine mortality on dryer sites with high stand competition, particularly for small‐diameter trees. Pine regeneration was low in comparison to its occurrence in the overstorey, whereas oak regeneration was comparably abundant. Although both species regenerated well at dry sites, pine regeneration was favoured at cooler sites at higher altitude and oak regeneration was more frequent at warmer sites, indicating a higher adaptation potential of oaks under future warming. Our results thus suggest that an extended shift in species composition is actually occurring in the pine forests in the Valais. The main driving factors are found to be climatic variability, particularly drought, and variability in stand structure and topography. Thus, pine forests at low elevations are developing into oak forests with unknown consequences for these ecosystems and their goods and services.     

Genotoxic and mutagenic effects of lipid-coated CdSe/ZnS quantum dots

We proposed to evaluate the genotoxicity and mutagenicity of a new quantum dots (QDs) nanoplatform (QDsN), consisting of CdSe/ZnS core–shell QDs encapsulated by a natural fusogenic lipid (1,2-di-oleoyl-sn-glycero-3-phosphocholine (DOPC)) and functionalized by a nucleolipid N-[5′-(2′,3′-di-oleoyl) uridine]-N′,N′,N′-trimethylammoniumtosylate (DOTAU). This QDs nanoplatform may represent a new therapeutic tool for the diagnosis and treatment of human cancers. The genotoxic, mutagenic and clastogenic effects of QDsN were compared to those of cadmium chloride (CdCl₂). Three assays were used: (1) the Salmonella/microsome assay with four tester strains, (2) the comet assay and (3) the micronucleus test on CHO cells. The contribution of simulated sunlight was studied in the three assays while oxidative events were only explored in the comet assay in aliquots pretreated with the antioxidant l-ergothioneine. We found that QDsN could enter CHO-K1 cells and accumulate in cytoplasmic vesicles. It was not mutagenic in the Salmonella/mutagenicity test whereas CdCl₂ was weakly positive. In the dark, both the QDsN and CdCl₂ similarly induced dose-dependent increases in single-strand breaks and micronuclei. Exposure to simulated sunlight significantly potentiated the genotoxic activities of both QDsN and CdCl₂, but did not significantly increase micronucleus frequencies. l-Ergothioneine significantly reduced but did not completely suppress the DNA-damaging activity of QDsN and CdCl₂. The present results clearly point to the genotoxic properties and the risk of long-term adverse effects of such a nanoplatform if used for human anticancer therapy and diagnosis in the future.