Multigene Phylogeny of Choanozoa and the Origin of Animals

Animals are evolutionarily related to fungi and to the predominantly unicellular protozoan phylum Choanozoa, together known as opisthokonts. To establish the sequence of events when animals evolved from unicellular ancestors, and understand those key evolutionary transitions, we need to establish which choanozoans are most closely related to animals and also the evolutionary position of each choanozoan group within the opisthokont phylogenetic tree. Here we focus on Ministeria vibrans, a minute bacteria-eating cell with slender radiating tentacles. Single-gene trees suggested that it is either the closest unicellular relative of animals or else sister to choanoflagellates, traditionally considered likely animal ancestors. Sequencing thousands of Ministeria protein genes now reveals about 14 with domains of key significance for animal cell biology, including several previously unknown from deeply diverging Choanozoa, e.g. domains involved in hedgehog, Notch and tyrosine kinase signaling or cell adhesion (cadherin). Phylogenetic trees using 78 proteins show that Ministeria is not sister to animals or choanoflagellates (themselves sisters to animals), but to Capsaspora, another protozoan with thread-like (filose) tentacles. The Ministeria/Capsaspora clade (new class Filasterea) is sister to animals and choanoflagellates, these three groups forming a novel clade (filozoa) whose ancestor presumably evolved filose tentacles well before they aggregated as a periciliary collar in the choanoflagellate/sponge common ancestor. Our trees show ichthyosporean choanozoans as sisters to filozoa; a fusion between ubiquitin and ribosomal small subunit S30 protein genes unifies all holozoa (filozoa plus Ichthyosporea), being absent in earlier branching eukaryotes. Thus, several successive evolutionary innovations occurred among their unicellular closest relatives prior to the origin of the multicellular body-plan of animals

The plasmid-encoded transcription factor ArdK contributes to the repression of the IMP-6 metallo-β-lactamase gene blaIMP-6, leading to a carbapenem-susceptible phenotype in the blaIMP-6-positive Escherichia coli strain A56-1S.

Carbapenemase-producing Enterobacteriaceae (CPE) are a global concern because these bacteria are resistant to almost all β-lactams. Horizontal interspecies gene transfer via plasmid conjugation has increased the global dissemination of CPE. Recently, an Enterobacteriaceae strain positive for carbapenemase gene but showing a carbapenem-susceptible phenotype was identified, suggesting that these susceptible strains may be challenging to detect solely via antimicrobial susceptibility tests without molecular analysis. Here, we isolated a blaIMP-6 carbapenemase-gene positive but imipenem- and meropenem-susceptible Escherichia coli (ISMS-E) strain A56-1S (imipenem and meropenem minimum inhibitory concentration, ≤ 0.125 mg/L), from a human urine specimen in Japan. A56-1S was carbapenemase negative by the Carba NP test, suggesting that IMP-6 production was low or undetectable. Thus, to characterize the mechanism of this phenotype, a meropenem-resistant E. coli A56-1R strain was obtained using meropenem-selection. A56-1R was positive for carbapenemase production by the Carba NP test, and blaIMP-6 transcription in A56-1R was 53-fold higher than in A56-1S, indicating that blaIMP-6 in A56-1S is negatively regulated at the transcriptional level. Comparative genomic analysis between the two strains revealed that the alleviation of restriction of DNA (ardK) gene encoding a putative transcription factor is disrupted by the IS26 insertion in A56-1R. A cotransformation assay of ardK and the regulatory element upstream of blaIMP-6 showed repression of blaIMP-6 transcription, indicating that ArdK negatively modulates blaIMP-6 transcription. ArdK binding and affinity assays demonstrated that ArdK directly binds to the regulatory element upstream of blaIMP-6 with dissociation constant values comparable to those of general transcription factors. The IMP-6 carbapenemase showed low hydrolytic activity against imipenem, resulting in an imipenem-susceptible and meropenem-resistant (ISMR) phenotype (previously reported as a stealth phenotype). However, the low expression of IMP-6 in the A56-1S strain could be a typical characteristic of ISMS-E due to gene repression, indicating that conventional antimicrobial susceptibility tests might be unable to detect such strains even when using both imipenem and meropenem. Bacteria that exhibit the ISMS phenotype could play a potential role as undetectable reservoirs and might facilitate gene transfer to other organisms while avoiding detection

Isolation and Structural Determination of Two Novel Phlorotannins from the Brown Alga Ecklonia kurome Okamura, and Their Radical Scavenging Activities

Abstract: Two novel phlorotannins with a molecular weight of 974, temporarily named 974-A and 974-B, were isolated from the polyphenol powder prepared from the edible marine brown alga Ecklonia kurome Okamura, and their chemical structures were determined by spectroscopic method. The isolated yield of the total of 974-A and 974-B was approximately 4 % (w/w) from the polyphenol powder. In 974-A, the carbon at the C2′ position in the A ring of phlorofucofuroeckol-A forms a C–C bond with the carbon at the C2 ″ position of the C ring of triphloretol-B, while in 974-B, phlorofucofuroeckol-B and triphloretol-B form a C–C bond in the same manner as in 974-A. These structures were supported by high resolution-MS/MS data. To evaluate the antioxidant activities, the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay and intracellular radical scavenging assay, using 2′,7′-dichlorofluorescin diacetate (DCFH-DA), were performed for 974-A, 974-B, and four known phlorotannins. The results of the DPPH assay showed that the IC50 values of 974-A, 974-B, phlorofucofuroeckol-A, and dieckol were significantly smaller than those of phlorofucofuroeckol-B, phloroglucinol, α-tocopherol, and ascorbicMar. Drugs 2013, 11 16

A possible role of low regulatory T cells in anti-acetylcholine receptor antibody positive myasthenia gravis after bone marrow transplantation

Abstract Background Chronic graft-versus-host disease (GVHD) appears several months following allogenic hematopoietic stem cell transplantation (HSCT) and is clinically analogous to autoimmune disorder. Polymyositis is a common neuromuscular disorder in chronic GVHD, but myasthenia gravis (MG) is extremely rare. Hence, its pathophysiology and treatment have not been elucidated. Case presentation A 63-year-old man with a history of chronic GVHD presented with ptosis, dropped head, and dyspnea on exertion, which had worsened over the previous several months. He showed progressive decrement of compound muscle action potential in the deltoid muscle evoked by 3-Hz repetitive nerve stimulation, a positive edrophonium test, and elevated levels of serum anti-acetylcholine receptor antibodies, which suggested a diagnosis of generalized MG. No thymoma was found. Flow cytometric analysis revealed a remarkable depletion of peripheral Tregs (CD4+CD25highFOXP3+ cells, 0.24% of the total lymphocytes). Administration of prednisolone and tacrolimus was insufficient to alleviate his symptoms; however, the use of rituximab successfully improved his condition. Conclusions Myasthenic symptoms appeared in the process of tapering prednisolone for the treatment of chronic GVHD, supporting the diagnosis of MG associated with chronic GVHD. The present case proposes a possibility that reduction of Tregs might contribute to the pathogenesis of MG underlying chronic GVHD. Immunotherapy with rituximab is beneficial for treatment of refractory MG and GVHD