Phylogenetic analysis of host–symbiont specificity and codivergence in bioluminescent symbioses

Several groups of marine fishes and squids form mutualistic bioluminescent symbioses with luminous bacteria. The dependence of the animal on its symbiont for light production, the animal's specialized anatomical adaptations for harboring bacteria and controlling light emission, and the host family bacterial species specificity characteristic of these associations suggest that bioluminescent symbioses are tightly coupled associations that might involve coevolutionary interactions. Consistent with this possibility, evidence of parallel cladogenesis has been reported for squid–bacterial associations. However, genetic adaptations in the bacteria necessary for and specific to symbiosis have not been identified, and unlike obligate endosymbiotic associations in which the bacteria are transferred vertically, bacterially bioluminescent hosts acquire their light‐organ symbionts from the environment with each new host generation. These contrasting observations led us to test the hypotheses of species specificity and codivergence in bioluminescent symbioses, using an extensive sampling of naturally formed associations. Thirty‐five species of fish in seven teleost families (Chlorophthalmidae, Macrouridae, Moridae, Trachichthyidae, Monocentridae, Acropomatidae, Leiognathidae) and their light‐organ bacteria were examined. Phylogenetic analysis of a taxonomically broad sampling of associations was based on mitochondrial 16S rRNA and cytochrome oxidase I gene sequences for the fish and on recA, gyrB and luxA sequences for bacteria isolated from the light organs of these specimens. In a fine‐scale test focused on Leiognathidae, phylogenetic analysis was based also on histone H3 subunit and 28S rRNA gene sequences for the fish and on gyrB, luxA, luxB, luxF and luxE sequences for the bacteria. Deep divergences were revealed among the fishes, and clear resolution was obtained between clades of the bacteria. In several associations, bacterial species identities contradicted strict host family bacterial species specificity. Furthermore, the fish and bacterial phylogenies exhibited no meaningful topological congruence; evolutionary divergence of host fishes was not matched by a similar pattern of diversification in the symbiotic bacteria. Re‐analysis of data reported for squids and their luminous bacteria also revealed no convincing evidence of codivergence. These results refute the hypothesis of strict host family bacterial species specificity and the hypothesis of codivergence in bioluminescent symbioses. © The Willi Hennig Society 2007.     

Cutaneous lymphocyte antigen is expressed on memory/effector B cells in the peripheral blood and monocytoid B cells in the lymphoid tissues.

Cutaneous lymphocyte antigen (CLA) is expressed on a subpopulation of human memory T cells and is involved in the primary step of their skin homing. T cells and some B cells in the peripheral blood express CLA, but the pathophysiologic roles of CLA(+) B cells have not yet been clarified. We examined the relationships among CLA expression in B cells and immunoglobulin heavy chain subtype, the localization of CLA(+) B cells in the peripheral lymphoid tissues, and their functional binding to E-selectin. CLA was expressed on class-switched, memory B cells in the peripheral blood and tonsils as revealed by flow cytometry. Immunohistochemical staining of the lymph nodes with various types of inflammation or reactive hyperplasia showed CLA on the monocytoid B cells, which correspond to memory cells. The functional study revealed that CLA on B cells bound to E-selectin transfectants. E-selectin was detected on some of the high endothelial venules in the monocytoid B-cell-rich lymph nodes. These findings suggest that CLA is also expressed on a subset of memory/effector B cells, in addition to a subset of memory T cells. Such B cells were located in the lymph nodes or tonsils and rarely in chronic dermatitis. Therefore, CLA seems to be related to memory/effector B-cell trafficking to the lymph nodes or tonsils. According to the multistep theory, mechanisms involved in the second or third step might be different between CLA(+) B and T cells.     

BAC/YAC contigs from the H2-M region of mouse Chr 17 define gene order as Znf173-Tctex5-Mog-D17Tu42-M3-M2

 A yeast artificial chromosome (YAC) contig from the C57BL/6 (H2 ^b ) mouse was created from the major histocompatibility complex (Mhc, H2 in mouse) class Ib subregion, H2-M. It spans approximately 1.2 megabase (Mb) pairs and unites the previous >1.5-Mb YAC contigs (Jones et al. 1995) into a single contig, which includes 21 Mhc class I genes distal to H2-T1. A bacterial artificial chromosome (BAC) contig from the 129 (H2 ^bc ) mouse, spanning approximately 600 kilobases, was also built from Znf173 (Afp, a gene for acid finger protein), through Tctex5 (t-complex testis expressed-5) and Mog (myelin oligodendrocyte glycoprotein), to H2-M2. Twenty-four sequence-tagged site (STS) markers were newly developed, and 35 markers were mapped in the YAC/BAC contigs, which define the marker order as Cen –Znf173–Tctex5 – Mog–D17Tu42–D17Mit232–H2-M3–D17Leh525–H2-M2– Tel. The gene order of Znf173 – Tctex5 – Mog – D17Tu42 is conserved between mouse and human, showing that the middle H2-M region corresponds to the subregion of the human Mhc surrounding HLA-A. Received: 25 July 1997 / Revised: 10 September 1997     

C-ABI3, the Carrot Homologue of the Arabidopsis ABI3, is Expressed during Both Zygotic and Somatic Embryogenesis and Functions in the Regulation of Embryo-Specific ABA-Inducible Genes

A carrot gene homologous to the ABI3 gene of Arabidopsis wasisolated from a carrot somatic embryo cDNA library and designatedC-ABI3. The sequence of C-ABI3 was very similar to those ofABI3 of Arabidopsis and VP1 of maize in certain conserved regions.The expression of C-ABI3 was detected specifically in embryogeniccells, somatic embryos and developing seeds. Thus, expressionof C-ABI3 was limited to tissues that acquired desiccation tolerancein response to endogenous or exogenous abscisic acid (ABA).Endogenous levels of ABA in seeds increased transiently andthen desiccation of seeds started. The expression of C-ABI3in developing seeds was observed prior to the increase in levelsof endogenous ABA that was followed by desiccation of seeds.In transgenic mature leaves in which C-ABI3 was ectopicallyexpressed, expression of ECP31, ECP63 and ECP40 was inducedby treatment with ABA, which indicates that the expression ofECP genes was controlled by the pathway(s) that involved C-ABI3and ABA. This suggests that C-ABI3 has the same function asVP1/ABI3 factor in carrot somatic embryos. (Received March 4, 1998; Accepted September 4, 1998)     

Potassium Currents in Freshly Dissociated Uterine Myocytes from Nonpregnant and Late-Pregnant Rats

In freshly dissociated uterine myocytes, the outward current is carried by K⁺ through channels highly selective for K⁺. Typically, nonpregnant myocytes have rather noisy K⁺ currents; half of them also have a fast-inactivating transient outward current (I_TO). In contrast, the current records are not noisy in late pregnant myocytes, and I_TO densities are low. The whole-cell I_K of nonpregnant myocytes respond strongly to changes in [Ca²⁺]_o or changes in [Ca²⁺]_i caused by photolysis of caged Ca²⁺ compounds, nitr 5 or DM-nitrophene, but that of late-pregnant myocytes respond weakly or not at all. The Ca²⁺ insensitivity of the latter is present before any exposure to dissociating enzymes. By holding at −80, −40, or 0 mV and digital subtractions, the whole-cell I_K of each type of myocyte can be separated into one noninactivating and two inactivating components with half-inactivation at approximately −61 and −22 mV. The noninactivating components, which consist mainly of iberiotoxin-susceptible large-conductance Ca²⁺-activated K⁺ currents, are half-activated at 39 mV in nonpregnant myocytes, but at 63 mV in late-pregnant myocytes. In detached membrane patches from the latter, identified 139 pS, Ca²⁺-sensitive K⁺ channels also have a half-open probability at 68 mV, and are less sensitive to Ca²⁺ than similar channels in taenia coli myocytes. Ca²⁺-activated K⁺ currents, susceptible to tetraethylammonium, charybdotoxin, and iberiotoxin contribute 30–35% of the total I_K in nonpregnant myocytes, but <20% in late-pregnant myocytes. Dendrotoxin-susceptible, small-conductance delayed rectifier currents are not seen in nonpregnant myocytes, but contribute ∼20% of total I_K in late-pregnant myocytes. Thus, in late-pregnancy, myometrial excitability is increased by changes in K⁺ currents that include a suppression of the I_TO, a redistribution of I_K expression from large-conductance Ca²⁺-activated channels to smaller-conductance delayed rectifier channels, a lowered Ca²⁺ sensitivity, and a positive shift of the activation of some large-conductance Ca²⁺-activated channels.     

The role of polyamines in the regulation of AMP deaminase isozymes

The differential effects of polyamines on the activity of AMP deaminase isozyme A (from rat muscle) and isozyme B (from rat liver) are reported. Polyamines activate isozyme B but inhibit isozyme A.     

Vonoprazan-based triple therapy is non-inferior to susceptibility-guided proton pump inhibitor-based triple therapy for <Emphasis Type="Italic">Helicobacter pylori</Emphasis> eradication

Background

All Helicobacter pylori-infected patients are recommended for eradication with an appropriate regimen in each geographic area. The choice of the therapy is somewhat dependent on the antimicrobial susceptibility. The rate of clarithromycin resistance has been increasing and is associated with failure; thus, susceptibility testing is recommended before triple therapy with clarithromycin. However, antimicrobial susceptibility testing is not yet clinically available and an alternative newly developed acid inhibitor vonoprazan is used for triple therapy in Japan. The aim of this study was to determine whether vonoprazan-based triple therapy is plausible treatment in H. pylori eradication.

Methods

A retrospective observational study of H. pylori eradication was conducted in a single institute. The patients who requested antimicrobial susceptibility testing were treated with susceptibility-guided proton pump inhibitor-based triple therapy in International University of Health and Welfare Hospital from 2013 to 2016. Other patients were treated with empirical treatment with a proton pump inhibitor. From 2015 to 2016, vonoprazan-based triple treatment (vonoprazan, 20 mg; amoxicillin, 750 mg; and clarithromycin, 200 or 400 mg, b.i.d.) was conducted, and its effectiveness was compared with susceptibility-guided proton pump inhibitor-based triple therapy. We also investigated the improvement in eradication rate when antimicrobial susceptibility testing was performed, and compared the outcomes of vonoprazan-based and proton pump inhibitor-based empirical therapy.

Results

A total of 1355 patients who received first-line eradication treatment were enrolled in the present study. The eradication rates of the empirical proton pump inhibitor-based therapy and the vonoprazan-based therapy group in a per-protocol analysis were 86.3% (95% CI 83.8–88.8) and 97.4% (95% CI 95.7–99.1), respectively. In 212 patients who received antimicrobial susceptibility testing, the rate of clarithromycin resistant was 23.5% and the eradication rate in susceptibility-guided treatment was 95.7% (95% CI 92.9–98.4). The difference between susceptibility-guided and vonoprazan-based therapy was ??1.7% (95% CI ??4.9 to 1.5%), and the non-inferiority of vonoprazan-based triple therapy was confirmed.

Conclusions

Vonoprazan-based triple therapy was effective as susceptibility-guided triple therapy for H. pylori eradication. An empirical triple therapy with vonoprazan is preferable even in area with high rates of clarithromycin-resistance.Trial registration The study was retrospectively registered in University Hospital Medical Information Network (UMIN000032351)

     

Biotechnological potential of plant growth-promoting bacteria from the roots and rhizospheres of endemic plants in ironstone vegetation in southeastern Brazil

Microorganisms associated with plants have a great biotechnological potential, but investigations of these microorganisms associated with native plants in peculiar environments has been incipient. The objective of this study was to analyze the plant growth-promoting bacteria potential of cultivable bacteria associated with rare plants from the ferruginous rocky fields of the Brazilian Iron Quadrangle. The roots and rhizospheres of nine endemic plants species and samples of a root found in a lateritiric duricrust (canga) cave were collected, the culturable bacteria isolated and prospected for distinct biotechnological and ecological potentials. Out of the 148 isolates obtained, 8 (5.4%) showed potential to promote plant growth, whereas 4 (2.7%) isolates acted as biocontrol agents against Xanthomonas citri pathotype A (Xac306), reducing the cancrotic lesions by more than 60% when co-inoculated with this phytopathogen in Citrus sinensis plants. Moreover, other 4 (2.7%) isolates were classified as potential bioremediation agents, being able to withstand high concentrations of arsenite (5 mM As³⁺) and arsenate (800 mM As⁵⁺), by removing up to 35% and 15% of this metalloid in solution, respectively. These same four isolates had a positive influence on the growth of both the roots and the aerial parts when inoculated with tomato seeds in the soil contaminated with arsenic. This is the first time that an investigation highlights the potentialities of bacteria associated with rare plants of ferruginous rocky fields as a reservoir of microbiota of biotechnological and ecological interest, highlighting the importance of conservation of this area that is undergoing intense anthropic activity.

Graphical abstract

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