On the evolutionary ecology of symbioses between chemosynthetic bacteria and bivalves

Mutualistic associations between bacteria and eukaryotes occur ubiquitously in nature, forming the basis for key ecological and evolutionary innovations. Some of the most prominent examples of these symbioses are chemosynthetic bacteria and marine invertebrates living in the absence of sunlight at deep-sea hydrothermal vents and in sediments rich in reduced sulfur compounds. Here, chemosynthetic bacteria living in close association with their hosts convert CO2 or CH4 into organic compounds and provide the host with necessary nutrients. The dominant macrofauna of hydrothermal vent and cold seep ecosystems all depend on the metabolic activity of chemosynthetic bacteria, which accounts for almost all primary production in these complex ecosystems. Many of these enigmatic mutualistic associations are found within the molluscan class Bivalvia. Currently, chemosynthetic symbioses have been reported from five distinct bivalve families (Lucinidae, Mytilidae, Solemyidae, Thyasiridae, and Vesicomyidae). This brief review aims to provide an overview of the diverse physiological and genetic adaptations of symbiotic chemosynthetic bacteria and their bivalve hosts

Severity and properties of cardiac damage caused by Streptococcus pneumoniae are strain dependent.

Streptococcus pneumoniae is an opportunistic Gram-positive pathogen that can cause invasive disease. Recent studies have shown that S. pneumoniae is able to invade the myocardium and kill cardiomyocytes, with one-in-five adults hospitalized for pneumococcal pneumonia having a pneumonia-associated adverse cardiac event. Furthermore, clinical reports have shown up to a 10-year increased risk of adverse cardiac events in patients formerly hospitalized for pneumococcal bacteremia. In this study, we investigated the ability of nine S. pneumoniae clinical isolates, representing eight unique serotypes, to cause cardiac damage in a mouse model of invasive disease. Following intraperitoneal challenge of C57BL/6 mice, four of these strains (D39, WU2, TIGR4, and 6A-10) caused high-grade bacteremia, while CDC7F:2617-97 and AMQ16 caused mid- and low-grade bacteremia, respectively. Three strains did not cause any discernible disease. Of note, only the strains capable of high-grade bacteremia caused cardiac damage, as inferred by serum levels of cardiac troponin-I. This link between bacteremia and heart damage was further corroborated by Hematoxylin & Eosin and Trichrome staining which showed cardiac cytotoxicity only in D39, WU2, TIGR4, and 6A-10 infected mice. Finally, hearts infected with these strains showed varying histopathological characteristics, such as differential lesion formation and myocytolysis, suggesting that the mechanism of heart damage varied between strains

Ayahuasca e redução do uso abusivo de psicoativos: eficácia terapêutica?

Trata-se de uma avaliação do possível papel do uso da ayahuasca, em contexto religioso, como auxiliar na redução do consumo abusivo de psicoativos, a partir de uma pesquisa de estudo de caso. Foi realizada uma entrevista aberta com uma usuária regular de cocaína, nicotina e álcool que abandonou este comportamento após entrar em contato com a ayahuasca num contexto ritualizado. O caso foi analisado à luz da comparação deste com a literatura existente sobre o assunto. Foi traçada uma relação entre o início do uso da ayahuasca e o abandono do uso de cocaína, nicotina e álcool pela entrevistada, a partir da avaliação das representações simbólicas e das descrições de suas primeiras experiências com a bebida

<i>Streptococcus pneumoniae</i> in the heart subvert the host response through biofilm-mediated resident macrophage killing

<div><p>For over 130 years, invasive pneumococcal disease has been associated with the presence of extracellular planktonic pneumococci, i.e. diplococci or short chains in affected tissues. Herein, we show that <i>Streptococcus pneumoniae</i> that invade the myocardium instead replicate within cellular vesicles and transition into non-purulent biofilms. Pneumococci within mature cardiac microlesions exhibited salient biofilm features including intrinsic resistance to antibiotic killing and the presence of an extracellular matrix. Dual RNA-seq and subsequent principal component analyses of heart- and blood-isolated pneumococci confirmed the biofilm phenotype <i>in vivo</i> and revealed stark anatomical site-specific differences in virulence gene expression; the latter having major implications on future vaccine antigen selection. Our RNA-seq approach also identified three genomic islands as exclusively expressed <i>in vivo</i>. Deletion of one such island, Region of Diversity 12, resulted in a biofilm-deficient and highly inflammogenic phenotype within the heart; indicating a possible link between the biofilm phenotype and a dampened host-response. We subsequently determined that biofilm pneumococci released greater amounts of the toxin pneumolysin than did planktonic or RD12 deficient pneumococci. This allowed heart-invaded wildtype pneumococci to kill resident cardiac macrophages and subsequently subvert cytokine/chemokine production and neutrophil infiltration into the myocardium. This is the first report for pneumococcal biofilm formation in an invasive disease setting. We show that biofilm pneumococci actively suppress the host response through pneumolysin-mediated immune cell killing. As such, our findings contradict the emerging notion that biofilm pneumococci are passively immunoquiescent.</p></div

Comparative gene expression analysis of HIP, BIP and pneumococci from <i>in vitro</i> biofilm and planktonic pneumococci.

<p><b>(A)</b> Dot plot representation of the whole genome transcriptomic profile for blood- isolated pneumococci, BIP (<i>blue</i>) and heart-isolated pneumococci, HIP (<i>red</i>) showing the average normalized number of RNA-seq reads identified, i.e. gene expression levels mapping to each TIGR4 gene within the blood and the heart. Y-axis denotes normalized expression levels (RPKMs) whereas X-axis denotes location of the genes on the TIGR4 chromosome. Established virulence determinants with expression levels >1000 RNA-seq reads (i.e. corresponding to top 10% of genes with highest expression levels) for BIP and HIP are indicated. <b>(B)</b> Dot plot representation of the differential gene expression profile for BIP and HIP spanning the TIGR4 genome. The fold changes are depicted as Log₂(HIP/BIP). Y-axis denotes log fold changes in gene expression levels whereas X-axis denotes location of the genes on the TIGR4 chromosome. Important differentially up-regulated pneumococcal genes for BIP and HIP are indicated in blue and red respectively. Genes clustered near the X-axis are consistently expressed. <b>(C)</b> Curve plot representation of gene expression levels for genes encoding designated pneumococcal virulence determinants in the BIP, HIP, <i>in vitro</i> biofilm-, and <i>in vitro</i> planktonic- TIGR4 samples. Y-axis denotes normalized expression levels (i.e. RPKMs) whereas X-axis denotes individual nucleotide location (nt coordinates) on the TIGR4 chromosome. Two pooled BIP samples (5 mice per sample), three HIP samples, three <i>in vitro</i> biofilms and three <i>in vitro</i> planktonic pneumococci samples were tested.</p

Heart invaded biofilm pneumococci subvert host immune response by releasing pneumolysin and rapidly kill cardiac macrophages.

<p><b>(A)</b> Western blots for pneumolysin levels in equal biomass of whole cell lysates (pellets) and supernatants of planktonic- wildtype TIGR4 (n = 3), biofilm- wildtype TIGR4 (n = 3), and planktonic T4ΩRD12 (ΩRD12) (n = 2). An isogenic pneumolysin deficient TIGR4 strain (T4 Δ<i>ply</i>) was tested as the negative control. Normalized densitometric quantification of pneumolysin levels in the supernatant is provided. Statistical analysis was performed by comparison supernatant pneumolysin levels from planktonic (PK)- wildtype TIGR4 (n = 3), and planktonic T4ΩRD12 (ΩRD12) (n = 2) to biofilm (BF)- wildtype TIGR4 (n = 3) using Welch’s <i>t</i>-test. <b>(B)</b> LDH release cytotoxicity assay of J774A.1 macrophages challenged with equal biomass of planktonic-, biofilm- TIGR4 (T4), planktonic-, biofilm- T4 Δ<i>ply</i> and planktonic-, biofilm- T4 Δ<i>ply</i> complemented with exogenous recombinant pneumolysin (rPLY, 0.3μg/mL) as determined at 0, 1, 2, 4 hours post-infection (n = 3 biological replicates, each with 3 technical replicates). Statistical analysis was performed using ordinary one-way ANOVA. <b>(C)</b> TNFα production by J774A.1 macrophages at designated time points following exposure to an equal biomass of planktonic-, biofilm- TIGR4 (T4), planktonic-, biofilm- T4 Δ<i>ply</i> and planktonic-, biofilm- T4 Δ<i>ply</i> complemented with exogenous recombinant pneumolysin (rPLY, 0.3μg/mL) as determined at 0, 1, 2, 4 hours post-infection (n = 3 biological replicates, each with 3 technical replicates). Statistical analysis was performed using ordinary one-way ANOVA. <b>(D)</b> Representative transmission electron microscopy (TEM) image of cardiac sections (magnification: 2,500X) from BALB/cJ mice infected with T4 Δ<i>ply</i> 30 hours post-infection (n = 3). <b>(E)</b> Representative high magnification immunofluorescent microscopy images of cardiac microlesions from uninfected-, passively immunized (αPly)- and naïve- mice infected with HIP or BIP 30 hours post infection, showing presence of: capsule (stained with anti-serotype 4 capsule antibody [CPS], <i>red</i>), cardiac macrophages (stained using anti-Mac-3 antibody [Mac-3], <i>green</i>), and infiltrated neutrophils (stained with anti-Ly-6G antibody [Ly-6G], <i>green</i>). A minimum of 4 stained heart sections were examined. <b>(F)</b> Absolute numbers of infiltrated neutrophils in hearts of uninfected-, passively immunized (αPly)- and naïve- mice infected with HIP or BIP 30 hours post infection. Neutrophils were identified as Gr-1⁺CD11b⁺Ly-6G⁺F4/80^- MHC-II^- cells. Statistical analysis was performed using student’s <i>t-</i>test. <b>(G)</b> Absolute numbers of cardiac macrophages in hearts of uninfected-, passively immunized (αPly)- and naïve- mice infected with HIP or BIP 30 hours post infection. Macrophages were identified as CD64⁺MerTK⁺F4/80⁺CD11b⁺ cells. Statistical analysis was performed using student’s <i>t-</i>test. <i>P</i> value: * ≤ 0.05, ** ≤ 0.01, *** ≤ 0.001; data are represented as mean ± SEM.</p

Morphogenesis of cardiac microlesions.

<p><b>(A)</b> Representative transmission electron microscopy (TEM) images of cardiac sections (magnification: 2,500X) from BALB/cJ mice infected with <i>S</i>. <i>pneumoniae</i> strain TIGR4 between 24 and 42 hours post-infection (n = 12). Panels A.1-7 depict the morphogenesis of cardiac microlesions beginning as pneumococci-containing microscopic vesicles within the myocardium. Hydropic degeneration (black bold arrows) and mitochondrial damage as evidenced by swelling (white arrows) adjacent to cardiac microlesions are evident. Images that are the most representative of what occurs during individual microlesion development are shown. The images do not necessarily depict the overall course of infection in a mouse which is mixed with different sized microlesions at late timepoints. <b>(B)</b> Representative high power (60,000X) TEM images of pneumococci within microlesions show heterogeneous capsule expression: (B.1) pneumococci within smallest vesicles surrounded by myocardium; (B.2) pneumococci at the periphery of larger microlesions; (B.3) pneumococci within the center of a larger microlesion. <b>(C)</b> Representative TEM image of TIGR4 within a 48-hour old static biofilm (n = 3) grown in a 6-well plate (3,000X). <b>Inset,</b> Representative high power (60,000X) TEM image of biofilm-pneumococci.</p