Characterizing the “fungal shunt”: Parasitic fungi on diatoms affect carbon flow and bacterial communities in aquatic microbial food webs

Microbial interactions in aquatic environments profoundly affect global biogeochemical cycles, but the role of microparasites has been largely overlooked. Using a model pathosystem, we studied hitherto cryptic interactions between microparasitic fungi (chytrid Rhizophydiales), their diatom host Asterionella, and cell-associated and free-living bacteria. We analyzed the effect of fungal infections on microbial abundances, bacterial taxonomy, cell-to-cell carbon transfer, and cell-specific nitrate-based growth using microscopy (e.g., fluorescence in situ hybridization), 16S rRNA gene amplicon sequencing, and secondary ion mass spectrometry. Bacterial abundances were 2 to 4 times higher on individual fungal-infected diatoms compared to healthy diatoms, particularly involving Burkholderiales. Furthermore, taxonomic compositions of both diatom-associated and free-living bacteria were significantly different between noninfected and fungal-infected cocultures. The fungal microparasite, including diatom-associated sporangia and free-swimming zoospores, derived ∼100% of their carbon content from the diatom. By comparison, transfer efficiencies of photosynthetic carbon were lower to diatom-associated bacteria (67 to 98%), with a high cell-to-cell variability, and even lower to free-living bacteria (32%). Likewise, nitrate-based growth for the diatom and fungi was synchronized and faster than for diatom-associated and free-living bacteria. In a natural lacustrine system, where infection prevalence reached 54%, we calculated that 20% of the total diatom-derived photosynthetic carbon was shunted to the parasitic fungi, which can be grazed by zooplankton, thereby accelerating carbon transfer to higher trophic levels and bypassing the microbial loop. The herein termed “fungal shunt” can thus significantly modify the fate of photosynthetic carbon and the nature of phytoplankton–bacteria interactions, with implications for diverse pelagic food webs and global biogeochemical cycles.

Parasitism is one of the most common consumer strategies on Earth (1–3). Recently, it has also been identified as one of the dominating interactions within the planktonic interactome (4, 5), and yet parasites remain poorly considered in analyses of trophic interactions and element cycling in aquatic systems (6, 7). The foundation of trophic interactions in plankton communities is set by single-cell phytoplankton, which contributes almost half of the world’s primary production (8). According to our common understanding, the newly fixed carbon (C) is channeled either through the microbial loop, classical food web, or viral shunt, which supports the growth of heterotrophic bacteria and nanoflagellates, zooplankton and higher trophic levels, or viruses, respectively (9). However, fungi, particularly fungal microparasites, are rarely considered as contributors to C and nutrient cycling, although they are present and active in diverse aquatic environments (10–12).Members of the fungal division Chytridiomycota, referred to as chytrids, can thrive as microparasites on phytoplankton cells in freshwater (11, 13, 14) and marine systems (15–17), infecting up to 90% of the phytoplankton host population (18–21). A recent concept, called mycoloop, describes parasitic chytrids as an integral part of aquatic food webs (22). Energy and organic matter are thereby transferred from large, often inedible phytoplankton to chytrid zoospores, which are consumed by zooplankton (23–27). Hence, parasitic chytrids establish a novel trophic link between phytoplankton and zooplankton. Our understanding of element cycling and microbial interactions during chytrid epidemics, however, remains sparse. For instance, the cell-to-cell C transfer from single phytoplankton cells to their directly associated chytrids has not been quantified to date. Moreover, the relationship between parasitic chytrids and heterotrophic bacteria is largely undescribed.Phytoplankton cells release substantial amounts of dissolved organic C (DOC) (28), whereby up to 50% of photosynthetic C is consumed as DOC by bacteria (29–32). Thus, bacterial communities are intimately linked to phytoplankton abundances and production (33). Phytoplankton–bacteria interactions are particularly strong within the phycosphere, the region immediately surrounding individual phytoplankton cells (33–35), where nutrient concentrations are several-folds higher compared to the ambient water (36, 37), and nutrient assimilation rates of phytoplankton-associated bacteria are at least twice as fast as those of their free-living counterparts (38, 39). Importantly, parasitic chytrids may distort these phytoplankton–bacteria interactions within and outside the phycosphere since they modulate substrate and nutrient availabilities and presumably also bacterial activity and community composition. The effects of this distortion are virtually unresolved, but the few available data indicate that chytrid infections alter the composition and concentration of DOC (40), while abundances of free-living bacteria increase (25, 40) or remain unchanged (24).To disentangle phytoplankton–fungi–bacteria interactions at a microspatial single-cell scale—the scale at which phytoplankton, fungi, and bacteria intimately interact—we used one of the few existing model pathosystems, composed of the freshwater diatom Asterionella formosa, the chytrid Rhizophydiales sp., and coenriched populations of heterotrophic bacteria. Our methodology included dual stable-isotope incubations (¹³C-bicarbonate and ¹⁵N-nitrate), single-cell–resolution secondary ion mass spectrometry (SIMS) (IMS 1280 and NanoSIMS 50L), 16S rRNA gene/16S rRNA sequencing, microscopy (e.g., fluorescence in situ hybridization [FISH]), and nutrient analyses. We particularly focused on the initial C transfer from the phytoplankton host to parasitic chytrids, which we term the “fungal shunt,” as part of the mycoloop. The objectives were twofold: 1) quantifying the transfer of photosynthetic C from phytoplankton cells to infectious chytrids, cell-associated bacteria, and free-living bacteria and 2) characterizing the effect of parasitic fungi on bacterial populations, considering bacterial abundances, bacterial–diatom attachment, single-cell activity rates, and community composition. The obtained data challenge the common perception of aquatic microbial food webs by demonstrating the significant role that parasitic fungi can play in microbial community structure, interactions, and element cycling during phytoplankton growth.     

Prostate cancer marker panel with single cell sensitivity in urine

Background

Over one million men undergo prostate biopsies annually in the United States, a majority of whom due to elevated serum PSA. More than half of the biopsies turn out to be negative for prostate cancer (CaP). The limitations of both the PSA test and the biopsy procedure have led to the development for more precise CaP detection assays in urine (e.g., PCA3, TMPRSS2‐ERG) or blood (e.g., PHI, 4K). Here, we describe the development and evaluation of the Urine CaP Marker Panel (UCMP) assay for sensitive and reproducible detection of CaP cells in post‐digital rectal examination (post‐DRE) urine.

Methods

The cellular content of the post‐DRE urine was captured on a translucent filter membrane, which is placed on Cytoclear slides for direct evaluation by microscopy and immuno‐cytochemistry (ICC). Cells captured on the membrane were assayed for PSA and Prostein expression to identify prostate epithelial cells, and for ERG and AMACR to identify prostate tumor cells. Immunostained cells were analyzed for quantitative and qualitative features and correlated with biopsy positive and negative status for malignancy.

Results

The assay was optimized for single cell capture sensitivity and downstream evaluations by spiking a known number of cells from established CaP cell lines, LNCaP and VCaP, into pre‐cleared control urine. The cells captured from the post‐DRE urine of subjects, obtained prior to biopsy procedure, were co‐stained for ERG, AMACR (CaP specific), and Prostein or PSA (prostate epithelium specific) rendering a whole cell based analysis and characterization. A feasibility cohort of 63 post‐DRE urine specimens was assessed. Comparison of the UCMP results with blinded biopsy results showed an assay sensitivity of 64% (16 of 25) and a specificity of 68.8% (22 of 32) for CaP detection by biopsy.

Conclusions

This pilot study assessing a minimally invasive CaP detection assay with single cell sensitivity cell‐capture and characterization from the post‐DRE urine holds promise for further development of this novel assay platform. Prostate 75: 969–975, 2015. © 2015 The Authors. The Prostate, published by Wiley Periodicals, Inc.     

Need for permanent pacemaker implantation following implantation of the rapid deployment valve in combined procedures: a single centre cohort study

BackgroundRapid deployment aortic valves may interfere with the cardiac conduction system. We investigated the need for permanent pacemaker implantation (PPI) following the implantation of Edwards INTUITY valve (Edwards Lifesciences, Irvine, CA).MethodsOne hundred twenty patients underwent aortic valve replacement (AVR) with the INTUITY valve in a combined procedure at the German Heart Centre Munich between April 2016 and December 2019. Twenty-four patients with prior PPI or concomitant ablation procedures (24/120, 20%) were excluded. Patient-specific, procedural and post-procedural outcomes were assessed in the remaining 96 cases.ResultsAVR was successful in all cases. Seventy-four percent of the study population were men. Mean age was 69.5±7.6 years. EuroSCORE II was 3.2±2.9. Forty-six patients (46/96, 47.9%) presented with pre-operative conduction disorders, right bundle branch block (RBBB) (17/96, 17.7%) and first-degree or second degree atrio-ventricular block (AVB) (18/96, 18.8%), in particular. In total, 9 patients (9/96, 9.4%) underwent PPI. PPI was required in 3 patients (3/50, 6.0%) who did not have a pre-existing conduction disorder due to new high degree AVB. 6 patients with pre-operative conduction disorders (6/46, 13%) needed PPI. Timing of PPI was 5.2±1.5 days (median 5). Independent predictors of PPI were preoperative RBBB [odds ratio (OR) =4.554, P=0.049] and large valve size (#27) (OR =5.527, P=0.031).ConclusionsThe analysis of the data collected enabled us to identify patient factors associated with higher risk for post-operative PPI following AVR with the INTUITY valve. Patient factors associated with post-operative PPI, were RBBB and large valve size. These patients should be closely monitored following the procedure, in particular.     

Ethnopharmacology in overdrive: the remarkable anti-HIV activity of Artemisia annua

Ethnopharmacological relevance

Artemisia annua contains the well-known antimalarial compound artemisinin, which forms the backbone of the global malaria treatment regime. In African countries a tea infusion prepared from Artemisia annua has been used for the treatment of malaria only for the past 10–20 years. Several informal claims in Africa exist that the Artemisia annua tea infusions are also able to inhibit HIV. Since HIV is a relatively newly emerged disease, the claims, if substantiated, could provide a very good example of “ethnopharmacology in overdrive”.The objective of this study was to provide quantitative scientific evidence that the Artemisia annua tea infusion exhibits anti-HIV activity through in vitro studies. A second objective was to determine if artemisinin plays a direct or indirect (synergistic) role in any observed activity. This was done by the inclusion of a chemically closely related species, Artemisia afra, known not to contain any artemisinin in our studies.

Materials and methods

Validated cellular systems were used to test Artemisia annua tea samples for anti-HIV activity. Two independent tests with different formats (an infection format and a co-cultivation format) were used. Samples were also tested for cellular toxicity against the human cells used in the assays.

Results

The Artemisia annua tea infusion was found to be highly active with IC₅₀ values as low as 2.0 μg/mL. Moreover we found that artemisinin was inactive at 25 μg/mL and that a chemically related species Artemisia afra (not containing artemisinin) showed a similar level of activity. This indicates that the role of artemisinin, directly or indirectly (synergism), in the observed activity is rather limited. Additionally, no cellular toxicity was seen for the tea infusion at the highest concentrations tested.

Conclusion

This study provides the first in vitro evidence of anti-HIV activity of the Artemisia annua tea infusion. We also report for the first time on the anti-HIV activity of Artemisia afra although this was not an objective of this study. These results open the way to identify new active pharmaceutical ingredients in Artemisia annua and thereby potentially reduce the cost for the production of the important antimalarial compound artemisinin.     

Transient lymphocyte decrease due to adhesion and migration following catumaxomab (anti-EpCAM x anti-CD3) treatment <Emphasis Type="Italic">in vivo</Emphasis>

Introduction  

In patients, a transient decrease in peripheral blood lymphocyte counts was observed following intraperitoneal administration of the trifunctional monoclonal antibody catumaxomab (anti-human EpCAM x anti-human CD3). The aim of this study was to clarify the observed effect in a preclinical mouse model and to analyse the related mechanism of action in vitro.     

Role of ventral striatum in reward-based decision making

So far, the specific role of the ventral striatum in reward-based decision making remains elusive. Here, we examined the role of the ventral striatum in reward-based decision making using functional MRI and a probabilistic object reversal task. During decision making, activity in the ventral striatum increased monotonically as a function of association learning and was greatest when the individuals expected to be rewarded for the decision with high certainty. Conversely, during the reward phase, activity in the ventral striatum showed an inverted U-shaped modulation by learning and was greatest when uncertainty about the outcome was maximal. Our data indicate that, during reward-based decision making, the ventral striatal signal dynamically changes over time dependent on the phase of the reward process and on the learning status and thereby acts as a motivational engine for the continuation of behavior.     

Therapy of pathological scars

A scar develops following the appearance of a deep tissue defect as part of the physiological wound healing process. The initial inflammatory response is followed by proliferation of connective tissue cells, which form fibrosis as a final tissue substitute. Disorders can occur at all stages of the process and are most commonly manifested as impaired wound healing or the formation of atrophic and hypertrophic scars or keloids. The focus of this article is on the treatment of pathologic scars, which are an indication for therapy due to functional limitations, complaints, and stigmatization, among other reasons. Conservative medical, physical, surgical and laser therapeutic approaches are pursued. The basis for this is an understanding of the pathophysiological mechanisms and factors influencing the choice of therapy, as well as an interdisciplinary and interprofessional therapeutic approach.