ALBERT

Description: The generation and functions of human peripheral blood (PB) IgM+IgD+CD27+ B lymphocytes with somatically mutated IgV genes are controversially discussed. We determined their differential gene expression to naive B cells and to IgM-only and IgG+ memory B cells. This analysis revealed a high similarity of IgM+(IgD+)CD27+ and IgG+ memory B cells but also pointed at distinct functional capacities of both subsets. In vitro analyses revealed a tendency of activated IgM+IgD+CD27+ B cells to migrate to B-cell follicles and undergo germinal center (GC) B-cell differentiation, whereas activated IgG+ memory B cells preferentially showed a plasma cell (PC) fate. This observation was supported by reverse regulation of B-cell lymphoma 6 and PR domain containing 1 and differential BTB and CNC homology 1, basic leucine zipper transcription factor 2 expression. Moreover, IgM+IgD+CD27+ B lymphocytes preferentially responded to neutrophil-derived cytokines. Costimulation with catecholamines, carcinoembryonic antigen cell adhesion molecule 8 (CEACAM8), and IFN-γ caused differentiation of IgM+IgD+CD27+ B cells into PCs, induced class switching to IgG2, and was reproducible in cocultures with neutrophils. In conclusion, this study substantiates memory B-cell characteristics of human IgM+IgD+CD27+ B cells in that they share typical memory B-cell transcription patterns with IgG+ post-GC B cells and show a faster and more vigorous restimulation potential, a hallmark of immune memory. Moreover, this work reveals a functional plasticity of human IgM memory B cells by showing their propensity to undergo secondary GC reactions upon reactivation, but also by their special role in early inflammation via interaction with immunomodulatory neutrophils.

Description: Foraminifera are a group of mostly marine protists with high taxonomic diversity. Species identification is often complex, as both morphological and molecular approaches can be challenging due to a lack of unique characters and reference sequences. An integrative approach combining state of the art morphological and molecular tools is therefore promising. In this study, we analysed large benthic Foraminifera of the genus Amphisorus from Western Australia and Indonesia. Based on previous findings on high morphological variability observed in the Soritidae and the discontinuous distribution of Amphisorus along the coast of western Australia, we expected to find multiple morphologically and genetically unique Amphisorus types. In order to gain detailed insights into the diversity of Amphisorus, we applied micro CT scanning and shotgun metagenomic sequencing. We identified four distinct morphotypes of Amphisorus, two each in Australia and Indonesia, and showed that each morphotype is a distinct genotype. Furthermore, metagenomics revealed the presence of three dinoflagellate symbiont clades. The most common symbiont was Fugacium Fr5, and we could show that its genotypes were mostly specific to Amphisorus morphotypes. Finally, we assembled the microbial taxa associated with the two Western Australian morphotypes, and analysed their microbial community composition. Even though each Amphisorus morphotype harboured distinct bacterial communities, sampling location had a stronger influence on bacterial community composition, and we infer that the prokaryotic community is primarily shaped by the microhabitat rather than host identity. The integrated approach combining analyses of host morphology and genetics, dinoflagellate symbionts, and associated microbes leads to the conclusion that we identified distinct, yet undescribed taxa of Amphisorus. We argue that the combination of morphological and molecular methods provides unprecedented insights into the diversity of foraminifera, which paves the way for a deeper understanding of their biodiversity, and facilitates future taxonomic and ecological work.

Description: Marine community diversity surveys require a reliable assessment to estimate ecosystem functions and their dynamics. For these, non-invasive environmental DNA (eDNA) metabarcoding is increasingly applied in zoological studies to complement or even replace traditional morphological identification methods. However, uncertainties remain about the accuracy of the diversity detected with eDNA to capture the actual diversity in the field. Here, we validate the reliability of eDNA metabarcoding in identifying metazoan biodiversity in highly dynamic marine waters of the North Sea. We analyzed biodiversity from water (eDNA) and zooplankton samples with cytochrome c oxidase subunit 1 (COI) and 18S rRNA (18S) metabarcoding at Helgoland Roads and validated the optimal molecular resolution by morphological and molecular zooplankton identification (metabarcoding) with the result of merely a few false-negative detections. eDNA and zooplankton metabarcoding resolved 354 species from all major and in total 16 metazoan phyla. This molecular genetic species inventory overlapped by 95.9% (COI) and 81.9% (18S) with published inventories of local, morphologically identified species, among them neozoa and rediscovered species. Even though half of all species were detected by both eDNA and zooplankton metabarcoding, the methods differed significantly in their detected diversity. eDNA metabarcoding performed very well in cnidarians and annelids, whereas zooplankton metabarcoding identified higher numbers of fish and malacostraca. Species assemblages significantly differed between the individual sampling events and the cumulative number of identified species increased steadily over the sampling period and did not reach saturation. About a third of the species were detected only once while a core community of 22 species was identified continuously. Our study confirms eDNA metabarcoding to be a powerful tool to identify and analyze North Sea fauna in highly dynamic waters and we recommend investing in high sampling efforts by repetitive sampling and replication using at least 0.45 μm filters to increase filtration volume.