Massisteria marina has a sister: Massisteria voersi sp. nov., a rare species isolated from coastal waters of the Baltic Sea

Disturbance frequency directs microbial community succession in marine biofilms exposed to shear

IMPORTANCE

Disturbances are major drivers of community succession in many microbial systems; however, relatively little is known about marine biofilm community succession, especially under antifouling disturbance. Antifouling technologies exert strong local disturbances on marine biofilms, and resulting biomass losses can be accompanied by shifts in biofilm community composition and succession. We address this gap in knowledge by bridging microbial ecology with antifouling technology development. We show that disturbance by shear can strongly alter marine biofilm community succession, acting as a selective filter influenced by frequency of exposure. Examining marine biofilm succession patterns with and without shear revealed stable associations between key prokaryotic and eukaryotic taxa, highlighting the importance of cross-domain assessment in future marine biofilm research. Describing how compounded top-down and bottom-up disturbances shape the succession of marine biofilms is valuable for understanding the assembly and stability of these complex microbial communities and predicting species invasiveness.

DNA metabarcoding focused on difficult-to-culture protists: An effective approach to clarify biological interactions

DNA metabarcoding on a single organism is a promising approach to clarify the biological interactions (e.g., predator-prey relationships and symbiosis, including parasitism) of difficult-to-culture protists. To evaluate the effectiveness of this method, Radiolaria and Phaeodaria, which are ecologically important protistan groups, were chosen as target taxa. DNA metabarcoding on a single organism focused on the V9 region of the 18S rRNA gene revealed potential symbionts, parasites and food sources of Radiolaria and Phaeodaria. Previously reported hosts and symbionts (parasites) were detected, and newly recognized combinations were also identified. The contained organisms largely differed between Radiolaria and Phaeodaria. In Radiolaria, members of the same order tended to contain similar organisms, and the taxonomic composition of possible symbionts, parasites, and food sources was fixed at the species level. Members of the same phaeodarian family, however, did not contain similar organisms, and body part (i.e., the central capsule or the phaeodium) was the most important factor that divided the taxonomic composition of detected organisms, implying that the selection of appropriate body part is important when trying to ascertain contained organisms, even for unicellular zooplankton. Our results show that DNA metabarcoding on a single organism is effective in revealing the biological interactions of difficult-to-culture protists.

Ciliary transition zone evolution and the root of the eukaryote tree: implications for opisthokont origin and classification of kingdoms Protozoa, Plantae, and Fungi

I thoroughly discuss ciliary transition zone (TZ) evolution, highlighting many overlooked evolutionarily significant ultrastructural details. I establish fundamental principles of TZ ultrastructure and evolution throughout eukaryotes, inferring unrecognised ancestral TZ patterns for Fungi, opisthokonts, and Corticata (i.e., kingdoms Plantae and Chromista). Typical TZs have a dense transitional plate (TP), with a previously overlooked complex lattice as skeleton. I show most eukaryotes have centriole/TZ junction acorn-V filaments (whose ancestral function was arguably supporting central pair microtubule-nucleating sites; I discuss their role in centriole growth). Uniquely simple malawimonad TZs (without TP, simpler acorn) pinpoint the eukaryote tree's root between them and TP-bearers, highlighting novel superclades. I integrate TZ/ciliary evolution with the best multiprotein trees, naming newly recognised major eukaryote clades and revise megaclassification of basal kingdom Protozoa. Recent discovery of non-photosynthetic phagotrophic flagellates with genome-free plastids (Rhodelphis), the sister group to phylum Rhodophyta (red algae), illuminates plant and chromist early evolution. I show previously overlooked marked similarities in cell ultrastructure between Rhodelphis and Picomonas, formerly considered an early diverging chromist. In both a nonagonal tube lies between their TP and an annular septum surrounding their 9+2 ciliary axoneme. Mitochondrial dense condensations and mitochondrion-linked smooth endomembrane cytoplasmic partitioning cisternae further support grouping Picomonadea and Rhodelphea as new plant phylum Pararhoda. As Pararhoda/Rhodophyta form a robust clade on site-heterogeneous multiprotein trees, I group Pararhoda and Rhodophyta as new infrakingdom Rhodaria of Plantae within subkingdom Biliphyta, which also includes Glaucophyta with fundamentally similar TZ, uniquely in eukaryotes. I explain how biliphyte TZs generated viridiplant stellate-structures.

Biofilm and planktonic microbial communities in highly acidic soil (pH < 3) in the Soos National Nature Reserve, Czech Republic

Biofilm formation is a typical life strategy used by microorganisms populating acidic water systems. The same strategy might be used by microbes in highly acidic soils that are, however, neglected in this regard. In the present study, the microbial community in such highly acidic soil in the Soos National Nature Reserve (Czech Republic) has been investigated using high-throughput DNA sequencing and the organisms associated with biofilm life mode and those preferring planktonic life were distinguished using the biofilm trap technique. Our data show the differences between biofilm and planktonic microbiota fraction, although the majority of the organisms were capable of using both life modes. The by far most abundant prokaryotic genus was Acidiphilium and fungi were identified among the most abundant eukaryotic elements in biofilm formations. On the other hand, small flagellates from diverse taxonomical groups predominated in plankton. The application of cellulose amendment as well as the depth of sampling significantly influenced the composition of the detected microbial community.

Culturing Heterotrophic Protists from the Baltic Sea: Mostly the "Usual Suspects" but a Few Novelties as Well

The study of cultured strains has a long tradition in protistological research and has greatly contributed to establishing the morphology, taxonomy, and ecology of many protist species. However, cultivation-independent techniques, based on 18S rRNA gene sequences, have demonstrated that natural protistan assemblages mainly consist of hitherto uncultured protist lineages. This mismatch impedes the linkage of environmental diversity data with the biological features of cultured strains. Thus, novel taxa need to be obtained in culture to close this knowledge gap. In this study, traditional cultivation techniques were applied to samples from coastal surface waters and from deep oxygen-depleted waters of the Baltic Sea. Based on 18S rRNA gene sequencing, 126 monoclonal cultures of heterotrophic protists were identified. The majority of the isolated strains were affiliated with already cultured and described taxa, mainly chrysophytes and bodonids. This was likely due to "culturing bias" but also to the eutrophic nature of the Baltic Sea. Nonetheless, ~ 12% of the isolates in our culture collection showed highly divergent 18S rRNA gene sequences compared to those of known organisms and thus may represent novel taxa, either at the species level or at the genus level. Moreover, we also obtained evidence that some of the isolated taxa are ecologically relevant, under certain conditions, in the Baltic Sea.