Increasing evidence for the important role of Labyrinthulomycetes in marine ecosystems

This review summarizes increasing evidence for the role of Labyrithulomycetes in marine ecosystems gathered over the last six decades. It focuses on their diversity, habitats, biomass, productivity and overall role in food webs and remineralization. Earlier studies contributed enormously to the cultured diversity of Labyrinthulomycetes. In recent years, their uncultured diversity has been demonstrated in exotic environments like the deep sea and anoxic waters. These findings emphasize the need for novel culture methods to grow these organisms. Many species seem to be substrate-specific in their occurrence. Their commensalistic or mutualistic occurrence in marine invertebrates deserves attention. The biomass of Labyrinthulomycetes in the water column may often match or even exceed that of bacteria, although such occurrences seem to be seasonal. There is a major knowledge gap on their productivity and turnover in the water column. The high biomass and production of several degradative enzymes indicate their importance as remineralizers in the ocean. However, the mechanisms by which they overcome bacterial competition are not clear. It is likely that they occupy special niches, such as marine aggregates. One role of the Labyrinthulomycetes suggested in this review, based on preliminary experiments, is that of ‘left-over scavenging’, following bacterial growth

Effect of coastal hypoxia on bacterial diversity as elucidated through 16S rRNA amplicon sequencing

The formation of oxygen-depleted zones in the bottom waters is one of the most widespread phenomena in coastal areas. Upwelling episodes along India’s west coast due to the southwest monsoon increase biological productivity, further lowering the dissolved oxygen in the upwelled waters, which intensifies annually between June and October. Here, we have determined the changes in the microbial community in response to the varying oxygen levels and other physicochemical parameters at the Candolim Time Series Station using high-throughput sequencing. Amplicon Sequence Variants across all the samples collected in different seasons were mostly affiliated to the phyla Proteobacteria, Actinobacteria, Bacteroidetes, Verrucomicrobia, Chloroflexi, Firmicutes and Planctomycetes, with the most dominant being Proteobacteria (21-41%). Statistical analysis revealed that microbial diversity differed significantly with changing DO, ammonia, nitrate and nitrite concentrations during different seasons. The microbial community shift due to seasonal hypoxia results in the differential biogeochemical cycling of essential nutrients, with certain years seeing redox conditions up to sulphate reduction while certain years seeing only nitrogen loss. Future global warming scenarios will serve as a big challenge for understanding the role of microbial diversity and its implications in the cycling of natural elements

An insight into the prokaryotic diversity from a polymetallic nodule-rich region in the Central Indian Ocean Basin using next generation sequencing approach

Deep sea is a vast, dark, and difficult-to-access terrain and is now looked upon as a unique niche harboring diverse microorganism. We used a metataxonomic approach to decipher the microbial diversity present in the water column (surface to near bottom), water overlaying the sediments, and the deep-sea sediments (up to 35 cm) from the Indian Contract Region (ICR) in the Central Indian Ocean Basin (CIOB). Samples were collected from #IRZ (Impact Reference Zone), #PRZ (Potential Reference Zone), and #BC20 (Control site, outside potential mining area) with an average water depth of 5,200 m. 16S rRNA (V3–V4 region) amplicon sequencing on the MiSeq platform resulted in 942,851 ASVs across 65 water and sediment samples. Higher prokaryotic diversity was observed below 200 m in the water column to the seafloor. Proteobacteria was the most dominant bacterial phylum among all the water samples while Firmicutes, Actinobacteria and, Bacteroidota dominated the sediments. Sediment (below 10 cm) was co-dominated by Firmicutes. Thermoplasmata was the dominant archaeal group in the water column while Crenarchaeota was in the sediments. BC20 was less diverse than IRZ and PRZ. Deep Sea microorganisms could play a vital role in the mineralization processes, nutrient cycling, and also different biogeochemical cycles

First-in-Human Clinical Trial of Oral ONC201 in Patients with Refractory Solid Tumors

Purpose: ONC201 is a small-molecule selective antagonist of the G protein–coupled receptor DRD2 that is the founding member of the imipridone class of compounds. A first-in-human phase I study of ONC201 was conducted to determine its recommended phase II dose (RP2D). Experimental Design: This open-label study treated 10 patients during dose escalation with histologically confirmed advanced solid tumors. Patients received ONC201 orally once every 3 weeks, defined as one cycle, at doses from 125 to 625 mg using an accelerated titration design. An additional 18 patients were treated at the RP2D in an expansion phase to collect additional safety, pharmacokinetic, and pharmacodynamic information. Results: No grade \u3e 1 drug-related adverse events occurred, and the RP2D was defined as 625 mg. Pharmacokinetic analysis revealed a Cmax of 1.5 to 7.5 μg/mL (∼3.9–19.4 μmol/L), mean half-life of 11.3 hours, and mean AUC of 37.7 h·μg/L. Pharmacodynamic assays demonstrated induction of caspase-cleaved keratin 18 and prolactin as serum biomarkers of apoptosis and DRD2 antagonism, respectively. No objective responses by RECIST were achieved; however, radiographic regression of several individual metastatic lesions was observed along with prolonged stable disease (\u3e 9 cycles) in prostate and endometrial cancer patients. Conclusions: ONC201 is a selective DRD2 antagonist that is well tolerated, achieves micromolar plasma concentrations, and is biologically active in advanced cancer patients when orally administered at 625 mg every 3 weeks

Macrobenthic communities in the polymetallic nodule field, Indian Ocean, based on multicore and box core analysis

Managing deep-sea mining is challenging due to limited data on species and habitat distribution, hindering decision-making. In less-explored polymetallic nodule sites in the Indian Ocean, management approaches are deemed unfeasible due to a substantial lack of data. In this study, we aim to bridge the knowledge gap through a detailed analysis of the macrobenthos (fauna > 300 µm) obtained with two sampling gears (multi- and box corer) in potential impact, preservation, and reference zones in the Central Indian Ocean Basin. In total, 337 individuals were categorized into 106 morphospecies and 18 higher taxa. The lowest abundance was reported in the box corer. Nematodes and copepods dominated the macrobenthos community, whereas polychaetes and tanaidaceans were the more prevalent macrofaunal taxa. Carbohydrates and total organic carbon showed a notable positive correlation with polychaetes, isopods, and bivalves, indicating their influence on larger-sized taxa. Various functional traits, i.e., less motile, discretely motile, biodiffusors, and upward/downward conveyers, were dominant in the study area. The comparative analysis of multi- and box corer sampling reveals distinct patterns in macrobenthic diversity, emphasizing the importance of employing both gears for accurate functional analysis. The paper underscores the significance of including large meiofaunal taxa in macrofauna analyses for assessing deep-sea ecosystem functioning and services. Additionally, the findings contribute significantly to environmental baseline and impact assessment, a crucial aspect of sustainable management in a highly promising polymetallic nodule mining area, aligning with the goals of exploring

Morphology and physiology of the marine straminipilan fungi, the aplanochytrids isolated from the equatorial Indian Ocean

326-340While thraustochytrids, a group of unicellular marine straminipilan protists, have been found to be abundant in the water column, little is known of aplanochytrids. These constitute one of the 3 groups belonging to the Labyrinthulomycetes. Aplanochytrids were isolated from 34 out of 76 zooplankton samples from different strata in the 0–1000 m water column in the equatorial Indian Ocean. None of the samples yielded thraustochytrids in culture, suggesting that aplanochytrids might be more prevalent in the zooplankton samples of these waters than thraustochytrids. Fourteen isolates of aplanochytrids were studied with reference to their colony and cell morphological characteristics, carbon and nitrogen nutrition and the production of four degradative enzymes. All isolates produced proteases, but not lipase, amylase or chitinase. Major interesting features of several isolates included the production of motile amoebae, preference to pentoses and disaccharides and the common preference to glutamate. Cluster analysis based on all the characters showed no clear relations to morphological or physiological traits of the isolates, thus indicating the unreliability of these characters in taxonomy of aplanochytrids. All isolates corresponded to taxon Aplanochytrium yorkensis. The differences observed in these isolates correspond to variations in populations of A. yorkensis inhabiting zooplankton in the Indian Ocean and not related to different species of the genus