Biology subjects

Nikitashina, V.

Publications and source records attributed to Nikitashina, V..

3 recordsLinked to original sources

bioRxiv2026

Algae bacteria associations provide metabolite-mediated protection against algicidal bacteria in a tripartite plankton community

Microalgal fitness in nature is shaped by interactions within a diverse microbial community, yet most experimental studies have examined algal-bacterial interactions in pairwise systems. It is well established that bacteria can exhibit growth promoting or inhibiting effects on co-existing algae. Comparatively little information is available about how additional partners can alter the outcome of diatom-bacteria interactions. In the present study, we screened the pairwise interaction of the marine diatom Skeletonema marinoi with ten different bacteria. This screening identified Marinobacter adhaerens as a growth promoting and Vibrio cyclitrophicus HSW24 as growth inhibiting partner. Growth inhibition of V. cyclitrophicus was associated with cell lysis, chain fragmentation and altered pigmentation whereas M. adhaerens supported increased chlorophyll a fluorescence, uniform pigmentation, intact chains and healthy cell morphology. In a tripartite community containing both bacteria and the alga, M. adhaerens protected S. marinoi from the inhibitory effect of V. cyclitrophicus in a density dependent manner. Comparative metabolomics revealed distinct metabolic profiles between the pairwise and tripartite interactions. This allowed to identify metabolites that were up-regulated in the tripartite community and therefore candidates for the observed protection. Among these, kynurenic acid and N-acetyltyramine were identified in bioassays as protective molecules, thus clearly highlighting the importance of secondary metabolites in this interaction. The present findings demonstrate that a third bacterial partner can alter the outcome of an antagonistic algal-bacterial interaction by means of chemical mediators. This work has implications for our understanding of microbial community functioning that cannot only be derived from the investigation of pairwise interactions.

microbiology↗

bioRxiv2025

The give and take in photosymbiosis unraveled by metabolomics of Radiolaria

Marine planktonic Radiolaria harboring symbiotic microalgae are ubiquitous in the oceans and abundant in oligotrophic areas. In these low-nutrient environments they are among the most important primary producers. Systematic studies of radiolarian biology are limited because Radiolaria are non-culturable and prone to damage during sampling. To obtain insight into the mechanistic basis of radiolarian photosymbiosis we address here the metabolic contributions of the partners to the performance of the holobiont. Therefore, we describe the metabolic inventory of two highly abundant photosymbiotic Radiolaria - colony-forming Collodaria and single-celled Acantharia and compare their metabolomes to metabolomes of respective free-living algae. Most of the metabolites detected in the symbiosis are not present in the free-living algae, suggesting a significant transformation of symbionts metabolites by the host. The metabolites identified in both the holobiont and the free-living algae encompass molecules of primary metabolism and a number of osmolytes, including dimethylsulfoniopropionate. Mass spectrometry imaging revealed the presence of dimethylsulfoniopropionate in both the symbionts and host cells, indicating that the algae provide osmolytic protection to the host. Furthermore, our findings suggest a possible dependence of Collodaria on symbiotic vitamin B3. Distinctive differences in phospholipid composition between free-living and symbiotic stages indicate that the algal cell membrane may undergo rearrangement in the symbiosis. Our results demonstrate a strong interdependence and rewiring of the algal metabolism underlying Radiolaria-microalgae photosymbioses.

microbiology↗

bioRxiv2023

Untargeted Metabolomics to Expand the Chemical Space of the Marine Diatom Skeletonema marinoi

Diatoms (Bacillariophyceae) are aquatic photosynthetic microalgae with an ecological role as primary producers in the aquatic food web. They account substantially for global carbon, nitrogen, and silicon cycling. Elucidating the chemical space of diatoms is crucial to understanding their physiology and ecology. To expand the known chemical space of a cosmopolitan marine diatom, Skeletonema marinoi, we performed High-Resolution Liquid Chromatography-Tandem Mass Spectrometry (LC-MS2) for untargeted metabolomics data acquisition. The spectral data from LC-MS2 was used as input for the Metabolome Annotation Workflow (MAW) to obtain putative annotations for all measured features. A suspect list of metabolites previously identified in the Skeletonema spp. was generated to verify the results. These known metabolites were then added to the putative candidate list from LC-MS2 data to represent an expanded catalogue of 1970 metabolites estimated to be produced by S. marinoi. The most prevalent chemical superclasses, based on the ChemONT ontology in this expanded dataset, were "Organic acids and derivatives", "Organoheterocyclic compounds", "Lipids and lipid-like molecules", and "Organic oxygen compounds". The metabolic profile from this study can aid the bioprospecting of marine microalgae for medicine, biofuel production, agriculture, and environmental conservation. The proposed analysis can be applicable for assessing the chemical space of other microalgae, which can also provide molecular insights into the interaction between marine organisms and their role in the functioning of ecosystems. ImportanceDiatoms are abundant marine phytoplankton members and have great ecological importance and biochemical potential. The cosmopolitan diatom Skeletonema marinoi has become an ecological and environmental research model organism. In this study, we used untargeted metabolomics to acquire a general metabolic profile of S. marinoi to assess its chemical diversity and expand the known metabolites produced by this diatom. S. marinoi produces a chemically diverse set of secondary metabolites with potential therapeutic properties, such as anti-cancer, antioxidant, and anti-inflammatory. Such metabolites are highly significant due to their potential role in drug discovery and bioeconomy. Lipids from S. marinoi also have potential in the biofuel industry. Furthermore, the environmental fluctuations in the water bodies directly affect the production of different secondary metabolites from diatoms, which can be key indicators of climate change.

microbiology↗