Biology subjects

Brussaard, C. P. D.

Publications and source records attributed to Brussaard, C. P. D..

5 recordsLinked to original sources

bioRxiv2025

Elemental allocation to molecular drivers of biogeochemistry in the Southern Ocean

Metabolic processes underpinning ocean biogeochemistry are powered by molecular machines, proteins, that require various elements to function. Yet, the allocation of elements to these proteins, and subsequent implications for biogeochemical processes, remain poorly characterized. Here we integrate elemental measurements with metaproteomics to quantitatively examine elemental use in Southern Ocean microbial proteins and metabolic processes. We demonstrate that iron availability influences elemental allocation, including decreased iron allocation to photosynthesis and compensatory incorporation of non-iron metals into metalloproteins under iron scarcity. Manganese was primarily allocated to photosynthesis in iron-replete conditions, and reallocated to other metabolic roles under low iron. Photosystem I:II protein mass ratios impacted both iron and manganese allocation, and appeared to be driven by iron availability. Approximately half of biogenic copper was found in plastocyanin, likely substituting for iron-containing cytochromes in photosynthesis. Moreover, biogenic nitrogen to phosphorus ratios were decoupled from ribosomal abundance, contrary to prevailing assumptions about ribosomal influence on stoichiometric regulation in the ocean. Instead, our results suggest that community composition and intracellular storage are important regulators of N:P in the Southern Ocean. Together, our findings identify key molecular mechanisms that modulate elemental demand and limitation, and provide a foundation for quantitatively connecting molecular measurements with biogeochemical models.

microbiology↗

bioRxiv2025

Superoxide dismutases shape manganese stoichiometry in Southern Ocean diatoms

Elemental stoichiometry of biomass is a focal point that connects different biogeochemical cycles. Yet, the mechanistic underpinnings of elemental stoichiometry are poorly quantified in many cases. We combined targeted and untargeted metaproteomics, Bayesian statistical modelling, and geochemical measurements to quantify the contribution of specific proteins to metal stoichiometry in natural populations of Southern Ocean diatoms. Our analyses indicate that a substantial amount of non-photosynthetic manganese (Mn) in diatoms in an Antarctic polynya can be attributed to superoxide dismutases ([~]0.7 {micro}mol Mn: mol Carbon; [~]20% of the total cellular Mn quota). We then used cultures and proteomic profiling of the key polar diatom Fragilariopsis cylindrus to identify environmental controls on superoxide dismutases, and discovered that iron concentration has little influence on the abundance of two Mn superoxide dismutases, while Mn limitation induces the depletion of these Mn superoxide dismutases and an accompanying increase of nickel superoxide dismutase. Overall, we combined metaproteomic approaches to quantify proteomic composition and connected these measurements to metal-to-carbon ratios and their responses to metal availability. Because metal quotas are key parameters in some biogeochemical models, our approach provides a direct mechanism for informing ecosystem-scale models with molecular measurements.

microbiology↗

bioRxiv2024

Latent infection of an active giant endogenous virus in a unicellular green alga

Latency is a common strategy in a wide range of viral lineages, but its prevalence in giant viruses remains unknown. Here we describe the activity and viral production from a 617 kbp integrated giant viral element in the model green alga Chlamydomonas reinhardtii. We resolve the integrated viral region using long-read sequencing and show that viral particles are produced and released in otherwise healthy cultures. A diverse array of viral-encoded selfish genetic elements are expressed during GEVE reactivation and produce proteins that are packaged in virions. In addition, we show that field isolates of Chlamydomonas sp. harbor latent giant viruses related to the C. reinhardtii GEVE that exhibit similar infection dynamics, demonstrating that giant virus latency is prevalent in natural host communities. Our work reports the largest temperate virus documented to date and the first active GEVE identified in a unicellular eukaryote, substantially expanding the known limits of viral latency.

microbiology↗

bioRxiv2023

Benchmarking Bioinformatic Virus Identification Tools Using Real-World Metagenomic Data across Biomes

As most viruses remain uncultivated, metagenomics is currently the main method for virus discovery. Detecting viruses in metagenomic data is not trivial. In the past few years, many bioinformatic virus identification tools have been developed for this task, making it challenging to choose the right tools, parameters, and cutoffs. As all these tools measure different biological signals, and use different algorithms and training/reference databases, it is imperative to conduct an independent benchmarking to give users objective guidance. We compared the performance of ten state-of-the-art virus identification tools in thirteen modes on eight paired viral and microbial datasets from three distinct biomes, including a new complex dataset from Antarctic coastal waters. The tools had highly variable true positive rates (0 - 68%) and false positive rates (0 - 15%). PPR-Meta best distinguished viral from microbial contigs, followed by DeepVirFinder, VirSorter2, and VIBRANT. Different tools identified different subsets of the benchmarking data and all tools, except for Sourmash, found unique viral contigs. Tools performance could be improved with adjusted parameter cutoffs, indicating that adjustment of parameter cutoffs before usage should be considered. Together, our independent benchmarking provides guidance on choices of bioinformatic virus identification tools and gives suggestions for parameter adjustments for viromics researchers.

bioinformatics↗

bioRxiv2022

Infection cycle and phylogeny of the Polinton-like virus Phaeocystis globosa virus virophage-14T

Virophages are small dsDNA viruses dependent on a nucleocytoplasmic large-DNA virus infection of a cellular host for replication. Putative virophages infecting algal hosts are classified together with polinton-like viruses, transposable elements widely found in algal genomes, yet the lack of isolated strains raises questions about their existence as independent entities. In this work we isolated and characterized a virophage (PgVV-14T) co-infecting Phaeocystis globosa with the Phaeocystis globosa virus-14T (PgV-14T). PgVV-14T decreases the fitness of its PgV-14T viral host, yet it does not salvage the cellular host population. We found viral-like elements resembling PgVV-14T in Phaeocystis genomes, suggesting that these virophages are capable of integrating to the cellular host genome, bridging the gap between Polinton-like viruses and virophages. This system, with a giant virus, a virophage and endogenous viral elements preying on an algal host, presents an opportunity to gain a better understanding on the evolution of eukaryotes and their viruses.

microbiology↗