Biology subjects

Starke, R.

Publications and source records attributed to Starke, R..

7 recordsLinked to original sources

bioRxiv2026

Plasmid-plasmid interactions reshape extracellular vesicle cargo and gene transfer potential

Plasmids are key drivers of horizontal gene transfer, yet their dissemination is not limited to conjugation. Extracellular vesicles (EVs) can transport plasmid DNA, but the factors governing plasmid incorporation into EVs remain poorly understood. Here, we tested whether principles of conjugative plasmid transfer, including plasmid mobility type and plasmid-plasmid interactions, extend to EV-mediated export. Using a conjugative plasmid (pKJK5) and a mobilizable plasmid (RSF1010) in two Gram-negative hosts, we quantified plasmid incorporation into EVs under single- and dual-plasmid conditions. When present individually, the conjugative plasmid was preferentially incorporated into EVs, exceeding RSF1010 by 10-23-fold despite its lower intracellular abundance. Under co-residence, this pattern reversed: RSF1010 became enriched by 13-39-fold, while pKJK5 was reduced by 2-7-fold. Consequently, EV-associated plasmid cargo shifted to RSF1010 dominance, deviating strongly from the expected 10-fold higher pKJK5 cargo if a stochastic model based on intracellular abundance and single-plasmid conditions were applicable. We propose that mobilizable plasmids under coexistence exploit conjugative plasmid transfer machinery to access membrane-associated sites, increasing their likelihood of incorporation into EVs. Our findings demonstrate that plasmid-plasmid interactions reshape EV cargo and identify a previously unrecognized mechanism that may influence extracellular gene transfer potential in microbial communities.

microbiology↗

bioRxiv2022

Database-independent analysis of probable post-translational modifications of soil proteins across ecosystems

The identification rate of measured peptide spectra to proteins barely scratches 1% in best-case scenarios. Hundreds of thousands of valuable spectra are lost as no viable match in the database is found. Here, we apply the delta m/z plot that was previously implemented in MSnbase as tool for quality control to 63 soil samples from three ecosystems with different vegetation (39 forests, 11 grasslands, and 13 shrublands) with the aim to extract probable post-translational modifications (PTM) without the need of a reference database. The validity of the approach was verified with amino acids proposed for their respective 1 Da mass interval and compared to their relative abundance in proteins. We found that the average probable PTM and most known PTMs proposed for the mass intervals are similar across ecosystems. Otherwise, 11 mass intervals changed significantly in relative abundance in the three ecosystems but only for one an annotation could be proposed. Our approach not only highlights the opportunity of the database-independent analysis in soil metaproteomics but paves the way for targeted analysis of the yet unknown PTMs.

ecology↗

bioRxiv2020

Explorative meta-analysis of 417 extant archaeal genomes to predict their contribution to the total microbiome functionality

Unveiling the relationship between taxonomy and function in microbiomes is crucial to determine their contribution to ecosystem functioning. However, while the relationship between taxonomic and functional diversity in bacteria and fungi was reported, this is not the case for archaea. Here, we used a meta-analysis of completely annotated extant genomes of 417 taxonomically unique archaeal species to describe intergenome and intragenome redundancy of functions and to predict the extent of microbiome functionality on Earth contained within archaeal genomes using accumulation curves of all known functions from the level 3 of KEGG Orthology. We found that intergenome redundancy as functions present in multiple genomes was inversely related to intragenome redundancy as multiple copies of a gene in one genome, implying the trade of between additional copies of functionally important genes or a higher number of different genes. A logarithmic model described the relationship between functional diversity and species richness better than both the unsaturated and the saturated model, which suggests a limited total number of archaeal functions in contrast to the potential of bacteria and fungi. Using a global archaeal species richness estimate of 13,159, the logarithmic model predicts a total of 4,164.1 {+/-}2.9 KEGG level 3 functions while the non-parametric bootstrap estimate yields a lower bound of 2,994 {+/-}57 KEGG level 3 functions. Our approach not only highlights similarities in functional redundancy but also the difference in functional potential of archaea compared to other domains of life.

ecology↗

bioRxiv2020

Quantification of the necessary labelling input in protein stable isotope probing

Even though protein stable isotope probing is at least 100-times more sensitive than nucleic acid approaches, it is still unknown how much labelling input is necessary to not lose incorporation. Here, I used the average peptide model together with primary incorporation rates from previous experiments to determine the minimally necessary labelling input to detect incorporation of atoms present in proteins. Carbon-13 showed the highest efficiency for incorporation with detection misses only below 20.24 atom% labelling input. Despite the highest abundance in proteins, deuterium incorporation is not lost with at least 32.22 atom% labelling input due to instable acidic protons that undergo HD-exchange. All incorporation of oxygen-18 is detected with at least 28.15 atom% labelling input due to the +2 mass shift between its isotopes making up for its low abundance in proteins. Nitrogen-15 is less abundant in proteins and therefore harbors the most inefficient incorporation, resulting in a minimally necessary labelling input of 73.10 atom% labelling input. Altogether, these results can be used to properly design stable isotope probing experiments with the aim to maximize incorporation that can be extrapolated to other nucleic acid approaches due to similar incorporation routes.

molecular biology↗

bioRxiv2020

Meta-analysis of 139 extant Tara ocean metagenomes to unveil the relationship between taxonomy and functionality in prokaryotes inhabiting aquatic ecosystems

The total microbiome functionality of bacteria was recently predicted to be 35.5 {+/-}0.2 million of KEGG functions. Logically, due to the limitation in space and resource availability of the local community, local functionality will only comprise a small subset of the total functionality but the relationship between taxonomy and functionality is still uncertain. Here, I used a meta-analysis of 139 extant Tara ocean seawater samples from 68 locations across to globe with information on prokaryotic taxonomy on species level from 16S metabarcoding and functionality of prokaryotes on eggNOG gene family level from metagenomes to unveil the relationship between taxonomy and functionality, and to predict the global distribution of functionality. Functional richness showed a statistically significant increase with increasing species richness (P <0.0001, R2 =0.64) and increasing species diversity (P <0.0001, R2 =0.26) while functional diversity was similar across the different waters, ranging from 2.96 to 3.22. Globally, the highest functional richness was found in the Northern Pacific Ocean and in the North Atlantic Ocean, and decreased at extreme latitudes. Taken together, I unveil the relationship between taxonomy and functionality, and predict the global distribution of functional richness in prokaryotes inhabiting aquatic ecosystems, implying more pronounced effects in terrestrial ecosystems due to larger differences in environmental parameters especially for functional diversity.

microbiology↗

bioRxiv2019

Gene copy normalization of the 16S rRNA gene cannot outweigh the methodological biases of sequencing

The 16S rRNA gene is the golden standard target of sequencing to uncover the composition of bacterial communities but the presence of multiple copies of the gene makes gene copy normalization (GCN) inevitable. Even though GCN resulted in abundances closer to the metagenome, it should be validated by communities with known composition as both amplicon and shotgun sequencing are prone to methodological biases. Here we compared the composition of three mock communities to the composition derived from 16S sequencing without and with GCN. In all of them, the 16S composition was different from the mock community and GCN improved the picture only in the community with the lowest Shannon diversity. Albeit with low abundance, half of the identified genera were not present in the mock communities. Our approach provides empirical evidence to the methodological biases introduced by sequencing that was only counteracted by GCN in the case of low -diversity, potentially due to the small number of bacterial taxa with known gene copy numbers. We thus cannot recommend the use of GCN moving forward and it is questionable whether a complete catalogue of 16S rRNA copy numbers can outweigh the methodological biases of sequencing.

microbiology↗

bioRxiv2019

The total fungal microbiome functionality

Unveiling the relationship between taxonomy and function of the microbiome is crucial to determine its contribution to ecosystem functioning. However, while there is a considerable amount of information on microbial taxonomic diversity, our understanding of its relationship to functional diversity is still scarce. Here we used a meta-analysis of 377 completely annotated and taxonomically different fungal genomes to predict the total fungal microbiome functionality on Earth with all known functions from level 3 of KEGG Orthology using both parametric and non-parametric estimations. The unsaturated model described the accumulation of functions with increasing species richness significantly better (P-value < 2.2e-16) than the saturated model suggesting the presence of widespread and rare functions. Consistent with the parametric approach, the non-parametric Chao-1 estimator that assumes a maximum functional richness did not reach a plateau. Based on previous estimates of fungal species richness on Earth, we propagated the unsaturated model to predict a total fungal microbiome functionality of 42.4 million. Of those, only 0.06% are known today since the vast majority belongs to yet unknown rare functions. Logically, our approach not only highlighted the presence of two types of functions but pointed towards the necessity of novel and more sophisticated methods to unveil the entirety of functions to fully understand the involvement of the fungal microbiome in ecosystem functioning.

ecology↗