Biology subjects

Narvaez-Barragan, D. A.

Publications and source records attributed to Narvaez-Barragan, D. A..

3 recordsLinked to original sources

bioRxiv2025

Algal Betaine Triggers Bacterial Hydrogen Peroxide Production that Promotes Algal Demise

Hydrogen peroxide (H2O2) plays various roles in the ocean, acting as a signaling molecule at low concentrations and causing oxidative stress when accumulated. While many marine microbes produce H2O2, its role in microbial interactions remains unclear. Here, we used transcriptomics, genetics, and metabolomics to study H2O2 dynamics in the interaction between Emiliania huxleyi algae and Phaeobacter inhibens bacteria. We found that H2O2 levels rise during algal death and that bacterial H2O2 production triggers this demise. Manipulating H2O2 levels shifted the outcome of the interaction. We also uncovered a link between H2O2 and betaine metabolism: aging algae release betaine, which promotes bacterial H2O2 production and, in turn, accelerates algal death. Genes involved in H2O2 and betaine metabolism were upregulated in environmental samples from an algal bloom. Together, our findings identify H2O2 and betaine as key molecules that modulate algal-bacterial interactions, potentially impacting microbial dynamics in marine ecosystems.

microbiology↗

bioRxiv2024

The bacterial Bmt methionine synthase is involved in lag phase shortening

Bacteria can shorten their lag phase by utilizing methyl groups from compounds such as dimethylsulfoniopropionate (DMSP). These methyl groups are then incorporated into cellular building blocks via the methionine cycle. However, the specific contribution of bacterial methionine synthesis, which is critical for assimilating and incorporating methyl groups, remains unclear. In this study, we employed transcriptomics, genetic manipulation and biochemical assays to explore the involvement of methionine synthesis in lag phase shortening using the model marine bacterium Phaeobacter inhibens. We mapped the expression profiles of the MetH-like methionine synthase components--an enzyme complex that is encoded by three genes--in response to DMSP during the lag phase. Our findings revealed transcriptional decoupling of the three genes. The deletion of the homocysteine-binding component of the MetH-like complex, namely bmt, disrupted lag phase shortening in response to DMSP. Through heterologous expression of the bmt gene product, we show that the individual Bmt enzyme produces methionine by directly demethylating DMSP and betaine in vitro. These findings reveal a metabolic route that was not previously described in marine bacteria. Since Bmt does not require tetrahydrofolate or cobalamin as co-factors for methionine synthesis, its potential to act alone as a demethylase and a methionine synthase represents a cost-effective metabolic shortcut for methyl group assimilation, which could be specifically beneficial under limiting conditions. Indeed, we show that under stress conditions, Bmt allows cells to shorten their lag phase in response to DMSP. This study enhances our understanding of the enzymatic mechanisms underlying bacterial lag phase shortening, revealing microbial adaptation strategies in response to environmental conditions.

microbiology↗

bioRxiv2023

Bacterial lag phase shortening is triggered by methyl groups

The bacterial lag phase is a key period for resuming growth. Despite its significance, the lag phase remains underexplored, particularly in environmental bacteria. Here, we explore the lag phase of the model marine bacterium Phaeobacter inhibens when it transitions from starvation to growth with a microalgal partner. Utilizing transcriptomics and 13C-labeled metabolomics, our study reveals that methylated compounds, which are abundantly produced by microalgae, shorten the bacterial lag phase. Our findings underscore the significance of methyl groups as a limiting factor during the lag phase and demonstrate that methyl groups can be harvested from algal compounds and assimilated through the methionine cycle. Furthermore, we show that methylated compounds, characteristic of photosynthetic organisms, induce variable reductions in lag times among bacteria associated with algae and plants. These findings highlight the adjustability of the bacterial lag phase and emphasize the importance of studying bacteria in an environmental context. One-Sentence SummaryBacteria use algal compounds as a metabolic shortcut to transition from starvation to growth.

microbiology↗