Biology subjects

Tinta, T.

Publications and source records attributed to Tinta, T..

5 recordsLinked to original sources

bioRxiv2025

Viral lysis of a toxigenic diatom triggers a microbial response mimicking hastened senescence

Diatom blooms influence carbon cycling through organic matter production and its subsequent deposition or remineralization - processes that are all tightly mediated by interactions with the microbial community. Viruses, as integral part of microbial communities, are known to influence diatom bloom dynamics and can even terminate blooms. However, the three-way interactions between diatoms, their viruses and associated bacteria remain poorly resolved. In this study we examined how infection of the toxigenic diatom Pseudo-nitzschia galaxiae by its ssRNA virus PnGalRNAV reshapes host physiology, microbiome structure and organic-matter processing in non-axenic batch cultures. With an integrated transcriptomics and microscopy-based approach, we investigated the response of the bacterial community to dissolved organic matter (DOM) released by viral lysis of diatoms and observed a significant increase of Flavobacteriaceae (Bacteriodetes) suggesting a specialized role in utilizing DOM released due to viral lysis. Despite overwhelming viral RNA, bacterial metatranscriptomes revealed upregulation of polysaccharide-degradation associated genes, indicating active utilisation of virus-derived diatom glycans. Host transcripts showed broad repression of photosynthesis, silicon metabolism and core biosynthetic pathways, alongside induction of heat-shock and other stress-related genes, consistent with a senescence-like state. Our results demonstrate that PnGalRNAV infection speeds the termination of P. galaxiae growth, rapidly converting a productive diatom culture into a detrital DOM-rich environment that selects for specialised polysaccharide degraders and redirects carbon through the viral shunt. Infected cultures reached senescence much sooner than uninfected ones, suggesting that the ssRNA virus of Pseudo-nitzschia galaxiae can shorten bloom duration and accelerate nutrient recycling, with implications for coastal biogeochemistry. By integrating spatially resolved microscopy with community and metatranscriptomic profiling, this study links microbial composition, localization, and functional activity during diatom viral lysis. Our comprehensive approach can be extended to diverse diatom-virus systems in the future to better predict when viral outbreaks will favour recycling versus export of phytoplankton-derived carbon.

microbiology↗

bioRxiv2025

Distinct functional potential of bacterial extracellular vesicles across biogeographic provinces of the South Pacific Ocean

Bacterial extracellular vesicles (BEVs) are nanoscale membranous structures released by diverse types of bacteria. Laboratory model systems indicate that these nanoparticles may play several roles in the ecophysiology of marine bacteria. However, their actual functionality in the environment remains unclear. Here we describe the proteomic composition of marine BEVs over more than 5,000 nautical miles of surface waters in the South Pacific, linking BEV cargoes to the bacterial communities producing them. BEVs were consistently present across a range of biogeochemical conditions, with an overall abundance comparable to that of bacterial cells. However, the protein content of the BEVs varied significantly between different ocean regions. The BEVs were enriched in carbohydrate transporters under phytoplankton bloom conditions, and contained iron and phosphate uptake-related proteins in nutrient-limited waters. This suggests that BEVs could enable cells to perform key extracellular functions in the marine environment. Our observations further highlight the prevalence of BEVs and the biogeographic patterns of their functional potential across oceanic scales.

microbiology↗

bioRxiv2024

Jellyfish blooms - an overlooked hotspot and potential vector for the transmission of antimicrobial resistance in marine environments

Jellyfish, and gelatinous zooplankton (GZ) in general, represent an important component of marine food webs. Certain GZ species are capable of generating massive blooms of severe environmental impact. These blooms are often followed by a sudden collapse of the entire population, introducing considerable amounts of organic matter (GZ-OM) in the oceans interior. GZ-OM represents an abundant substrate to promote bacterial growth and copious colonizable surface for microbial interactions. Hence we hypothesized that this GZ-OM serves as a yet overlooked hotspot for transmitting antimicrobial resistance genes (ARGs) in marine environments. For this we experimentally evolved and analyzed marine microbial communities in microcosms in presence and absence of OM from scyphozoan Aurelia aurita s.l. and ctenophore Mnemiopsis leidyi. Communities evolved under GZ-OM exposure displayed an up to 4-fold increase in relative ARG and an up to 10-fold increase in abundance of horizontally transferable mobile genetic elements (MGEs) per 16S rRNA gene copy compared to the controls. This trait was consistent across ARG and MGE classes and independent of the GZ species, suggesting that the underlying mechanism is indeed based on the general influx of nutrients and colonizable surfaces. Potential ARG carriers included known key GZ-OM degraders, but also genera containing potential pathogens hinting towards an increased risk of ARG transfer to pathogenic strains. Here, Vibrio were pinpointed as potential key species directly associated with several significantly elevated ARGs and MGEs. Subsequent whole-genome sequencing of a Vibrio isolate from the microcosm experiment revealed the genetic potential for the mobilization and transfer of ARGs in GZ-OM degrading microbial consortia. With this study, we established the first link between two emerging issues of marine coastal zones, jellyfish blooms and AMR spread, both likely increasing in projected future ocean scenarios.

microbiology↗

bioRxiv2023

Bacterial degradation of ctenophore Mnemiopsis leidyi organic matter

Blooms of gelatinous zooplankton, an important source of protein-rich biomass in coastal waters, often collapse rapidly, releasing large amounts of labile detrital organic matter (OM) into the surrounding water. Although these blooms have the potential to cause major perturbations in the marine ecosystem, their effects on the microbial community and hence on the biogeochemical cycles have yet to be elucidated. We conducted microcosm experiments simulating the scenario experienced by coastal bacterial communities after the decay of a ctenophore (Mnemiopsis leidyi) bloom in the northern Adriatic Sea. Within 24 h, a rapid response of bacterial communities to the M. leidyi OM was observed, characterized by elevated bacterial biomass production and respiration rates. Compared to our previous microcosm study of jellyfish (Aurelia aurita s.l.), M. leidyi OM degradation revealed that, despite the fundamental genetic and biochemical differences between the two species, a similar pattern in the bacterial community response was observed. Combined metagenomic and metaproteomic analysis indicated that the degradation activity was mainly performed by Pseudoalteromonas, producing a large amount of proteolytic exoenzymes and exhibiting high metabolic activity. Interestingly, the reconstructed metagenome-assembled genome (MAG) of Pseudoalteromonas phenolica was almost identical (average nucleotide identity >99%) to the MAG previously reconstructed in our A. aurita microcosm study. Taken together our data suggest that blooms of different gelatinous zooplankton are likely triggering a consistent response from natural bacterial communities, with specific bacterial lineages driving the remineralization of the gelatinous OM. ImportanceJellyfish blooms are increasingly becoming a recurring seasonal event in marine ecosystems, characterised by a rapid build-up of gelatinous biomass that collapses rapidly. Although these blooms have the potential to cause major perturbations, their impact on marine microbial communities is largely unknown. We conducted an incubation experiment simulating a bloom of the ctenophore Mnemiopsis leidyi in the Northern Adriatic, where we investigated the bacterial response to the gelatinous biomass. We found that the bacterial communities actively degraded the gelatinous organic matter, and overall showed a striking similarity to the dynamics previously observed after a simulated bloom of the jellyfish Aurelia aurita s.l. In both cases we found that a single bacterial species, Pseudoalteromonas phenolica, was responsible for most of the degradation activity. This suggests that blooms of different jellyfish are likely to trigger a consistent response from natural bacterial communities, with specific bacterial species driving the remineralisation of gelatinous biomass.

microbiology↗

bioRxiv2018

Bacteria associated with jellyfish during bloom and post-bloom periods

This study is the first to investigate bacterial community associated with live medusa Aurelia sp. in the Gulf of Trieste (northern Adriatic Sea) using both culture independent and culture-based methods. We have analysed bacterial community composition of different body parts of medusa: exumbrella surface, oral arms ( outer body parts) and of gastric cavity ( inner body part) and investigated possible differences in medusa associated bacterial community structure at the time of jellyfish population peak and during senescent phase at the end of bloom, when jellyfish start to decay. Based on 16S rRNA clone libraries and denaturing gradient gel electrophoresis (DGGE) analysis, we demonstrated significant difference between bacterial community associated with Aurelia and the ambient seawater bacterial assemblage. Comparing bacterial community composition between different Aurelia medusa body parts, communities differed significantly, especially the one within the gastral cavity. The pronounced difference is dominance of Betaproteobacteria (Burkholderia, Cupriavidus and Achromobacter) in gastral cavity of medusa and Alpha- (Phaeobacter, Ruegeria) and Gamma- proteobacteria (Stenotrophomonas, Alteromonas, Pseudoalteromonas and Vibrio) on outer body parts. This suggests that body-part specific bacterial association might have an important functional roles for the host. The results of bacterial isolates showed the dominance of Gammaproeteobacteria, especially Vibrio and Pseudoalteromonas in all body parts. Finally, comparison of medusa associated bacterial community structure, at the time of jellyfish population peak and during senescent phase at the end of bloom showed increased abundance of Gammaproteobacteria, especially Vibrio. Our results suggest members of Vibrio group are possible commensal opportunistic visitors, later becoming consumer of moribund jellyfish biomass and that the structure of jellyfish bacterial community might be affected by anthropogenic pollution in the marine environment.

ecology↗