Microbial interactions, whether symbiotic, beneficial, antagonistic, or pathogenic, are crucial in the marine environment, as they can shape community composition and influence nutrient cycles, energy flow, and overall ecosystem function. Despite their significance, the complex web of interactions among planktonic microbes remains enigmatic, mainly due to marine environments' dynamic nature and our limited ways of sampling the interactions that occur at the scale of the single cells. This session aims to bring together experts in aquatic microbial ecology to discuss the implications of recent advancements in technologies and methodologies that are revolutionizing our ability to decipher and characterize marine microbial interactions.
Lead Organizer: Uri Sheyn, Virginia Tech (urisheyn@gmail.com)
Co-organizers:
Shiri Graff van Creveld, University of Washington Center for Environmental Genomics (shirig@uw.edu)
Flora Vincent, EMBL Heidelberg (flora.vincent@embl.de)
Presentations
06:00 PM
SHORELINE BACTERIAL COMMUNITY DYNAMICS IN SEAWATER AND SAND: INSIGHTS ALONG THE MISSISSIPPI GULF COAST (8808)
Primary Presenter: Stephanie Vaughn, University of Mississippi (snvaughn@olemiss.edu)
Understanding how marine bacterial communities vary along spatial and temporal gradients could aid in assessing ecosystem health along the Gulf Coast. To investigate seasonal and spatial patterns in bacterial community structure, seawater and sand samples were collected from 10 sites along the Mississippi Gulf Coast over the course of a year. 16S rRNA gene sequencing revealed that the coastal bacterial community differed between sample types, and by location and month of collection. Spatial patterns were more pronounced than temporal patterns, with sand and seawater communities influenced more by distance between sample sites than month of collection. Seawater bacterial community composition was driven by pH, salinity, and temperature, while sand bacterial communities were influenced primarily by temperature. Bacterial species richness and diversity were higher in sand than water, with both varying by site and month. Relative abundances of major bacterial phyla differed between sample type, location, and collection month, although members of the Bacteroidetes, Gammaproteobacteria, and Alphaproteobacteria were predominant across samples. Cyanobacteria accounted for a greater proportion of the seawater bacterial community compared to sand, and proportions of Cyanobacteria were positively correlated with water temperature. These findings reveal the dynamic nature of nearshore bacterial communities along the Mississippi Gulf Coast, potentially offering insights for coastal ecosystem management across seasons.
06:00 PM
PHYSIOLOGICAL FLUCTUATIONS UNDERLYING THE METABOLIC INTERACTIONS OF A CRYPTIC SULFUR CYCLING BACTERIAL CONSORTIUM (8963)
Primary Presenter: Braulio Castillo Villaseñor, University of California, Santa Barbara (bscvillasenor@gmail.com)
Cryptic sulfur cycling consists of tightly coupled sulfur exchange between bacteria that are often missed by bulk geochemical measurements, enabling important “hidden” carbon transformations. To investigate this cryptic cycling, we studied the “pink berries”, a consortium of sulfide oxidizing phototrophs and sulfate reducing bacteria. To probe this syntrophic metabolism and elucidate links between the carbon and sulfur cycles, we used a multipronged approach consisting of PacBio HiFi metagenomes, paired to metaproteomic and metabolomic sampling. Pink berries were incubated in sterile marsh water over 48 hours and sampled during peak light and peak dark conditions. Proteins were then extracted, run on an LC-MS/MS and compared to a peptide database assembled from contemporaneous metagenomes of complete genomes in megabase-size contigs. Parallel aggregates were sampled for both exo/endometabolites. Our high quality metaproteomes identified ~2000 proteins per sample, with a good ratio of spectra matching to our database(~half). From the endometabolomic data, we detected 184 putative distinct metabolites spanning central carbon pathways to secondary metabolites. Integrating these data, we find fluctuations in and metabolic connections between carbon and sulfur pathways. This work sheds light on the intimate metabolic interactions in cryptic biogeochemical interactions and offers new insights about the chemical basis of bacterial symbiosis.
06:00 PM
PLANKTONIC POLYPHOSPHATE CONTENT ACROSS TWO WATER MASSES IN THE LOW-PHOSPHATE WESTERN MEDITERRANEAN SEA (9001)
Primary Presenter: Alba Filella, The University of Arizona (afilella@arizona.edu)
Phosphorus (P) is indispensable for life, and its cycling is linked to that of carbon and nitrogen. Notwithstanding, P can be scarce in regions of surface seawater, such as the Mediterranean Sea. To cope with variability in P availability, plankton can accumulate P in the form of polyphosphate (polyP) when ambient phosphate is available and use polyP when phosphate is depleted. PolyP is produced by all living organisms, is highly bioavailable for marine plankton, and is ubiquitous in marine systems. However, knowledge gaps remain regarding the distribution, chain-length composition, and function of marine polyP. Preferential retention of polyP over other forms of cellular P has been observed in P-stressed microbial communities, which contradicts the perceived primary role of polyP as a P storage molecule. We hypothesize that community composition controls polyP retention over other P-biomolecules in oligotrophic seawater. To test our hypothesis, we sampled planktonic communities across two water masses separated by a sharp front in the low-P Western Mediterranean Sea. We measured the concentration of P-rich biomolecules, including phospholipids, nucleic acids, and polyP, at the bulk and group-specific-levels (by flow cytometry sorting of heterotrophic bacteria, Prochlorococcus, Synechococcus, and small eukaryotes). Our results will provide a quantitative understanding of marine polyP pools, shedding new light on their biological origin and function, with implications for food web dynamics, nutrient cycling, and carbon sequestration.
06:00 PM
Role of environment and host genotype on the microbial and viral diversity of the cnidarian Nematostella vectensis (9119)
Primary Presenter: Adam Reitzel, University of North Carolina at Charlotte (areitze2@charlotte.edu)
The estuarine environment has a plethora of microorganisms that allow for diverse animal-microbe interactions which may impact the behavior and physiology of host animals. The sea anemone Nematostella vectensis, is a model cnidarian found along the east coast of North America, ranging from Nova Scotia to Florida. Previous research has shown that anemones from different locations have unique microbial communities and that some of these differences are maintained in the laboratory for long periods of time. However, how the genotype of individuals impacts the association with bacteria and viruses in more natural environmental conditions remains unexplored. Here we used mesocosms in two locations (New Hampshire and South Carolina) to determine holobiont variation for anemones originating from different locations along the Atlantic coast. Using a combination of flow cytometry, metagenomics, and metatranscriptomics, we compared the number and diversity of bacteria and viruses in individuals exposed to a common environment. We identified significant differences in anemone gene expression as well as microbial and viral communities, some of which separate along a latitudinal cline. A portion of the observed variations correlate with genomic structural variants, including copy number variation of several immune genes. We will present our current findings and future plans for this research which is focused on characterizing how genomic variation can help explain the diversity of the associated microbes and viruses of coastal invertebrates.
06:00 PM
Investigating Recalcitrant Dissolved Organic Matter Production through a Probabilistic Method in Marine Bacterial Metabolism (9307)
Primary Presenter: Loreto Paulino, Boston University (lpaulino@bu.edu)
About 90% of the ocean’s dissolved organic matter pool consists of long-lived recalcitrant dissolved organic matter (RDOM), which comprises stable compounds resistant to biological degradation. This stability allows RDOM to store significant amounts of fixed carbon, playing a crucial role in mitigating the effects of anthropogenic climate change. According to the microbial carbon pump hypothesis, vast quantities of RDOM may originate from marine heterotrophic bacteria through the successive transformation of labile dissolved organic matter (LDOM). However, the bacterial-mediated pathways from LDOM to RDOM remain poorly studied due to the naturally low concentrations and rapid turnover rates of microbial metabolites, complicating their detection and analysis.To further investigate RDOM production from the utilization and transformation of LDOM by marine heterotrophic bacteria, we will employ a probabilistic method inspired by percolation theory to calculate the metabolic capabilities of individual genome-scale metabolic models (GEMs) in producing precursors of carboxyl-rich alicyclic molecules (CRAM), a major component of RDOM throughout the water column. Utilizing 80 draft GEMs representing a diverse set of marine bacterial strains from temperate and cold waters, as well as deep and surface environments, we will predict the biosynthetic capabilities of various CRAM-like metabolites across each strain. Our analysis of the predicted results will explore potential taxonomic and depth-related trends, aiming to identify possible drivers of RDOM production by marine bacteria.
06:00 PM
North Pacific Isolated Alteromonas macleodii Strain has a Broad Algicidal Effect, Likely Mediated by Protease Secretion (9614)
Primary Presenter: Riley Dunklin, Cypress College (riley.dunklin@gmail.com)
Algae account for roughly half of global carbon dioxide absorption and are a large and diverse group of primary producers. Understanding the complexities of algal interactions with its environment is important in furthering understanding of important biogeochemical cycles. Previous research has determined that marine bacteria Alteromonas macleodii (A. mac) independently secretes an extracellular substance that kills model diatom Thalassiosira pseudonana. The specific mechanism is unknown, but a potential candidate is extracellular protease. We designed an experiment to test whether A. mac secretes proteases at an easily detectable concentration. Our results distinctly indicated that A. mac independently secretes extracellular proteases. Additionally, we tested the specificity of A. mac’s algal killing effect by replicating the preliminary experiment on five additional species spanning 3 classes and 5 genera. Four out of six species were negatively affected, suggesting a broad spectrum of the killing effect. In the open ocean, A. mac encounters an abundance of algal species. Deepening the understanding of the range of A. mac's effect provides more information about how networks of microbes may impact each other in the environment and the potential impacts these interactions may have on biogeochemical cycles.
SS25P - Marine microbial interactions at the molecular and cellular scale
Description
Time: 6:00 PM
Date: 29/3/2025
Room: Exhibit Hall A