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Nano- to microscale characterization of metabolic cooperation facilitated by physical associations between phototrophic microalgae and heterotrophic bacterial symbionts


EMSL Project ID
50220

Abstract

Attachment between phototrophic microalgae and heterotrophic bacteria is an integral yet understudied facet of microbial ecology. Such inter-kingdom cooperative partnerships have important consequences for biogeochemical cycling, ecosystem function, and bioenergy production driven by the enhanced ecological success of each member. The goal of this proposal is to begin detailing the nano- and microscale features defining these interactions in co-cultures of the model microalgal and biofuel species Phaeodactylum tricornutum and 4 individual bacterial species. This work represents a first order approach toward upscaling these interactions to systems-scale processes and observations. We will use helium ion microscopy (HIM) and cryo-TEM to visualize the macromolecular structures on the cell surfaces of P. tricornutum and bacteria, contextually describing how they sense, attach, and exchange compounds. This will be followed by glycan analyses to determine how the chemical composition of organic matter sheathing the microalgae is altered by the bacterial attachment compared to no bacteria (axenic cultures), which constrains the microalgal constituents produced to facilitate interactions with the bacteria that incorporate them. The next phase of work aims to identify how intracellular metabolites and structural components (lipids, proteins, polysaccharides) of P. tricornutum are altered by presence of the attached bacteria. Through a combination analyses, we will respectively characterize the metabolic and molecular dynamics at high mass resolution and aggregate spatial scale in microalgal and bacterial colonies on agar using FT-ICR-SIMS, followed by analysis of single cells immobilized and distributed on flat surfaces with TOF-SIMS. Proteomic and metabolomic data from LC-MS/MS analyses of bulk co-cultures will also be employed to link patterns in metabolite production to protein content and identity. In the final phase, we will identify the exometabolites produced between microalgae and bacteria using MALDI-MSI in concert with a new device that mimics the diffusive organic matter region surrounding microalgae (known as the phycosphere), to which bacteria are attracted and attach. Leveraging preliminary data from LC-MS/MS analyses of exometabolites, we will identify and quantify metabolites as a function of distance within the experimental phycospheres of P. tricornutum, again comparing microalgal-bacterial co-cultures versus axenic microalgae. This multi-thrust investigation will significantly advance our understanding of how attachment mediates mutually beneficial outcomes between physically-associating microalgae and bacteria by connecting genomic potential to direct observations of metabolite and molecule production, fate, and influence.

Project Details

Project type
Large-Scale EMSL Research
Start Date
2018-10-01
End Date
2021-10-31
Status
Closed

Team

Principal Investigator

Ty Samo
Institution
Lawrence Livermore National Laboratory

Co-Investigator(s)

Peter Weber
Institution
Lawrence Livermore National Laboratory

Team Members

Cullen Buie
Institution
Massachusetts Institute of Technology

Christopher Ward
Institution
Bowling Green State University

Rhona Stuart
Institution
Lawrence Livermore National Laboratory

Xavier Mayali
Institution
Lawrence Livermore National Laboratory

Trent Northen
Institution
Lawrence Berkeley National Laboratory