Dataset Information

Combining SIMS and mechanistic modelling to reveal nutrient kinetics in an algal-bacterial mutualism.

ABSTRACT: Microbial communities are of considerable significance for biogeochemical processes, for the health of both animals and plants, and for biotechnological purposes. A key feature of microbial interactions is the exchange of nutrients between cells. Isotope labelling followed by analysis with secondary ion mass spectrometry (SIMS) can identify nutrient fluxes and heterogeneity of substrate utilisation on a single cell level. Here we present a novel approach that combines SIMS experiments with mechanistic modelling to reveal otherwise inaccessible nutrient kinetics. The method is applied to study the onset of a synthetic mutualistic partnership between a vitamin B12-dependent mutant of the alga Chlamydomonas reinhardtii and the B12-producing, heterotrophic bacterium Mesorhizobium japonicum, which is supported by algal photosynthesis. Results suggest that an initial pool of fixed carbon delays the onset of mutualistic cross-feeding; significantly, our approach allows the first quantification of this expected delay. Our method is widely applicable to other microbial systems, and will contribute to furthering a mechanistic understanding of microbial interactions.

SUBMITTER: Laeverenz Schlogelhofer H

PROVIDER: S-EPMC8136852 | biostudies-literature | 2021

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Combining SIMS and mechanistic modelling to reveal nutrient kinetics in an algal-bacterial mutualism.

Laeverenz Schlogelhofer Hannah H Peaudecerf François J FJ Bunbury Freddy F Whitehouse Martin J MJ Foster Rachel A RA Smith Alison G AG Croze Ottavio A OA

PloS one 20210520 5

Microbial communities are of considerable significance for biogeochemical processes, for the health of both animals and plants, and for biotechnological purposes. A key feature of microbial interactions is the exchange of nutrients between cells. Isotope labelling followed by analysis with secondary ion mass spectrometry (SIMS) can identify nutrient fluxes and heterogeneity of substrate utilisation on a single cell level. Here we present a novel approach that combines SIMS experiments with mecha ...[more]

PMID: 34014955

Similar Datasets

Project description:Background and Aims:Transport of carbohydrates and water are essential aspects of plant function. The aim of this study was to develop and test the methods for mechanistic modelling of quasi-stationary coupled phloem/xylem transport in the context of functional-structural plant modelling. Methods:The novelty of this approach is in combining analytical and computational methods. The plant structure is modelled at a metamer level with the internodes represented by conduit elements and the lateral organs represented by sources and sinks. Transport equations are solved analytically for each internode and then the solutions are adjusted and 'sewn' together using an iterative computational procedure taking into account concentration-dependent sinks and sources. The model is implemented in L-studio and uses the aspect-oriented modelling approach for phloem/xylem coupling. Key Results:To our knowledge, this is the first transport model that provides continuous distributions of the system variables in a complex developing structure. The model takes into account non-linear dependence of phloem resistance and osmotic potential on the local carbohydrate concentration. The model solutions show excellent agreement with the existing results of other analytical and numerical models. These comparisons confirm the validity of the approximations made in the model. Combining analytical and computational methods made it possible to take into account continuous sink/source distribution within internodes without much increase in the complexity of the computational procedure, because the necessary changes in the model were mostly in the analytical part. The results emphasize sensitivity of phloem flux and lateral xylem flux to the presence of distributed sinks and sources along the transport system. Conclusions:The presented approach provides a new insight into mechanistic modelling of phloem/xylem transport in growing plants. It will be useful for both fine-scale modelling of carbohydrate dynamics and for creating simpler models at a growth unit level.

Project description:Unicellular algae, termed phytoplankton, greatly impact the marine environment by serving as the basis of marine food webs and by playing central roles in biogeochemical cycling of elements. The interactions between phytoplankton and heterotrophic bacteria affect the fitness of both partners. It is becoming increasingly understood that metabolic exchange determines the nature of such interactions, but the underlying molecular mechanisms remain underexplored. Here, we investigated the molecular and metabolic basis for the bacterial lifestyle switch, from coexistence to pathogenicity, in Sulfitobacter D7 during interactions with Emiliania huxleyi, a cosmopolitan bloom-forming phytoplankter. The interaction displays two distinct phases: first, there is a coexisting phase in which the alga grows exponentially and the bacterium grows as well. The interaction shifts to pathogenic when the virulence of Sulfitobacter D7 towards E. huxleyi is invoked upon exposure to high concentrations of algal dimethylsulfoniopropionate (DMSP), which occurs when the algae reach stationary growth or when DMSP is applied exogenously to algae in exponential growth. We aimed to unravel the response of Sulfitobacter D7 to the pathogenicity-inducing compound, DMSP, and to different algae-derived infochemicals that affect the lifestyle of the bacterium. We grew Sulfitobacter D7 in conditioned media (CM) derived from algal cultures at the different growth phases, exponential and stationary (Exp-CM and Stat-CM, respectively), in which DMSP concentration is low and high, respectively. This enabled us to separate between different phases of the interaction with E. huxleyi, i.e., Exp-CM representing the coexisting phase, and Stat-CM representing the pathogenic phase. An additional pathogenicity-inducing treatment was Exp-CM supplemented with 100 µM DMSP (herein Exp-CM+DMSP). This condition mimicked co-cultures to which we added DMSP exogenously and thus induced Sulfitobacter D7 pathogenicity, which lead to death of exponentially growing E. huxleyi. In order to identify bacterial genes that are specifically responsive to DMSP, and are not affected by other algae-derived factors, we grew Sulfitobacter D7 in defined minimal medium (MM), lacking algal metabolites, supplemented with 100 µM DMSP (herein MM+DMSP), and examined the transcriptional response. After 24 h of Sulfitobacter D7 growth in all 5 media, triplicates were taken for transcriptomic analysis. Altogether, this experimental design allowed to expand our understanding on the bacterial response to DMSP, algal infochemicals and which of these are essential for coexistence and pathogenicity.

Dataset Information

Combining SIMS and mechanistic modelling to reveal nutrient kinetics in an algal-bacterial mutualism.

Publications

Combining SIMS and mechanistic modelling to reveal nutrient kinetics in an algal-bacterial mutualism.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets