<i>Prochlorococcus</i>
            Exudate Stimulates Heterotrophic Bacterial Competition with Rival Phytoplankton for Available Nitrogen

Calfee, Benjamin C; Glasgo, Liz D; Zinser, Erik R.

doi:10.1128/mbio.02571-21

Cited by 10 publications

(5 citation statements)

References 104 publications

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“…This may reflect a response to a comparatively high affinity for N in cyanobacteria adapted to the permanently oligotrophic open ocean, making them much stronger competitors for limiting N than coastal CC9311. N competition with EZ55 has been observed to increase the relative competitive fitness of Prochlorococcus vs. Synechococcus (coastal strain WH7803) in 3-way co-cultures [ 53 ]. In contrast, WH8102 appears to have higher N demand under 800 ppm pCO 2 , significantly upregulating a nitrate transporter and several genes related to urea utilization (Fig.…”

Section: Discussionmentioning

confidence: 99%

Community context and pCO2 impact the transcriptome of the “helper” bacterium Alteromonas in co-culture with picocyanobacteria

Filho

Walker

et al. 2022

ISME Communications

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Many microbial photoautotrophs depend on heterotrophic bacteria for accomplishing essential functions. Environmental changes, however, could alter or eliminate such interactions. We investigated the effects of changing pCO2 on gene transcription in co-cultures of 3 strains of picocyanobacteria (Synechococcus strains CC9311 and WH8102 and Prochlorococcus strain MIT9312) paired with the ‘helper’ bacterium Alteromonas macleodii EZ55. Co-culture with cyanobacteria resulted in a much higher number of up- and down-regulated genes in EZ55 than pCO2 by itself. Pathway analysis revealed significantly different transcription of genes involved in carbohydrate metabolism, stress response, and chemotaxis, with different patterns of up- or down-regulation in co-culture with different cyanobacterial strains. Gene transcription patterns of organic and inorganic nutrient transporter and catabolism genes in EZ55 suggested resources available in the culture media were altered under elevated (800 ppm) pCO2 conditions. Altogether, changing transcription patterns were consistent with the possibility that the composition of cyanobacterial excretions changed under the two pCO2 regimes, causing extensive ecophysiological changes in both members of the co-cultures. Additionally, significant downregulation of oxidative stress genes in MIT9312/EZ55 cocultures at 800 ppm pCO2 were consistent with a link between the predicted reduced availability of photorespiratory byproducts (i.e., glycolate/2PG) under this condition and observed reductions in internal oxidative stress loads for EZ55, providing a possible explanation for the previously observed lack of “help” provided by EZ55 to MIT9312 under elevated pCO2. If similar broad alterations in microbial ecophysiology occur in the ocean as atmospheric pCO2 increases, they could lead to substantially altered ecosystem functioning and community composition.

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Section: Discussionmentioning

confidence: 99%

Community context and pCO2 impact the transcriptome of the “helper” bacterium Alteromonas in co-culture with picocyanobacteria

Filho

Walker

et al. 2022

ISME Communications

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“…Laboratory experiments show that these equilibria fluctuate as one partner or the other obtains beneficial mutations during evolution ( 39, 44 ). Both chemostat ( 45 ) and transcriptomic evidence ( 8 ) indicate that Alteromonas competes for N with phytoplankton in co-culture, so it is reasonable to expect that its apparent “helping” ability should decrease as it evolves to more efficiently compete with Prochlorococcus , but that the general dynamic would persist. An open question, however, is why Prochlorococcus in nature does not appear to favor the putative antioxidant mutations observed in this experiment, but instead maintains a much higher degree of vulnerability to oxidative stress than is strictly necessary given its genomic capacities.…”

Section: Figurementioning

confidence: 99%

Marine phytoplankton and heterotrophic bacteria rapidly adapt to future pCO₂conditions in experimental co-cultures

Lu,

Entwistle,

Kuhl

et al. 2024

Preprint

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The CO2 content of Earth's atmosphere is rapidly increasing due to human consumption of fossil fuels. Models based on short-term culture experiments predict that major changes will occur in marine phytoplankton communities in the future ocean, but these models rarely consider how the evolutionary potential of phytoplankton or interactions within marine microbial communities may influence these changes. Here we experimentally evolved representatives of four phytoplankton functional types (silicifiers, calcifiers, coastal cyanobacteria, and oligotrophic cyanobacteria) in co-culture with a heterotrophic bacterium, Alteromonas, under either present-day or predicted future pCO2 conditions. Growth rates of cyanobacteria generally increased under both conditions, and the growth defects observed in ancestral Prochlorococcus cultures at elevated pCO2 and in axenic culture were diminished after evolution, possibly due to regulatory mutations in antioxidant genes. Except for Prochlorococcus, mutational profiles suggested phytoplankton experienced primarily purifying selection, but most Alteromonas lineages showed evidence of directional selection, especially when co-cultured with eukaryotic phytoplankton, where evolution appeared to favor a broad metabolic switch from growth on small organic acids to catabolism of more complex carbon substrates. Evolved Alteromonas were also poorer helpers for Prochlorococcus, supporting the assertion that the interaction between Prochlorococcus and heterotrophic bacteria is not a true mutualism but rather a competitive interaction stabilized by Black Queen processes. This work provides new insights on how phytoplankton will respond to anthropogenic change and on the evolutionary mechanisms governing the structure and function of marine microbial communities.

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“…In one of the most quantitatively important interactions, marine bacteria convert the organic compounds present in phytoplankton exometabolites back into their inorganic components, with the remineralised nutrients subsequently used by phytoplankton to fuel new primary production. This relationship has the added complexity, however, of subsequent competition between phytoplankton and bacteria for the newly available nutrients (Bratbak & Thingstad, 1986 ; Calfee et al, 2022 ). Complex reciprocal interactions are also evident in microbial vitamin exchange (Cooper et al, 2019 ; Croft et al, 2005 ; Kazamia et al, 2012 ), antagonistic relationships (Findlay & Patil, 1984 ; Segev et al, 2016 ; Seyedsayamdost et al, 2011 ) and chemotaxis and attachment (Kogure et al, 1981 ; Mayali et al, 2011 ; Stocker & Seymour, 2012 ).…”

Section: Introductionmentioning

confidence: 99%

Heterotrophic bacteria trigger transcriptome remodelling in the photosynthetic picoeukaryote Micromonas commoda

Hamilton,

Ferrer‐González,

Moran

2024

Environ Microbiol Rep

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Marine biogeochemical cycles are built on interactions between surface ocean microbes, particularly those connecting phytoplankton primary producers to heterotrophic bacteria. Details of these associations are not well understood, especially in the case of direct influences of bacteria on phytoplankton physiology. Here we catalogue how the presence of three marine bacteria (Ruegeria pomeroyi DSS‐3, Stenotrophomonas sp. SKA14 and Polaribacter dokdonensis MED152) individually and uniquely impact gene expression of the picoeukaryotic alga Micromonas commoda RCC 299. We find a dramatic transcriptomic remodelling by M. commoda after 8 h in co‐culture, followed by an increase in cell numbers by 56 h compared with the axenic cultures. Some aspects of the algal transcriptomic response are conserved across all three bacterial co‐cultures, including an unexpected reduction in relative expression of photosynthesis and carbon fixation pathways. Expression differences restricted to a single bacterium are also observed, with the Flavobacteriia P. dokdonensis uniquely eliciting changes in relative expression of algal genes involved in biotin biosynthesis and the acquisition and assimilation of nitrogen. This study reveals that M. commoda has rapid and extensive responses to heterotrophic bacteria in ways that are generalizable, as well as in a taxon specific manner, with implications for the diversity of phytoplankton‐bacteria interactions ongoing in the surface ocean.

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Prochlorococcus Exudate Stimulates Heterotrophic Bacterial Competition with Rival Phytoplankton for Available Nitrogen

Cited by 10 publications

References 104 publications

Community context and pCO2 impact the transcriptome of the “helper” bacterium Alteromonas in co-culture with picocyanobacteria

Community context and pCO2 impact the transcriptome of the “helper” bacterium Alteromonas in co-culture with picocyanobacteria

Marine phytoplankton and heterotrophic bacteria rapidly adapt to future pCO₂conditions in experimental co-cultures

Heterotrophic bacteria trigger transcriptome remodelling in the photosynthetic picoeukaryote Micromonas commoda

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Prochlorococcus Exudate Stimulates Heterotrophic Bacterial Competition with Rival Phytoplankton for Available Nitrogen

Cited by 10 publications

References 104 publications

Community context and pCO2 impact the transcriptome of the “helper” bacterium Alteromonas in co-culture with picocyanobacteria

Community context and pCO2 impact the transcriptome of the “helper” bacterium Alteromonas in co-culture with picocyanobacteria

Marine phytoplankton and heterotrophic bacteria rapidly adapt to future pCO2conditions in experimental co-cultures

Heterotrophic bacteria trigger transcriptome remodelling in the photosynthetic picoeukaryote Micromonas commoda

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Marine phytoplankton and heterotrophic bacteria rapidly adapt to future pCO₂conditions in experimental co-cultures