TY - JOUR
T1 - Heterotrophic bacteria enhance the aggregation of the marine picocyanobacteria prochlorococcus and synechococcus
AU - Cruz, Bianca N.
AU - Neuer, Susanne
N1 - Funding Information:
This research was supported by the National Science Foundation (OCE-1658527).. We thank the Passow Lab at UC Santa Barbara for the pre-calibrated Alcian Blue solution and f-factor, and Uta Passow for helpful comments on an earlier version of the manuscript. We also thank the crew of the R/V Atlantic Explorer for their technical support at sea, the J. J. MacIsaac Facility for Aquatic Cytometry at the Bigelow Laboratory for Ocean Sciences for their flow cytometry services, and Catrina L. Shurtleff and Kevin Roy for their technical support in the lab.
Funding Information:
This research was supported by the National Foundation (OCE-1658527).
Publisher Copyright:
© 2019 Cruz and Neuer.
PY - 2019
Y1 - 2019
N2 - Marine picocyanobacteria are ubiquitous primary producers across the world’s oceans, and play a key role in the global carbon cycle. Recent evidence stemming from in situ investigations have shown that picocyanobacteria are able to sink out of the euphotic zone to depth, which has traditionally been associated with larger, mineral ballasted cells. The mechanisms behind the sinking of picocyanobacteria remain a point of contention, given that they are too small to sink on their own. To gain a mechanistic understanding of the potential role of picocyanobacteria in carbon export, we tested their ability to form “suspended” (5–60 µm) and “visible” (ca. > 0.1 mm) aggregates, as well as their production of transparent exopolymer particles (TEP)—which are a key component in the formation of marine aggregates. Additionally, we investigated if interactions with heterotrophic bacteria play a role in TEP production and aggregation in Prochlorococcus and Synechococcus by comparing xenic and axenic cultures. We observed TEP production and aggregation in batch cultures of axenic Synechococcus, but not in axenic Prochlorococcus. Heterotrophic bacteria enhanced TEP production as well as suspended and visible aggregate formation in Prochlorococcus, while in Synechococcus, aggregation was enhanced with no changes in TEP. Aggregation experiments using a natural plankton community dominated by picocyanobacteria resulted in aggregation only in the presence of the ballasting mineral kaolinite, and only when Synechococcus were in their highest seasonal abundance. Our results point to a different export potential between the two picocyanobacteria, which may be mediated by interactions with heterotrophic bacteria and presence of ballasting minerals. Further studies are needed to clarify the mechanistic role of bacteria in TEP production and aggregation of these picocyanobacteria.
AB - Marine picocyanobacteria are ubiquitous primary producers across the world’s oceans, and play a key role in the global carbon cycle. Recent evidence stemming from in situ investigations have shown that picocyanobacteria are able to sink out of the euphotic zone to depth, which has traditionally been associated with larger, mineral ballasted cells. The mechanisms behind the sinking of picocyanobacteria remain a point of contention, given that they are too small to sink on their own. To gain a mechanistic understanding of the potential role of picocyanobacteria in carbon export, we tested their ability to form “suspended” (5–60 µm) and “visible” (ca. > 0.1 mm) aggregates, as well as their production of transparent exopolymer particles (TEP)—which are a key component in the formation of marine aggregates. Additionally, we investigated if interactions with heterotrophic bacteria play a role in TEP production and aggregation in Prochlorococcus and Synechococcus by comparing xenic and axenic cultures. We observed TEP production and aggregation in batch cultures of axenic Synechococcus, but not in axenic Prochlorococcus. Heterotrophic bacteria enhanced TEP production as well as suspended and visible aggregate formation in Prochlorococcus, while in Synechococcus, aggregation was enhanced with no changes in TEP. Aggregation experiments using a natural plankton community dominated by picocyanobacteria resulted in aggregation only in the presence of the ballasting mineral kaolinite, and only when Synechococcus were in their highest seasonal abundance. Our results point to a different export potential between the two picocyanobacteria, which may be mediated by interactions with heterotrophic bacteria and presence of ballasting minerals. Further studies are needed to clarify the mechanistic role of bacteria in TEP production and aggregation of these picocyanobacteria.
KW - Aggregation
KW - Bacteria
KW - Prochlorococcus
KW - Synechococcus
KW - Transparent exopolymeric particles
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U2 - 10.3389/fmicb.2019.01864
DO - 10.3389/fmicb.2019.01864
M3 - Article
AN - SCOPUS:85071954046
SN - 1664-302X
VL - 10
JO - Frontiers in Microbiology
JF - Frontiers in Microbiology
IS - AUG
M1 - 1864
ER -