Seasonal niche differentiation between evolutionary closely related marine bacteria

Bjorbækmo

et al. 2021

Preprint

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BackgroundOcean microbes constitute ∼70% of the marine biomass, are responsible for ∼50% of the Earth’s primary production, and are crucial for global biogeochemical cycles. Marine microbiotas include core taxa that are usually key for ecosystem function. Despite their importance, core marine microbes are relatively unknown, which reflects the lack of consensus on how to identify them. So far, most core microbiotas have been defined based on species occurrence and abundance. Yet, species interactions are also important to identify core microbes, as communities include interacting species. Here, we investigate interconnected bacteria and small protists of the core pelagic microbiota populating a long-term marine-coastal observatory in the Mediterranean Sea over a decade.ResultsCore microbes were defined as those present in >30% of the monthly samples over 10 years, with the strongest associations. The core microbiota included 259 Operational Taxonomic Units (OTUs) including 182 bacteria, 77 protists, and 1,411 strong and mostly positive (∼95%) associations. Core bacteria tended to be associated with other bacteria, while core protists tended to be associated with bacteria. The richness and abundance of core OTUs varied annually, decreasing in stratified warmers waters and increasing in colder mixed waters. Most core OTUs had a preference for one season, mostly winter, which featured subnetworks with the highest connectivity. Groups of highly associated taxa tended to include protists and bacteria with predominance in the same season, particularly winter. A group of 13 highly-connected hub-OTUs, with potentially important ecological roles dominated in winter and spring. Similarly, 18 connector OTUs with a low degree but high centrality were mostly associated with summer or autumn and may represent transitions between seasonal communities.ConclusionsWe found a relatively small and dynamic interconnected core microbiota in a model temperate marine-coastal site, with potential interactions being more deterministic in winter than in other seasons. These core microbes would be essential for the functioning of this ecosystem over the year. Other non-core taxa may also carry out important functions but would be redundant and non-essential. Our work contributes toth e understanding of the dynamics and potential interactions of core microbes possibly sustaining ocean ecosystem function.

Section: Discussionsupporting

confidence: 91%

Long-term patterns of an interconnected core marine microbiota

Bjorbækmo

et al. 2021

Preprint

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“…Our approach focused in the connectivity of microorganisms and how they organize themselves from a network perspective. Similar to previous studies 13,14,28,34 , our temporal network displayed seasonality with annual periodicity for most global network metrics. In general, our measured global network metrics are within previous work range [22][23][24][25][35][36][37] (Table 2 for edge density, transitivity, and average path length).…”

Section: Discussionsupporting

confidence: 89%

“…Previous work found yearly recurrence in microbial community composition at the BBMO 13,28,34 , and at the Bay of Banyuls 14 , both in the NW Mediterranean Sea. Our approach focused in the connectivity of microorganisms and how they organize themselves from a network perspective.…”

Section: Discussionmentioning

confidence: 81%

“…Identifying different potential association partners of closely related Cyanobacteria, may indicate adaptations to different niches. A recent study found distinct seasonal patterns of closely related taxa indicating niche partitioning at the BBMO, including Synechococcus ASVs 34 . Our approach can complement and further characterize "sub"-niches by providing association partners for different ASVs.…”

Section: Discussionmentioning

confidence: 96%

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Disentangling temporal associations in marine microbial networks

et al. 2021

Preprint

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Microbial interactions are fundamental for Earth’s ecosystem functioning and biogeochemical cycling. Nevertheless, they are challenging to identify and remain barely known. The omics-based censuses are helpful to predict microbial interactions through the inference of static association networks. However, since microbial interactions are highly dynamic, we have developed an approach to generate a temporal network from a single static network. We applied it to understand the monthly microbial associations’ dynamics occurring over ten years in the Blanes Bay Microbial Observatory (Mediterranean Sea). For the decade, we identified persistent, seasonal, and temporary microbial associations. Moreover, we found that the temporal network appears to follow an annual cycle, collapsing and reassembling when transiting between colder and warmer waters. We observed higher repeatability in colder than warmer months. Altogether, our results indicate that marine microbial networks follow recurrent temporal dynamics, which need to be accounted to better understand the dynamics of the ocean microbiome.

“…Previous work found yearly recurrence in microbial community composition at the BBMO (Giner et al ., 2019; Auladell et al ., 2020; Krabberød et al ., 2021), and at the Bay of Banyuls (Lambert et al ., 2019), both in the NW Mediterranean Sea. Our approach focused in the connectivity of microorganisms and how they organize themselves from a network perspective.…”

Section: Discussionmentioning

confidence: 99%

Disentangling temporal associations in marine microbial networks

Latorre

et al. 2021

Preprint

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Microbial interactions are fundamental for Earth's ecosystem functioning and biogeochemical cycling. Nevertheless, they are challenging to identify and remain barely known. The omics-based censuses are helpful to predict microbial interactions through the inference of static association networks. However, since microbial interactions are highly dynamic, we have developed a post-network-construction approach to generate a temporal network from a single static network. We applied it to understand the monthly microbial associations' dynamics occurring over ten years in the Blanes Bay Microbial Observatory (Mediterranean Sea). For the decade, we identified persistent, seasonal, and temporary microbial associations. Moreover, we found that the temporal network appears to follow an annual cycle, collapsing and reassembling when transiting between colder and warmer waters. We observed higher repeatability in colder than warmer months. Altogether, our results indicate that marine microbial networks follow recurrent temporal dynamics, which need to be accounted to better understand the dynamics of the ocean microbiome.