Co-occurrence Networks Among Bacteria and Microbial Eukaryotes of Lake Baikal During a Spring Phytoplankton Bloom

Abstract

The pelagic zone of Lake Baikal is an ecological niche where phytoplankton bloom causes increasing microbial abundance in spring which plays a key role in carbon turnover in the freshwater lake. Co-occurrence patterns revealed among different microbes can be applied to predict interactions between the microbes and environmental conditions in the ecosystem. We used 454 pyrosequencing of 16S rRNA and 18S rRNA genes to study bacterial and microbial eukaryotic communities and their co-occurrence patterns at the pelagic zone of Lake Baikal during a spring phytoplankton bloom. We found that microbes within one domain mostly correlated positively with each other and are highly interconnected. The highly connected taxa in co-occurrence networks were operational taxonomic units (OTUs) of Actinobacteria, Bacteroidetes, Alphaproteobacteria, and autotrophic and unclassified Eukaryota which might be analogous to microbial keystone taxa. Constrained correspondence analysis revealed the relationships of bacterial and microbial eukaryotic communities with geographical location.

Community Compositions of Phytoplankton and Eukaryotes during the Mixing Periods of a Drinking Water Reservoir: Dynamics and Interactions

“…In December, Teleaulax and Dinobryon were other abundant genera after Aulacoseira and Thalassiosira, with an average relative abundance of 11.33% and 11.17%, respectively. Teleaulax belongs to Cryptophyta, which was also detected by Mikhailov et al [60] during spring algal blooms in Lake Baikal. It contributed the highest proportions of 15% for total eukaryotic reads, and was positively correlated with Cryptococcus.…”

“…Among these correlations, 18 were negative and only one was positive (with Bromeliophrya), indicating that Penicillium negatively affected the growth of the majority of other genera, or that there might be an antagonistic and competitive [36], or saprophytic [14], association between Penicillium and these genera. Correlations from modules II and V-VII were all positive, and positive correlations from modules V-VII were especially significant, indicating that the eukaryotic genera from these modules might arise from similar niches or mutualism [60,61,66]. Additionally, in module II, Phanerochaete was observed to have the highest positive correlations with other eukaryotic genera (adegree of 20), followed closely by Pleiochaeta with a degree of 13.…”

“…Similarly, as the common dominant taxon, Ciliophora were also observed with a maximal relative abundance (10.93%) in November (at a depth of 2 m). Ciliophora and Cercozoa are widely distributed and ubiquitous in lakes [11,14,32,60,61] and reservoirs [15,62], and they are important consumers of algae and bacteria, which occupy a pivotal position in aquatic food webs by transferring nutrients to higher trophic levels [61]. Nematoda, Ciliophora, and Cercozoa are also affiliated with zooplankton, inducing a decrease of algal density by predation and altering the structure of phytoplankton communities by selecting specific algae [31].…”

“…The authors also observed that rare and non-rare taxa exhibited synergistic effects that might contribute to maintaining the stability and resilience of eukaryotic communities and ecological function. Mikhailov et al [60] found that species from the microbial metacommunity occupied positive correlations and were highly interconnected with one another within a specific domain. Positive associations between bacteria and eukaryotes may be used as evidence of mutualistic interactions, whereas negative associations may indicate competition.…”

Tracing the Origin of Planktonic Protists in an Ancient Lake

“…The first study [28] provided insights on the genetic diversity of protists from the southern basin of Lake Baikal (see Figure 1), pointing to novel diversity. Another study investigated co-occurrence networks of bacteria and microbial eukaryotes during the spring season [29], indicating positive correlations between specific Operational Taxonomic Units (OTUs) as well as the influence of geography on the microbial community structure. Despite the insights provided by these studies, more efforts are needed in order to understand protist diversity and evolution in Lake Baikal.…”