Responses of Cyanobacterial Aggregate Microbial Communities to Algal Blooms

Abstract

BackgroundFreshwater lakes are threatened by harmful cyanobacterial blooms; whose basic unit is Cyanobacterial Aggregate (CA). Community variations of CA-attached bacteria are substantial during different blooming stages. However, little is known about their transcriptional and metabolic variations. Most bacterial genomes in CA were not constructed in existing database, which limits our understanding of the bacterial variations as responses to cyanobacterial blooms. ResultsIn this longitudinal study, 16 CA samples were collected from Lake Taihu, one of the largest freshwater lakes in China, from April of 2015 to February of 2016. By sequencing the V4 region of 16S rRNA genes, full metagenomes (MG) and metatranscriptomes (MT), we generated 424 Mb of 16S rRNA gene data, 122 Gb of high-quality MG data and 160 Gb of high-quality MT data. We analyzed the taxonomic, functional and transcriptional variations of microbes in CAs along three blooming stages, and constructed metagenome-assembled genomes (MAGs) by binning analysis. First, 55 OTUs, 456 genes and 37 transcripts mainly associated with pathways of transporters, photosystem and energy metabolism showed significantly different abundance among the three stages. Second, 161 high-quality MAGs in CAs were achieved, with 19 of which significantly shifted in relative abundance among three stages. The most abundant MAGs have gene capacities to synthesize flagella and divers of transporters, and participate in metabolic pathways of nitrogen, phosphorus and sulfur. Finally, 22 high-quality cyanobacterial MAGs were constructed and can be divided into four functional clusters, which showed significant differences on the energy pathways, transporters and prokaryotic defense system.ConclusionOverall, these results demonstrated the taxonomic, functional and transcriptional variations of microbes in CAs among three different blooming stages. Genome construction and metabolic analysis of cyanobacteria and their attached bacteria suggested that the material exchange and signal transmission do, indeed, exist among them. Our understanding of the underlying molecular pathways for cyanobacterial blooms could potentially lead to the control of blooms by interventional strategies to disrupt the expression of critical microbes.

Cyanopeptides Restriction and Degradation Co-mediate Microbiota Assembly During a Freshwater Cyanobacterial Harmful Algal Bloom (CyanoHAB)

“…Recent studies have suggested that the turnover of microbial communities is tightly associated with CyanoHABs due to prevalent nutrient cycling and signal transduction between bloom-associated microbiota (Wang et al 2020, Zhu et al 2021a, Zhu et al 2019, as well as dynamic of microcystins (Lezcano et al 2017). Here, we extended the scope to cyanopeptide components beyond microcystin and showed that assembly of bloom-associated microbiota is strongly determined by cyanopeptides, with variances between size-fraction niches and communities.…”

“…Specifically, taxonomic composition and biogeochemical function of bloom-associated microbiota showed clear succession over the course of toxigenic blooms (Tang et al 2018, Wan et al 2019. Size fractions of biomass can form distinct ecological niches within which interactions between cyanobacteria and bloom-associated microbiota are imperative and diverse (Chen et al 2018, Cook et al 2020, Tang et al 2017, Xu et al 2018, Zhu et al 2021a. For example, microorganisms colonized on cyanobacterial aggregates (> 100 μm) are functionally linked with their host in a commensal relationship (Cook et al 2020).…”

Gene expression in the microbial consortia of colonial Microcystis aeruginosa‐a potential buoyant particulate biofilm

“…The specific bacterial communities attached to Microcystis colonies are different from free‐living bacterial communities and those in settled sediment (Shi et al, 2012; Smith et al, 2021). Microcystis and microbes are highly interdependent (Chun et al, 2019; Zhu et al, 2021). Furthermore, metagenomic analysis revealed that a suite of biochemical pathways, such as the nitrogen and sulfur cycles, fatty acid catabolism, vitamin synthesis, and aromatic compound degradation, were complementary between Microcystis and associated microbes (Cook et al, 2020; Li et al, 2018; Xie et al, 2016).…”