Bringing the uncultivated microbial majority of freshwater ecosystems into culture.

Axenic cultures are essential for studying microbial ecology, evolution, and genomics. Despite the importance of pure cultures, public culture collections are biased towards fast-growing copiotrophs, while many abundant aquatic prokaryotes remain uncultured due to uncharacterized growth requirements and oligotrophic lifestyles. Here, we applied high-throughput dilution-to-extinction cultivation using defined media that mimic natural conditions to samples from 14 Central European lakes, yielding 627 axenic strains.

Ecophysiology and global dispersal of the freshwater SAR11-IIIb genus Fontibacterium.

The SAR11-IIIb genus Fontibacterium within the order 'Ca. Pelagibacterales' is recognized for its ubiquitous presence in freshwater environments. However, cultivation limitations have hampered deeper ecophysiological understanding of this genus, with most data limited to lakes in the Northern Hemisphere.

Ubiquitous genome streamlined in freshwater environments.

are abundant in soil, peatlands, and sediments, but their ecology in freshwater environments remains understudied. UBA12189, an genus, is an uncultivated, genome-streamlined lineage with a small genome size found in aquatic environments where detailed genomic analyses are lacking. Here, we analyzed 66 MAGs of UBA12189 (including one complete genome) from freshwater lakes and rivers in Europe, North America, and Asia.

Isolation of phages infecting the abundant freshwater Actinobacteriota order 'Ca. Nanopelagicales'.

Low-GC Actinobacteriota of the order 'Ca. Nanopelagicales' (also known as acI or hgcI clade) are abundant in freshwaters around the globe. Extensive predation pressure by phages has been assumed to be the reason for their high levels of microdiversity.

Postglacial adaptations enabled colonization and quasi-clonal dispersal of ammonia-oxidizing archaea in modern European large lakes.

Ammonia-oxidizing archaea (AOA) play a key role in the aquatic nitrogen cycle. Their genetic diversity is viewed as the outcome of evolutionary processes that shaped ancestral transition from terrestrial to marine habitats. However, current genome-wide insights into AOA evolution rarely consider brackish and freshwater representatives or provide their divergence timeline in lacustrine systems.

Adaptive genetic traits in pelagic freshwater microbes.

Pelagic microbes have adopted distinct strategies to inhabit the pelagial of lakes and oceans and can be broadly categorized in two groups: free-living, specialized oligotrophs and patch-associated generalists or copiotrophs. In this review, we aim to identify genomic traits that enable pelagic freshwater microbes to thrive in their habitat. To do so, we discuss the main genetic differences of pelagic marine and freshwater microbes that are both dominated by specialized oligotrophs and the difference to freshwater sediment microbes, where copiotrophs are more prevalent.

Ecogenomics sheds light on diverse lifestyle strategies in freshwater CPR.

Background: The increased use of metagenomics and single-cell genomics led to the discovery of organisms from phyla with no cultivated representatives and proposed new microbial lineages such as the candidate phyla radiation (CPR or Patescibacteria). These bacteria have peculiar ribosomal structures, reduced metabolic capacities, small genome, and cell sizes, and a general host-associated lifestyle was proposed for the radiation. So far, most CPR genomes were obtained from groundwaters; however, their diversity, abundance, and role in surface freshwaters is largely unexplored.

Heliorhodopsin Evolution Is Driven by Photosensory Promiscuity in Monoderms.

Rhodopsins are light-activated proteins displaying an enormous versatility of function as cation/anion pumps or sensing environmental stimuli and are widely distributed across all domains of life. Even with wide sequence divergence and uncertain evolutionary linkages between microbial (type 1) and animal (type 2) rhodopsins, the membrane orientation of the core structural scaffold of both was presumed universal. This was recently amended through the discovery of heliorhodopsins (HeRs; type 3), that, in contrast to known rhodopsins, display an inverted membrane topology and yet retain similarities in sequence, structure, and the light-activated response.

Insight into Unprecedented Diversity of Cyanopeptides in Eutrophic Ponds Using an MS/MS Networking Approach.

Man-made shallow fishponds in the Czech Republic have been facing high eutrophication since the 1950s. Anthropogenic eutrophication and feeding of fish have strongly affected the physicochemical properties of water and its aquatic community composition, leading to harmful algal bloom formation. In our current study, we characterized the phytoplankton community across three eutrophic ponds to assess the phytoplankton dynamics during the vegetation season.