Scientists discover a new supergroup of rare single-celled predators
Scientists discover a new supergroup of rare single-celled predators
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Aurich Lawson | Getty Images
At the time, taxonomists had to characterize organisms based primarily on their appearance. Molecular phylogeny changed that; once scientists were able to isolate and amplify DNA, they began to classify organisms based on their genetic sequences. But this still usually required the organisms to be grown (and therefore culturable) in a lab.
High-throughput sequencing technology has alleviated this constraint. Now researchers can simply throw a drop of pus, urine or pond water into a DNA sequencer and find a host of previously unidentified microbes.
Yet rare sequences (and the organisms they come from) are still rare, and therefore still hard to find. Eukaryotic microbial predators are single cells with complex internal structures, and they are among the rarest taxa of all. To find them, the researchers spiked seawater samples with bacterial prey to stimulate the growth of the protists that ate them. The growth of the protists in turn stimulated the growth of the predators that fed on them. Only then did the researchers perform their metagenomic analysis. They found 10 new strains of predators that they believe form a new supergroup. They named it Provara (to devour voracious protists).
Provara have been found in marine habitats around the world; in brackish and fresh water; in coral reefs; near the surface and in the depths. They are "superficially mundane flagellates" that feed on other single-celled eukaryotes. Scientists then divided them into two clades. One of them, with two previously identified but so far unclassified or misclassified species, gobbles up their prey whole. The other group, including the new species, are much smaller and tend to nibble at their prey, bite, and ingest small pieces of prey cells larger than themselves.
In a nomenclature worthy of Dr. Seuss, their discoverers named the two groups Nebulidia and Nibbleridia respectively. They share parts of their body plan with distant relatives, indicating that their lineage is ancient.
Metagenomics has greatly expanded our ability to find new microbial species. But it has limitations - it always favors more abundant taxa and therefore may not adequately reveal microbial diversity. Rare taxa are often given orphan status simply because their rarity means we are lucky to come across a single species, let alone several.
But that may belie their place in their ecosystem. They may not be the isolated relics they appear to be on our phylogenetic trees - we may not have discovered their lineage yet. And it can be vast. Revisiting culture as a way to find new microbes, including eukaryotic predators, can provide a fuller and more complete picture of the early evolution of complex cells.
At the time, taxonomists had to characterize organisms based primarily on their appearance. Molecular phylogeny changed that; once scientists were able to isolate and amplify DNA, they began to classify organisms based on their genetic sequences. But this still usually required the organisms to be grown (and therefore culturable) in a lab.
High-throughput sequencing technology has alleviated this constraint. Now researchers can simply throw a drop of pus, urine or pond water into a DNA sequencer and find a host of previously unidentified microbes.
Yet rare sequences (and the organisms they come from) are still rare, and therefore still hard to find. Eukaryotic microbial predators are single cells with complex internal structures, and they are among the rarest taxa of all. To find them, the researchers spiked seawater samples with bacterial prey to stimulate the growth of the protists that ate them. The growth of the protists in turn stimulated the growth of the predators that fed on them. Only then did the researchers perform their metagenomic analysis. They found 10 new strains of predators that they believe form a new supergroup. They named it Provara (to devour voracious protists).
Provara have been found in marine habitats around the world; in brackish and fresh water; in coral reefs; near the surface and in the depths. They are "superficially mundane flagellates" that feed on other single-celled eukaryotes. Scientists then divided them into two clades. One of them, with two previously identified but so far unclassified or misclassified species, gobbles up their prey whole. The other group, including the new species, are much smaller and tend to nibble at their prey, bite, and ingest small pieces of prey cells larger than themselves.
In a nomenclature worthy of Dr. Seuss, their discoverers named the two groups Nebulidia and Nibbleridia respectively. They share parts of their body plan with distant relatives, indicating that their lineage is ancient.
Metagenomics has greatly expanded our ability to find new microbial species. But it has limitations - it always favors more abundant taxa and therefore may not adequately reveal microbial diversity. Rare taxa are often given orphan status simply because their rarity means we are lucky to come across a single species, let alone several.
But that may belie their place in their ecosystem. They may not be the isolated relics they appear to be on our phylogenetic trees - we may not have discovered their lineage yet. And it can be vast. Revisiting culture as a way to find new microbes, including eukaryotic predators, can provide a fuller and more complete picture of the early evolution of complex cells.
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Aurich Lawson | Getty Images
