The study on the microbiome of ciliates; which explaining that a microbiome is a community of microorganisms that inhabit an ecological niche. Microbiomes exist in environmental biotopes, for example, a water body or forest soil; as well as in living multicellular host organisms such as humans, animals or plants.
A microbiome may be composing of bacteria; archaea, and unicellular eukaryotes like protists and fungi. analyzing the microbiomes of two ciliates, paramecium and stentor. The results of the study on paramecium were published last winter. The new publication is the next step in the study of protistan microbiomes. The human and animal microbiome studies are at the cutting edge of biology; while only few studies investigated bacterial consortia associated with protists.
As protists host their own microbiomes that is; they harbor prokaryotic communities had not been properly addressed. Therefore, the results of our study are setting a new direction for scientific research; The idea that ciliates might have their own microbiomes was not random. Microbiologists know that in sterile conditions, these organisms die. Their viability depends strongly on the presence of bacteria in the environment.
Microbiomes of ciliates
However, it was almost impossible to characterize their bacterial composition in detail; nor to separate the lodgers of the ciliates from the inhabitants of their aquatic environment water source there were no available methods. Metagenomic analysis, which not been using extensively for this purpose; enabled the researchers to deepen their inquiries.
This approach enables us to sequence a complete set of certain genetic markers in the total DNA of a sample. Hence, all sequences are assigned to their hosts, allowing us to identify them. For bacteria and archaea, this is the 16S rRNA gene sequence. Metagenomics and high throughput sequencing have expanded our understanding of the microbial diversity in natural environments tremendously over the last 10 to 15 years.
Common freshwater ciliate
But in this study it is using metagenomic analysis; to identify bacteria associating with the cells of two common freshwater ciliate genera stentor and paramecium. The researchers have discovered that the bacterial community of environments such as stream water or a laboratory culture medium differs significantly from the microbial consortium associated with ciliates. The variety of microorganisms in natural reservoirs is always richer than in ciliates.
The associated bacteria, however, rarely thrive in association with protists to be able to propagate rapidly. Their numbers, as our analyzes have showing, are always small, but they are comfortable enough to survive the challenging times. Thus, ciliates (and, most likely, other protists) may play the role of transient reservoirs for bacteria outside their preferred multicellular host.