A study in the online open access journal, BMC Evolutionary Biology, shows that some protozoa are globally dispersed, while others are geographically restricted - by looking at a new fast-evolving DNA marker. The study also reveals that the biodiversity of protozoa may be much higher than previously realised.
It has long been argued that the small size and huge populations of microorganisms aids their global dispersal. 'Everything is everywhere, but the environment selects' said Lourens Baas-Becking in 1934. Today, this Ubiquitous Dispersal Hypothesis (UDH) remains controversial compared to the alternative possibility of endemicity - the tendency of organisms to be confined to specific regions - as is found for many macro-organisms. While previous morphological and molecular analyses of environmental samples from around the world have provided evidence for UDH, these markers evolve too slowly to allow a really rigorous test of the hypothesis.
David Bass and colleagues at the University of Oxford and elsewhere, have carried out an analysis of the global distribution and diversity of three narrow taxonomic groups of cercomonads (heterotrophic flagellate protozoa) based upon PCR, cloning and sequencing of ITS1 rDNA sequences from samples gathered from around the world. ITS1 is a faster-evolving marker than the more commonly used 18S rDNA and therefore allowed the study to be done at a higher phylogenetic resolution. This approach is robust, being independent of the ability to culture or see the organism being studied.
They sequenced gene libraries of soil, freshwater, and marine cercomonads constructed from 47-80 samples per group from a wide range of habitats in locations including Panama, the Pacific, the Caribbean, Peru, UK, Greece, France, Germany, India, Japan, British Columbia, Australia and New Zealand. The study is unique in screening such large numbers of globally distributed environmental DNA sequences with such narrowly targeted PCR primers.
Identical ITS sequences were found in widely separated sites from all continents for several of the genotypes studied, suggesting relatively rapid global dispersal. Some ITS types were found in both marine and non-marine environments, which usually have different protist populations. However, other ITS sequences had patchy or restricted distributions, indicating at least a moderate degree of endemicity.
Moreover, strains of cercomonads with the same 18S but different ITS1 sequences differed in phenotype with respect to characteristics such as morphology, salinity tolerance, and propensity for cyst formation. This suggests that global protist biodiversity may be richer than previously suspected.
The authors conclude that these new findings support the moderate endemicity model of microbial biogeography, with some cercomonad strains being globally dispersed while others are geographically restricted. The issue of possible under-sampling of the rich diversity of the protozoa needs to be taken into account in further studies; this way, a more accurate picture of their global distribution and importance may be obtained.
Charlotte Webber | alfa
New study: How does Europe become a leading player for software and IT services?
03.04.2017 | Fraunhofer-Institut für System- und Innovationsforschung (ISI)
Reusable carbon nanotubes could be the water filter of the future, says RIT study
30.03.2017 | Rochester Institute of Technology
Scientists have developed a new method of characterizing graphene’s properties without applying disruptive electrical contacts, allowing them to investigate both the resistance and quantum capacitance of graphene and other two-dimensional materials. Researchers from the Swiss Nanoscience Institute and the University of Basel’s Department of Physics reported their findings in the journal Physical Review Applied.
Graphene consists of a single layer of carbon atoms. It is transparent, harder than diamond and stronger than steel, yet flexible, and a significantly better...
The world's highest gain high power laser amplifier - by many orders of magnitude - has been developed in research led at the University of Strathclyde.
The researchers demonstrated the feasibility of using plasma to amplify short laser pulses of picojoule-level energy up to 100 millijoules, which is a 'gain'...
Staphylococcus aureus is a feared pathogen (MRSA, multi-resistant S. aureus) due to frequent resistances against many antibiotics, especially in hospital infections. Researchers at the Paul-Ehrlich-Institut have identified immunological processes that prevent a successful immune response directed against the pathogenic agent. The delivery of bacterial proteins with RNA adjuvant or messenger RNA (mRNA) into immune cells allows the re-direction of the immune response towards an active defense against S. aureus. This could be of significant importance for the development of an effective vaccine. PLOS Pathogens has published these research results online on 25 May 2017.
Staphylococcus aureus (S. aureus) is a bacterium that colonizes by far more than half of the skin and the mucosa of adults, usually without causing infections....
Physicists from the University of Würzburg are capable of generating identical looking single light particles at the push of a button. Two new studies now demonstrate the potential this method holds.
The quantum computer has fuelled the imagination of scientists for decades: It is based on fundamentally different phenomena than a conventional computer....
An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.
We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...
24.05.2017 | Event News
23.05.2017 | Event News
22.05.2017 | Event News
30.05.2017 | Life Sciences
30.05.2017 | Life Sciences
30.05.2017 | Physics and Astronomy