Featured Research

from universities, journals, and other organizations

DNA Analysis Shows True Dispersal Of Protozoa

Date:
September 19, 2007
Source:
BioMed Central
Summary:
In contrast to previous findings, it seems that the global distribution of macro- and microorganisms might be similar. A new study 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 realized.

In contrast to previous findings, it seems that the global distribution of macro- and microorganisms might be similar. A study in 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.

Related Articles


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.

Article: David Bass, Thomas A. Richards, Lena Matthai, Victoria Marsh and Thomas Cavalier-Smith, "DNA evidence for global dispersal and probable endemicity of protozoa" BMC Evolutionary Biology (in press)


Story Source:

The above story is based on materials provided by BioMed Central. Note: Materials may be edited for content and length.


Cite This Page:

BioMed Central. "DNA Analysis Shows True Dispersal Of Protozoa." ScienceDaily. ScienceDaily, 19 September 2007. <www.sciencedaily.com/releases/2007/09/070913081118.htm>.
BioMed Central. (2007, September 19). DNA Analysis Shows True Dispersal Of Protozoa. ScienceDaily. Retrieved October 24, 2014 from www.sciencedaily.com/releases/2007/09/070913081118.htm
BioMed Central. "DNA Analysis Shows True Dispersal Of Protozoa." ScienceDaily. www.sciencedaily.com/releases/2007/09/070913081118.htm (accessed October 24, 2014).

Share This



More Plants & Animals News

Friday, October 24, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Deep Sea 'mushroom' Could Be Early Branch on Tree of Life

Deep Sea 'mushroom' Could Be Early Branch on Tree of Life

Reuters - Innovations Video Online (Oct. 24, 2014) Miniature deep sea animals discovered off the Australian coast almost three decades ago are puzzling scientists, who say the organisms have proved impossible to categorise. Academics at the Natural History of Denmark have appealed to the world scientific community for help, saying that further information on Dendrogramma enigmatica and Dendrogramma discoides could answer key evolutionary questions. Jim Drury has more. Video provided by Reuters
Powered by NewsLook.com
Black Bear Cub Goes Sunday Shopping

Black Bear Cub Goes Sunday Shopping

Reuters - Light News Video Online (Oct. 23, 2014) Price check on honey? Bear cub startles Oregon drugstore shoppers. Rough Cut (no reporter narration). Video provided by Reuters
Powered by NewsLook.com
Dances With Wolves in China's Wild West

Dances With Wolves in China's Wild West

AFP (Oct. 23, 2014) One man is on a mission to boost the population of wolves in China's violence-wracked far west. The animal - symbol of the Uighur minority there - is under threat with a massive human resettlement program in the region. Duration: 00:41 Video provided by AFP
Powered by NewsLook.com
Breakfast Debate: To Eat Or Not To Eat?

Breakfast Debate: To Eat Or Not To Eat?

Newsy (Oct. 23, 2014) Conflicting studies published in the same week re-ignited the debate over whether we should be eating breakfast. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins