Nucl Acids Res 2006, 34:D446–451.PubMedCrossRef Authors’ contributions ZLL designed SRT2104 mw the qRT-PCR array and conceived the experiment. MM performed strain adaptation, experimental fermentation, sample collection, RNA extraction, qRT-PCR and data analysis. ZLL and MM analyzed the data and wrote the manuscript. All

authors read and approved the final manuscript.”
“Background Microorganisms usually exist in populations of huge sizes and are highly prone to long-distance dispersal by vectors such as wind, water, animals and humans [1–5]. Obvious barriers to dispersal are lacking, especially in the marine habitat [4–8]. The ubiquitous dispersal of microorganisms has been a prevalent view since the turn of the last century, summarized in the statement “”everything is everywhere, but, the environment selects”" [9,

10]. This view has been challenged however, by investigations of environmental DNA clone libraries as a large number of cryptic species and restricted biogeographies have been revealed [11–20]. High levels of genetic diversity have been found, even within the slowly evolving small ribosomal subunit gene [21, 22]. However, as more localities are being investigated and the variety of sampling strategies increase, the geographic ranges of many microorganisms have been expanded, showing that under-sampling of the diversity can cause a false impression of endemism [see [4, 5]]. Some surveys have therefore interpreted the diversity as consistent with the “”Moderate AZD8931 in vitro Endemicity Model”" (MEM), which states that some microbial lineages do in fact have a global distribution, but that

PI-1840 there also exists species with restricted dispersal and local adaptations [4, 23–25]. The vast majority of 18S rDNA environmental surveys conducted so far have involved universal primers designed to capture the broadest diversity of eukaryotes possible. However, much diversity is most likely overlooked by applying only a single pair of universal primers [26–28]. This could be due to a number of reasons, e.g. the primers are less suitable for some groups of organisms, there are great variations in rDNA copy number, as well as bias introduced in the PCR reaction. One of the most efficient approaches to address these problems has been to apply a group-specific PCR strategy with primers targeting the particular taxonomic group of interest [29–32]. These studies have shown that the use of such primers is detecting far more diversity than the universal approach. Telonemia is one of the groups of unicellular eukaryotes that are frequently detected in marine 18S rDNA environmental clone libraries, but usually represents only a relatively small part of the total diversity [11, 33–36].