10 - PROKARYOTIC DIVERSITY BIOL 4125 SPRING 2009 LECTURE 10...

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PROKARYOTIC DIVERSITY BIOL 4125 SPRING 2009 LECTURE 10 The Proteobacteria Part 2 - The SAR11 Saga
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Giovannoni et al. (1990). Genetic diversity in Sargasso Sea bacterioplankton. Nature 345:60-63. Surveys of 16S rRNA genes in surface ocean waters revealed the presence of a novel microbial group: the SAR11 cluster • 16S rRNA sequences in the SAR11 group dominated the clone library. • When the 16S rRNA gene sequences were compared to those present in the database, they were most similar to members of alphaproteobacteria. • The SAR11 group was clearly phylogenetically distinct from any cultivated species and was a deep branching member of the group. • It was demonstrated that 15% of prokaryotic rRNA (12.5% of total) in the Sargasso Sea was from the SAR11 group.
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The SAR11 The SAR11 clade clade consists of very small, heterotrophic marine consists of very small, heterotrophic marine α α - - proteobacteria proteobacteria that are found throughout the oceans, where that are found throughout the oceans, where they account for about they account for about 25% of all microbial cells 25% of all microbial cells Morris et al. (2002) Nature , 420:806-810. Surface water 200 m Stars indicate marine waters where SAR11 16S rRNA sequences have been detected Blue – DAPI stained (all cells) – DAPI stained + fluorescent DNA probe (SAR11 cells only)
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Why is it important to cultivate Why is it important to cultivate microorganisms in the laboratory? microorganisms in the laboratory? • Examine species adaptations and the effect of environmental change • Obtain genome sequence • Discover novel natural products (e.g. antibiotic production) • Study cell-cell interactions • Link microbial diversity to metabolic potential • Understanding physiology will yield information on the roles of “uncultivable” species in biogeochemical cycling
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The main challenge of designing artificial media to mimic natural seawater is the accurate reconstruction of the complex composition of dissolved organic carbon (DOC) and trace elements Most researchers have relied on media that contain high concentrations of organic carbon. Marine broth, which is still widely used for culturing heterotrophic bacteria, has 170-fold more
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This note was uploaded on 08/04/2009 for the course BIOL 4125 taught by Professor Christner during the Spring '08 term at LSU.

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10 - PROKARYOTIC DIVERSITY BIOL 4125 SPRING 2009 LECTURE 10...

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