BIOL0129_Lecture 6

BIOL0129_Lecture 6 - Eukaryotic microorganisms Introductory...

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1 Introductory Microbiology Lecture 6 Eukaryotic microbial diversity: Protists Eukaryotic microorganisms • The earliest fossilized remains of eukaryotic microbes are around 1.2-1.5 billion years old – From the Proterozoic Era – Fossils from the Bitter Springs rock formation in Australia • Genetic evidence suggests that they may have evolved even earlier – Perhaps as early as 2 billion years ago – I.e fairly recently after the Archaea evolved • The huge diversity in form, physiology, habitat etc suggests modern eukaryotic microbes may have independently evolved many times from different prokaryotic ancestors –They are probably ‘polyphyletic’ (evolved from evolutionarily distinct lineages) • The eukaryotic cell is: –larger than a prokaryotic cell –Has membrane-bound organelles –Greater internal complexity –Specialized method of cell division that involves meiosis (genetic recombination) = sex !
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2 A generalized eukaryotic cell • The approach to classifcation is still debated, but we will Follow the ‘six kingdom’ approach • Here the (mainly) unicellular eukaryotic microbes are grouped into the Protista • It is envisaged that From these all ‘higher’ multicellular eukaryotes evolved The fungi are descended from fungi-like single celled heterotrophic eukaryotes called chytrids Animals are descended from single celled heterotrophic eukaryotes called choanoflagellates The plants are descended from single celled photosynthetic eukaryotes called chlorophytes
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3 Think about it for a moment, All this has taken less than 600 million years: Archaea Phylogenetic tree of eukaryotes based upon ribosomal RNA gene sequences Entamoebae Diplomonads • The diplomonads are obligate human pathogens –They lack mitochondria Giardia causes giardiasis, a common infection from poor restaurant hygiene in Hong Kong Giardia lamblia
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This note was uploaded on 10/28/2010 for the course BIO microbiolo taught by Professor Point during the Spring '09 term at HKU.

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BIOL0129_Lecture 6 - Eukaryotic microorganisms Introductory...

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