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LM0Lect1 - Some features of microbes Microbes either...

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1 Some features of microbes Microbes either prokaryotic (lack a true nucleus) or eukaryotic (have a true nucleus) Prokaryotic organisms are classified into 2 main groups (Domains) Bacteria Archaea Eukaryotic micro-organisms (Domain Eukarya) include fungi and protists (protists = algae + protozoa) Most microbes are single-celled, but some may come together at different times of the life cycle Microbes vary in size ( E. coli , for example , is 1 x 2 μ m), but almost all cannot be seen without the aid of a microscope Microbes comprise the earliest life forms
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Evolution of life from microbial origins (Fig. 17.1) Only microbes lived on the earth for the first 2 billion years that life has existed, and it was during this time that basic biological processes evolved As microbes evolved, they changed the planet, removing CO 2 and producing O 2 Much later multi-cellular eukaryotic organisms developed Search for life on other planets is often focused on looking for H20, then microbes 2
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3 Microbes are everywhere Some microbes survive extremely high levels of radiation (10,000 times the human lethal dose) Microbes can grow at pHs ranging from 1 to 11.4 Microbes can live at temperatures ranging from -15 to 121 0 C (but all require liquid H 2 0) Microbes can grow at low and high osmolarity (up to 5.2 M NaCl) Microbes can grow at high hydrostatic pressures (>1500 atmospheres) Many microbes grow without oxygen
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