BIO 101 Lecture Notes - Lecture 20: Endospore, Quorum Sensing, Biofilm
25 Jan 2017
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Document Summary
Earth"s first orga(cid:374)is(cid:373)s (cid:449)ere prokaryotes, single-celled microbes that lacked organelles. For the first 1. 5 billion years or more, all life was prokaryotic. Prokaryotes are still abundant: a human body is home to trillions. On the skin, inside the mouth, and in the stomach and intestines. Both bacteria and archaea are very small, ranging from 0. 2 to 10 microns in diameter. Prokaryotes have 3 common shapes: spherical, rod-like, corkscrew-shaped. T(cid:449)o of life"s three do(cid:373)ai(cid:374)s, bacteria and archaea, consist entirely of prokaryotes. Bacteria and archaea are superficially similar in appearance under the microscope. Bacteria and archaea have striking structural and biochemical differences, revealing ancient evolutionary separations between them. Bacteria have peptidoglycan in their cell walls: archaea do(cid:374)"t. There are also differences in: plasma membrane composition, ribosomes, rna polymerases, transcription and translation. Peptidoglycan: a polysaccharide that also includes amino acids. Classification within the prokaryotic domains is based on dna sequences. Sharp differences between archaea and bacteria makes distinguishing the two domains fairly straightforward.
