BIOL 1202 Chapter 27

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Louisiana State University
Biological Sciences
BIOL 1201

1Bio 1202CHAPTER 27Bacteria and ArchaeaThe organisms that make up the two prokaryotic domains Bacteria and Archaea were the first organisms to arise on earth about 35 billion years agoSome general chacteristicsUnicellular but they do grow in coloniesNo membranebound organellesCircular chromosomesMost prokaryotes range in size from 0250 micrometers in diameter see fig 272How big or small is a micrometer11000000 of a meterBut just how small is thatThe thickness of a dime is about 1 millimeter 1000 micrometersThe two domains appear similar in many respects however they are different in some very basic ways One main distinction between the Bacteria and the Archaea is the type of a semirigid permeable cell wallThis bacterial cell wall is composed of peptidoglycan peptidoglycanWhile only about 5000 prokaryotic species have been described there may be as many as 1001000 times that number The cell wall of a bacterium gives characteristic shapes see fig 272bacilli cocci spirilla These are some shapes but there are many variations of these basic shapesThe peptidoglycan cell wall of bacteria can be stained by a specific stain known as a Gram stain named for Hans Christian Gram a Danish physicianThe Domain Bacteria can be divided into two groups based on the ability to be stained with Gram stainGram positive bacteria have the cell wall exposed to the environmentSome bacteria are not stained by
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