Prokaryotes

Prokaryotes

1. brief history

   • girolamo fracastoro suggested disease was caused by unseen organisms
   • spontaneous generation was still a popular thing in the 19th century
     • louis pasteur debunked with swan necked flask experiment

2. prokaryotic structure

   • unicellularity
     • few exc. but pro. usually single-celled
     • most bac. capable of forming complex comm. of diff. spec. called biofilm
   • cell size
     • most pro. 1 microm. or less in diameter
     • most eu. cells 10x larger
   • nuceloid
     • pro. lack mem. bound nucelus..have single circular chromo.
     • pro. have accessory DNA mole. called plasmids

3. bacteria and archaea

   • both have cell wall
     • bacteria: peptidoglycan
       • gram stain test: diff between two types of bacteria
         • positive: thick peptido. cell wall layer
         • neg: thinner layer
       • capsule
         • in some bac., additional outer layer called capsule can surround cell
         • enables pro. to adhere to surfaces and evade immune surfaces
     • archaea: similar structure called pseudomurein
   • both do dna replication
     • circular dna with one point of origin
     • arc. initiation of dna rep. is more similar to eu!!
   • gene expression
     • archaea have more than 1 rna poly..more similar to eu
     • archaeal machinery used for TRANSLATION more closely related to eu
   • bacteria shapes
     • cocci: spheres
     • bacilli: rods
     • spirilla: spirals
     • some can mix together like coccobacilli

4. endospore formation

   • some pro. able to form endospores when exposed to envi. stress
   • endospores: thick wall around genome and small portion of cytoplasm
   • highly resistant to env. and wait for conditions to improve
     • germinate and reproduce

5. genetic recombination

   • binary fission = asexual = dau. cells same copies of chromo.
   • three ways of genetic recomb.
     • conjugation
       • when a donor cell passes DNA directly to recip. cell
         • temp. linked together thru conjugation pilus
           • pilus: hairlike structure around cell that mainly used for adhesion and xchange of genetic info
     • transformation
       • when bact. picks up free pieces of dna
         • can be from DNA from live pro. or dead bac.
     • transduction
       • transfer of dna portion from one bac. to another by bacteriophages (virus)

6. bacterial nutrition

   • pro. metabollically diverse
   • cyanobacteria: photosynthetic bacteria

7. bacteria and environment

   • agriculture: legumes, nitrogen fixers
   • natural flora: our gut and intestine flora may be ass. with obesity and other health probs

8. types of archaea

   • methanogens: swamps, intestinal tracts
   • halophiles: require high salt con.
   • thermoacidophiles: extreme hot and acidic en.