Download - Bacteria
Ch. 19 - Bacteria and Viruses
Chapter 19
19-1 Bacteria• Common name for all prokaryotes
• unicellular organisms without a nucleus• Were all in Monera
• Eubacteria• live nearly everywhere• normally protected by cell wall containing
peptidoglycan - cell membrane inside of cell wall
• Archaebacteria• lack peptidoglycan• DNA similar to eukaryotic DNA• most are extremophiles – live in harsh
environments• methanogens; halophiles; extreme thermophiles
Prokaryotic Body Plan
DNA
ribosomes in cytoplasm
plasma membrane
capsule
bacterial flagellum
cytoplasmcell wall
pilus
Identifying Prokaryotes1. Shape
a. bacilli(us) – rod-shapedb. cocci(us) – sphericalc. spirilla(us) – spiral and corkscrew shaped
2. Cell Wallsa. Gram-positive – have thick peptidoglycan cell
walls that take and hold stainb. Gram-negative – thinner cell walls with lipids
on outside – does not hold stain
3. Movement Gram Positive Gram Negative
Metabolic Diversity1. Chemoheterotrophs – must
take in organic molecules for energy and a supply of carbon
2. Photoheterotrophs – use photosynthesis for energy, but take in organic compounds for carbon source
3. Photoautotrophs – use photosynthesis for both energy and carbon source
4. Chemoautotrophs – use chemosynthesis – get energy from chemical reactions and use carbon
dioxide as carbon source
Releasing Energy- bacteria release energy by cellular respiration
and fermentationA.Obligate Aerobes
- require a constant supply of oxygenB. Obligate Anaerobes
- must live in the absence of oxygenC. Facultative Anaerobes
- can survive with or without oxygen
Growth and Reproduction- under good conditions
bacteria can reproduce every 20 minutes
Binary Fission- normal asexual
reproduction of bacteria- replicate DNA and then
divideConjugation- exchange of genetic
material between bacterial cells
- increases genetic diversity
Spore Formation- allows survival of bad
conditions for a long time
Prokaryotic Fission - 1
DNA replication begins
Bacterium before DNA replication
Figure 21.7Page 350
bacterial chromosome
Prokaryotic Fission - 2
parent DNA molecule
DNA copy
DNA replication completed
Membrane growth moves DNA molecules
apart
Prokaryotic Fission - 3
New membrane and cell-wall material deposited
Cytoplasm divided in two
ConjugationTransfer of plasmid
nicked plasmidin donor cell
conjugation tubeto recipient cell
Importance of Bacteria- while we usually think of bacteria negatively they are actually
essential to correct functioning in ecosystemsA. Decomposers
- primary decomposers who make nutrients available to plants- used in sewage treatment plants also
B. Nitrogen Fixers- Rhizobium in nodules of legume roots fix nitrogen in a form the plants can use
C. Human Uses • in food production• in industry – can clean-up oil spills• to synthesize drugs and chemicals• genetic engineering now has them producing
human hormones• Mutualism with Eschecaria coli in our colon
where they help us make vitamins