Bacteria Notes

Classification of Bacteria

Domain:  Archaea

                Kingdom:  Archaebacteria – Unicellular prokaryotes that have cell walls that

                                                               do not contain peptidoglycan

                                                               Live in extreme environmental conditions such as

                                                               the Great Salt Lake (halophiles) and geysers

                                                              (thermophiles)

                                                               DNA sequence of key genes more similar to

                                                               eukaryotes than those of Eubacteria

                                                               Methanogens are archaebacteria.  They produce

                                                               methane gas.

Domain:  Bacteria

                Kingdom:  Eubacteria – Unicellular prokaryotes that have cell walls made up of

                                                        peptidoglycan

                                                        Larger of the two prokaryotic kingdoms

                                                        Live almost everywhere.

                                                        Gram-positive bacteria stain purple

                                                        Gram-negative bacteria stain red, have an additional

                                                        cell membrane that protects against the host and

                                                        makes them more resistant to antibiotics, so they are

                                                        more threatening as pathogens.  Often produce

                                                        endotoxins in their cell walls.

Characteristics Used to Classify Bacteria

1. Shape
2. cell wall composition
3. locomotion
4. energy source
5. type of respiration

Shapes:

1. bacillus (bacilli)  â€“ rod shaped 
2. coccus (cocci) – spherical
3. spirillium (spirilla) – spiral shaped

Cell Wall Composition:

Archaebacteria do not contain peptidoglycan

Eubacteria contain peptidoglycan

Locomotion:

1. Non-motile – don’t move
2.  flagella – whiplike structures that are few in number
3. glide on slime they produce

Energy Source

1. Autotrophs – make their own food
   1. chemotrophs – use chemicals to make their food
   2. phototrophs – use sunlight to make their own food

                             Cyanobacteria (blue-green bacteria) are phototrophs.

                             Cyanobacteria contain the blue pigment phycocyanin.

2. Heterotrophs – cannot make their own food

                               rely on autotrophs for their food

Type of Respiration

1. Obligate aerobe – require oxygen

                                   example:  bacterium that causes tuberculosis

2. Obligate anaerobe – cannot live in the presence of oxygen

                                       example:  Clostridium botulinum causes the food poisoning

                                                       called botulism

                                       example:  Clostridium tetani the bacterium that causes

                                                        tetanus

3. Facultative anaerobe – can live with or without oxygen

                         example:  E. coli lives in the human intestine

Reproduction In Bacteria

1. binary fission – asexual reproduction, the cell divides by mitosis and cytokinesis,

                                since it is a unicellular organism it has reproduced

2. endospore – spore formed when a bacterium forms a thick internal wall that

                          encloses its DNA and a portion of its cytoplasm

                          The endospore protects the bacterium against unfavorable

                          environmental conditions.

                          The endospore may remain dormant for months and when conditions

                          become favorable it will grow.

3. conjugation – sexual reproduction, two bacteria exchange DNA through a tube

                             called a pilus

 

 

Evaluate the medical and economic importance of bacteria:

 

 

 

•Bacteria have the medical  importance of causing diseases such      as Lyme disease, rocky mountain spotted fever, tetanus, and TB.

 

 

 

 

•Bacteria also are necessary for the health of our digestive system,      such as E. coli, which is found in the intestine.

 

 

 

 

 

•Bacteria are important in nature as saprophytes or decomposers,      breaking down dead organisms.

 

 

 

 

•Bacteria can also be used to clean up toxic spills and oil spills.

 

 

 

•Bacteria are also important because they can fix atmospheric     nitrogen into a usable form for plants, such as legumes, which     puts the nitrogen necessary for proteins and nucleic acids into the     food chain.

 

 

 

 

 

 

•Bacteria such as E. coli are used in genetic engineering to make      insulin and human growth hormone

 

 

Describe the relationship between the germ theory of disease and immunology and control of infectious disease.

Germ Theory of Disease (Koch’s Postulates) – a set of criteria used to establish that a particular infectious agent causes a disease

Koch’s Postulates:

üThe microorganism should always be found in the body of the     host organism and not in a healthy organism.

üThe microorganism must be isolated and grown in a pure     culture away from the host

üWhen the microorganisms grown in pure culture are injected     into a new host organism, they produce disease

üThe same microorganisms should be reisolated from the second    host and grown in a pure culture, after which the microorganisms    should still be the same as the original microorganisms