D. Intestinal tract
Areas of colonization - epithelial surface of small intestines (low numbers), and
large intestines (high numbers). Highest numbers of bacteria in the body! Only
Helicobacter pylori colonize the stomach.
Environment - moist surfac
Lets digress for a moment and talk about transposons.
1. Three major types
a. Insertion sequences. Can be only detected by DNA probe or by the fact they
insert into chromosomes, sometimes inactivating genes and sometime causing
Natural transformation is also a stepwise reaction
1. Reversible binding of DNA to the cell wall (ionic attraction)
2. Irreversible binding to the cell membrane (binding proteins induced by
3. Incoming DNA becomes resistant to DNase. Up to thi
9. Bacteria have taken up human, animal and plant DNA forever, but
it never was integrated and thereby never expressed.
10. Cloning industry takes DNA from anywhere and puts it in plasmids then
into bacteria by transformation. No homology re
1. Can make as many as 1000 or as few as 10 copies
2. Dependent on type of virus and physiology of cell
3. Early proteins are DNA and RNA replicating enzymes
4. Late proteins are structural proteins of coat
5. Eclipse is defined as the time when there are
3. Very rare, and this is the rarest of the genetic exchange mechanisms,
the bacteriophage head makes a mistake and instead of filling with
viral DNA from the DNA concatomers (tandem viral chromosomes
assembled in a large circle), the empty head goes and
Specialized transduction (not responsible for this information)
1. Explains lysogenic conversion.
2. Done by temperate viruses
3. Since the viruses interact with the chromosome, they
have ready access to chromosome material.
4. Just like F excised wrong,
IV. The Human Body - Areas of Colonization
1. Areas of colonization- most superficial layers of epidermis and
upper hair follicles
(20% beyond reach of normal disinfection).
2. Environment - relatively dry, sparse nutrients (lipids), low pH,
Areas of colonization - lip-cheek-palate area, tongue, tooth surfaces, gingiva, saliva.
Each area has its own type of microflora.
Environment- moist surfaces, salivary secretions (amylase, lysozyme, lactoferrin,
C. Respiratory tract
Areas of colonization - epithelial surface of nasal cavity, nasopharynx, and
- no normal flora in trachea, bronchi and lung alveoli, although
transient bacteria and fungi are trapped on the airway mucosa
during normal br
g. The endogenous chromosomal DNA is huge and complexed in the
bacterial cytoplasm, yet the RecA will find the region of homology for the
entering single strand within a minute or two.
h. Classical recombination (strand into duplex) integrates the incomin