Bacteria

Bacterial Structure A. Contain: 1. Cell wall 2. plasma membrane 3. Cytoplasm 4. Ribosomes (smaller than eukaryotic ribosomes and differ in protein and RNA content, why antibiotics work on prokaryotes to stop protein synthesis and not eukaryotes.) 5. Plasmid (small circular DNA, replicates independently, carries only a few genes. B. Reproduce by binary fission

Genetic recombination 1. Transformation 2. Transduction 3. Conjugation

Transformation Transformation: when bacteria uptake foreign DNA from surroundings.  Ex. Nonpathogenic cell takes up a piece of DNA with allele for pathogenicity and replaces it’s own allele with foreign allele  DNA is from closely related species

Figure 16.2 Living S cells (pathogenic control) Experiment Results Living R cells (nonpathogenic control) Heat-killed S cells (nonpathogenic control) Mouse dies Mouse healthy Mouse dies Mixture of heat- killed S cells and living R cells Living S cells

Transduction Transduction: When viruses transfer DNA from one cell to another. Bacteriophage: virus that infects bacteria  Virus’s can not reproduce on their own. Normally for a virus to reproduce it must infect a cell, overtake the cell and cause the cell to reproduce the viral DNA and proteins  Sometimes bacterial DNA is fragmented and the fragments get incorporated into the virus. When the virus infects new bacteria, the virus brings foreign bacterial DNA. Animation

Figure Phage infects bacterial donor cell with A + and B + alleles. Donor cell Phage DNA A+A+ B+B+ 1

Figure Phage infects bacterial donor cell with A + and B + alleles. Phage DNA is replicated and proteins synthesized. Donor cell Phage DNA A+A+ B+B+ A+A+ B+B+ 1 2

Figure Phage infects bacterial donor cell with A + and B + alleles. Phage DNA is replicated and proteins synthesized. Fragment of DNA with A + allele is packaged within a phage capsid. A+A+ Donor cell Phage DNA A+A+ B+B+ A+A+ B+B

Figure Phage infects bacterial donor cell with A + and B + alleles. Phage DNA is replicated and proteins synthesized. Fragment of DNA with A + allele is packaged within a phage capsid. Phage with A + allele infects bacterial recipient cell. A+A+ Donor cell Phage DNA A+A+ B+B+ A+A+ B+B+ A+A+ B−B− A−A− Crossing over Recipient cell

Figure Phage infects bacterial donor cell with A + and B + alleles. Phage DNA is replicated and proteins synthesized. Fragment of DNA with A + allele is packaged within a phage capsid. Phage with A + allele infects bacterial recipient cell. Incorporation of phage DNA creates recombinant cell with genotype A + B −. A+A+ Donor cell Phage DNA A+A+ B+B+ A+A+ B+B+ A+A+ B−B− A−A− Crossing over Recombinant cell Recipient cell B−B− A+A

Figure 16.3 Phage head DNA Tail sheath Tail fiber Genetic material Bacterial cell 100 nm

Conjugation Conjugation: bacterial ‘sex’  Two bacterial cells are temporarily joined, DNA is transferred from one cell to the other (one way transfer, one cell donates the other receives  Typically occurs between the same species.

Figure Sex pilus 1 µm

Figure Bacterial chromosome F plasmid F + cell (donor) Mating bridge Bacterial chromosome (a)Conjugation and transfer of an F plasmid F − cell (recipient) Hfr cell (donor) F factor F − cell (recipient) Recombinand F − bacterium (b)Conjugation and transfer of part of an Hfr bacterial chromosome, resulting in recombination A−A− A+A+ A−A− A+A+ A−A− A−A− A+A+ A+A+ A+A+ A+A+

Figure 27.13a-1 Bacterial chromosome F plasmid F + cell (donor) Mating bridge Bacterial chromosome (a)Conjugation and transfer of an F plasmid F − cell (recipient) One strand of F + cell plasmid DNA breaks at arrowhead. 1

Figure 27.13a-2 Bacterial chromosome F plasmid F + cell (donor) Mating bridge Bacterial chromosome (a)Conjugation and transfer of an F plasmid F − cell (recipient) One strand of F + cell plasmid DNA breaks at arrowhead. Broken strand peels off and enters F − cell. 1 2

Figure 27.13a-3 Bacterial chromosome F plasmid F + cell (donor) Mating bridge Bacterial chromosome (a)Conjugation and transfer of an F plasmid F − cell (recipient) One strand of F + cell plasmid DNA breaks at arrowhead. Broken strand peels off and enters F − cell. Donor and recipient cells synthesize complementary DNA strands

Figure 27.13a-4 Bacterial chromosome F plasmid F + cell (donor) Mating bridge Bacterial chromosome (a)Conjugation and transfer of an F plasmid F − cell (recipient) One strand of F + cell plasmid DNA breaks at arrowhead. Broken strand peels off and enters F − cell. Donor and recipient cells synthesize complementary DNA strands. Recipient cell is now a recombinant F + cell