Bacterial genetics. Gram-positive bacteria transform DNA using a transformasome complex. Figure 9.1.

Bacterial genetics

• Gram-positive bacteria transform DNA using a transformasome complex.

Figure 9.1

Gene Transfer by Conjugation• Conjugation is the transfer of DNA from one

bacterium to another, following cell-to-cell contact.

- It is typically initiated by a special pilus protruding from the donor cell.

Figure 9.2

Figure 9.3

Figure 9.4

• An integrated F-factor can excise from the chromosome.

• - Aberrant excision results in an F factor′ or F ′plasmid, which carries chromosomal genes.

Figure 9.5

Hfr leu+ thr+pro+lac+bio+Sms XF- leu- thr-pro-lac-bio-SmR

What medium should we use to obtain1. leu+ transconjugants2. pro+ transconjugants3. lac+ transconjugants

Hfr leu+ thr+pro+lac+bio+Sms XF- leu- thr-pro-lac-bio-SmR

1. leu+ transconjugants2. pro+ transconjugants3. lac+ transconjugants

What are the map positions of leu, pro, and lac?

time No.of colonies on medium1 2 3

0 0 0 0

5 0 0 0

10 8 0 0

15 28 6 1

20 48 16 6

25 68 26 11

0

1020

3040

50

6070

80

1 2 3 4 5 6

time

no

.co

lon

ies

Figure 9.7

Generalized Transduction

Figure 9.9

Figure 9.8 Specialized Transduction

Figure 9.14

Generalized Recombination

Figure 9.15

Figure 9.30

• IS elements transfer by one of 2 mechanisms:• - Replicative or nonreplicative transposition

Mobile Genetic Elements

Figure 9.31