LECTURE 9: GENETICS OF BACTERIA

1
LECTURE 9 GENETICS OF BACTERIA THEIR
VIRUSES II

• bacterial conjugation (rev)
• bacterial transformation
• bacteriophage genetics

2
BACTERIAL CONJUGATION

• interrupted-mating
• selective markers
• donor is strs
• recipient is strr
• origin of replication transferred first
• 1st transferred markers most frequent in
  exconjugants

3
BACTERIAL CONJUGATION

• bias in recovery of markers
• gradient of transfer used for determination of
  gene order only

4
Schaums Outlines Genetics 3rd Ed., CH12, pp.
321 325 4th Ed., CH10, pp. 349 355
5
BACTERIAL CONJUGATION

1. exogenote enters cell ... merozygote partial
   diploid
2. single recombination event (3x, 5x, ...)
   nonviable
3. double recombination event (4x, 6x, ...) viable

6
BACTERIAL CONJUGATION

• bias in recovery of markers
• gradient of transfer used for determination of
  gene order only
• ? to determine map distances, select late marker
  to ensure transfer of all relevant genes ... high
  resolution mapping

7
BACTERIAL CONJUGATION

• high-resolution mapping by recombinant frequency

8
Schaums Outlines Genetics 3rd Ed., CH12, pp.
321 325 4th Ed., CH10, pp. 349 355
9
TRANSFORMATION IN BACTERIA

• conversion of one genotype to another by uptake
  of exogenous DNA
• transformation principle demonstrated that DNA
  was responsible for inherited differences in
  polysaccharide character of S. pneumoniae (CH8)

10
TRANSFORMATION IN BACTERIA

• extracted DNA (in an experiment) breaks at random
  
• co-transformation of 2 tightly linked donor genes
  is more likely than 2 distant donor genes
• cells must be made competent to enable DNA entry
• detergents
• electrical fields

11
TRANSFORMATION IN BACTERIA

• dependent on concentration of DNA in the medium

12
TRANSFORMATION IN BACTERIA

• DNA must enter and recombine into the host

13
TRANSFORMATION IN BACTERIA

• practice question, p. 237, 18

14
BACTERIOPHAGE GENETICS

• bacteriophage eaters of bacteria
• T-phages well studied T-even and T-odd

15
BACTERIOPHAGE GENETICS

• bacteriophage eaters of bacteria
• T-phages well studied T-even and T-odd

16
BACTERIOPHAGE GENETICS
17
BACTERIOPHAGE GENETICS

• lysis breaking of cell wall and release of
  phage particles
• bacteriophage lytic cycle ...

18
BACTERIOPHAGE GENETICS

• phage plaques on a lawn of bacteria
• 1 plaque forming unit PFU 1 phage particle
• plaque morphology
• host range

19
BACTERIOPHAGE GENETICS

• phage cross
• h r x h r
• h infect strain 1
• h infect strains 1 2
• r slow lysis, small plaques
• r slow lysis, large plaques

20
BACTERIOPHAGE GENETICS

• lawn of 2 E. coli strains 1 immune to h phage

21
BACTERIOPHAGE GENETICS

• phage cross
• h r x h r
• h clowdy
• h clear
• r small
• r large
• RF h r h r
• TOTAL

22
TRANSDUCTION IN BACTERIA

• alternative life cycles of temperate
  bacteriophage

23
TRANSDUCTION IN BACTERIA

• generalized transduction random incorporation
• lytic cycle, non-integrated phage

24
TRANSDUCTION IN BACTERIA

• co-transduction
• donor leu thr azir ? recipient leu thr azis

25
TRANSDUCTION IN BACTERIA

• genetic map of the purB ? cysB region in E. coli

26
TRANSDUCTION IN BACTERIA

• phage integration

27
TRANSDUCTION IN BACTERIA

• specialized transduction non- random
  incorporation
• lysogenic cycle, integrated phage

28
TRANSDUCTION IN BACTERIA

• specialized transduction non- random
  incorporation
• lysogenic cycle, integrated phage

29
TRANSDUCTION IN BACTERIA

• transduction phage acquire host genes and
  transfer them to other bacterial cells
• generalized transduction transfers any host
  gene and occurs when phage randomly package host
  DNA
• specialized transduction faulty separation of
  prophage (phage incorporated into host genome)
  new phage contains adjacent host genes only

30
GENETIC MAPS IN BACTERIA

• E. coli linkage map (minutes)

31
GENETIC MAPS IN BACTERIA

• 5 minutes of the E. coli linkage map

32
GENETIC MAPS IN BACTERIA

• correlated genetic and physical maps in E. coli

33
SUMMARY RECOMBINATION IN BACTERIA
34
BACTERIAL CONJUGATION AND RECOMBINATION MAPPING
PROBLEMS

• in Griffiths chapter 5, beginning on page 179,
  add these questions to those listed at the end of
  lecture 8 4, 14, 16-21, 24, 28 (eg. in
  class)-32
• begin with the solved problems on page 177 if you
  are having difficulty
• look Schaums Outline (pp. 358-9)
• try Schaums Outline questions 10.7 10.12