l16 bacterial genetics
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Bacterial Genetics
Dr. P. K. Rajesh. M.D, M.BA
Preclinical CoordinatorFOM, AIMST
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Lecture 16: Bacterial Genetics
OBJECTIVES:The objectives of this lecture are to introduce the basic principles of molecular biology
describe the bacterial extra chromosomal geneticelements (plasmids, episomes, transposons)
define mutation and categorize the various types ofmutation.
describe the genetic mechanisms of transfer of drugresistance (Transformation, Transduction,Conjugation)
Explain the effects of mutation and genetic transfer(Lysogenic conversion, Transfer factors (F, Col,RTF), Genotypic and Phenotypic variations)
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Learning outcomes
At the end of this lecture, student should be able to:
compare and contrast between prokaryotic andeukaryotic genetics.
illustrate a bacterial cell and its extrachromosomal genetic elements.
relate the bacterial genetic transfer and
mutation mechanisms to drug resistance. compare and contrast between mutationaland transferable drug resistance. (will bereinforced in Lecture 41/42)
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BACTERIAL DNA
A single circular double stranded DNA
Length 1000 micrometre or 1m
When straightened (expressed as kilobase, around 4000 kb)
Super coiled like a thread to accommodate
within the bacterial cellNotes on BG PKR.doc
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Extrachromosomal genetic elements
PLASMIDS
EPISOME*
(Integrated exogenote)
TRANSPOSONS
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Plasmid/ episome
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Plasmids
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Transposons
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Transposons-moving part of DNA
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?Question time?
10% of road accidents are due to drunken driving.
Which makes it a logical statement that
90% of accidents are due to driving without drinking!
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MutationGenerally
Random
undirected, heritable variation
+,- or substitution of bases
Missense,Nonsense,TransversionBacteriologically
Supressor, lethal, conditional
MutagensDrug resistance*
Live vaccines**
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Transmission of genetic material
TransformationTransduction
Lysogenic conversion
ConjugationTransfer factors
F, Col, RTF
Drug resistance
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?Question time?
Only 20 percent boys have brains, resthave girlfriends!
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Lytic
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-Sex pili-For your eyes/ears only
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Drug resistance
Mutational TransferableResistance to one drug at a time
Low degree of resistance
High dosage overcomes resistance
Combination of drugs overcomes
No spread of resistance
Mutants metabolically defective
Mutants have Low virulence
Multiple drugs at the same time
High degree of resistance
High dosage cannot overcome
Combination cannot overcome
Resistance spreads
Bacteria Metabolically active
No loss of Virulence
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Uses ofMolecular biology
PCR
RFLP
MICROARRAY
DIAGNOSTICS
RESEARCH
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MOLECULAR
Universal PCR
Genus-species-identified
Drug resistant gene identified
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Self study
1) General principles of bacterial recombination-SSM?2) Mechanisms of drug resistance-Intrinsic and Extrinsic(Lecture 41/42)
3) Antibiotic sensitivity testing (Element 6 practical and
lecture 41)4) Bacteriophage (prophage) and transduction
Suggested reading/References
1) Clinical Microbiology made ridiculously simple-
Edition 2 Mark Galdwin2) Prescott-Microbiology-5th Edition
3) The links attached to this PPT
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(B14)-Vote for Human or Microbe?
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A comparative study on the antimicrobial activity of meropenem and other
antimicrobials-original article
The 2007 Annual Conference on Antimicrobial Resistance
NFID, Bethesda, Maryland, USA
References
1) Lynda R.Wiseman, Antona J.Wagstaff, Rex N.Brogden and Harriet M.Bryson.
Meropenem, A review of its antibacterial activity, Pharmacokinetic Properties and
Clinical Efficacy. Drugs 50 (1): 73-101, 1995
2) J.S.Bradley, J.Garau, H.Lode et al. International Journal of Antimicrobial agents 11 (1999) 93-100
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highly influenced by..