L16 Bacterial Genetics

8/9/2019 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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