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Bacterial Genetics PowerPoint Presentation

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This medical is about bacterial genetics, the study of genetic material, inheritance patterns, and gene expression in bacteria. Bacteria are single-celled organisms that reproduce through a process called binary fission, which involves the division of one cell into two identical daughter cells. Bacterial genetics is an important area of research because bacteria are responsible for many diseases, as well as being used in many important biotechnological applications.

One of the key features of bacterial genetics is the presence of plasmids, small circular pieces of DNA that can be transferred between bacteria. Plasmids often contain genes that confer antibiotic resistance or other advantageous traits, and their transfer can lead to the spread of these traits among bacterial populations. Bacterial genetics also involves the study of horizontal gene transfer, which is the transfer of genetic material between different bacterial species.

In addition, bacterial genetics involves the study of gene regulation, which refers to the mechanisms by which genes are turned on or off in response to different environmental signals. This is important because bacteria must be able to adapt to changing environments in order to survive. Bacterial genetics also includes the study of bacterial viruses, called bacteriophages, which can infect and replicate within bacterial cells and can play a role in genetic transfer between bacteria.

Overall, bacterial genetics is a broad and important field that encompasses many different aspects of the biology of bacteria. By understanding bacterial genetics, researchers can develop new strategies for treating bacterial infections and can also use bacteria for a wide range of biotechnological applications.

Tags : Bacterial Genetics, genetic material, inheritance patterns, gene expression in bacteria, Medical Genetics, Medical Genetics

Published on : Jun 01, 2023 | Views : 1005 | Downloads : 0

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Slide 1-

Bacterial Genetics
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GENETICS-Study of genes their structure & function, heredity & variation Genomics-Study & analysis of nucleotides of DNA Nucleic acid-DNA and RNA
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Bacterial DNA Single Haploid Chromosome Super coiled circular dsDNA=1mm Exception: 2 chromosomes : Vibro cholerae
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Nucleotides-Structural units of Nucleic acids Nitrogenous bases-Purines(A,G) and Pyrimidines(T,U,C) Nucleoside Pentose sugar-Deoxyribose Phosphate group
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Bacterial DNA Ratio of A+T to G+C constant for each species Genetic information is stored as a code Codon-unit,triplet(3 bases) 64 codon 61 sense codon code for 20 AA AGA/AGG/CGA-arginine— code is degenerate 3 codon UAA/UAG/UGA- nonsense codons
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Gene or cistron Segment of DNA carrying codons for a particular polypeptide synthesis Locus a large no of genes Genome large no of loci Letter---------word-----sentence—paragraph--- Nucleotide—Codon-----Gene--------Locus--- 1000-3000 Gene 580 -5200 kbp length1-1.3mm
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DNA Replication: Bidirectional replication Rolling circle mechanism
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RNA mRNA rRNA tRNA
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Extra chromosomal elements Plasmids Free Circular dsDNA-In Cytoplasm for several generations Replicate independently Episome-integrated form Not essential for life of bacteria Number: up to 40/cell contain 50-100 genes
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Extra chromosomal elements Plasmids Curing: process of eliminating plasmid from bacteria Spontaneous induced Acridine Radiation Thymine starvation High temp
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Classification On the basis of ability to perform conjugation: Conjugative/self transmissible plasmid Non conjugative plasmid Based on compatibility b/w plasmid: Compatible Incompatible
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Classification Based on function: Fertility/F plasmid: contain tra gene: sex pili expression Resistance/R plasmid Col plasmid Virulence plasmid Metabolic plasmid
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Variation Phenotypic Genotypic
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MUTATIONRandom, heritable variation caused by alteration in nucleotide sequence of DNA Frequency 10-2 -10-10/bacterium/division CAUSES Spontaneous Induced (mutagen) – Physical: UV Chemical: alkylating agent, 5-FU, acridine dye
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Functionally affect: Not able to produce Capsule/flagella Antigenic structure alteration Altered sensitivity to Bacteriophage Drug resistance Altered pigment production Altered Biochemical reactions Altered colony morphology
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Types: Forward mutation Substitution Transversion: Transition:
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Types: Forward mutation Substitution Silent: New codon code for same AA Neutral: New codon code for functional equivalent AA Missense: Different AA Non-sense: Stop
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Types: Forward mutation Substitution Silent: New codon codes for same AA Neutral: New codon codes for functionally equivalent AA Missense: Different AA Non-sense: Stop
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Types: Addition or deletion Frame Shift Reverse Mutation True reversion
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Types: Reverse Mutation Equivalent reversion: 2nd Mutation different codon but same AA
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Types: Reverse Mutation Suppressor mutation: 2nd mutation in a different gene that revert the phenotypic effects of already existing mutation
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Demonstration of Mutation Gene sequencing Phenotypic changes Fluctuation test Replica plating
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Fluctuation test Luria and Delbruck-Mutation is SPONTANEOUS and RANDOM- Growth in presence of selective inhibitory pressure Bacteriophage and E. coli
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Replica plating-Auxotrophic mutant
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Ames Test (carcinogenicity testing) Mutational reversion assay Estimate Mutagenicity of mutant
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GENETIC TRANSFER Vertical Horizontal Transformation Transduction Lysogenic conversion Conjugation
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Transformation- Random uptake of free / naked DNA incorporation into chromosome Natural – S. pneumoniae express DNA-binding proteins on cell surface natural competent state allows uptake of "naked DNA"
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Transformation- random uptake of free / naked DNA incorporation into chromosome
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1928: Frederick Griffith (London): First demonstrated bacterial transformation
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An "S" or SMOOTH coat strain, which is lethal to mice.
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An “R" or rough coat strain, which is NOT lethal to mice.
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Griffith found that he could heat inactivate the smooth strain.
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heat-inactivated S strain, mixed with the R strain, the mouse would die. Thus there was some Material in the heat-killed S strain that was responsible for "transforming" the R strain into a lethal form.
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GENETIC TRANSFER Vertical Horizontal Transformation Transduction Lysogenic conversion Conjugation
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Transduction- Transfer of genetic material through bacteriophage
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Transduction 2 types: Generalized: Packaging error 3 outcome on transduction: Abortive transduction: 70-90% Stable gene transfer Unstable gene transfer
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Transduction 2 types:
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Transduction 2 types: Restricted/specialized Defect in disintegration of lysogenic phage 2 outcome when transduced to new bacteria Cross over Integrated as prophage
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Transduction 2 types:
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Importance of transduction Drug resistance: Pn resistance in Staphylococci Treatment: Genetic mapping, inborn error of metabolism Phage vectors used in molecular transformation of bacteria
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Lysogenic Conversion In Lysogenic bact prophage acts as additional segment of bact chromosome-new characters-lysogenic conversion eg. C.diphtheriae and its bacteriophage Phage coded Toxins: Diphtheria toxin cholera toxin Verocytotoxin of E. coli Streptococcus pyrogenic exotoxin A & C Botulism toxin C & D
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Lysogenic conversion: Phage DNA itself behave as new genetic element Transduction: Phage act as vehicle carrying bacterial gene
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GENETIC TRANSFER Vertical Horizontal Transformation Transduction Lysogenic conversion Conjugation
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Bacterial Conjugation Transfer of genetic information from one bacterium (donor or male) to another bacterium (recipient or female) bacterium by mating or contact with each other & forming conjunction tube
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F+ F- Mating HFR conjugation F’ Conjugation Col factor R factor-RTF + r determinants
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Colicinogenic (col) factor Bacteriocins are the antibiotic like substances produced by one bacterium that inhibit other bacteria Bacteriocins produced by coliform bacteria are called as colicin Bacteria other than coliforms also produce similar kind of substances e.g. pyocin, diphthericin
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FATE OF DONOR DNA:
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Bacterial Recombination Integration of Donor DNA to recipient chromosome General or Homologous Site specific
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General or Homologous Recombination b/w similar DNA sequences Reciprocal: Exchange of pair of Homologous DNA sequence b/w donor & recipient Non Reciprocal: Bacterial transformation Donor ssDNA is inserted into host chromosome & replace piece of host DNA
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Site specific Integration of bacteriophage DNA into Bacterial DNA is site specific Donor DNA not homologous with chromosome it joins
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TRANSPOSONS
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Genetic engineering Deliberate modification of organism genetic information by directly altering its genome Done using recombinant DNA technology Gene coding for desired property (protein) ---isolated from organism-----inserted to vector----cloned---desired property express
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POLYMERASE CHAIN REACTION Kary Mullis-1983 PCR is a DNA amplification system that produces a large amount of DNA in vitro from small amounts of starting material. It amplifies a specific DNA sequence (or gene) or interest. Primer mediated , temp dependant enzymatic amplification of specific target sequence to detectable levels
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Target DNA Primers Polymerase Enzyme- Thermus aquaticus Nucleotide Thermocycler
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Denaturation-940C Annealing of primers-50-600C Extension of primers 30-40 cycles for 3 hrs- 106 copies Detection-gel electrophoresis and ethidium bromide staining.
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PCR in Diagnosis Bacteria Viruses Fungi
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DNA PROBES Radiolabelled or chromogenically labelled pieces of ss DNA which can be used for the detection of homologous DNA by hybridization. Hybridisation is the technique in which two single-strands of nucleic acid come together to form a stable double-stranded molecule.
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Applications of DNA Probes In clinical microbiology : Direct detection of microbes in specimens To detect microbes which are difficult or impossible to culture Identification of culture isolates Strain identification To identify toxins, virulence factors Identification of resistant markers
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BLOTTING TECHNIQUES SOUTHERN BLOT WESTERN BLOT NORTHERN BLOT EASTERN BLOT
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Thank you Thank you
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Operons- An operon is a group of genes that are transcribed at the same time. Jacob, Monod & Lwoff They usually control an important biochemical process. They are only found in prokaryotes.
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Lac Operon The lac operon consists of three genes each involved in processing the sugar lactose One of them is the gene for the enzyme β-galactosidase (galactoside permease,transacetylase) This enzyme hydrolyses lactose into glucose and galactose
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E. coli can use either glucose, which is a monosaccharide, or lactose, which is a disaccharide However, lactose needs to be hydrolysed (digested) first So the bacterium prefers to use glucose when it can
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When glucose is present and lactose is absent the E. coli does not produce β-galactosidase. When glucose is present and lactose is present the E. coli does not produce β-galactosidase. When glucose is absent and lactose is absent the E. coli does not produce β-galactosidase. When glucose is absent and lactose is present the E. coli does produce β-galactosidase
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Sexduction Hfr F+
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Antibiotic: A drug used to treat infections caused by bacteria and other microorganisms. Originally, an antibiotic was a substance produced by one microorganism that selectively inhibits the growth of another. Synthetic antibiotics, usually chemically related to natural antibiotics, have since been produced that accomplish comparable tasks.
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In 1926, Alexander Fleming discovered penicillin produced by fungi that inhibited bacterial growth. In 1939, Edward Chain and Howard Florey further studied penicillin and later carried out trials of penicillin on humans (with what were deemed fatal bacterial infections). Fleming, Florey and Chain shared the Nobel Prize in 1945 for their work which ushered in the era of antibiotic
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An antimicrobial is a substance that kills or inhibits the growth of microbes such as bacteria, fungi, or viruses. microbicidal or microbistatic.
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Chemotherapy Refers to treatment of disease by chemicals that kill cells, specifically those of micro-organisms or cancer
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Mechanism of action Penicillin Cephalosporins Vancomycin Bacitracin Polymyxin Colistin Aminoglycosides Tetracycline Chloramphenicol Macrolide Lincomycin Sulfonamides PAS INNH Trimethoprim Rifampin Quinolones Antimetabolites
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PABA Pteridine Dihydropteroate synthetase Dihydropteroic acid Di hydroFolic Acid Dihydrofolate reductase Tetrahydrofolate acid purines Nucleic Acid synthesis
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PABA Pteridine sulfonamides Dihydropteroate synthetase Dihydropteroic acid Di hydroFolic Acid trimethoprim Dihydrofolate reductase Tetrahydrofolate acid purines Nucleic Acid synthesis
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Selective toxicity An ideal antimicrobial agent should exhibit ST Drug is harmful to parasite without being harmful to host at the particular dose Receptor specific Biochemical event
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Mechanism of Drug Resistance NON GENETIC AND GENETIC NON GENETIC- Metabolically inactive/non multiplying M.orgs lose specific target site Drug unable to penetrate the site of infection
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Antimicrobial Chemotherapy Modern Chemotherapy-Paul Ehrlich(18450-1915)-arsenicals for syphilis and m.blue for malaria Domagk-1935-Prontosil Alexander Fleming-Penicillium notatum-Penicillin Antibiotic- Antimicrobial Chemotherapeutic
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GENETIC Mutation Transfer of genes Conjugation Transduction Transposition Transformation
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Drug Resistance Mutational Transferable Decreased permeability to drug/alt metabolic path/inactivating enzymes Single drug Low degree of resistance Not transferable Metabolically defective Virulence maybe lowered Combination of drugs useful Inactivating enzymes Multidrug High degree of resistance Transferable Metabolically normal No decrease in virulence -----------
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Biochemical mechanism of Drug resistance Production of enzymes that destroy the active drug Beta lactamases Adenylating/phosphorylating/acetylating Acetyl transferase Change of permeability Develop altered structural target Altered metabolic pathway Altered enzyme