L1 - Bacterial Structure And Genetics.pdf

L1 - Bacterial Structure And Genetics File Edit Index: Main Text Girls Slides Important Doctors Notes Boys Slides Extra Info OBJECTIVES Define the cellular organization of bacteria an...

L1 - Bacterial Structure And Genetics File Edit Index: Main Text Girls Slides Important Doctors Notes Boys Slides Extra Info OBJECTIVES Define the cellular organization of bacteria and recall the differences between Eukaryotes and Prokaryotes Recall major structures of bacteria and its functions Describe the structure of cell wall of bacteria including the differences between Gram positive and Gram negative bacteria and main functions Describe the internal and external structures of bacteria and their functions Recall basic information about bacterial genetics and replication of bacteria Describe the plasmid origin, types and its importance in medical practice  Cellular Organization of Bacteria: Bacteria is a heterogeneous (diverse) group of unicellular organisms, about 1-8μm in diameter. Bacteria is a prokaryote No mitochondria It has a primitive nucleus It has only one chromosome No nuclear membrane Contains an extra piece of DNA called plasmid No sterols Shapes and Types of Bacteria: Vibreo, Fusiform Coccobacilli Cocci Spirochaetes Basilli Campylobacter Very short Spherical & Club-shaped Tapered end Helical & spiral Rods curved bacilli oval curved Vibreo Campylobacter - Pairs: Diplococci Arrangement among cocci Chains: Streptococci Clusters: Staphylococci In four: Tetrad Palisades: Corynebacterium  Cell wall of Bacteria : One of the most important structures is the cell wall Bacteria are prokaryotic cells with rigid cell walls that surround the cytoplasmic membrane and internal structures. Functions of Cell Wall Rigidity Protection Shapes bacteria Antigenic determinants Porous & Permeable to low molecular weight molecules Cell Division  Cell wall of Bacteria Bacteria are classified into two groups depending on their reaction to GRAM stain: Chemical structure of bacterial cell wall: Gram Stain Peptidoglycan : Rigid part, mucopeptide composed of alternating strands of N-acetylmuramic acid and Gram negative: Gram positive: Stain Stain Blue/purple N-acetyl glucosamine cross linked with peptide Red subunits Peptidoglycan: Building blocks of cell wall Note : Mycoplasma naturally have no cell wall (therefore, gram stain are not useful for the diagnosis of this organism)  Doctor’s notes: - Due to cell wall thickness, the purple stain will only Types of Bacteria (Gram stain) : remain on the thick cell wall (+ve) - Iodine prevents the easy removal of the crystal violet dye Gram-Positive Gram-Negative Retains the crystal violet stain. Do not retain the crystal violet stain. Appears purple under the microscope. Appears pink under the microscope Closely associated with the cytoplasmic membrane - Thick peptidoglycan & multilayered Thin peptidoglycan & single layered Outer membrane is present Outer membrane is absent (Peptidoglycan surround) ‫ﻓرق ﺟدار اﻟﺧﻠﯾﺔ‬ Cell wall contains: Outer membrane contains: -Teichoic acid protein associated with cell wall to anchor it to cell -Lipopolysaccharides (Endotoxins): are part of the outer membrane membrane, epithelial cell adhesion. of the cell wall of Gram-negative bacteria. (In the case of infection, -Antigens: polysaccharides: (Lancefield) protein: (Griffith) (these are cause septic shock) used to identify streptococci infection) -Specific proteins (porins) important in the transport of hydrophilic molecules Bacteria Structures : Bacteria Structures : Girls Slides External protrude from the cell into the environment: External Internal Pilli Capsule & Flagella Core of bacteria Mesosomes Slime layer Cytoplasmic Ribosomes Nucleoid inclusions External Structure of Bacteria : Flagella Pili Capsules & Slime layer Shape Structures surrounding the outside of Fine short filaments extruding from Helical filaments the cell envelope. They can be seen cytoplasmic membrane by India ink or some special stains. Composed of usually a polysaccharide, but in some a protein called FLAGELLIN a protein called Pilin bacteria it is composed of polypeptide (protein) Found in both gram positive & gram negative the surface of many gram positive & Some strains within species produce bacteria gram negative bacteria capsule while others do not. They are not essential for cell viability Function motility and chemotaxis. (movement 1- Common pili Attachment of an organism in response to Also called fimbriae, covers the Protection from phagocytic chemical stimulus) surface of the bacteria. Responsible engulfment Some bacterias flagella aren’t motile for adhesion & colonization (Antiphagocytic) 2- Sex pili Resistant to dryness In some bacteria only. Reservoir (‫ )ﻣﺧزن‬for certain Responsible for conjunction (mating) nutrients Pictures (Single (Single (Multiple (Multiple flagellum on flagellum at flagella flagella each of two one pole) located at all over opposite the same the cell ) ends) point )  Internal Structure : Cytoplasmic Membrane (plasma membrane) Double layered structure = phospholipid+protein Semi-permeable membrane (passive diffusion) Site of numerous enzymes which are involved in active transport of nutrients and other metabolic processes Mainly for passive diffusion Mesosomes Convoluted (folded) invaginations of the plasma membrane into the cytoplasm Helps in DNA segregation and cell division and chemotaxis (chemotaxis is moving towards a certain signal) Functions : 1. Coordinates DNA and cytoplasmic segregation during cell division 2. Contains respiratory enzymes 3. Contains receptors involved in chemotaxis 4. Permeability Barrier (active transport of solutes) Extra  Girls Slides Internal Structure of Bacteria:(Core) Core composed of : Cytoplasmic inclusions Nucleoid ( nuclear body) Ribosomes Cytoplasmic Inclusions Ribosomes Bacterial Chromosomes Nucleoid Site of protein synthesis Circular molecule of double Single circular chromosome Nutritional Storage Granules store: Distributed (found) stranded DNA (Haploid) No Nuclear Membrane Volutin : IC phosphate throughout the cytoplasm located in the cytoplasm. DNA undergoes reservoir Composed of 2 subunits Packed with RNA molecules semiconservative replication, Lipid (Small+Large)(30s & 50s) and proteins to form bidirectional from a fixed Starch/Glycogen: reservoir irregular shaped structure point of carbohydrate and energy Nucleoid (Nuclear Body) RNA and Protein could be Genetic code in purine and found within it pyrimidine bases of nucleotides that make the DNA strand Replication is Semiconservative which takes place by Binary Fission  Spores (endospores) of bacteria spores: Only occurs in gram (+ve) bacteria Spores only form when needed (depends on the environment/situation they are in) It gives them strength and protection Small dense metabolically inactive, non-reproductive structures produced by Bacillus & Clostridium species. Enables the bacteria to survive adverse environmental conditions Contains high concentration of Calcium dipicolinate (Which is the reason they can survive harsh environments) Resistant to heat, desiccation & disinfectants Often remains associated with the cell wall Spores germinate when growth conditions become favorable to produce vegetative cells Application in medical practice: Spore strips are used for checking the efficacy of Autoclaves eg: Bacillus subtilis & Bacillus stearothermophilus terminal central sub-terminal Bacterial Genetics : Definition: Genetics is the study of inheritance and variation, how the genetic information is transferred to the offspring or into other bacteria. Full collection of genetic Genotype The genetic information is encoded in the DNA In bacteria, genetic variation is due to: determinants of an organism. 1.Gene Transfer It remains constant. 2.Mutation Physiology or expression of specific genetic material Function of Genetic material genome Phenotype The set of genes being expressed at any point in time determining the cell Replication of the genome activity observable characteristic Expression of DNA to mRNA then to Reference Strain (Parent) protein (transcription & translation) Wild type No Mutation No Changes Types of DNA in Bacteria: 1.Chromosomal Mutant Progeny with Mutation 2.Extra-chromosomal DNA (Plasmid)  Mutation: Mutation: Inheritable changes in the structure of genes (DNA). Chemical changes in one or more bases of DNA. Mutation / gens It leads to an altercation in: Transcription Defect: Amino acid sequences Function: Bacteria becomes more resistant to Antibiotics Mutation Depends on biological sequencing: Classification: Affects structure of cell protein. Resistance Main application in medical practices. Mutation Bacteria become more resistant to Antibiotics Affects biosynthetic enzyme resulting in a nutritional Auxotrophic requirement of mutant cell. (Unable to synthesize an Mutation essential compound) Change of nutritional requirements Lethal Mutation Leads to the death of the Bacteria  Types of Bacterial DNA: Extrachromosomal Types of plasmids: Chromosomal (Plasmids) Haploid, circular molecule of double extrachromosomal DNA composed stranded DNA attached to cell of double stranded DNA membrane Genetic code in Purine and Pyrimidine F-Plasmids Fertility Col-Plasmids Found in most species of bacteria, bases of nucleotides that makes DNA Factor, transfer of In Enterobacteria, and the origin is unknown codes for strand chromosomes during mating (conjugation) extracellular toxins 3 bases comprise one code, each Govern their own replication triplet codon codes for one amino acid Transfer to other bacteria by conjugation Application: In genetic exchange, R-Plasmids genes amplify Replication is Semiconservative, takes Gene code for place by Binary Fission antibiotic Resistance, Plasmids are not necessary, bacteria particularly Gram can live without them negative bacteria.  Transduction and Conjugation videos for Gene Transfer among Bacteria : help :) Iodine prevents the easy removal of the crystal violet dye Ways of gene Transfer among Bacteria Transformation Conjugation (Mating) They transfer through sex pilli Transduction (phage/virus) Cell contact is required, and Mostly fragments of A fragment of exogenous genes reside on plasmid dead bacteria naked bacterial DNA, are resident within donor cells and Phage mediated transfer (by transfer to recipient cells taken up and absorbed into virus) of genetic information (mating) recipient cells from donor to recipient cells Plasmids could carry Common way of transfer of different types of genes resistant to antibiotics resistance Bacteria becomes resistant to 1- Beta-lactamase (enzyme) among bacteria in hospitals Plasmids are ampicillin production in staphylococcus extrachromosomal DNA aureus: resistant to penicillin Major way bacteria acquire additional genes - Haemophilus influenzae 2- Toxin production by -Streptococcus Pneumoniae Corynebacterium diphtheria Plasmid mediated F factor  Gene Transfer among Bacteria : Team 444: Transposable Genetic Element Facilitates transfer The gene jumps from plasmid to chromosomal and chromosomal to plasmid Just to clarify  Genetic Recombination : 01 Exogenous DNA is degraded by nuclease (enzyme). After Gene transfer there are 3 possible fates: 02 Stabilized by circularization and becomes plasmid. Forms a particular Hybrid 03 Chromosome with segment derived from each source.  Quiz Q1: Bacterial Spores can survive harsh environmental conditions due to.? Calcium Disodium Presence of flagellin A Calcium Dipicolinate B Lipoteichoic Acid C Edetate D protein Q2:Endotoxins are found in? Outer membrane of Outer membrane of A Gram +ve B Cell wall of gram +ve C Gram -ve D Cell cytoplasm Q3: What does the gram +ve cell wall contain? A Lipid B Porins C Uric acid D Teichoic Acid Q4: In bacteria, it is the inheritable changes in the structure of genes (DNA)? A Inheritable disease B Conjunction C Mutation D Transformation Q5: Which of the following flagella have a distribution of a tail on both sides ? A Monotrichous B Peritrichous C Lophotrichous D Amphitrichous 1/A 2/C 3/D 4/C 5/D  Our Team Leaders Members Osama Sarah Basma TBD Aban Alahmari Alshwirkh albahkly Alanazi Yousef TBD Lamar Reema Alzahrani Alkharraz Alniwaisry Omar Fayan Layan TBD Norah Alharbi Alqahtani alotaibi Alrashid Ghazi TBD Jawaher Deemah Almodarra alarfaj alotabi Nada Haya TBD TBD Nada alMuhawwis Alhazani Alzahrani TBD TBD Ghada Alsagar Wareef Albalawi