Lecturers : Lecturers : Prof Hanan Habib & Dr. Albdulaziz Al-Khattaf Department of Pathology,...

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Lecturers : Lecturers : Prof Hanan Habib & Dr. Albdulaziz Al-Khattaf Department of Pathology, Microbiology Unit, KSU Title: Title: Bacterial Structure & Genetics ) ) (Foundation Block, (Foundation Block, Microbiology Microbiology

Transcript of Lecturers : Lecturers : Prof Hanan Habib & Dr. Albdulaziz Al-Khattaf Department of Pathology,...

Page 1: Lecturers : Lecturers : Prof Hanan Habib & Dr. Albdulaziz Al-Khattaf Department of Pathology, Microbiology Unit, KSU Title: Title: Bacterial Structure.

Lecturers : Lecturers : Prof Hanan Habib & Dr. Albdulaziz Al-Khattaf

Department of Pathology, Microbiology Unit, KSU

Title:Title:

Bacterial Structure & Genetics

)) (Foundation Block, Microbiology (Foundation Block, Microbiology

Page 2: Lecturers : Lecturers : Prof Hanan Habib & Dr. Albdulaziz Al-Khattaf Department of Pathology, Microbiology Unit, KSU Title: Title: Bacterial Structure.

Bacteria A heterogenous group of uni-cellular organisms about 1-8 μm in diameter , Prokaryotic (has a primative nucleus)with :

- one chromosome - no nuclear membrane - no mitochondria - no sterols -Plasmids: extra piece of DNA.

Page 3: Lecturers : Lecturers : Prof Hanan Habib & Dr. Albdulaziz Al-Khattaf Department of Pathology, Microbiology Unit, KSU Title: Title: Bacterial Structure.

Structures of bacteria

• Shapes : Spherical / Oval…….Cocci

• Rods…………… …Bacilli• very short Bacilli…

Coccobacilli• Tapered end ………

Fusiform• Club-shaped /

Curved….Vibrio• Helical /

Spiral… ..Spirochaetes

Page 4: Lecturers : Lecturers : Prof Hanan Habib & Dr. Albdulaziz Al-Khattaf Department of Pathology, Microbiology Unit, KSU Title: Title: Bacterial Structure.
Page 5: Lecturers : Lecturers : Prof Hanan Habib & Dr. Albdulaziz Al-Khattaf Department of Pathology, Microbiology Unit, KSU Title: Title: Bacterial Structure.

ArrangementsArrangements

among Cocci :• Pairs………Diplococci• Chains……Streptococci• Clusters…..Staphylococci• In four……Tetrad• Pallisades…..Corynebacterium

Page 6: Lecturers : Lecturers : Prof Hanan Habib & Dr. Albdulaziz Al-Khattaf Department of Pathology, Microbiology Unit, KSU Title: Title: Bacterial Structure.

Major structures of bacteriaMajor structures of bacteriacell wall / appendeges & cytosolcell wall / appendeges & cytosol

Page 7: Lecturers : Lecturers : Prof Hanan Habib & Dr. Albdulaziz Al-Khattaf Department of Pathology, Microbiology Unit, KSU Title: Title: Bacterial Structure.

Cell wallCell wall• Bacteria are cells with rigid cell wall

surround cytoplasmic membrane and internal structures.

Functions of cell wall:- Rigidity- Shapes bacteria- Protection-Porous / permeable to low molecular weight

molecules.-Cell division- Antigenic determinants

Page 8: Lecturers : Lecturers : Prof Hanan Habib & Dr. Albdulaziz Al-Khattaf Department of Pathology, Microbiology Unit, KSU Title: Title: Bacterial Structure.

Structure of cell wallStructure of cell wall• Two groups of cell wall depending

on reaction to GRAM STAIN• Gram positive bacteria• Gram negative bacteria

Page 9: Lecturers : Lecturers : Prof Hanan Habib & Dr. Albdulaziz Al-Khattaf Department of Pathology, Microbiology Unit, KSU Title: Title: Bacterial Structure.

Chemical Structure of Cell Chemical Structure of Cell WallWall• Peptidoglycan : rigid part , mucopeptide

composed of alternating strands of N- acetyl muramic acid and N- acetyle glucosamine linked with peptide sub units.

Page 10: Lecturers : Lecturers : Prof Hanan Habib & Dr. Albdulaziz Al-Khattaf Department of Pathology, Microbiology Unit, KSU Title: Title: Bacterial Structure.
Page 11: Lecturers : Lecturers : Prof Hanan Habib & Dr. Albdulaziz Al-Khattaf Department of Pathology, Microbiology Unit, KSU Title: Title: Bacterial Structure.
Page 12: Lecturers : Lecturers : Prof Hanan Habib & Dr. Albdulaziz Al-Khattaf Department of Pathology, Microbiology Unit, KSU Title: Title: Bacterial Structure.
Page 13: Lecturers : Lecturers : Prof Hanan Habib & Dr. Albdulaziz Al-Khattaf Department of Pathology, Microbiology Unit, KSU Title: Title: Bacterial Structure.

Gram Gram NegativeNegative Cell Wall Cell Wall• Thin Peptidoglycan• Outer membrane that contains : - specific proteins (porins)

important in the transport of hydrophilic molecules

- lipopolysaccharide & lipid (ENDOTOXIN)

Page 14: Lecturers : Lecturers : Prof Hanan Habib & Dr. Albdulaziz Al-Khattaf Department of Pathology, Microbiology Unit, KSU Title: Title: Bacterial Structure.

Gram Gram Positive Positive Cell WallCell Wall• Peptidoglycan thicker than Gram

negative bacteria.• Closely associated with

cytoplasmic membrane.• Techoic acid : anchors cell wall to

cell membrane , epithelial cell adhesion.

• Antigens : - polysaccharides (Lancefield)

• - protein (Griffith)

Page 15: Lecturers : Lecturers : Prof Hanan Habib & Dr. Albdulaziz Al-Khattaf Department of Pathology, Microbiology Unit, KSU Title: Title: Bacterial Structure.
Page 16: Lecturers : Lecturers : Prof Hanan Habib & Dr. Albdulaziz Al-Khattaf Department of Pathology, Microbiology Unit, KSU Title: Title: Bacterial Structure.

Bacteria with defective cell Bacteria with defective cell wallwall

4 types: 1-Mycoplasma: natural , stable,

clinically significant.2-L- form3- Spheroplasts4- Protoplasts

Page 17: Lecturers : Lecturers : Prof Hanan Habib & Dr. Albdulaziz Al-Khattaf Department of Pathology, Microbiology Unit, KSU Title: Title: Bacterial Structure.

External StructuresExternal Structures

Protrude from the cell into the environment.:

• Flagella• Pili• Capsule

Page 18: Lecturers : Lecturers : Prof Hanan Habib & Dr. Albdulaziz Al-Khattaf Department of Pathology, Microbiology Unit, KSU Title: Title: Bacterial Structure.

FlagellaFlagella• Helical filaments• Composed of protein FLAGELLIN.• Found in Gram positive & Gram

negative bacteria. Function of flagella : Motility Chemotaxix

Page 19: Lecturers : Lecturers : Prof Hanan Habib & Dr. Albdulaziz Al-Khattaf Department of Pathology, Microbiology Unit, KSU Title: Title: Bacterial Structure.

Distribution of flagella on bacteria

Monotrichous

Lophotrichous

Peritrichous

Page 20: Lecturers : Lecturers : Prof Hanan Habib & Dr. Albdulaziz Al-Khattaf Department of Pathology, Microbiology Unit, KSU Title: Title: Bacterial Structure.

PilliPilli

Fine short filaments extruding from cytoplasmic membrane.

Found on the surface of many Gram negative & Gram positive bacteria.

Composed of protein Pilin.Two classes: 1- Common pili (fimbriae): covers the

surface— responsible for: adhesion & colonization

2- Sex pili : in some bacteria only, responsible for conjugation.

Page 21: Lecturers : Lecturers : Prof Hanan Habib & Dr. Albdulaziz Al-Khattaf Department of Pathology, Microbiology Unit, KSU Title: Title: Bacterial Structure.

• Capsule : Amorphous material surrounds bacteria usually polysaccharide, occasionally protein

• Function : - Inhibits phagocytosis - Virulence factor.

Page 22: Lecturers : Lecturers : Prof Hanan Habib & Dr. Albdulaziz Al-Khattaf Department of Pathology, Microbiology Unit, KSU Title: Title: Bacterial Structure.

• Cytoplasmic membrane (cell membrane)– Double layered structure composed of

phospholipid & protein– Act as semi- permeable membrane (passive

diffusion)– Site of numerous enzymes involved in

active transport of nutrients and various metabolic processes

Page 23: Lecturers : Lecturers : Prof Hanan Habib & Dr. Albdulaziz Al-Khattaf Department of Pathology, Microbiology Unit, KSU Title: Title: Bacterial Structure.

Internal structures : Mesosomes :convoluted

invaginations of cytoplasmic membrane.»Involved in DNA segregation

during cell division & respiratory activity»Contain receptors involved in

chemotaxis»Permeability barrier (active

transport of solutes).

Page 24: Lecturers : Lecturers : Prof Hanan Habib & Dr. Albdulaziz Al-Khattaf Department of Pathology, Microbiology Unit, KSU Title: Title: Bacterial Structure.

CoreCore• Cytoplasmic inclusions Nucleoid Ribosome• Cytoplasmic inclusions:Nutritional storage granules , eg. - Volutin - Lipid - Starch / or Glycogen

Page 25: Lecturers : Lecturers : Prof Hanan Habib & Dr. Albdulaziz Al-Khattaf Department of Pathology, Microbiology Unit, KSU Title: Title: Bacterial Structure.

Nucleoid (nuclear body)Nucleoid (nuclear body)• Circular single stranded

chromosome (bacteria genome or DNA)

• No nuclear membrane• DNA undergoes semi-conservative

bidirectional replication .

Page 26: Lecturers : Lecturers : Prof Hanan Habib & Dr. Albdulaziz Al-Khattaf Department of Pathology, Microbiology Unit, KSU Title: Title: Bacterial Structure.

RibosomesRibosomes• Distributed throughout the

cytoplasm• Site of protein synthesis• Composed of RNA and protein

Page 27: Lecturers : Lecturers : Prof Hanan Habib & Dr. Albdulaziz Al-Khattaf Department of Pathology, Microbiology Unit, KSU Title: Title: Bacterial Structure.

SporesSpores• Small ,dense, metabolically

inactive , non- reproductive structures produced by Bacillus & Clostridium

• Enables the bacteria to survive adverse environmental conditions.

• Contain high con. of Calcium dipicolinate

• Resistant to heat, diseccation & disinfectants

• Often remain associated with the cell wall

Page 28: Lecturers : Lecturers : Prof Hanan Habib & Dr. Albdulaziz Al-Khattaf Department of Pathology, Microbiology Unit, KSU Title: Title: Bacterial Structure.

continue -sporescontinue -spores• Described as :1- Terminal spores2- Sub-terminal spores3- Central sporesGerminate when growth conditions

become favorable to produce vegetative cells.

Spore preparations used for checking the efficacy of Autoclaves.

Page 29: Lecturers : Lecturers : Prof Hanan Habib & Dr. Albdulaziz Al-Khattaf Department of Pathology, Microbiology Unit, KSU Title: Title: Bacterial Structure.

Bacterial geneticsBacterial genetics• Genetics is the study of

inheritance and variation.• Genetic information encoded in

DNA.Function of genetic material:• 1- Replication of the genome• 2- Expression of DNA to mRNA

then to protein.

Page 30: Lecturers : Lecturers : Prof Hanan Habib & Dr. Albdulaziz Al-Khattaf Department of Pathology, Microbiology Unit, KSU Title: Title: Bacterial Structure.

DefinitionsDefinitions• Genotype: the complete set of

genetic determinants of an organism.

• Phenotype: expression of specific genetic material .

- Wild type: reference (parent) strain–Mutant: progeny with mutation

Page 31: Lecturers : Lecturers : Prof Hanan Habib & Dr. Albdulaziz Al-Khattaf Department of Pathology, Microbiology Unit, KSU Title: Title: Bacterial Structure.

Bacterial DNABacterial DNA

2 types of DNA in bacteria:• - Chromosomal• - Extra-chromosomal

(plasmid).

Page 32: Lecturers : Lecturers : Prof Hanan Habib & Dr. Albdulaziz Al-Khattaf Department of Pathology, Microbiology Unit, KSU Title: Title: Bacterial Structure.

Bacterial chromosomeBacterial chromosome• Haploid, circular molecule of double

stranded, DNA attached to cell membrane. No nuclear membrane (prokaryotes).

• DNA a double helical structure, genetic code in Purine and Pyrimidine bases of nucleotides that makes DNA strand.

• 3 bases comprise one code, each triplet codon codes for one amino acid.

Page 33: Lecturers : Lecturers : Prof Hanan Habib & Dr. Albdulaziz Al-Khattaf Department of Pathology, Microbiology Unit, KSU Title: Title: Bacterial Structure.
Page 34: Lecturers : Lecturers : Prof Hanan Habib & Dr. Albdulaziz Al-Khattaf Department of Pathology, Microbiology Unit, KSU Title: Title: Bacterial Structure.
Page 35: Lecturers : Lecturers : Prof Hanan Habib & Dr. Albdulaziz Al-Khattaf Department of Pathology, Microbiology Unit, KSU Title: Title: Bacterial Structure.

PlasmidsPlasmids• Extrachromosomal DNA• Found in most species of bacteria.• Origin?• Govern their own replication• Genetic exchange, amplify genes• Transfer by conjugation• Code for resistance to antibiotics &

toxins

Page 36: Lecturers : Lecturers : Prof Hanan Habib & Dr. Albdulaziz Al-Khattaf Department of Pathology, Microbiology Unit, KSU Title: Title: Bacterial Structure.
Page 37: Lecturers : Lecturers : Prof Hanan Habib & Dr. Albdulaziz Al-Khattaf Department of Pathology, Microbiology Unit, KSU Title: Title: Bacterial Structure.

Genetic variation in bacteriaGenetic variation in bacteria

Takes place by : • 1- Mutation• 2-Gene transfer.

Page 38: Lecturers : Lecturers : Prof Hanan Habib & Dr. Albdulaziz Al-Khattaf Department of Pathology, Microbiology Unit, KSU Title: Title: Bacterial Structure.

MutationMutation• Inheritable changes in the

structure of genes (DNA).• Result in alteration in amino acid

sequence.• Antibiotic resistance.

Page 39: Lecturers : Lecturers : Prof Hanan Habib & Dr. Albdulaziz Al-Khattaf Department of Pathology, Microbiology Unit, KSU Title: Title: Bacterial Structure.

Gene Exchange between Gene Exchange between bacteria & clinical bacteria & clinical significancesignificance

Three types:• 1- Transformation• 2- Transduction• 3- Conjugation.

Page 40: Lecturers : Lecturers : Prof Hanan Habib & Dr. Albdulaziz Al-Khattaf Department of Pathology, Microbiology Unit, KSU Title: Title: Bacterial Structure.

TransformationTransformation• A fragment of exogenous naked

bacterial DNA are taken up and absorbed into recipient cells.

• Common in Haemophilus influenzae & Streptococcus pneumoniae.

Page 41: Lecturers : Lecturers : Prof Hanan Habib & Dr. Albdulaziz Al-Khattaf Department of Pathology, Microbiology Unit, KSU Title: Title: Bacterial Structure.

TransductionTransduction• Phage mediated transfer of genetic

information from donor to recipient cells.

Example: • Beta – lactamase production in

Staphylococcus aureus, • toxin production in

Corynebacterium diphtheriae.

Page 42: Lecturers : Lecturers : Prof Hanan Habib & Dr. Albdulaziz Al-Khattaf Department of Pathology, Microbiology Unit, KSU Title: Title: Bacterial Structure.

ConjugationConjugation

• Major way bacteria acquire additional genes.

• Plasmid mediated• Cell contact required and genes reside

on plasmid within donor cells transfer to recipient cell (mating).

• Sex pilus involved• Differs between Gram positive & Gram

negative bacteria.

Page 43: Lecturers : Lecturers : Prof Hanan Habib & Dr. Albdulaziz Al-Khattaf Department of Pathology, Microbiology Unit, KSU Title: Title: Bacterial Structure.
Page 44: Lecturers : Lecturers : Prof Hanan Habib & Dr. Albdulaziz Al-Khattaf Department of Pathology, Microbiology Unit, KSU Title: Title: Bacterial Structure.

Genetic RecombinationGenetic Recombination

After gene transfer, there are 3 possible fates:

• 1-Exogenous DNA degraded by nuclease.

• 2-Stabilized by circulization, become plasmid.

• 3- Form a partially hybrid chromosome with segment derived from each source.

Page 45: Lecturers : Lecturers : Prof Hanan Habib & Dr. Albdulaziz Al-Khattaf Department of Pathology, Microbiology Unit, KSU Title: Title: Bacterial Structure.

Transposable ElementsTransposable Elements

Types: 1- Transposons . 2- Insertion sequence.

Page 46: Lecturers : Lecturers : Prof Hanan Habib & Dr. Albdulaziz Al-Khattaf Department of Pathology, Microbiology Unit, KSU Title: Title: Bacterial Structure.

Reference bookReference book

Sherries Medical Microbiology, an Introduction to Infectious Diseases. Latest edition, Kenneth Ryan and George Ray. Publisher : McGraw Hill .

Chapter 2 & 4