dr. iman ibrahim. structure of bacterial genome 1- bacterial nucleoid 2- plasmids or large - the...
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Bacterial Genetics
Dr. Iman Ibrahim
Structure of Bacterial genome1 -Bacterial nucleoid
2 -plasmids or large -The nucleic acids are polymeric macromolecules known forms of life, biological molecules, essential for all
(deoxyribonucleic acid ) - and The nucleic acids includes DNA RNA (ribonucleic acid)
- it is composed of Simple units called nucleotides, connected in long chains
Nucleotides have 3 parts:
1 -5-Carbon sugar (pentose).2 -Nitrogenous base .
3 -A phosphate group ( P ).Dr. Iman Ibrahim
1 -Ribonucleic acids (RNA)
The pentose sugar is Ribose (has a hydroxyl group in the 2nd carbon---OH)
2 -Deoxyribonucleic acids (DNA)
The pentose sugar is Deoxyribose( has just an hydrogen in the same place--- H)
Deoxy = “minus oxygen“
Dr. Iman Ibrahim
DNA Nucleotides Composition (3 parts):
1 -Deoxyribose sugar (no O in 2nd carbon)2 -Phosphate group
3 -One of 4 types of bases (all containing nitrogen) : - Adenine
- Thymine (Only in DNA) - Cytosine - Guanine
RNA Nucleotides
Composition ( 3 parts):1 -Ribose sugar (with O in 2nd carbon)
2 -Phosphate group3 -One of 4 types of bases (all containing nitrogen) :
-Adenine -Uracyl (only in RNA)
-Cytosine -Guanine
Dr. Iman Ibrahim
Dr. Iman Ibrahim
A gene is the molecular unit of heredity of a living organism. It is widely accepted by the scientific community as a name given to some stretches of deoxyribonucleic acids (DNA) and
ribonucleic acids (RNA) that code for a polypeptide
Dr. Iman Ibrahim
AUG The start codon always codes for methionine
stop codon (DNA) TAA or TAG or TGAStop codon (RNA) UAG, UAA, UGA
Dr. Iman Ibrahim
Bacteriophage
-Bacteriophage are bacterial viruses which pass through minute pore filters and live at the expense of reproducing bacteria, it has strict species.
-Phage distributed in nature and found wherever the bacteria are found
Dr. Iman Ibrahim
Structure of phage
Bacteriophage has spermatoid shape
1 -Head : Consisted of protein coat (capsid) and enclosing a core of nucleic acids
2 -Hollow core
3 -Tail : -Helical contractile sheath
-Base plate -Tail pins ( perferator)
Dr. Iman Ibrahim
Uses of phages:1 -Used in diagnosis of unknown bacteria.2 -Used for serotyping of different bacteria
Mechanism of interaction between phage and bacteria
1 -The phage particles come in contact with the bacterial cell
2 -the phage adsorbed on bacteria by its tail3 -the tail penetrate the bacterial cell wall
4 -the contents of the head flow into the bacterial cell 5 -replication of the phage DNA and assembly of the
phage structure6 -Lysis of the bacterial cell and exit of new phages
Dr. Iman Ibrahim
Dr. Iman Ibrahim
Bacterial Variation
Dr. Iman Ibrahim
Variation in bacterial characters occurs by acquiring a new characters or by loss of characters
Bacterial variation
Permanent (Genotypic)
Temporary (Phenotypic)
Dr. Iman Ibrahim
Phenotypic Genotypic Item
Temporary Permanent Action
Extrinsic factors, don’t affect DNA
Extrinsic or Intrinsic factors, affect DNA
causes
reversible Irreversible and constant Nature
The second generation similar to the parent cells
The second generation differ completely than the parent cells
The characters of the second generation
1 -loss of motility of some strains due to subleathal dose of phenol, when we remove the phenol the daughter cells
posses the flagella
1 -attenuation of virulent strains2 -change in sensitivity to
antibiotics3 -biochemical characters
4 -antigenic structure
examples
Dr. Iman Ibrahim
Bacterial variation may be
1 -Phenotypic2 -Genotypic
1 -variation in morphology (mutation) (pleomorphism) : -Short bacilli becomes long
-sporulated or capsulated bacteria loss this characters -flagellated bacteria loss flagella
-pigmented bacteria stop its production
2 -variation in biochemical characters : -bacteria produce indole stop its production
-bacteria ferment sugars stop fermenting -bacteria needs CO2 for growth may grow under aerobic
conditions
3 -variation in cultural characters (Dissociation) : -Change of colonies from smooth form to rough form
Dr. Iman Ibrahim
Rough form Smooth form Item
Saprophytic bacteria Parasitic bacteria Type
Rough, irregular, dull, opaque Glistening, smooth, round colonies
Filamentous, pleomorphism Regular in shape Organism morphology
Pale Deeply stained staining
Non-motile or slow motion Motile in motile species motility
Sediment or supernatant Uniform turbidity Subculture in broth
Weakly antigenic Highly antigenic antigenicity
Low or no virulence Virulent except B.anthracis pathogenicity
Difficult to S-form Easily to R-form change
Suspended spontaneously Easily suspended suspension
In laboratory Fresh materials isolation
Non- capsulated Well developed capsule capsule
Less active Active Biochemical activity
Less sensitive sensitive Effect of phage
Dr. Iman Ibrahim