Morphologg &ultra – structures of microbiology
Lectuer (1)
Dr.Baha,Hamdi.AL-Amiedi
Ph.D.Microbiology
Microbiology:
It is science that deals with micro – organisms that cannot visible in the naked eyes, encompasses the study of organisms that cause the disease; the host response to infection & the ways in which such infection may be prevented.
dental student study microbiology by basic understanding of general and medical microbiology and detailed about the clinical oral microbiology in order to diagnosis oral microbial infection which are intimately related to the overall treatment plan for their patients. Moreover the two major oral disorders are caries and periodontal disease.
The cellular organisms classified into:
Eukaryotes : a- alge , b- fungi c-protozoa
Prokaryotes : ( bacteria )
Eukaryotes
It is the organism have true nucleus surrounded by membrane its also contains membrane-bound organelles such as Golgi bodies & chloroplast, there are metabolic function and energy conversion chromosomes present in the nucleus of microorganism there are two types of cell division sexual& A sexual,DNA is complex with histone proteins, peptidoglycan is not present in the cell wall in these microorganisms :
Prokaryotes:
organisms related to this group don’t have nucleus; chromosomal DNA is in a circular loop &a plasmid they have few internal structures in the cytoplasm on this group, peptidoglycan present in cell wall of these group,the cell division occur by a process called binary fission
Bacteria:
it is prokaryotic microorganism can be seen easily by using microscope it is unicellular free living organisms they are capable of performing all essential processes like metabolism and reproduction . they have rigid cell wall containing muramic acid, cytoplasm with no nucleus and contain one chromosomes is present freely in cytoplasm in a region called nucloid .
bacteria can produce many - enzymes for achieving their metabolic processes and also can synthesize many factors associated with these pathological called virulence factors also contain number of ribosome s some of these attached to plasma membrane other are free
Bacteria is classified according to their shape into :
1. cocci ( spherical )
2. Rods ( bacilli )
3. Spiral
4. vibrio.
Gram-staining characteristics:
Gram stain classified bacteria into two major subgroups according to the cell walls: .
*The gram positive (purple) and **gram negative (pink) groups. this classified is useful both for their identification & in the therapy of bacterial infection.
Cytoplasmic bacterial cell:
Bacterial cytoplasm is suspension of organic & inorganic solutes in viscous watery solution it contain ribosome s Many bacteria accumulate in organic phosphate which is called volutin granules which is metachromatic granule e. g (corynebacterium spp) it is a reserve of energy & phosphate
for cell metabolism &they are characteristically in diphtheria bacilli
Ribosomes
Ribonucleic acid-complex particles, distributed throughout the cytoplasm, They are held together by a strand of (m RNA )Which are the site of enzymatic concerned with the synthesis of protein.
Bacterial chromosomes:
It is a single and contain all the genes involved in the growth & survival of bacteria , Bacteria containes about 1000 genes are located in circular chromos-.Two DNA strands are stabilized by hydrogen bound to form duble helix , the four nucleotides present in (DNA) molecule contain nitrogenous base purine (adenine & guanine)
Pyrimidine (Thymine ,Cytosine) are attached to sugar. There is a back bone of alternating deoxyribose and phosphate .
However other genetic elements are found with the bacteria these element called plasmid, transposons
Plasmid:
Plasmid : the plasmid usually circular DNA present independently for the chromosome and can perform some additional activities to the bacteria, plasmid code for enzymes , toxin or resistance factors and transmit these pathogenic factors in bacteria
Transposons:
It is genetic transferring which can jump from one location to the other in the same or from the plasmids to the chromosome .
Mesosomes:
It is cytoplasmic membrane invaginations of gram-positive bacteria and some gram-negative bacteria,it is:
1-coordinate nuclear and cytoplasmic division during binary fission 2..responsible for compartmenting DNA during sporulation.
Baterial cell wall:
It is the outermost supporting layer which Protect the internal structure.cell wall is External to cytoplasmic membrane, the structural component of cell wall;composed of mucopeptide(murein) Scaffolding formed by N-acetyl glucosamine &N- acetyl-muramic acid molecule alternating in chain cross linked by peptid The lipopolysacchride are covalently bound to peptidoglycan it is the antigen of Gram negative organisms act as endotoxine.
The Gram positive cell wall
is peptidoglycan represent between 40-80% of the total cell wall . Gram positive cell wall also contain the chemical constituent the techoic acid.
Techoic acid is a polymer of ribitol phosphate and glycerol Phosphate and is associated with cell wall &cell membrane in gram positive Bacteria.
Functions of Bacterial Cell Wall:
1-protection of internal structure
2-give shape of cell
3-confers rigidity ductility
4-role in division of bacteria
5-offers resistance to harmful effect of environment
Cytoplasmic membrane:
It is semi permeable membrane which lies just beneath the cell wall , it is 5-10 nm in width
Electron microscopy shows the presence of three layers
Constituting a unit membrane structure chemically consist of phospholipid with small amount of protein.
Function of cytoplasmic membrane:
1-It control inflow and outflow of metabolites to and from protoplast.
2-presence in the membrane of specific enzyme which plays important role in passage through membrane
3-It contains some other respiratory enzymes and pigment (cytochrom system)
4-It provid little mechanical strength to bacterial cell