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Bacterial structure and taxonomy

By
Assist. Prof
Eman Abdul-Aziz
Department of Basic Science
College of Dentistry
University of Mosul

Department of Basic Science

College of Dentistry
University of Mosul

Microorganisms can be classified in to major groups:

Algae Protozoa Fungi Bacteria Viruses and a number of intermediate between bacteria and viruses (e .g Rickettsiae and Chlamediae)

1-Animal kingdom
2-Plant kingdom
3-Protists kingdom {bacteria; fungi protozoa }
This kingdom is differentiate from animals and plants by being unicellular or relatively simple multicelular organisms.
Bacterial Structure And Taxonomy


Viruses Cellular organisms
* The inner core of genetic * cell posses anucleus or
Material is either DNA In the case of bacteria
Or RNA, but they have no anucleiod with DNA. This is
Cytoplasm (depend on the surrounding by cytoplasm
Host for( energy and protein) (energy is generated and
They are metabolically inert proteins are synthesized)
Reproduction :
* Viruses disassemble, produce * bacteria reproduce by
Copies of their nucleic acid binary fission (apparent
and protein. And then reassemble cell divides into two similar
To produce another generation cells.
Of viruses
* Viruses must replicate * bacteria can replicate
Within host cells. Extracellulary (except
Rickettsiae and Chlamydia

Department of Basic Science

College of Dentistry
University of Mosul

Department of Basic Science

College of Dentistry
University of Mosul
Fungi
Viruses
Chlamydiae
Rickettsia
Mycoplasma
Bacteria
+
-
+
+
+
+
Visible with light microscope
+
-
-
-
+
+
Capable of free growth
+
-
+
+
+
+
Both DNA and RNA present
+
-
+
+
+
+
Muramic acid in cell wall
+
-
variable
+
-
+
Rigid cell wall
-
-
-
-
-
variable
Susceptible to Penicillin
-
-
+
+
+
variable
Susceptible to Tetracycline
-
-
+
+
+
+
Reproduce essentially by binary fission
Table Differential characteristics of major groups of organism

Department of Basic Science

College of Dentistry
University of Mosul
Prokaryotes Eukaryotes
1- Bacteria are prokaryotes Fungi, Protozoa, human
2-Only one chromosome More than one chromosome,
Copies of each chromosome
may present.
3- No nuclear membrane There is nuclear membrane
4- 70S Ribosome (S mean 80S Ribosome
Specific gravity)
5- Cell division not occur by Cell division by mitosis and
Mitosis and meiosis meiosis
6- Cell wall peptidoglycan Polysaccharide cell wall,
where present, are generally
cellulose or chitin

Department of Basic Science

College of Dentistry
University of Mosul
7- Flagella consist of one protein Flagella have a complex structure
Flagellin (9 outer fibrils+ 2 innerfibrils)
Microtubular arrangement.
8-DNA associated with histone DNA complex with histone
Like proteins proteins.
9-No mitochondria or chloroplasts There is mitochondria &
cholorplasts
10- May contain extra chromosomal Plasmids only found in Yeast
Elements called plasmid
11- Introns not found in mRNA Introns found in all genes
12- There is mesosome No mesosome

Department of Basic Science

College of Dentistry
University of Mosul

Department of Basic Science

College of Dentistry
University of Mosul
The basic groups are :
Spherical = Cocci
Rods = Bacilli
Spirochaetes =Helical
Note : Some bacteria with a
variable shapes appearing
both coccal and bacillary form
called pleomorphic
Shapes of bacteria


Appendages – f lagella, pili or fimbriaeSurface layers - capsule, cell wall, cell membraneCytoplasm - nuclear material, ribosome, mesosome etc.Special structure - endospore

Department of Basic Science

College of Dentistry
University of Mosul

Size of bacteria

Department of Basic Science
College of Dentistry
University of Mosul
Bacteria which ever shape, they
may be arrange themselves according to the plane of cell division as :
Pairs ( diplococci)
Chains (streptococci)
Angled pairs ( Corynebacterium )

Arrangement

Department of Basic Science
College of Dentistry
University of Mosul

Department of Basic Science

College of Dentistry
University of Mosul
Gram stain method (First developed by (Christian Gram )
1- Gram positive blue / purple.
2-Grame negative / red.
3- Non-gram stained (Mycoplasma)
Gram stain is useful both for :
Identification of bacteria
In the therapy of bacteria infection because in general gram + bacteria are more susceptible to penicillin than gram negative bacteria
Classification according to staining

Department of Basic Science

College of Dentistry
University of Mosul

Cell membrane in all bacteria is surrounded by rigid cell wall except in one group (Mcyoplasma ) wall less bacteria.
1-The cell wall confers rigidity of bacteria cell.
2-Determine the shape of bacteria
3-Anchor for capsule, pili and flagella.
4-Maintian hypertonicity of bacteria protoplasm
5-Permeable to substance of low molecular weight.
Cell wall

Department of Basic Science

College of Dentistry
University of Mosul

The basic unit is peptidoglycan.

P. G . also called mucopeptide or murein P.G. composed of peptide and glycan (which is sugar ).
P. G. consist of repeating:

Subunit 1 (N-acetyle glucose amine)
Subunit 2 (N-acetyle muramic acid)

Each raw (liner polymer glycan) joined together with other glycan chain by tetra peptide, the tetrapeptide chain connect together by penta peptide chain.

Attached together and forms raws
Composition of cell wall

Department of Basic Science

College of Dentistry
University of Mosul

Department of Basic Science

College of Dentistry
University of Mosul

Department of Basic Science

College of Dentistry
University of Mosul

Department of Basic Science

College of Dentistry
University of Mosul

G + cell wall G – cell wall (Chemically & morphology are more complex*Thick peptidoglycan layer *Contain one layer of (15-20) layers peptidoglycan *Contain Teichoic acid * Contain (outer memberane) which Composed of: 1- 30% Lipopoly saccharides Lipid A Poly sacchrides Component of endotoxin which responsible Antigen of organisms which for clinical feature of disease like fever, surface AgShock. somatic Ag

Department of Basic Science

College of Dentistry
University of Mosul

2- 45-50% Lipoprotein 3- 20—25% Phospholipid*0.2% or less of lipid * Rich in Lipids (20%)* High amount of a. a. * Low amount of a.a.*Contain lipoteichoic acid * contain L.P.SNotes: Cell wall of M. tuberculosis contain lipid called (Mycolicacids) * Peri Plasmic space: space between cytoplasmic membrane and outer *membrane in this space some bacteria produce enzyme example lactamase which destroy drugs such as penicillin G+bacteria secrete B lactamase extracellularly,while G- bacteria have the enzyme in the peri plasmic place.
**Teichoic acids are polymers of ribitol phosphate & glycerol phosphate and are associated with cell wall and cell membrane of bacteria.

Department of Basic Science

College of Dentistry
University of Mosul

Gram positive bacterial cell wall

Thick peptidoglycan layer
pentaglycin cross linkage.
Teichoic acid: ribitol TA & glycerol TA
Some have peptioglycan teichoic acid.
All have lipoteichoic acid.

Function of TA:

* Antigenic determinant
* Participate in the supply of Mg to the cell by binding Mg++
* regulate normal cell division.

Department of Basic Science

College of Dentistry
University of Mosul

Lies just inside the peptidoglycan layer of cell wall and is composed of phospholipids bilayer similar in appearance to that of eukaryotic cells , however ,eukaryotes membranes contain sterols, whereas prokaryotes genera
lly do not not.
Functions:
1-Active transport of molecules in to the cell .
2-Passive diffusion of other nutrients through the semi permeable membrane.
3-Energy generation by oxidative phosphorylation .
4-Secretion of enzymes and toxins .
5-Synthesis of cell wall precursors
Cytoplasmic membrane :

Department of Basic Science

College of Dentistry
University of Mosul

Mesosome:

This is a convoluted invagination of the cytoplasmic
Membrane:
1-Origin of the transverse septum that divides the cell
During cell division .
2-Its also the binding site of DNA which will become
The genetic of each daughter cell.
Note:
Bacterial DNA is a single supercoied, circular chromosome ,that contains about 2000 genes .

Department of Basic Science

College of Dentistry
University of Mosul

Gelatinous material surrounds the bacterium ,composed of polysaccharide (e,g.Str.pneumoniae ) and sometimes protein(e.g. Bacillus anthracis ) the sugar components of polysaccharide vary in different bacteria species (used to determine the serological type within the species )e.g.Streptococcus pneumoniae can be distinguished by the antigenic differences of the sugars in the polysaccharide capsule.
Capsule is important because :
1-It mediate the adhesion of bacteria to human tissues.
2-It inhibits phagocytosis .
3- It help in laboratory of identification of organisms.
4- It protect bacteria from environmental condition .
5-Its polysaccharides are used as antigens in certain vaccines,because they elicit protective antibodies (e.g.Str.pneumoniae ).

Capsule :

Department of Basic Science
College of Dentistry
University of Mosul

Are whip like filaments contain of protein flagellin.

Flagella composed of many subunits
Classification of bacteria according to flagella location:
*Monotrichous (one flagella at one end)e.gPseudomonas aeruginosa.
*lophotrichous(many flagella at one end)e.g.P.fluorescens ..
*Amphitrichous(flagella at both poles ,either single or cluster e.g. spirillum serpens .
*Peritrichous(many flagella around cell.)e.g.Salmonella typhi.
NOT: many bacilli have flagella but most cocci do not,they are therefore non motile
NOT. The hook and basal body of flagella attached it to the cell.
Flagella:

Department of Basic Science

College of Dentistry
University of Mosul

Flagella consist of 3 parts: Hook ,filament and basal body.

The central rod of basal body connect the disks.
The disks of basal body insert in the cytoplasmic membrane and outer membrane of bacteria.

Department of Basic Science

College of Dentistry
University of Mosul

Department of Basic Science

College of Dentistry
University of Mosul

Are fine hair like filaments found mainly in G- bacteria,

originate frome the cytoplasmic memb.
Difference between pili and flagella.
*Pili is shorter and thiner than flagella.
*Lenghth of flagella is more than pili.
*Pili is arranged (Peritrichously).
*Pili consist of protein called pillin.
*Pili is examined by E. M., While flagella by L.M.
NOT.There are several type of pili and all types may present in one organism.
Function of pili :
Help in adhesion of bacteria to receptor of human cell surface,for initiate of infection.
Help in attachment between cell to cell.
Sex pilus ,help in reproduction
Pili and fimbriae:

Department of Basic Science

College of Dentistry
University of Mosul

Department of Basic Science

College of Dentistry
University of Mosul

Its polysaccharide coating that covers the outer surface of many bacteria (capsulated bacteria and non capsulated bacteria) and allow the bacteria to adhere to various structures e.g.Oral mucosa,teeth ,heart valves.
NOT:Streptococcus mutans( amajor cariogenic organism adhere to enamel and have no pili )
Glycocalyx(Slime layer)

Department of Basic Science

College of Dentistry
University of Mosul

Usually produced by:

Bacillus(obligate aerobic gram +ve genus)
Clostridium(obligate anaerobic gram + ve genus
These bacteria form spores whene nutrients such as C,N
are scarce.
Contents of spores of bacteria:
DNA
Small amount of cytoplasm
Cell memb.P.G.
Little of water.
Thick keratin like coat which contain high con. of Ca++ dipicolonate and small amount of enzymes.
The impermeability of this layer give the spores their resistance to antibacterial ,chemical agents ,radiation ,Heat&dehydration.
Bacterial spores :

Department of Basic Science

College of Dentistry
University of Mosul

1-Low of metabolic activity.
2-Low of enzymic activity.
3-Low of water.
4-High amount of Ca dipicolonate(5-15)%of spore dry weight.
NOT:
The spore is resistant to staining due to no passive diffusion.
There is only one endospore for each bacteria cells.
Resistance of spore due to:

Department of Basic Science

College of Dentistry
University of Mosul

Department of Basic Science

College of Dentistry
University of Mosul

Department of Basic Science

College of Dentistry
University of Mosul

Bacteria can be classifieds according to a –Phenotypic feature b- Genotypic feature*Morphology (shape of bacteria) Cocci,bacilli,spirochaetes.*Staining properties:Gram positive bacteriaGram negative bacteria*Gultural requirements: Aerobic facultative anaerobic ,anaerobic*Biochemical reactions: saccharolytic and asaccharolytic *Antigenic structure ( Serotypes). Taxonomy :

Department of Basic Science

College of Dentistry
University of Mosul

Cocci
Staphylococcus
Aerobes
Clusters
Chain pairs
Anaerobes
Staph aureus
Streptococcus
S. penumoniae
S.viridans
S. pyogenes
Chains pairs
Pepto streptococcus
Ex. P. anaerobius

Department of Basic Science

College of Dentistry
University of Mosul

How do organisms get their name

Organisms are named according to hierarchical system, beginning with Taxonemic rank kingdom followed by division, subdivision, order, family genus and species.

Department of Basic Science

College of Dentistry
University of Mosul

Taxobomic rank Example

Kindom Procaryotae
Division Firmcutes
Subdivision Low GC content of DNA
Order
Family Streptococaceae
Genus Streptococcus
Species Str. salivarius

Department of Basic Science

College of Dentistry
University of Mosul
Genotypic classification of organisms becoming increasingly important and useful.
These methods essentially evaluate the degree of DNA homology of organisms in order to speciate them,for example by assessing molecular
Guanine and Cytocine content.

Department of Basic Science

College of Dentistry
University of Mosul

Department of Veterinary Surgery &Obstetrics

College of Veterinary Medicine
University of Mosul

Department of Veterinary Surgery &Obstetrics

College of Veterinary Medicine
University of Mosul

Department of Veterinary Surgery &Obstetrics

College of Veterinary Medicine
University of Mosul



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