Basic Microbiology
Micro biology: It is science dealing with the study of minute microorganism. Microbiology included bacteriology, virology, Mycology, immunology.
Bacteriology:
It is science to deal with the study of the bacteria.
Virology:
It is science to deal with the study of the virus.
Mycology:
It is science to deal with the study of fungi.
Immunology:
It is the science to deal with the resistance of the body to any foreign substance.
Parasitology – It is the science to deal with Parasites.
Bacteriology:
Bacteria: It is unicellular microorganism capable of living independently performing all the physiological function essential for life as it contains all enzymes to perform vital activity. It is prokaryotes & reproduce by binary fission what is the type of cells depends on structure:
1- Prokaryote.
2- Eukaryote.
Prokaryote cells / Eukaryote cells· Has primitive nucleus.
· Multiply by binary fission.
· Has no nuclear membrane.
· The DNA is one set of single circular chromosome of double standard DNA in the cytoplasm.
· Has no organelles .
· Include bacteria, Rickttsia, Chlamydia & Mycoplasma. / · Has true nucleus.
· Multiply by mitosis.
· Has nuclear membrane.
· Double set of chromosome inside the nuclear membrane.
· Has organelles
· Fungi & protozoa.
Morphology of bacteria
Shape arrangement size
(1) Shape :
The bacteria is characterized by different shape and size
( Pleomorphism) . So to determine the shape of bacteria must be during the lonarithmic phase of growth.
(a) Cocci :
Means coccus i e spherical or oval or avoid.
Example :
Staphylococcus bacteria .
Streptococcus bacteria.
(b) Bacilli or Bacillus :
Means stick like . it's length is more than breadth .
Example :
Bacillus bacteria.
Clostridium bacteria.
(c ) Coccobacilli :
Example
Coryne bacteria, Escherichia coli.
(d) Spiral bacteria :
The simplest form is coma shape:
Example
Vibreo cholea.
(e) Spirullum:
Non flexuous rod, spiral .
(f) Spirocheates :
Spiral but flexuous move by axial filament.
(g) long filamentous branched rod :.
Example:
Actinomycetes
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(B) Arrangement ( Cell Aggregates ) :
- When the bacteria reproduce by binary fission without separation form cell aggregates.
- The shape of cell aggregates or the arrangement depend on
o No. of division
o Plane of division.
Cocci / Diplococci / Single divistion & single plane of division e.g. Nisseria & pneumococci.Tefrad / 4 group due to double division & double plane of division . e.g. Micrococcus.
Sarcina / 8 group dut to plane & number of division. .
Streptococci
chain / Single plane of division & more than one number of division from chain OOOOO
Staphylococci / More than ome division & more than plane of division.
Bacilli / Diplobacilli : e.g. Klebsiella, B. anthacoides.
Single or separately arranged . e.g. salmonella
Streptobacilli – e.g. B. anthraces.
Chinese letter arrangement: v or L letter.
e.g. Corynebacteria diphtheriae .
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(C ) Size :
Bacteria is measured by micron.
Microne is the unite of measurement
m = 1 millimeter
1000
While nanometer ( millimicron ) = 1 m
1000
Angestron = 1 millimicron - for virus
How to measure the bacterial size ?
1- Occular and stage micrometry.
2- Electron microscope.
3-Photographic method
- Cocci is 1 m in f bacilli vary [4] to [8] m by 1 to 1.5 micron
Mesosome Nucleus
cytoplasm
Ribosomes metachromtic
Granule (volatin)
Slime layer capsule cell membrane granules or
inclusion
cell wall
The bacterial structure is classified in to :
Essential Accessory
Found in all bacteria may be found or not
- Cell wall - Capsule
- Cell membrane - Slime layer.
- Cytoplasm or protoplasm - Spores
- Nucleus of nuclear material - Flagella
( Chromatin material ) - Axial filament
- Pilli
- Metachromtic
granules.
Capsule :
Some bacteria has capsule or not ( called capsulated bacteria or not ).
· Others has capsule & slime layer while others contain capsules only.
· It is gelatinous material compose of Lipopolysaccharde or protein as in B. anthraces or glycoprotein .
· Not stained e ordinary stain or appear as halos around the organism but accept stain with capsular stain [ Indian ink ] and negative stain .
Function :
1- protection against phagocytosis (antiphagocytic function) for virulence.
2- Protection from dryness ( loss of water & nutritive substance).
3- Carry ( capsular Ag ) ( K ) .
4- Help in diagnosis because is high specific chemically & immunologically & thus allow for type differentiation as in case of Macfadean reaction – B. anthracis , quelling reaction – pneamococci .
Slime layer :
Is loose soluble layer chemical structure as capsule but the water contents is high . This colloidal substance gives surface colonies a mucoid appearance as in klebseilla.
.
Cell Wall :
Bacteria have well defined cell wall in compare with eukaryote.
· It is non living – rigid – consider as exoskeleton.
· The bacteria are classified into gram positive & gram negative bacteria . according to the structure of cell.
(1) Gram positive bacteria :
A thick layer of peptidoglycan (50-60%) of the cell wall content) + teichoic acid (acidic polysaccharide). So the bacteria accept the crystal violet not decolorize by ethyl alcohol because the stain in integrate in the cell.
(2) Gram negative bacteria :
A thin layer of peptidoglycan (5-20%) of cell wall and another membrane are made up of lipids, lipopolysaccharide (LPS) & Protein lipopolysacharide is a harmful substance classified as an endotoxin .
Gram's stain : consist of :
1- Crystal violet ( primary-1ry stain ) – gram positive take violet
2- Gram iodine(mordant).
3- Ethyl alcohol . ( decolourization )
4- Carbol fuschin ( counter stain ) – gram negative take pink color .
Function of cell wall :
1- Act as exoskeleton.
2- Determines the shape.
3- Allow the classification of bacteria into gram positive and gram negative.
4- Protection to the cell from rupture e g. due to change in pressure (rigidity).
5- Carry somatic (O Ag) which is importance in virulence.
Flagella :
Definition: whip like process, make of flagellin protein (contractile protein) resemble to myosin protein in muscle, originates from the cytoplasm.
- When it beats backward, the bacteria move forward.
- It can be seen e electron microscope.
Function:
1- It is responsible for motility.
2- It is carry H antigen.
3- I. m in identification.
Flagella are of great practical I . m to bacteriology since specific antisera can be prepared & used for serological differentiation.
Distribution and number of flagella:
Bacteria
Motility:
Non motile bacteria motile bacteria
Brownian Movement True movement
( False movement )
Method of detection of motility:
1-Dark field microscope.
2-Phase contrast microscope.
3-Wet mount method.
4-Hanging drop technique.
Pilli or fimbria:
Define: short hair – like structure arising from cytoplasm made up of protein, shorter than flagella.
- Present in some gram negative bacteria e.g. E.coli or Neisseria gonorrhoea.
Function :
a) Attachment to each other, or attachment to host cells.
b) For transfer of genetic material from one cell to another where they are able to be specialized pilli called sex pilli. (F.pilli).
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Spores ( not in all bacteria )
When conditions for vegtative growth are not favourable, bacteria of the genera Bacillus and Clostridium are able to survive by forming resistance endospore.
· These spores are able to with stand cold, heat dehydration, or the action of disinfectants . A spore is unable to multiply , but when condition for vegetative growth return , it is able to produce bacterial cell which is capable of reproducing.
· Spore is not stained e ordinary stains as it appear as halos around the organism. It take special stain called schaeffer – fulton ( malchite green ) or Dorner method.
Malchite green + heat ® the spore( green ) & the bacteria (Pink)
Also modified Ziehl – Neelsen stain in to we decolourize e 0.5% H2SO4 spore ® appear pink & the body of bacilli ® blue.
Type and position of spores :
Shape Position bulged or
Spherical central non bulged
Oval or ovoid subterminal
Terminal
e.g. clostridium tetani drumstick spore ( Spherical , terminal and projected ).
Function :
1- Protection of the bacteria from unfavorable condition.
2- I.m in identification of bacteria .
e.g. B . subtilis with stand radiation , UV light , boiling at 120ْC for 15 minute.
Formation of spore :
The cell is divided by septum into two unequal cell. The larger one is called "mother cell" and the daughter cell. And the mother cell is surrounded the spore.
Axial filament = rotates giving a twisting and flexing movement
Cell membrane :
Formation :
- It is formed due to condensation of cytoplasm toward outside.
- It is formed of a lipid bilayer with protein embedded in between.
Define :
It is semi permeable membrane found in all bacteria formed of phospholipids and protein.
Function :
1- It is the active part of bacterial cell function for prokaryotes instead of organelles in eukaryotes.
2- It is the place of metabolic & enzymatic activities e.g. respiration (transport energy e transport system ).
3- Control the entry electrolytes , water & transport of nutrients into the cell via carrier protein ( transport protein permease ) .
4- Exit of wastes out of the cell.
Mesosomes: are folding up of cell membrane into finger like protrusions or pockets that extend to cytoplasm. A place where chromosome is a attached during replication.
Cytoplasm or protoplasm :
Internal content of cell gelatin like solution made up of mainly water + nutrient ( sugar , a – a , salt ….) .
Within cytoplasm :
Chromatin (Nucleod):
Genetic material is made up of a single circular strand of DNA called the chromatin and no nuclear membrane ( no true nucleus ). The area in which DNA concentrated is called nucleoid.
Function :
Carry information for function and survival of cell.
Ribosomes :
Function : Place for protein synthesis .
Made up of 2 unit ® protein + r RNA
It give the cytoplasm of bacteria a granular appear .
Granules ( Inclusions ) :
Function : to store different types of nutrient and consume them – when nutrients are not available in the environment .
Stored nutrient as : Energy rich organic compound .
e.g. glycogen ( Stored glucose )
sulfur granules – phosphate.
Metachromatic granule ( volatin )
Found due to abnormal metabolic or it is stored nutrient. It is scattered in cytoplasm as in case of Corynbacterium diphteria or in both poles of cell ( Bipolarity) ® Pasteurella. Stained e special stain Function identification.
Main Protoplasmic compounds.
Carbohydrates / Lipids / Proteins / NucleicComposition (building block)
Rol.c in the cell / Simple sugars + amino group found as Glycogen (Stored glucose)
Cell wall synthesis
Essential energy source / Triglycerides of F.A phosphors in phospholipids
Cell membrane Energy source / a. a.
- Enzymes
- Synthesis of organelles + other cell structures / Nucleotides complex combination with protein (Nucleoproteins)
- DNA :
Code for cell function + structure
Transverse Binary Fission
a) Parental cell .
b) Cell elongation size enlarged walls chromosome.
Duplication + attached to mesosomes.
c)Cell wall septum grow inwards , chromosomes move to opposite ends. Septum formation + chromosome separate from mesosomes.
d) Two identical daughter cells.
Phases of Growth :
4 Phases :
1- Lag phase
2- Log phase .
3- Stationary phase .
4- Death phase.
1-Lag phase :
· Bacteria are first introduced into an environment or media.
· Bacteria are checking out their surrounding.
· Cell are v . active metabolically.
· No of cells changes v. little ( does not increase ).
· I hr to several days according to type of bacteria media and accommodation of the bacteria.
2- Log phase :
· Rapid cell growth ( exponential growth ) .
· Population doubles every generation.
· Microbes are sensitive to adverse condition . eg. Antibiotic & antimicrobial agents.
3- Stationary phase :
· Death rate = rate of reproduction .
· Cells begin to encounter environmental stress .
· Lack of nutrient & H2O , metabolic wastes & spore form now.
Death phase
ESSENTIAL ELEMENTS
NEEDED FOR BACTERIAL GROWTH
ELEMENTS / ROLEI ) Elements needed for synthesis of structural components.
II) Elements needed for cellular function (mineral salts )
III ) Trace elements ( needed in minute quantities.)
IV) Growth factors ( earn it be synthesized by the cell ) / C1 H2 O2
Nitrogen phosphorus.
K1 Mg1 Fe
Ca
Copper Cobalt Maganize Zn
Vitamines purine pyrimidine / Synthesis of : sugars amino acids , lipids, nucleic acid.
a.a. + nucleic acid ATP nucleic acid phospholipids.
Activation and function of certain enzymes.
Enzyme activity spore formation.
Activation of enzymes.
Precursors of nucleic acid ( DNA )
Factors affecting microbial growth :
Environmental Conditions :
1- Temperature :
Temperature affect microbial growth and structure , especially it affects enzymes. There groups of M.O according to temperature requirements.
a. Psychrophiles : - 5ْC ® 25ْC .
b. Mesophiles : between 25 ® 45ْC
c. Thermophiles between 45ْC ® 70ْ ® 110ْC
2- Gases :
a – Oxygen gas (O2)
Four groups according to O2 . requirements :
i) Strict anaerobes : O2 is toxic .
Organism die in presence of O2 . not contain catalase nor supreoxide mismutase
ii) Strict aerobes : O2 is a must if O2 is absent organisms die20%, contain catalase.
iii) Facultative anaerobes: Can live in the presence or absence of O2 .contain catalase & superoxide dismutase.
iv) Microaerophilic: Require little amounts of O2 to grow (2-10%) contain superoxide dismutase.
b- Carbon dioxide gas : CO2 All bacteria need little amounts of CO2 to grow . Bacteria produce the CO2 as end product of metabolisms ( carboxyphilic organism can live in presence of carbon dioxide ) .
3- Hydrogen Ion concentration ( pH) :
pH affects the reproduction of M.O majority lives at neutral pH=7 neutrophiles .