Maha Al-HussbanMicrobiology - sheet# 1Date; 16/9/2013

Microbiology: The study of organisms too small to be seen without magnification

Micro=very small ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, biology=related to living things

*things that are very small to be seen by naked eyes

*a(100) microns…. that what we can see by our naked eyes

*micron = 1/(10^6) m

In order to have an idea what the micron is ,, usually we take RBCSas a scale …which is about 7 microns in diameter

Microorganisms need a microscope to be seen except ;

√some worms( which maybe reached 10 m )

√fungi when it grow ,, to form Mycelium

√also bacteria when grow >produce collection of million of bacteria which is known as colony

*if you can't see it(the microorganism)  you should use the microscope,,either light or electron microscope

*the light microscope has a resolving power which is about 0.2 microns(compared it with the naked eye which can't see less than 100 micron as we said )

((microscope resolving power : the smallest thing that can be seen with that microscope ))

Put in your mind that's everything less than 0.2 ,,, we can't see it with the light microscope !_!

*Allkinds of bacteria can be seen with light microscope as it's typically between1-2microns (but might be more/less than 0.2)

((for torsional purposes we Supposed that all bacteria can be seen under light microscope))

Mmmm !! what's about viruses ?

Viruses almost always less than 0.2 micronsso we can't see it under light microscope we should use an electron microscope exceptthere's only one type of viruses(which's Responsible for smallpox) > it's about 0.3 micron and can be seen under light microscope

Branches of microbiology:

•Bacteriology: study of bacteria

•Mycology: study of fungi

•Parasitology: study of protozoa and parasitic worms

•Virology: study of viruses

(we will concentrate mainly on bacteriology in micro 1)

Things that we are going to deal with in the study of microbiology ara:

- chemotherapy the use of medicine &drugs in order to kill the concerned bacteria

-Immunology study of immunity

*when we talked about microbes mainly bacteria we usually take about bad things and this's not really true

Bacteria is found everywhere you go ,,,, and that doesn't mean that all of them are harmful to the human being …. In fact mostof them don't produce diseases (are really non-pathogenic) …but on other hand someof them produce diseases and called pathogenic bacteria ( the minority ) ::::: such a thing in other microbes:::::

Some benefits of microorganisms:

√Yeast (fermentation)

√bacteria that's live in the soil & they convert the organic material to inorganic material>this is useful for plants

(the doctor said that's the fungi ,,, the true is the bacteria not fungi ,,,You can check it as I done ^_^ )

√produce nitrogen from the air

√produce food(cheese production)

Classification of microorganisms

Microorganisms and all other living organisms are classified as prokaryotes or eukaryotes.

Prokaryotes: bacteria , archaebacteria

Eukaryotes: fungi , parasites ,animal &plant cells

*viruses ,prionsviroids these aren't really cells per say but these are a package of DNA or RNA … they can't metabolize & divide as the cells

Prokaryotes have a : Cell Wall (peptidoglycan) ,Teichoic Acids, LPS(lipopolysaccharide) , Endospores , Circular DNA Plasmids(extra DNA in the cytoplasm) .

Eukaryotes have a : nuclear membrane , Golgi apparatus , mitochondria ,EPR(Endoplasmic reticulum)linearDNA .

Ribosomes & plasma membrane present in both

Some of bacterial cells has the ability to produce endospores while that doesn’t happen in animal cells .

The diagram above represents the main structures that are present in prokaryote ; this is bacterium & we can see nucleoid , DNA which is circular ,the cytoplasm has inclusions , ribosomes (bacterial ribosomes differ from animal ribosomes ,, 70s in bacteria & 80s in human cells)…. In the outside there's a cytoplasmic membrane (phospholipid bilayer that carry out all function of all organelles which is absent In prokaryotic (like mitochondria , Golgi apparatus ,EPR) .

The projection or invagination here is called misosome ,some scientists say that these are only artifacts(doesn’t have specific function) that's found in dead/fixed cells ,,,not in living cells.

Plasma membrane of bacteria lacks animportant ingredient for rigidity …which is steroids(act to give rigidity & strength in animal cells ) ,,,so bacteria is weak & can't protect itself from outside conditions .

the function is done by THE CELL WLL ,, Which play the role of strength & rigidity here ,,cell wall can be either thin (2-3 layers) or thick (up to 70 layers).

Sometime in the outside of cell wall there's another layer which's known as a capsule (polysaccharide layer).

*some bacteria shows process like appendages can be big & called flagellum (for movement),,or very small &thin called fimbria or pilus (for adhesion or conjugation )

.:: we gonna talk about them later on ::.

Classification of microorganisms  look at them in microscope , stain them with various stains , and look for their morphology(the shape , # of extensions,,etc) & biochemical properties(Whether it produce acids , chemicals ,,,etc) ,, and serology (using of antibodies)  then classified them accordingly .

So classification is according to : 1- morphology 2- biochemical properties & 3- serology

which's the most common(1,2&3)

Nowadays to make a proper classifications ,, relation/connection of one bacteria to another ,,molecular methods are donewhich's the study of DNA , RNA, PCR (Polymerase Chain Reaction)  which's the most accurate(the whole molecular methods).

Genus and species:

Genus (like abig Clan) ,,,while,, the species (like a family from that clan )

As an example :Escherichia coli

Escherichia(the name of genus),,,,must start with capital letter

Coli (the name of species)

It's also can be written as(( E. coli))

As we said before ,,that almost all bacteria is bout 1-2 micron(as in spherical shape bacteria)& might be

smaller(0.2 or 0.3 )

Larger around (5,7 ,..) as in Bacillar shape bacteria ,, around (15 microns) as inSpiral shape bacteria .

Shapes of Bacteria

*Spherical (Cocci),,1-2 microns

Single  coccus

*Rod Shape (Bacilli) ,,4-5 microns

Single bacillus

*Coccobacilli

In between cocci & bacilli

*Comma shape (Vibrios)

*Spirillum

*Spirochete

*Square

*Star

According to the angle Cocci may be:

* as strips,,long chains streptococcus ,,,fig(a) (by alinear angle )

*accumulation on each other,, fig(b) (by aright angle)

2togother diplococcus*

Best wishes ^_^

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