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Chapter 27: Bacteria and Archaea
27.1 structural and functional adaptations contribute to prokaryotic success:
In the past they used to depend on the external look to sort animals and creatures. But now
they depend on the sequence of the poly peptide RNA in the small ribosomal subunit
(sequence of nucleotide) which is called molecular systematic (comparing depending on
macro molecules ).
They used to consider the kingdom as the highest taxonomic level, but now they created a
new level, the domain. There’re only three domains:
1- Archaea: creatures used to live longtime ago, they found out that they have similar
prosperities to both eubacteria and eukarya.
2- Eubacteria: the bacteria that live nowadays.
3- Eukarya: protista, fungi, plants and animals.
Domain 1 and 2 together are called Prokaryotes
Prokaryotes divided into: 1-eubacteria
some are make aggregates : temporary or permanent (such as colony )
their size (.5-5) micrometer (in normal range but it may smaller or larger )
((eukaryotes size (10-100 micro meter ))
Their shape (figure 27.2)
‫الماده الوراثية‬
single DNA molecule (long and coiled )
single double strand
associated with few amount of protein (NOT AS A CHROMOSOME OF EUKARYOTES )
each chromosome contain single DNA with equale amount of protein_)
DNA placed cytoplasm (Nucleoli) NOT enclosed to the nuclear envelop.
cell wall
burst in hypotonic
shrink in hypertonic
-unicellular They lack any membrane bound organelles.
** DNA  transcription  mRNA ---‫تترجم االوامر‬---> Ribosomes.
 Ribosomes  not surrounded with a membrane.
 sub cellular structure NOT organelle.
Sub unit (1.RNA 2.protein)
All cells have ribosomes , enzymes / proteins but organelles X (*ER,
*mitochondria in photosynthetic bacteria (aerobic bacterial))
Cell membrane  cell wall :1.plant (cellulose)
2.funji (chitin)
3. bacteria (unique with this feature
Glycane in carbohydrate polymers of modified
Sugars crosslink by short polypeptide.
 Outside the cell wall some has capsule consisting of 1.protein
2.polysaccaride, and others have surface appendages (1.poli (long)
*bacteria motile via flagella  scattered
 size : ‫حسب النوع‬
-mycoplasma doesn’t have cell wall.
-all are surrounded by cell wall.
-cell wall functions:
1. prdeatior for the cell shape.
3.hypo x (turgid) they don’t burst.
Hypo: when solution around the cell is less than the inside.
Hyper: shrink (plasmolyze) ‫لهذا يضع على االطعمة لحفظها‬.
-gram (9th) has exper. ‫غسلها بالكحول‬
Crystal violet iodine  alcohol
(time is important here):
*purple (positive)  plasma  there is a large amount of peptidoglycane
*pink(negative) cell wall outside the plasma there is little amount of
Outside it another phospholipid bilayer protein.
 Capsules :
-out of cell wall there is capsul.
-some bacteria doesn’t have capsules.
-consist of polysaccharide , proteins or mixture of them
-steamy layer: thin where capsules are thicker and multi layer.
-whither capsules of steamy layer, their functions:
-more protection.
-enable cells to adhere to each other and to substratum above which
they are
-also because of polysaccharide , they are sticky to help adhering.
-graphreth experiment:
Back to inquiry.
H cells
R cells  heating  there is no capsule  ‫جهاز المناعة تغلب عليهم‬.
S  pathogenic  because of capsules to appear smooth  also, capsules
protect them from immune system.
On the surface there is appending.
Fimbriae  helps cells to attach each other and adhering.
- long
* ‫اسماء البكتيريا الموجودة بالكتاب قراءة لالستفادة منها في مادة‬microbiology .
.‫المهم هو التركيز على الصفات‬
- Evolution : ‫غير مهم‬
-not all bacteria have fambrae.
*another appendage longer than fambria is pili also called sex pili because they
play a role in conjugation.
-they sencer mating between 2 cells.
‫ يمسك بالخلية االخرى يسحبها لتصبح خليتين متجاورتين اما من خالله او انه يصنع ينتقل من‬--– ‫يمد ال‬
.‫خاللها من خلية لخلية اخرى‬
 Motility:
50% of bacteria are motile.
*motility by Flagilla.
Motile bacteria show directional movement (taxies) which means directional
1.toward stimuli  positive taxies.  such as nutrient and O2 which called chemo
2.away from  they show negative taxies  if there’s toxic.
*Flagella are almost the same between archea and bacteria with some difference.
-in eukaryotes and prokaryotes they show the same mechanism in movement.
-they are different in composition:
-inside having microtubules.
-they arrange (9+2 microtubules) extension with plasma membrane.
2.prokaryotic flagellum.
- there is no (9+2)
-their diameter is (
) of ekaryotic flagellum.
-there is 42 kinds of protein that makes bacterial flagellum.
-they consist of three pieces :
a.filament  consist of one kind of protein called flagellum .
b.motor  include the rod  motor consist of 36 kind of protein.
c. hook
- the motor depends on proton pumps { means features to plant cell membrane
where as bacterial cell membrane.
*Proton pumps :# they are ATP driven which means that the ATP play the main role
to do their function.
# they pump protons from cytosol to cell wall.
#they invent action potential but protons are back  when thet get back they drive
the motor  motor cycle  stimuli the rod to cycle (rod cycle)  filament cycle 
cell then move.
Internal organization:
-there’s no internal organelle such mitochondria or ER.
* but bacteria such cyano bacteria and photosynthesis bacteria needs membrane
organelle. To solve this problem  pieces of membrane are infolding inside and
specialized according to require function. For example 1. In cyano bacteria it
specialized such a thylakoid. aerobic bacteria specialized such cryste.
-No mitosis.
-No meiosis.
* there is no sexual reproduction in the same means of higher organisms.
- They reproduce by binary fission (one of asexual kinds of reproduction)
* DNA doubling.
*increases the cytoplasm size.
*longing of cell and
the cell fission to give 2 cells.
- after a period of time by this mechanism they become colony.
-genetic are identical to parent cell. ‫الخاليا الناتجه مطابقه لألصليه‬
Again there is no meiosis, mitosis, meta phase, pro phase… only binary fission.
 Three key features of bacteria:
1) Cells are very small
2) They reproduce by binary fission.
3) They have very short generation time.
E.coli  model bacteria used in the libratory because its generation time takes only
20 min ( in optimal conditions) but E.coli that lives in our intestine takes 12-24 hours
to reproduce.
Population clone ( ‫)عدد الخاليا التي تنتج‬
- If only one bacterial cell is put in optimal condition in 2 days they reproduce
and gives number of cells impossible in environment because with decreasing
number of cells they exist food resources and high.