A)- ProkaryotesA)- Prokaryotes

A)- ProkaryotesA)- Prokaryotes

It includes two Major Domains: It includes two Major Domains: ArchaeaArchaea and and BacteriaBacteria

Prokaryotes are single-celled organisms that do not Prokaryotes are single-celled organisms that do not have a membrane-bound nucleus, and can live in have a membrane-bound nucleus, and can live in nearly every environment on Earth.nearly every environment on Earth.

Although tiny, prokaryotes differ greatly in their genetic Although tiny, prokaryotes differ greatly in their genetic traits, their modes of nutritiontraits, their modes of nutrition, however,, however, their habitats their habitats are similar.are similar.

Based on genetic differences, prokaryotes are Based on genetic differences, prokaryotes are grouped in two domains: grouped in two domains: Domain Archaea and Domain Archaea and Domain Bacteria.Domain Bacteria.

1. Domain: 1. Domain: ArchaeaArchaea

Archaea are extremophiles, “ ُم�حبالقاسية of extreme ”للظروف

environments and can be classified can be classified into:into:

a)- a)- Extreme halophilesExtreme halophiles للملوحة للملوحة ُم�حب :: ُم�حب live in such saline places as the Great live in such saline places as the Great

Salt Lake and the Dead Sea.Salt Lake and the Dead Sea.

Some species require an extremely Some species require an extremely saltysalty الملوحة الملوحة شديدة environment to environment to شديدةgrow.grow.

b)- b)- Extreme thermophilesExtreme thermophiles للحرارة للحرارة ُم�حب live live ُم�حبin hot environments.in hot environments.

The optimum temperatures for most The optimum temperatures for most thermophiles are 60 - 80thermophiles are 60 - 80°°C. C.

بالزمى بالزمى غشاء غشاء

الخلوى الخلوى الجدار الجدار

شبه شبه نواةنواةالريبوزوماتالريبوزومات

الكبسالكبساألسوااألسواولةولة

طط

Bacteria occur in many shapes and sizes. Most bacteria have one of Bacteria occur in many shapes and sizes. Most bacteria have one of three basic shapes: three basic shapes: rod-shaped, sphere-shaped, or spiral-shapedrod-shaped, sphere-shaped, or spiral-shaped..

2. Domain: Bacteria2. Domain: Bacteria

Prokaryotic CellProkaryotic Cell

CapsuleCapsuleCell WallCell WallPlasma Plasma membranemembrane

Cytoplasm Cytoplasm ((CytosolCytosol))

NucleoidNucleoidRibosomesRibosomes

Bacteria occur in many shapes and sizes. Most bacteria have one of Bacteria occur in many shapes and sizes. Most bacteria have one of three basic shapes: three basic shapes: rod-shaped, sphere-shaped, or spiral-shapedrod-shaped, sphere-shaped, or spiral-shaped..

SpiralSpiral shaped shaped bacteria are called bacteria are called spirillaspirilla (singular, spirillum). (singular, spirillum).

SphereSphere-shaped-shaped bacteria are called bacteria are called coccicocci (singular, coccus). An (singular, coccus). An example of cocci is example of cocci is Micrococcus luteusMicrococcus luteus. . CocciCocci that form chains similar that form chains similar to a string of beads are called to a string of beads are called streptococcistreptococci..

RodRod-shaped-shaped bacteria are called bacteria are called bacillibacilli (singular, bacillus). An example (singular, bacillus). An example of bacilli is of bacilli is Escherichia coliEscherichia coli..

Shapes of BacteriaShapes of Bacteria

It is a tool for identifying تعريف specific bacteria, based on differences in their cell walls.

A)- Gram-positive (A)- Gram-positive (Gram +veGram +ve) bacteria:) bacteria:

Their cell walls have large amounts كبيرة of peptidoglycans كميةthat react with Gram’s stain (appear violet-violet-stained بنفسجيا بنفسجيا تُـصبغ .(تُـصبغ

The Gram’s stain: The Gram’s stain: صبغة صبغةجرامجرام

B)- Gram-negativeB)- Gram-negative (Gram -ve) bacteria:

their cell walls have no or small amount of peptidoglycan. So, do not react or very weakly react with Gram’s stain (do not appear stained الصبغة ال الصبغة تظهر تظهر )

The Gram’s stain: The Gram’s stain: صبغة صبغةجرامجرام

Gram StainGram Stain

Most species of bacteria are classified into two Most species of bacteria are classified into two categories based on the structure of their cell walls as categories based on the structure of their cell walls as determined by a technique called the determined by a technique called the Gram stainGram stain..

1.1. Gram-positive bacteriaGram-positive bacteria have a thick layer of have a thick layer of

peptidoglycan in their cell wall, and they appear purple peptidoglycan in their cell wall, and they appear purple under a microscope after the Gram-staining procedure.under a microscope after the Gram-staining procedure.

2.2. Gram-negative bacteriaGram-negative bacteria have a thin layer of have a thin layer of peptidoglycan in their cell wall, and they appear reddish-peptidoglycan in their cell wall, and they appear reddish-pink under a microscope after the Gram-staining pink under a microscope after the Gram-staining procedure. procedure.

The Gram’s stain: The Gram’s stain: صبغة صبغةجرامجرام

Gram Staining of BacteriaGram Staining of Bacteria

Gram +ve bacteria:Gram +ve bacteria: have Large amount of peptidoglycan have Large amount of peptidoglycan that stained that stained violet violet ((most of them are most of them are non-pathogenicnon-pathogenic ممرضة ممرضة غير ..((غير

Gram –ve bacteria:Gram –ve bacteria: Have small amount or no peptidoglycan Have small amount or no peptidoglycan (no staining) ((no staining) (most of them are most of them are pathogenicpathogenic ممرضةممرضة).).

Gram-negative species are pathogenic (Gram-negative species are pathogenic (ُممرضةُممرضة ) more threatening ) more threatening (( خطورة خطورة أكثر .than gram-positive species. than gram-positive species ((أكثر

Gram-negative bacteria are commonly more resistant (Gram-negative bacteria are commonly more resistant ( ُممانعة ُممانعة أكثر ( (أكثرthan gram-positive species to antibiotics than gram-positive species to antibiotics الحياتية الحياتية للمضادات ..للمضادات

Many prokaryotes (bacteria) Many prokaryotes (bacteria) secrete a sticky secrete a sticky protective layer called protective layer called capsulecapsule outside outside the cell wall. the cell wall.

CapsuleCapsule has the has the following functions following functions وظائفوظائف::

Adhere Adhere تثبيت bacteria cells to their substratum bacteria cells to their substratum السطح.. Increase bacteria resistance Increase bacteria resistance المقاومة to host defenses to host defenses مناعة

..العائل StickStickتلصقتلصق)) ) ) bacterial bacterial cells cells togethertogether when live as colonies.when live as colonies. Protect Protect تحمى bacterial cell.bacterial cell.

I - the bacterial capsuleI - the bacterial capsule

In all prokaryotes, the functions of the cell wall are as

following:

1. maintains تحافطتحافط the shape of the cell,

2. affords physical protection الطبيعية الطبيعية الحماية توفرتوفر الحماية

3. prevents the cell from bursting ((إنفجارإنفجار) ) in a

hypotonic environment ذات ذات البيئة يياألسموز األسموز التركيزالتركيزالبيئة

.المنخفضالمنخفض

Most bacterial cell walls contain peptidoglycanpeptidoglycan

(a polymer of modified sugars cross-linked by short

polypeptides).

The walls of Archaea lack ((تـفـتـقـدتـفـتـقـد) ) peptidoglycan.

II - The bacterial cell wallII - The bacterial cell wall

Structural Characteristics of a Bacterial CellStructural Characteristics of a Bacterial Cell

Prokaryotes reproduce (تـتـكاثر) only asexually (ال ) by binary fission (جنسيا الثـنائ البسيط ياإلنقسـام ).

A single cell produce a colony of offspring.

Reproduction of Bacteria Reproduction of Bacteria ف ف التكاثر البكتريا البكتريا ييالتكاثر

Nutrition of Prokaryotes Nutrition of Prokaryotes األحياء الدقيقةيالتغذية ف

• Prokaryotes are grouped Prokaryotes are grouped (فَـت; into four into four (ُص�ن

categories categories (أنواع) according to how they according to how they

obtain energy and carbonobtain energy and carbon

Nutrition refers to how an organism obtains energy and a carbon source from the environment to build the organic molecules of its cells.

PhototrophsPhototrophs ( التغذية التغذية ضوئية Organisms that obtain energy from :(ضوئية

light.

ChemotrophsChemotrophs ( التغذية التغذية كيميائية Organisms that obtain energy :(كيميائية

from chemicals in their environment.

AutotrophsAutotrophs ( التغذية التغذية ذاتية Organisms that use CO2 as a carbon :(ذاتية

source.

HeterotrophsHeterotrophs ( التغذية التغذية متعدد Organisms that use organic :(متعدد

nutrients as a carbon source.

Nutrition of Prokaryotes Nutrition of Prokaryotes التغذية فى األحياء الدقيقة

PhotoautotrophsPhotoautotrophs ( الضوئية التغذية :(ذاتية use light energylight energy as energy source, and COCO2 2 as carbon source to synthesis (تخلق) organic compounds.

ChemoautotrophsChemoautotrophs الكيميائية التغذية :((ذاتية use chemical inorganic substancesinorganic substances as energy source, and COCO22 as a carbon source.

PhotoheterotrophsPhotoheterotrophs ( الضوئية التغذية :(ُمتعدد use use lightlight as energy source, and organic substancesorganic substances as carbon source.

ChemoheterotrophsChemoheterotrophs ( الكيميائية التغذية :(ُمتعدد use organic substancesorganic substances as a source for both energy and carbon.

There are four major modes of nutritionThere are four major modes of nutrition

Prokaryotic modes of nutritionProkaryotic modes of nutrition

Based on Based on Carbon sourceCarbon source and and Energy sourceEnergy source that can be used that can be used by a prokaryote organism to synthesize organic compounds. by a prokaryote organism to synthesize organic compounds.

AutotrophsAutotrophs HeterotrophsHeterotrophs

Photo-Photo-autotrophautotroph

Chemo-Chemo-autotrophautotroph

Chemo-Chemo-HeterotrophHeterotroph

Photo-Photo-HeterotrophHeterotroph

COCO22 as Carbon Source as Carbon SourceOrganic compounds as Organic compounds as

Carbon SourceCarbon Source

- Light as energy source

-CO2 as C source

- Light as energy source

-CO2 as C source

- Chemicals as energy source

-CO2 as C source

- Chemicals as energy source

-CO2 as C source

- Light as energy source

-Organic compounds as C source

- Light as energy source

-Organic compounds as C source

- Chemicals as energy source

- Organic compounds as C source

- Chemicals as energy source

- Organic compounds as C source

ProkaryotesProkaryotes