A)- Prokaryotes

1. A)- Prokaryotes

2. A)- Prokaryotes • It includes two Major Domains: Archaea and Bacteria • Prokaryotes are single-celled organisms that do not have a membrane-bound nucleus, and can live in nearly every environment on Earth. • Although tiny, prokaryotes differ greatly in their genetic traits, their modes of nutrition, however, their habitats are similar. • Based on genetic differences, prokaryotes are grouped in two domains: Domain Archaea and Domain Bacteria.

3. 1. Domain: Archaea Archaea are extremophiles, “مُحب للظروف القاسية” of extreme environments and can be classified into: a)- Extreme halophilesمُحب للملوحة: live in such saline places as the Great Salt Lake and the Dead Sea. Some species require an extremely saltyشديدة الملوحة environment to grow. b)- Extreme thermophilesمُحب للحرارة live in hot environments. The optimum temperatures for most thermophiles are 60 - 80°C.

4. شبه نواة الريبوزومات غشاء بلازمى الجدار الخلوى الكبسولة الأسواط 2. Domain: Bacteria Bacteria occur in many shapes and sizes. Most bacteria have one of three basic shapes: rod-shaped, sphere-shaped, or spiral-shaped.

5. Plasma membrane Cell Wall Capsule Ribosomes Nucleoid Cytoplasm (Cytosol) Prokaryotic Cell

6. Shapes of Bacteria • Bacteria occur in many shapes and sizes. Most bacteria have one of three basic shapes: rod-shaped, sphere-shaped, or spiral-shaped. • Spiral shaped bacteria are called spirilla (singular, spirillum). • Sphere-shaped bacteria are called cocci (singular, coccus). An example of cocci is Micrococcus luteus. Cocci that form chains similar to a string of beads are called streptococci. • Rod-shaped bacteria are called bacilli (singular, bacillus). An example of bacilli is Escherichia coli.

7. It is a tool for identifying تعريف specific bacteria, based on differences in their cell walls. A)- Gram-positive (Gram +ve) bacteria: Their cell walls have large amountsكمية كبيرةof peptidoglycans that react with Gram’s stain (appear violet-stained تـُصبغ بنفسجيا). The Gram’s stain: صبغة جرام

8. B)- Gram-negative(Gram -ve) bacteria: their cell walls have no or small amount of peptidoglycan. So, do not react or very weakly react withGram’s stain (do not appear stained لا تظهر الصبغة) The Gram’s stain: صبغة جرام

9. The Gram’s stain: صبغة جرام • Gram Stain • Most species of bacteria are classified into two categories based on the structure of their cell walls as determined by a technique called the Gram stain. • Gram-positive bacteria have a thick layer of peptidoglycan in their cell wall, and they appear purple under a microscope after the Gram-staining procedure. • Gram-negative bacteria have a thin layer of peptidoglycan in their cell wall, and they appear reddish-pink under a microscope after the Gram-staining procedure.

10. Gram Staining of Bacteria Gram +ve bacteria: have Large amount of peptidoglycan that stained violet (most of them are non-pathogenicغير ممرضة). Gram –ve bacteria: Have small amount or no peptidoglycan (no staining) (most of them are pathogenicممرضة). • Gram-negative species are pathogenic (ممرضة ) more threatening (أكثر خطورة) than gram-positive species. • Gram-negative bacteria are commonly more resistant (أكثر ممانعة) than gram-positive species to antibiotics للمضادات الحياتية.

11. I - the bacterial capsule • Many prokaryotes (bacteria) secrete a sticky protective layer called capsule outside the cell wall. • Capsule has the following functions وظائف: • Adhere تثبيت bacteria cells to their substratum السطح. • Increase bacterial resistance المقاومة to host defenses مناعة العائل. • Stickتلصق)) bacterial cells togetherwhen live as colonies. • Protect تحمى bacterial cell.

12. II - The bacterial cell wall • In all prokaryotes, the functions of the cell wall are as following: • maintains تحافط the shape of the cell, • affords physical protection الحماية الطبيعيةتوفر • prevents the cell from bursting (إنفجار) in a hypotonic environment البيئة ذات التركيز الأسموزي المنخفض. • Most bacterial cell walls contain peptidoglycan (a polymer of modified sugars cross-linked by short polypeptides). • The walls of Archaea lack (تـفـتـقـد) peptidoglycan.

13. Structural Characteristics of a Bacterial Cell

14. Reproduction of Bacteria التكاثر في البكتريا • Prokaryotes reproduce (تـتـكاثر) only asexually(لاجنسيا) by binary fission(الإنقسـام الثـنائي البسيط). • A single cell produce a colony of offspring.

15. Nutrition of Prokaryotes التغذية في الأحياء الدقيقة • Nutrition refers to how an organism obtains energy and a carbon source from the environment to build the organic molecules of its cells. • Prokaryotes are grouped (صُنٍفـَت)into four categories (أنواع)according to how they obtain energy and carbon

16. Nutrition of Prokaryotes التغذية فى الأحياء الدقيقة • Phototrophs(ضوئية التغذية):Organisms that obtain energy from light. • Chemotrophs(كيميائية التغذية):Organisms that obtain energy from chemicals in their environment. • Autotrophs(ذاتية التغذية):Organisms that use CO2 as a carbon source. • Heterotrophs(متعدد التغذية):Organisms that use organic nutrients as a carbon source.

17. There are four major modes of nutrition • Photoautotrophs(ذاتية التغذية الضوئية): use light energy as energy source, and CO2 as carbon source to synthesis (تخلق) organic compounds. • Chemoautotrophsذاتية التغذية الكيميائية)):usechemical inorganic substances as energy source, andCO2 as a carbon source. • Photoheterotrophs (متعدد التغذية الضوئية):use light as energy source, and organic substances as carbon source. • Chemoheterotrophs(متعدد التغذية الكيميائية): use organic substances as a source for both energy and carbon.

18. Prokaryotic modes of nutrition Organic compounds as Carbon Source CO2 as Carbon Source Based on Carbon sourceand Energy source that can be used by a prokaryote organism to synthesize organic compounds. Prokaryotes Autotrophs Heterotrophs Photo-autotroph Chemo-autotroph Photo-Heterotroph Chemo-Heterotroph - Light as energy source -CO2 as C source - Chemicals as energy source -CO2 as C source - Light as energy source -Organic compounds as C source - Chemicals as energy source - Organic compounds as C source