A Prokaryotes What are Prokaryotes l It includes

A)- Prokaryotes

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

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

2. Domain: Bacteria occur in many shapes and sizes. Bacteria of four shapes: rodshaped, sphere-shaped, spiral-shaped, or filamentous-shaped. ﺍﻷﻬﺪﺍﺏ ﺷﺒﻪ ﻧﻮﺍﺓ ﺍﻟﺮﻳﺒﻮﺯﻭﻣﺎﺕ ﻏﺸﺎﺀ ﺑﻼﺯﻣﻰ ﺍﻟﺠﺪﺍﺭ ﺍﻟﺨﻠﻮﻯ ﺍﻟﻜﺒﺴﻮﻟﺔ ﺍﻷﺴﻮﺍﻁ

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

Shapes of Bacteria l l 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 in the form of spirilla (singular, spirillum) or vibrio (comma like). Sphere-shaped bacteria are called cocci (singular, coccus). An example of cocci is Micrococcus luteus. Cocci are single or aggregate cells in different shapes. Rod-shaped bacteria are called bacilli (singular, bacillus). An example of bacilli is Escherichia coli. Bacilli are single or aggregate cells in different shapes also.

The Gram’s stain: ﺻﺒﻐﺔ ﺟﺮﺍﻡ l l l It is a tool for identifying ﺗﻌﺮﻳﻒ bacteria, based on differences in their cell walls. A)- Gram-positive (Gram +ve) bacteria: Their cell walls have large amounts ﻛﻤﻴﺔ ﻛﺒﻴﺮﺓ of peptidoglycans that react with Gram’s stain (appear violet-stained )ﺗﺻﺒﻎ ﺑﻨﻔﺴﺠﻴﺎ.

The Gram’s stain: ﺻﺒﻐﺔ ﺟﺮﺍﻡ l B)- Gram-negative (Gram -ve) bacteria: l their cell walls have no or small amount of peptidoglycan. So, do not react or very weakly react with Gram’s stain (appear red-stained )ﺗﺼﺒﻎ ﺑﺎﻷﺤﻤﺮ

The Gram’s stain: ﺻﺒﻐﺔ ﺟﺮﺍﻡ l Gram Stain l 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. l Gram-positive bacteria have a thick layer of peptidoglycan in their cell wall, and they appear violet under a microscope after the Gram-staining procedure. l Gram-negative bacteria have a thin layer of peptidoglycan in their cell wall, and they appear reddishpink under a microscope after the Gram-staining procedure.

Gram Staining of Bacteria l Gram +ve bacteria: have Large amount of peptidoglycan that stained violet. l Gram –ve bacteria: Have small amount or no peptidoglycan stained red. l Most Gram-negative species are pathogenic ( ) ﻣﻤﺮﺿﺔ more threatening ( )ﺃﻜﺜﺮ ﺧﻄﻮﺭﺓ than gram-positive species. l Gram-negative bacteria are commonly more resistant ( )ﺃﻜﺜﺮ ﻣﻤﺎﻧﻌﺔ than gram-positive species to antibiotics ﻟﻠﻤﻀﺎﺩﺍﺕ ﺍﻟﺤﻴﻮﻳﺔ.

I - the bacterial capsule l l Many prokaryotes (bacteria) secrete a sticky protective layer called capsule outside the cell wall. Capsule has the following functions ﻭﻇﺎﺋﻒ : 1. 2. 3. 4. Adhere ﺗﺜﺒﻴﺖ bacterial cells to their substratum ﺍﻟﺴﻄﺢ. Increase bacterial resistance ﺍﻟﻤﻘﺎﻭﻣﺔ to host defenses ﻣﻨﺎﻋﺔ ﺍﻟﻌﺎﺋﻞ. Stick ( )ﺗﻠﺼﻖ bacterial cells together when live in colonies. Protect ﺗﺤﻤﻰ bacterial cell.

II - The bacterial cell wall l In all prokaryotes, the functions of the cell wall are as following: 1. maintains ﺗﺤﺎﻓﻆ the shape of the cell, 2. affords physical protection ﺗﻮﻓﺮ ﺍﻟﺤﻤﺎﻳﺔ ﺍﻟﻄﺒﻴﻌﻴﺔ 3. prevents the cell from bursting ( )ﺇﻧﻔﺠﺎﺭ in a hypotonic environment ﺍﻟﺒﻴﺌﺔ ﺫﺍﺕ ﺍﻟﺘﺮﻛﻴﺰ ﺍﻷﺴﻤﻮﺯﻯ ﺍﻟﻤﻨﺨﻔﺾ. l Most bacterial cell walls contain peptidoglycan (a polymer of modified sugars cross-linked by short polypeptides). l The walls of Archaea lack ( )ﺗـﻔـﺘـﻘـﺪ peptidoglycan.

Structural Characteristics of a Bacterial Cell

Reproduction of Bacteria ﺍﻟﺘﻜﺎﺛﺮ ﻓﻲ ﺍﻟﺒﻜﺘﺮﻳﺎ l Prokaryotes reproduce ( )ﺗـﺘـﻜﺎﺛﺮ only asexually ( )ﻻ ﺟﻨﺴﻴﺎ by binary fission ( )ﺍﻹﻧﻘﺴـﺎﻡ ﺍﻟﺜـﻨﺎﺋﻲ ﺍﻟﺒﺴﻴﻂ. l A single cell produces a colony of offspring.

Nutrition of Prokaryotes ﺍﻟﺘﻐﺬﻳﺔ ﻓﻲ ﺑﺪﺍﺋﻴﺎﺕ ﺍﻟﻨﻮﺍﺓ l 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 ( )ﻓﺕ into four categories ( )ﺃﻨﻮﺍﻉ according to how they obtain energy and carbon

Nutrition of Prokaryotes ﺍﻟﺘﻐﺬﻳﺔ ﻓﻰ ﺑﺪﺍﺋﻴﺎﺕ ﺍﻟﻨﻮﺍﺓ l Phototrophs ( )ﺿﻮﺋﻴﺔ ﺍﻟﺘﻐﺬﻳﺔ : l Chemotrophs ( )ﻛﻴﻤﻴﺎﺋﻴﺔ ﺍﻟﺘﻐﺬﻳﺔ : Organisms that obtain energy from light. Organisms that obtain energy from chemicals in their environment. l Autotrophs ( )ﺫﺍﺗﻴﺔ ﺍﻟﺘﻐﺬﻳﺔ : l Heterotrophs ( )ﻣﺘﻌﺪﺩ ﺍﻟﺘﻐﺬﻳﺔ : a carbon source. Organisms that use CO 2 as a carbon source. Organisms that use organic nutrients as

There are four major modes of nutrition v Photoautotrophs ( )ﺫﺍﺗﻴﺔ ﺍﻟﺘﻐﺬﻳﺔ ﺍﻟﻀﻮﺋﻴﺔ : use light energy as an energy source, and CO 2 as a carbon source to synthesize ( )ﺗﺨﻠﻖ organic compounds. v Chemoautotrophs ( )ﺫﺍﺗﻴﺔ ﺍﻟﺘﻐﺬﻳﺔ ﺍﻟﻜﻴﻤﻴﺎﺋﻴﺔ : use chemical inorganic substances as an energy source, and CO 2 as a carbon source. v Photoheterotrophs ( )ﻣﺘﻌﺪﺩ ﺍﻟﺘﻐﺬﻳﺔ ﺍﻟﻀﻮﺋﻴﺔ : use light as an energy source, and organic substances as carbon sources. v Chemoheterotrophs ( )ﻣﺘﻌﺪﺩ ﺍﻟﺘﻐﺬﻳﺔ ﺍﻟﻜﻴﻤﻴﺎﺋﻴﺔ : use organic substances as a source for both energy and carbon.

Prokaryotic modes of nutrition Based on Carbon source and Energy source that can be used by a prokaryotic organism to synthesize organic compounds. Prokaryotes Autotrophs CO 2 as Carbon Source Heterotrophs Organic compounds as Carbon Source Photoautotroph Chemoautotroph Photo. Heterotroph - Light as energy source - Chemicals as energy source -CO 2 as C source -Organic compounds as C source - Organic compounds as C source Chemo. Heterotroph