1. Bacteria Mrs. Dalia Kamal Eldien MSC in Microbiology Mrs. Dalia Kamal Eldien MSC in Microbiology Lecture NO: 2

2. Question for revision  Define microbiology?  Identify & define the discipline of microbiology?  Identify the biological classification of living cells?  Define microbiology?  Identify & define the discipline of microbiology?  Identify the biological classification of living cells?

3. Objectives At the end of this lecture, the student should know  Feature of bacteria  Bacterial structure  External bacterial structures

4. Bacteria Feature of bacteria  All bacteria are prokaryotic cell  Bacteria are unicellular organism  Most are saprophytic and free-living microorganisms  The unit of measurement used in bacteriology is the micron (micrometer) =one thousandth of a millimeter  Varying in size from 0.1–10 m long.  The bacteria contain both deoxyribonucleic acid (DNA) and ribonucleic acid (RNA)  Reprduce by binary fission. Mrs.:Dalia Kamal Eldien MSC in microbiology

5. Bacterial structure  Bacteria, despite their simplicity, contain a well developed cell structure which is responsible for many of their unique biological structures. Mrs.:Dalia Kamal Eldien MSC in microbiology

6. Bacteria cell anatomy  Bacteria cell structure consisting of:- a.Cell wall (except bacteria with deficient cell walls). b.Cytoplasmic membrane &Mesosomes. c.Chromosome d.Ribosome e.Cytoplasm f.External structures(depending on species) including a capsule, fimbriae (pili), flagella& spore

7. Bacterial structure

8. Cell wall  The cell wall of bacteria protects the cell from osmostic shock and physical damage. In addition, it also confers rigiditiy and shape of bacterial cells.  The bacterial cell walls all consist of peptidoglycan, also known as murein or mucopeptide, they differ in certain properties in two groups of bacteria, namely gram- negative and gram-positive.  Some bacteria lack the cell wall (Mycoplasma)

9. Cytoplasmic membrane  The cytoplasmic membrane encloses the cytoplasm.  It regulates the specific transport of substance between the cell and the environment.  The cytoplasmic membrane contains 2 main components: lipid and protein.

10. Chromosome  The chromosome in bacteria is typically a single, closed circle DNA (deoxyribonuclic acid) that is concentrated in a nucleoid region  Genetic information in bacteria is stored in the sequence of DNA in two forms, that is bacterial chromosome and plasmid (extra-chromosomal fragments).

11. Ribosome  Bacterial cells can contain thousands of ribosomes, which are the sites of protein synthesis.  Bacterial cells contain 70S ribosomes (Svedberg units)

12. Cytoplasm  Cytoplasm or protoplasm.  It is gel-like in consistency  Most of cell organelles are floating in cytoplasm  Containing the bacterial chromosome (genome), ribosomes, stored energy inclusions, plasmids, vitamins, ions, fatty acids & amino acids, ect…………

13. External structures 1-Flagella:-  A flagellum is a whip-like structure that allows a cell to move toward favorable environments.  A flagellum comprises of three parts, filament, hook and basal body.  The flagellum is attached to the cell body by hook and basal body. While the filament called an axoneme is free  Made of chains of protein (flagellin)  Cells may have one or many flagella.  Flagella are highly antigenic

14. Types of flagella arrangement in bacteria  There are basically four different types of flagella arrangements: 1. A single flagellum can extend from one end of the cell - if so, the bacterium is Monotrichous. 2. A single flagellum can extend from both ends of the cell - Amphitrichous. 3. Several flagella can extend from one end or both ends of the cell - Lophotrichous. 4. Multiple flagella may be randomly distributed over the entire bacterial cell - Peritrichous.

15. Types of flagella arrangement in bacteria

16. Identify the following types of flagella???

17. External structures 2-Fimbria (plural fimbriae)  Are short, Hair-like structures called fimbriae.  Made up of protein pilin  Arise from plasma membrane  They Enable organisms to adhere to host cells and to one another.  Specialized fimbriae named as sex pili enable genetic material to be transferred from one bacterium to another  Fimbriae are shorter and straighter or flexible than flagella and are more numerous.  Visible with the use of an electron microscope

18. Flagella& Fimbriae

19. External structures 3- Capsule  Many bacteria secrete around themselves a polysaccharide substance (or sometimes protein) which may become sufficiently thick to form a definite capsule.  Possessing a capsule usually increases the virulence of an organism.

20. Capsule under microscope

21. External structures 3-Spores:  When conditions for vegetative growth are not favorable, especially when carbon and nitrogen become unavailable, bacteria of the genera Bacillus and Clostridium are able to survive by forming resistant Endospores.  This process is known as sporulation.  Spore formation involves a change in enzyme activity and morphology.  The spore may be positioned at the end (terminal) of the bacterium or centrally (median).  It may be round, oval, or elongate.

22.  When the condition became favorable signal the process of endospore germination.  Germination of a spore results in a break in the spore wall and the outgrowing of a new vegetative cell.  The newly formed vegetative cell is capable of growth and reproduction.

23. Spore structure

24. Spore under microscope

26. Identify?