Bacterial Cell Structure Lecture Notes PDF

Bacterial Cell Structure Dr. Nasreldin Elhadi, PhD Professor of Microbiology CLS Department, College of Applied Medical Sciences Imam Abdulrahman Bin Faisal University 1  Bacterial Cell Structure  Taxonomy  Kingdom, Division...

Bacterial Cell Structure Dr. Nasreldin Elhadi, PhD Professor of Microbiology CLS Department, College of Applied Medical Sciences Imam Abdulrahman Bin Faisal University 1  Bacterial Cell Structure  Taxonomy  Kingdom, Division, Class, Order, Family, Tribe, Genus and Species Family = has “–aceae” ending Genus = “Human last name” Species = “Human first name” When in print, genus and species are& - italicized. (Staphylococcus aureus) When written, genus and species are-underlined. (Staphylococcus aureus) -  Staphylococcus sp. is used when referring to the genus as a whole when the species is not identified.  “sp.” – singular (Staphylococcus sp.)  “spp.” – plural (Staphylococcus spp.) 2  Bacterial Cell Structure Q  Bacteria Identification: test each bacterial culture for - a variety of metabolic characteristics and compare the - results with known results. -  All organisms are either “prokaryotes”, “eukaryotes”, or “archaebacteria”  Archaebacteria &  Resembles eukaryotes -  Found in microorganisms that grow under extreme - environmental conditions - & - - 3  Bacterial Cell Structure  EUKARYOTES – Q fungi, algae,② - - ③ protozoa, animal ② -- cells, and plant cells - =  Cells have nuclei that contains &DNA - & and are complex D Most cells - - do NOT have a cell wall -- 4  Bacterial Cell Structure  PROKARYOTES - D bacteria ⑳Do not have a membrane-bound nucleus - -  DNA - - is a single circular chromosome -  Have both cell - - (plasma) ② membrane AND cell wall. - - ② 5  Bacterial Cell Structure  Bacterial morphology  The study of the morphology of bacteria requires the use of - microscopes (light > ① microscope, phase contrast microscope, thame - a dark-field microscope, fluorescence microscope and electron microscope). 3 - -  bacteria range in> - size from 0.2 micrometers (m) to O 1.5 micrometers.  human eye can only see objects& >200 m - 6  Bacterial Cell Structure  There are various shapes - including Q cocci, - ② curves, - ③ spirals and -  rods.- - Some bacterial shapes 7  bacterial shapes ↳ - Spirals rods curves cocci SpiriLLum bacillus coccus Vibrio Spirochete coccobacillus  Bacterial Cell Structure Arrangements Pairs:  diplococci  diplobacilli Clusters: T  staphylococci Chains:  Streptococcus  Streptobacilli 8  Bacterial Cell Structure Anatomy of a bacterial cell 9 Bacterial Cell Structure Cell wall:  Bacteria maintain their shape by a strong rigid outer - - cover, the cell wall. - - You are here. - elgodbi  Bacteria can be divided broadly into two main groups according to their - => Gram stain reaction which reflect - - the structure of their cell walls.  Some bacteria stain Gram - positive (purple), whereas other gram - & negative (red). 10  Bacterial Cell Structure  Gram Positive (G+) Cell Wall Very thick protective peptidoglycan layer -  Many& --- - G+ antibiotics act by preventing synthesis of peptidoclycan  Consists of cross-linked chains of glycan =  Also contain teichoic acid and liptoeichoic acid Unique structure makes these bacteria G+  - S 11  Bacterial Cell Structure  Gram Negative (G-) Cell Wall  Two layers; inner is much thinner than 0 - G+ cell walls  The outer membrane contains - - lipopolysaccharides (LPS). Outer wall contains several molecules & ② like lipopolysaccharides (LPS) and- ⑳ Lipid A which is responsible for producing &fever and - shock in infections with & G- bacteria - > - 12  Bacterial Cell Structure  Gram Negative (G-) Cell Wall 0  Lipopolysaccharides (LPS) are a characteristic feature of gram negative bacteria and are also termed endotoxins. -  Endotoxins are involved in the pathogenesis of gram negative bacteria infections. 13  & Bacterial Cell Structure compare Comparison between G+ and G- cell wall G+ cell wall G- cell wall  Very thick peptidoglycan layer Very thin peptidoglycan  Contain Teichoic acids and No teichoic acids liptoeichoic Outer wall contains several  In acid-fast cells, contains mycolic molecules, including acid Lipid A which is responsible for  Many G+ antibiotics act by producing fever and shock in preventing synthesis of infections with G- bacteria peptidoclycan  Unique structure makes these bacteria G+ Bacterial Cell Walls 14  Bacterial Cell Structure  G+ cocci in clusters→  G- bacilli (rods)→ 15  * Bacterial Cell Structure  Acid Fast Cell Wall – mainly Mycobacteria and Nocardia ·i 100  Have a G+ cell wall structure but also a waxy layer of glycolipids and fatty acids (mycolic acid) -  Waxy layer makes them difficult to gram stain  Can be decolorized - by acid-alcohol, hence the name “acid fast” Tl'dI ' ; 16  Bacterial Cell Structure  Absence of Cell Wall – mainly Mycoplasma and Ureaplasma  Lack of cell wall > - results in a variety of shapes microscopically.  (They may be spherical or disc like). don't have - a specific share  Some bacteria produce slime layers a Slime layer is a lose gelatinous sheath usually deposited around the bacterial cell wall.  It is usually composed of polysaccharides.  In some bacteria, the slime layer becomes thick due to the - =presence of some nitrogen compounds and forms a capsule. ② 17  D Bacterial Cell Structure  Some bacteria produce a capsule caps  In most bacterial species it is made up of a complex polysaccaharide - -  Protect the bacteria from phagocytosis > - -- capsule  Capsule usually does not stain, cell but can appear as a clear area (halo-like) ⑳ 18  Bacterial Cell Structure  Cell Appendages ①  Flagella – exterior protein filaments that &rotate - - and cause bacteria to be motile. - & -  There are four types of arrangement of flagella:  Monotrichous: These organisms have a single - polar flagellum. -  Lophotrichous: they have a multiple flagella at - one pole. -  Amphitrichous: The have single polar flagella or - - multiple of flagella at both poles.  Peritrichous: Flagella are distributed all round the cell. - -  A large number of bacteria including a few coccal forms, about one half of bacilli and almost all of the spirilla and vibrios are motile by means of flagella. 19  Bacterial Cell Structure  Cell Appendages  Flagella 20  Bacterial Cell Structure  Cell Appendages  Pili (fimbriae) –& hairlike projections that aid in - attachment to surfaces.  Fimbriae are virulence factors enabling bacteria - 51 to adhere to = various mammalian cell surfaces, an important initial step to - - colonization of -mucosal surfaces, e.g. Nisseria gonorrhoeae produce fimbriae that bind to specific - receptors of cervical epithelial cells. - -  Fimbriae or pili are involved in genetic -- material (DNA) transfer between bacteria, a process called - G conjugation. - 21  Bacterial Cell Structure  Nuclear material On  Single circular molecule of double stranded DNA. >  Smaller extra-chromosomal DNA molecules called& plasmids, that can - replicate independently, may also - be present.  Plasmids control important phenotypic properties of - pathogenic bacteria, including - antibiotic resistance and toxin production. - -  Ribosomes: The cytoplasm has many ribosomes which contain & RNA - + and proteins, and are involved in protein synthesis. - = 22  Bacterial Cell Structure  Cytoplasmic inclusion - - and  Various cellular inclusions which serve as energy nutrient reserves may be present in the - & cytoplasm. - -  Inclusions can be => organic (glycogen) or - inorganic - (Sulfur, polyphosphate). - --  The size of these inclusions can increase in a --favourable environment and decrease when conditions are adverse, e.g. Corynebacterium diphtheriae may contain high energy phosphate reserves inclusions. - - ---- 23  Bacterial Cell Structure  Endospores (Spores) &  Spores are ⑳ small, metabolically dormant ⑳ cells with a thick wall, formed - intracellular by members of the genera = Bacillus and Clostridium. - -  Spores are highly resistant to adverse - environmental conditions- and may - survive desiccation, disinfectants, or - boiling water for several hours. - - -  Spores can remain dormant for long periods, and they are able to germinate/) in response to certain conditions such as - > - the presence of specific sugars. - 24  Bacterial Cell Structure  Endospores (Spores)  Spores have important role in the epidemiology of certain human diseases such as anthrax,Q 1. tetanus and gas gangrene. ⑤ S - & -----  The eradication of spores is of particular importance in some - processes, e.g. in the -YI9 sterilization of instruments prior - to surgery and in food canning for the removal of - Clostridium botulinum to prevent botulism. ↓ E & it using find 95 to endospore 3 the 25 Bacterial Cell Structure  Microscopic Shapes  Cocci (spherical) isS /as  Bacilli (rod-shaped) -  Spirochetes (helical) 5 d  Groupings  Singly  Pairs Fusiform  Clusters Palisading  Chains  Palisading 26  not important Bacterial Cell Structure  Size and length  Short  Long  Filamentous  Fusiform  Curved  Pleomorphic 27  Bacterial Cell Structure  Common Bacterial Stain  Gram Stain (Differential stain) – to be covered in lab The gram stain was developed in - 1884 by the Danish bacteriologist & Hans Gram. Q ② The Gram stain classifies bacteria into# gram-positive and gram- negative. - & Gram stain of Staphylococcus aureus 28  Bacterial Cell Structure  Gram Stain (Differential stain) 29  Thank you…questions 30  Thank you…questions 30