Bacterial Cell Structure Lecture 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...

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 In  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) a wet  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  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 in  Resembles eukaryotes  Found in microorganisms that grow under extreme environmental conditions ClikeSeawater 3  Bacterial Cell Structure s It Q whichoftheoptions  EUKARYOTES – is eukaryotic fungi, algae, protozoa, animal cells, and plant cells  Cells have nuclei that contains DNA and are complex  Most cells do NOT have a cell wall 4  Bacterial Cell Structure  PROKARYOTES - bacteria  Do not have a membrane-bound nucleus  DNA is a single circular chromosome  Have both cell (plasma) membrane AND cell wall. 5  Bacterial Cell Structure  Bacterial morphology  The study of the morphology of bacteria requires the use of microscopes 1(light example microscope,2phase contrast microscope, 3dark-field microscope,a fluorescence microscope and 5electron microscope).  bacteria range in size from 0.2 micrometers (m) to 1.5 micrometers.  human eye can only see objects >200 m 6  Bacterial Cell Structure  There are various shapes including  cocci,  curves,  spirals and  rods. Some bacterial shapes 7  Bacterial Cell Structure I A Arrangements Pairs: 551  diplococci im  diplobacilli Clusters: b ee  staphylococci III Chains: 1  Streptococcus i'm  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.  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 in  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+ 11  Bacterial Cell Structure  Gram Negative (G-) Cell Wall  Two layers; inner is much thinner than G+ cell walls  The outer membrane contains lipopolysaccharides (LPS). Outer wall contains several molecules like lipopolysaccharides (LPS) and Lipid A which is responsible for producing fever and shock in infections with G- bacteria 12  Bacterial Cell Structure  Gram Negative (G-) Cell Wall  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. toxin 13  Bacterial Cell Structure important 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  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” 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).  Some bacteria produce slime layers  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. 17  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) Adevice forexamining this bacteria 18  Bacterial Cell Structure 4111566  Cell Appendages  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 main caus c way 20  Bacterial Cell Structure IIIb  Cell Appendages Important forabsorption  Pili (fimbriae) – hairlike projections that aid in attachment to surfaces.  Fimbriae are virulence factors enabling bacteria 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 conjugation. 21  Bacterial Cell Structure  Nuclear material  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  Various cellular inclusions which serve as energy and 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) slat  Spores are small, metabolically dormant cells with a thick wall, formed intracellular by members of the genera own Bacillus and Clostridium. itspreseffechiffpportant  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 EH  Endospores (Spores)  Spores have important role in the epidemiology of certain human diseases such as anthrax, aww tetanus way and gasaway gangrene.  The eradication of spores is of particular importance in some processes, e.g. in the sterilization of instruments prior to surgery and in food canning for the removal of Clostridium botulinum to prevent botulism. Adevice forexamining Botoxis extracted this bacteria from 25 Bacterial Cell Structure  Microscopic Shapes  Cocci (spherical)  Bacilli o.ws (rod-shaped) as  Spirochetes (helical)  Groupings  Singly It is notimportant that we  Pairs talked aboutabove Fusiform is  Clusters to Palisading  Chains  Palisading 26  Bacterial Cell Structure  Size and length  Short  Long It is notimportant that we talked aboutabove  Filamentous  Fusiform  Curved  Pleomorphic 27  Bacterial Cell Structure  Common Bacterial Stain Reading  Gram Stain (Differential stain) – to be covered in lab The gram stain was developed in 1884 by the Danish bacteriologist Hans Gram. The Gram stain classifies bacteria into gram-positive and gram- negative. Gram stain of Staphylococcus aureus 28  Bacterial Cell Structure  Gram Stain (Differential stain) i 29  Thank you…questions 30