Microbiology Lecture 1 PDF

Bacterial structure Microbiology and immunology department Faculty of medicine PLOs: -1Identify the main differences between prokaryotes and eukaryotes. -2Recognize different components of the bacterial cell. -3Outline the functions for each component of the bacterial cell....

Bacterial structure Microbiology and immunology department Faculty of medicine PLOs: -1Identify the main differences between prokaryotes and eukaryotes. -2Recognize different components of the bacterial cell. -3Outline the functions for each component of the bacterial cell. -4Define bacterial endospores and recognize their medical importance. 5-Describe different shapes and arrangements of bacterial cells.  Microbiology and Immunology Microbiology Study of organisms too small to be seen with the naked eye. These organisms include viruses, bacteria, fungi, and protozoa.  Microbiology The science that deals with microorganisms as: Bacteria- Virus- fungi -1Bacteriology = Study-bacteria General bacteriology Systemic bacteriology -2Virology = study virus General Virology Systemic Virology 3-Mycology (fungi) = study fungi Microorganisms Non-cellular organism Virus Prokaryotes Bacterium Eukaryotes Fungi  Differences between Prokaryotes and Eukaryotes Prokaryotes Eukaryotes MEx. bacteria Fungi- animal-human Ccell wall Present =yes Absent =no peptidoglycan  Differences between Prokaryotes and Eukaryotes Characteristic Prokaryotic cells Eukaryotic cells Chromosome number One Multiple Nuclear membrane & nucleoli No Yes Method of replication Binary fission Mitotic division Size of ribosomes 70S 80S mitochondria) No Yes Cell wall peptidoglycan Yes No  True or False 1- Peptidoglycans are important component in cell walls of Fungi CHAPTER-1: Bacterial Cell Structure  Microscopic Identification of bacteria by Microscope after staining by: 1 Simple stain 2 Gram stain Generally, All Bacteria classified according to Gram stain into Gram positive Or Gram Negative bacteria and we always mention Gram reaction If Gram positive bacteria →bacteria appear violet under microscope If Gram negative bacteria →bacteria appear pink under microscope 3 Ziehl Nilsen stain as in Mycobacteria So Bacteria classified according to Gram stain into: Gram positive cocci or Gram positive bacilli or Gram Negative cocci or Gram Negative bacilli Gm +ve cocci & Gm -ve bacilli Size , shape and arrangement of bacteria Size of bacteria 8 - 0.2 →um Shape of bacteria →maintained by cell wall and its either Cocci -Bacilli –Spirals-comma Arrangement of bacteria determined by plane of dividion →cocci in pairs as in pneumococci →cocci in Chains as in streptcocci → cocci in Grape like as in staphylococci Structure of bacteria Bacterial cell structure from outside to inside 1. Flagella 2. Pili 3. Capsule 4. Cell wall 5. Cell membrane 6. Single DNA 7. Plasmid-transposon 8-Ribosomes 8. food Granules 9. Spore if present  Structure of Bacterial cell Essential structures Non-essential structures Cell wall Capsule-Glycocalyx Cytoplasmic membrane Flagella DNA single chromosome Pili/fimbriae Ribosomes= (70S) → Plasmid function for protein Food granules Spores Structure of Bacterial cell in relation to cell wall outside cell wall Inside cell wall -1Capsule-Glycocalyx -1Cytoplasmic membrane -2Flagella -2single circular chromosome -3Pili -3Ribosomes(70S) → -4Plasmid (if present) -5Spore -6Inclusion body 1- Which of the following bacterial structures is responsible for protein synthesis? A. pilli B. ribosomes C. cell wall D. cytoplasmic membrane Structure outside cell wall  -1Capsule –Glycocalyx a. It is layer outside cell wall in some bacteria formed of Polysaccharide except in Anthrax bacillus polypeptide b. virulence factor → protect from phagocytosis- as it mask sites for attachment of macrophages  Capsules are not stained by Gram stain (appear as unstained halos around the organism)  True or False 1- Capsules are essential bacterial structure 2- Bacterial capsule protects it from phagocytosis  --2Flagella organ of motility composed of protein flagellin  -3Pili/fimbriae. -1Ordinary pili= Colonization antigens mediate adherence of bacteria to receptors on human cell surface -2Sex pili attach male to female during gene transfer Structure Inside cell wall  -1DNA single chromosome single circular chromosome with no nuclear membrane  -2Ribosomes 70(S) function for protein syntheses with 30s and 50S subunit -differ from eukaryotes  -3-Plasmid extrachromosomal circular DNA  -4Bacterial cytoplasmic membrane  Bilayer- semi- permeable structure → control transport of ions from in to outside cell  Think pair share True or False\MCQ - Cytoplasmic membranes are essential bacterial structure - Bacterial flagella is responsible for 1. Motility 2. colonization 3. Protein synthesis 4. Osmotic protection Bacterial Cell wall Cell wall of Gram positive Cell wall of Gram negative -1Peptidoglycan layer -1Peptidoglycan layer ( protein + sugar) ( protein + sugar) Peptidoglycan 50% of cell Peptidoglycan 5-10% of cell wall 2( wall (40 layers) layers) -2Teichoic acid -2Lipoprotein -3Outer membrane bilayer structure contain multiple channel called porins for diffusion of nutrients -4Lipopolysaccharide (LPS) the outer part (LPS= endotoxin) outside outer membrane -5Periplasmic space between cell membrane and outer membrane and filled enzymes as B- lactamase that destroy drugs as penicillin Outer membrane  What is Peptidoglycan layer -1Peptidoglycan layer which is multilayer and each layer is formed of Connected chains of identical Peptidoglycan monomer= disaccharide units + Tetra-peptide chain = 4 amino acids Chemical structure of peptidoglycan  Cell wall functions: 1. Maintains bacterial shape. 2. Classify bacteria to Gram positive and negative according to Gram stain. 3. Peptidoglycan is present only in bacteria so that it’s the target site of anti bacterial drugs as penicillins and cephalosporins. 4. In Gram negative bacteria LPS act as Endotoxin. -natural Cell wall deficient bacteria is mycoplasma Enumerate functions of bacterial cell wall  L i p o p o l y s a c c h a r i d e O - a n t i g e n H i g h l y v a r i a b l e n C o r e H e p t o s e s K e t o d e o x y o c t o n i c a c i d L i p i d A G l u c o s a m i n e d i s a c c h a r i d e B e t a h y d r o x y f a t t y a c i d s 1 7 Lipopolysaccarides (LPS= endotoxin) outside outer membrane the outer part of gram negative wall formed of 3 part From inner to outer only released when bacteria die A-Lipid A= endotoxin Released into blood after death of bacteria causing toxic shock=septic shock or endotoxic shock B-polysaccharide core c- Somatic –o-antigen (the antigenic part of cell wall)  Bacterial Spore Definition Highly resistant resting forms of some Gram positive bacteria formed due to exposure to unfavourable conditions. Causes of spore formation depletion of nutrients – heat - dryness Example of spore forming organisms 1 aerobic genus Bacillus 2 anaerobic genus Clostridium  Clostridium species Cl. tetani Cl. perfringens Cl. botulinum Cl. difficile Medical importance Highly resistance to heat –chemicals due to 1 thick cortex 2 calcium dipicolinate in core 3 dehydrated state low metabolic activity So Sterilization of any thing from spores : Need autoclaving at 121 °C for 20-30 m  True or False Bacterial spores are essential bacterial structure Visual aids 1-Video of bacterial cell structure https://www.youtube.com/watch?v=b15Hy3jCPDs 2- Video of bacterial spore formation animation https://www.youtube.com/watch?v=NAcowliknPs