Presentation on theme: "Unit:01 Introduction To Microbiology Instructor:Shagufta Iqbal January,2018."— Presentation transcript:
Unit:01 Introduction To Microbiology Instructor:Shagufta Iqbal January,2018
1.Components present External To Cell Wall: Capsule Flagella Pili and Fimbriae 2.Cell Wall 3.Components present internal to cell wall: CytoplasmicMembeane Bacterial Nucleus Plasmid Ribosomes Inclusion bodies Endospores
Capsule/Glycocalyx/Slime layer Glycocalyx: Is a viscous,gelatinous material that is synthesized and excreted by the cell. It accumulates on the external surface of the cell wall and thus surrounds by the cell.
Composition: It is composed of polysaccharide or polypeptide depending on the type of species. Glycocalyx type: Capsule: If extracellular material is thick,well defined and organized and layer tightly formed around the cell.
Slime layer: If extracellular material is thin,undefined,unorganised loose matrix of fibre called as alime layer. Functions of Capsule/Glycocalyx/Slime layer: Capsules may protect pathogens from phagocytosis and increase the pathogenicity of pathogen. Capsules enable adherence to surfaces, prevent desiccation, and may provide nutrients.
Note: All microorganisms donot have capsule/salime layers Organisms those having capsule called as capsulated Microorganisms e.g(Streptococcus pneumoniae,Klebsiella pneumoniae,Pseudomonas aeruginosa) Organisms donot have capsule called as Non- capsulated Microorganisms (e.g E.coli,S.typhi)
Think Capsule enhaces the ability of pathogen to cause infection.why?
Flagella Flagellum(plural,flagella) is a long thin,helical,hair like filamentous structure it present on the surface of certain bacteria. Bacteria having flagellum called flagellated bacteria Bacteria donot having flagellum called as Non-flagellated or aflagellated bacteria.
Composition: The bacterial flagellum is made up of the protein flagellin Function of Flagella: The primary role of the flagellum is locomotion it also often has function as a sensory organelle, being sensitive to chemicals and temperatures outside the cell.
Arrangments Of Flagella: There are 4 types of flagellar distribution on bacteria- 1. Monotrichous – Single polar flagellum – Example: Vibrio cholerae 2. Amphitrichous – Single flagellum on both sides – Example: Alkaligens faecalis
3. Lophotrichous – Tufts of flagella at one or both sides – Example: Spirillum 4. Peritrichous – Numerous falgella all over the bacterial body – Example: Salmonella Typhi
Pili and Fimbriae Pili: are hair-like structures occuring in gram negative- bacteriae. They play vital role in conjugation. They comprise subunits called pillin that forms a canal that provides exchange of DNA (plasmids for example) between the bacterial cells.
Fimbriae: are hair-like structures present on the surface of some nega-bacteriae, however they may occur in some fungi (Candida albicans, Saccharomyces cerevise) They are 2-10 nm in diameter and 100-5000 nm lenght. They facilitate adhession to the surfaces and/or host organisms.
Cell Wall On the Basis Of cell wall There are two types of Bacteria Gram positive bacteria Gram Negative bacteria
Cell wall Gram Positive Bacteria Gram-positive cell walls are thick and the peptidoglycan ( also known as murein) layer. The gram-positive bacteria take up the crystal violet dye and are stained purple
Cell wall Gram positive Bacteria The cell wall of some gram-positive bacteria can be completely dissolved by lysozymes which attacks the bonds between GA and MA. In other gram-positive bacteria There are two main types of teichoic acid: ribitol teichoic acids and glycerol teichoic acids The main function of teichoic acids is to provide rigidity to the cell-wall by attracting cations such as magnesium and sodium.
Gram Negative Bacteria Cell wall An inner cell membrane is present (cytoplasmic) A thin peptidoglycan layer is present (This is much thicker in gram- positive bacteria) outermembrane containing lipopoly saccharides(LPS, which consists of lipid A, core polysaccharide, and O antigen) in its outer leaflet and phospholipids in the inner leaflet
Gram Negative Bacteria Cell wall Porins exist in the outer membrane, which act like pores for particular molecules Between the outer membrane and the cytoplasmic membrane there is a space filled with a concentrated gel-like substance called periplasm Teichoic acids or lipoteichoic acids are absent Lipoproteins are attached to the polysaccharide backbone
Components present internal to cell wall Endospore: There are few bacterial genera which are characterized by their ability to produce resistant structure with in the cytoplasm called endospore. The main function of bacterial spore is survival. They make the cells to survive in adverse environmental condtion such as heat,dryness and harmful chemical agents. Resistance Of Bacterial Spore: Absence of free water molecue Presence of calcium dipicolinate Impermeability of spore coat
Think Why its esstential to kill bacterial spores during sterilization?
Obligate Aerobes: Require oxygen to live. Example: Pseudomonas, common nosocomial pathogen Facultative Anaerobes: Can use oxygen, but can grow in its absence Examples: E. coli, Staphylococcus, yeasts, and many intestinal bacteria.
Obligate Anaerobes: Cannot use oxygen and are harmed by the presence of toxic forms of oxygen. Examples: Clostridium bacteria that cause tetanus and botulism. Aerotolerant Anaerobes: Can’t use oxygen, but tolerate its presence. Can break down toxic forms of oxygen Example: Lactobacilluscarries out fermentation regardless of oxygen presence.
Microaerophiles: Require oxygen, but at low concentrations. Sensitive to toxic forms of oxygen. Example: Campylobacter.
Think Why obligate anaerobes can not tolerate oxygen?
Psychrophiles: “Cold-loving”. Can grow at 0 oC. True Psychrophiles: Sensitive to temperatures over 20oC. Optimum growth at 15oC or below. Found in very cold environments (North pole, ocean depths). Seldom cause disease or food spoilage.
Mesophiles: “Middle loving”. Most bacteria. Include most pathogens and common spoilage organisms. Best growth between 25 to 40oC. Optimum temperature commonly 37oC. Many have adapted to live in the bodies of animals.
Thermophiles: “Heat loving”. Optimum growth between 50 to 60oC. Many cannot grow below 45oC. Adapted to live in sunlight soil, compost piles, and hot springs. Some thermophiles form extremely heat resistant endospores. Extreme Thermophiles: (Hyperthermophiles): Optimum growth at 80oC or higher. Archaebacteria. Most live in volcanic and ocean vents.
Think How H.pylori cause infection in the acidic environment of stomach keep in mind that its not an acidophile?
What Is Virus? Viruses may be defined as acellular organisms Virus genomes consist of nucleic acid(DNA or RNA) virus is obligately replicate inside host cells using host metabolic machinery and ribosomes to form a pool of components which assemble into particles called VIRIONS,that’s why its called as Obligate intracellular parasite
Host Range: The specific types of virus can infect in its host species represent the host range of the virus. Usually species specific Classification: Animal virus Plant virus Bacterial virus (bacteriophage) Host range is determined by attachment sites (receptors).
Viral Structure Nucleic acid: Viral genomes are either DNA or RNA (not both). Nucleic acid may be single- or double- stranded Nucleic acid may be circular or linear or separate molecules.
Capsid Capsid is protein coat Capsomeres are subunits of the capsid Protomeres are capsomere subunits. Envelope:the outer covering of some viruses, the envelope is derived from the host cell plasma membrane when the virus buds out. Some enveloped viruses have spikes, which are viral glycoproteins that project from the envelope. Influenzavirus has two kinds of spikes, H (hemagglutinin) and N (neuraminidase). The H spike allows the virus to attach to host cells (and red blood cells), the N spike is an enzyme that allows the mature viral particles to escape from the host cell.
Think write Discuss Endospore is a resistant body? Why gram positive bacteria stain purple while gram negative bacteria stain red? The capsule is considered virulence factor? Virus can not grow on artificial media? Why virus regarded as intra cellular obligate parasite? H.pylori is not an acidophile bacteria but can tolerate acid how?
Think write Discuss Mesophile can cause disease in human being but thermophile cannot.why? Why obligate anaerobes grow at the bottom of nutrient broth tube? Is Bacteriophage virus can cause infection in Animals? when viral genome is called prophage? Gram positive bacteria converted into protoplast when treated with lysozyme? Capsule enhance the ability of Microorganism to cause infection?
Think write Discuss Some mutant bacteria become resistant to phages?How Why penicillin have low toxcitiy to human cells?