Viruses, Parasites, and Fungi PDF

10/7/2024 VIRUSES Instructional objectives Knowing the structure of a virus Knowledge of bacteriophages; their involvement in gene transfer in bacteria Classification of parasites 1 ...

10/7/2024 VIRUSES Instructional objectives Knowing the structure of a virus Knowledge of bacteriophages; their involvement in gene transfer in bacteria Classification of parasites 1  10/7/2024 Definitions Viruses = very small infectious particles (20-300 nm) Missing: energy-producing enzymes biosynthesis capabilities Viruses do not grow, cannot divide, are replicated by living cells, for which they are obligate intracellular parasites Virion - complete viral particle that is infectious Dimensions : 20-300 nm 2  10/7/2024 Definition Contain only one type of nucleic acid, DNA or RNA Protected by the capsid, a protein coating The protein coat may be surrounded by an envelope, a lipoprotein membrane 3  10/7/2024 easily break down non-envelope the outside contain = structure on the surface have some receptors glycoprotein,structural protein, viruses outside of any live cell doesn't exist lipid bilayer and in the inner part is the naked viruse which contain nucleoplam They make metabolism slower influenza viruses: they recognize species(humane, plants,...) 4  10/7/2024 EM we need antibody in order to recognize antigen viruses to see them in EM Adenovirus animal are effected and after bite human are infected and after that there is no cure and it's prevent with vaccines filoebola Rabies virus Ebola virus 5  10/7/2024 Viral genome they mostly have RNA and fewer have DNA genome - represented by an RNA molecule (most viruses) or DNA; - holds the information needed to replicate - DNA most commonly has a - double-stranded structure (single-stranded in parvoviruses) parvo - Linear structure (circular in papovaviruses and hepadnaviruses) papavova and hepadna - RNA most commonly has a single-stranded structure (double-stranded in reoviruses), with positive sense (functions as mRNA) or negative sense (has an associated RNA polymerase) segmented (orthomyxoviruses, reoviruses) e.g influenza viruses RNA viruses are usually single-stranded. They can have positive-sense RNA (works directly like mRNA) or negative-sense RNA (needs to be converted before it works). hepatit ?C viruses are dangers, bc have dramatically high risk 6  10/7/2024 Viral capsid - consisting of repetitive protein molecules (capsomeres) encoded by the viral genome; - capsomers have a symmetrical arrangement helical, around the nucleic acid helix (ortho- and para-mixoviruses, rhabdoviruses); icosahedral (cubic), being differentiated into * pentones (at each peak of the icosahedron), * hexones (on the faces and edges of the icosahedron) * examples: adenoviruses, herpesviruses, picornaviruses; mixed - bacteriophages complex (poxviruses) - one nucleoid, 2 side bodies, lipoprotein envelope formed by tubules. 7  10/7/2024 Functions of the viral capsid ⮚protects the viral nucleic acid, ⮚binds the (naked) virus to specific receptors on the cell surface, ⮚contains antigenic determinants to which the host reacts by immune response. 8  10/7/2024 Envelope - present in viruses with helical symmetry and some viruses with icosahedral symmetry; - viruses without an envelope are naked - derive from the host cell membrane system (cytoplasmic membrane, nuclear membrane, endoplasmic reticulum); - includes glycoproteins encoded by the viral genome (peplomeres) with the role of ligands to cellular receptors (e.g. haemagglutinins) receptors for Fc and C3b (in herpesviruses) enzyme (ex hyaluronidase) fusion with the host cell membrane point of attack for neutralizing Ac - naked viruses are more resistant to external environmental factors than enveloped viruses Nucleus Spike Glycoproteins matrix protein bud virion contains= genome viruses, matrix protein, spike glycoprotein 9  10/7/2024 Viral taxonomy Family - includes the suffix -viridae in the name; Subfamily - includes the suffix -virinae in the name; Genus - includes the suffix -virus in the name. Classification criteria the shape and size of the virus, number and arrangement of capsomeres, presence or absence of the envelope, genome structure, site and mode of replication, antigenic structure, sensitivity to physical and chemical agents. 10  10/7/2024 Viral replication viruses are replicated by living cells infectivity disappears from the moment of decapsidation of the virion entering the cell until the appearance of progeny virions = eclipse period stages: all of them are going to be extended and you will undrstand them better adsorption penetration decapsidation early protein biosynthesis viral genome replication late protein biosynthesis morphogenesis release of virions 11  10/7/2024 Stages of viral replication 1. adsorption - attachment of ligands (viral surface structures) to specific cell receptors (cell tropism) Stages of viral replication 2. penetration 1. naked viruses - receptor- dependent endocytosis 2. enveloped viruses - fusion of the envelope with the cyto- plasmic membrane 3. direct translocation of the cell membrane (e.g. picornaviruses, papovaviruses) for small viruses 12  10/7/2024 Stages of viral replication 3. decapsidation 1. dissolution of the infectious element as a preliminary stage of multiplication singles out viruses among infectious agents 2. RNA viruses replicate in the cytoplasm (except influenza virus) 3. DNA viruses replicate in the nucleus (except poxviruses) Stages of viral replication 4. synthesis of viral components 1. viral genome (cellular/viral polymerases), 2. mRNA, 3. protein synthesis Early means enzyme in general but they lost when they do there job Late 13  10/7/2024 Stages of viral replication 5. morphogenesis 1. possible hollow icosahedral caps, never for those with helical symmetry 2. excess accumulated viral components → viral inclusions (herpes) we can see in nucleus DNA viruses Cytomegalovirus. Intranuclear inclusions shape of inclusions this cytopathic effect, only amplify by sample 14  10/7/2024 Rabies virus - Babes – Negri bodies (acidophilic intracytoplasmic inclusions) Stages of viral replication 6. release of virions 1. naked viruses- host cell lysis 2. enveloped viruses - budding through modified cell membranes (viral glycoproteins) in size of nm we can't use light microscopy 15  10/7/2024 HAV replication 16  10/7/2024 Evolution of viral infection Resolution (represent antibodies) Transformation (cancer) Acute infection Chronic infection Persistent infection Latent infection Reactivation can be reactivated and like in acute infection 17  10/7/2024 Bacteriophages - viruses that parasitize bacteria; - are similar in structure to animal viruses; - T-phages, the most well-known, are made up of head - nucleocapsid with icosahedral symmetry with dsDNA at the centre. tail - with helical symmetry, includes a rigid axial tube and a contractile sleeve; hexagonal base plate, each tip with a tail fibre; - The replication cycle in the bacterial cell is similar to that described for viruses of medical interest. Mixed/binary symmetry tail and basal plate channel of the grame negative=> Porins (general and specific) allow small molecules to diffuse into the periplasm. Efflux pumps expel harmful substances, contributing to drug resistance. TonB-dependent transporters and outer membrane proteins handle the transport of specific nutrients, like iron and vitamins. Secretory systems facilitate the transport of proteins and toxins. 18  10/7/2024 The phage - bacterial cell relationship ▪ Virulent phage = causes lytic infection (lytic phage). ▪ Temperate phage = integrates into the bacterial genome and replicates at the same time (prophage). ▪ Lysogenic bacterium = cell in which the prophage can evolve into a lytic phage under the effect of environmental factors (phage induction). 19  10/7/2024 DEFINITION AND CLASSIFICATION OF PARASITES 20  10/7/2024 Parasite Definition Organism that lives in association with another organism, of another species, called "host" Feeds on it (host provides food and shelter) It's pathogenic to it Classification: Protozoa (unicellular, eukaryotic organisms) Metazoans (multicellular organisms) Helminths (parasitic worms) Arthropod (articulated limbs) for mobality not only flaggie they belong to 4 classes have another options to use Legend: Relationships of the medically important parasites. 21  10/7/2024 PROTOZOARE Single-celled microorganisms, eukaryotic, 1-150 μm Trilaminated cell membrane Has its own movement organs: pseudopodia, flagella or cilia One nucleus (rarely 2); multinucleate reproductive forms Asexual (binary/multiple division) or sexual reproduction It has 2 forms of existence Vegetative form (trophozoite) - the form it adopts under favourable living conditions in some condtion to become resistance they become cyst Resistance form (cyst) - under unfavourable living conditions PROTOZOA Amoebae (mobile by emitting pseudopods) Entamoeba histolytica, Entamoeba coli Flagellate (mobile by flagella) Giardia intestinalis, Trichomonas vaginalis sexual transmitted disease Sporozoa(without flagella, cilia or pseudopodia; spore → sporozoite = infecting form) Class Haematozoa: Plasmodium (P. malariae, P. ovale, P. falciparum, P. vivax) Class Coccidia: Toxoplasma gondii, Cryptosporidium they form toxoplasmosis(worst for pregency) casue sever malformation, cat are the host for this Ciliate (mobile by cilia) Balantidium coli 22  10/7/2024 HELMINTS metazoa 2 phylums Plathelmintes (flatworms) Nemathelminthes (roundworms) With flattened dorso-ventral Spindle-shaped body body Differentiated genra 2 classes: o Ascaris lumbricoides Trematoda - flukes (non-segmented) o Enterobius vermicularis o Fasciola hepatica o Trichuris trichuria Cestoda - tapeworms (segmented) o Trichinella spiralis o Taenia spp.it's a flatworms in meat o Echinococcus granulosus Trematodes (flukes) Most are flat, dorso-ventrally flattened, leaf-shaped worms Exceptions; e.g., schistosomes – thread-like Suckers = anchoring organ Mouth sucker - around the mouth opening, connected to the oesophagus and intestine Ventral sucker The body surface forms a syncytial envelope through which nutrients from the environment can be incorporated Most species are hermaphroditic; with the exception of schistosomes In the evolutionary cycle The first intermediate host is a mollusc Second intermediate host for some species - arthropods and fishes 23  10/7/2024 Cestodes (tapeworms) Body consisting of Head (scolex) Neck - non-segmented proliferation zone Body segments - chain of segments (proglottids) Genitals are hermaphroditic No digestive system (nutrients are absorbed through the cuticle) Evolutionary cycle has 1-2 intermediate hosts Larval stages (metacestodes, cysticerci) of various cestode species can colonize human tissues and cause more extensive damage than intestinal damage Nematodes (roundworms) Spindle-shaped, unsegmented metazoans, a few mm to 1 m long, of differentiated genera External integument with complex structure Internal organs (digestive tract, reproductive organs) Central pseudo-coelomic cavity Males smaller than females; have genitals with species-typical characteristics 24  10/7/2024 ARTHROPODS (parasitic insect) - have jointed limbs, symmetrical and chitinous body, with development by metamorphosis (successive molts); - can act as vectors ensuring the transmission of a pathogen by being involved in the life cycle or by simply carrying the pathogen. Class Arachnidae -arthropods without antennae and 4 pairs of limbs in adults Family Sarcoptidae Genus Sarcoptes Class Insecta -arthropods with antennae and 3 pairs of limbs in adults Family Pediculidae Genus Pediculus Genus Pthirius DEFINITION AND CLASSIFICATION OF FUNGI 25  10/7/2024 Definition Fungi are microscopic, eukaryotic, unicellular or multicellular, heterotrophic bioentities containing chitin in the cell wall Form spores, being the form of resistance, but also of reproduction Classification of fungi: Yeasts Filamentous and Dimorphic Fungal spores: can be part of asexual or sexual reproduction cycles; have a unique role in fungal life cycles, as they provide the genetic link between one generation and the next; can be dispersed - some fungi have partnered with insects, establishing mutual symbiotic relationships; have thick walls, energy reserves, low metabolic rate and abilities to withstand environmental stress that allows them to survive during dispersal. 26  10/7/2024 Spore formation and germination Sporulation (spore-formation) occurs in a narrow range of special nutritional and environmental conditions and involves: signal transduction; gene activation; metabolic fluctuation. Germination: the conditions necessary for germination reflect the particular biological adaptations and requirements of fungi; provides additional somatic growth sequence. Sporulation and germination are coordinated by: changes in light and temperature that mark the day and night cycles; seasons; the life cycles of their host. YEASTS single-celled microorganisms; round or elongated shape; asexual multiplication by budding or fission. Candida spp. (C. albicans, C. tropicalis, C. glabrata, C. lusitaniae, etc.) Cryptococcus neoformans they are species Trichosporon spp. Malassezia spp Rhodotorula spp. 27  10/7/2024 FILAMENTOUS FUNGI multicellular microorganisms; the body (also called thallus) is made of hyphae (tubular filaments, septate or not) Aspergillus spp. Microsporum spp. Trichophyton spp. Epydermophyton floccosum DIMORPHIC FUNGI microorganisms that occur: in the form of yeasts in the tissues of parasitized organisms or at 37°C in vitro; in filamentous form, when grown at room temperature or at 30° on normal media. Histoplasma capsulatum 28  10/7/2024 Take away messages Viruses are very small infectious particles with no protein or energy synthesis capacity, so they are obligate intracellular parasites. Viruses contain a single type of nucleic acid (DNA or RNA), capsid and, only some of them, envelope. Naked viruses are more resistant to external environmental factors than enveloped viruses. Viruses are replicated by living cells after attachment to specific cell receptors. Viral infections can be: Acute infections Persistent infections: chronic infections or latent infections. Latent infections can reactivate. Bacteriophages are viruses that parasitize bacteria; they play a role in gene transfer between bacteria. Parasites are unicellular (protozoa) or multicellular (helminths, arthropods) organisms. Fungi are microscopic, eukaryotic, unicellular or multicellular, heterotrophic bioentities that contain chitin in the cell wall Figure : (A) Basic shape of bacteria. (B) Fungal spores. (C) Fungal hyphae. (D) Morphology and structure of viruses: 1. Poxvirus, 2. Orthomyxovirus, 4. Coronavirus, 5. Togaviridae, 6. Adenovirus, 7. Bullet-shaped virus, 8. Herpes virus, 9. T2 bacteriophage, 10. reovirus, 11. papovavirus, 12. picornavirus, 13. picodnavirus, 14. tobacco mosaic virus. Chapter 1 - Basic Biology of Oral Microbes Atlas of Oral Microbiology, 2015, 1-14 http://dx.doi.org/10.1016/B978-0-12-802234-4.00001-X 29 10/7/2024 30