Intro to microbiology Flashcards
(27 cards)
Compare viruses, bacteria, fungi, protozoa&helminths in terms of: cells, nucleic acid, types of nucleus, ribosomes, membrane bound organelles, nature of outer surface, method of replication
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Compare macroparasites and microparasites in terms of: organism, size, replication product, immunity
ref. notes
What kind of characteristics for bacteria are used for its classification
Morphological characteristics (nature of the cell wall, staining, shape, spore forming abilities), Biochemical properties (metabolism, production of specific enzymes), DNA sequencing their genome
What kind of characteristics for viruses are used for its classification
Types of nucleic acid, number of strands of nucleic acid, and their physical condition, polarity of viral genome, symmetry of nucleocapsid, lipid envelope
What are helminths and how can it be transmitted
Multicellular worms that infest organs e.g. GI tract
transmission: indirect=via intermediate non human hosts direct=swallowing infective stages or by larvae penetrating skin
What are protozoa and how can it be transmitted
single cell organisms, free living/host requiring,
Transmission: ingestion of contaminated water/food
What types of fungal diseases are there and where do they arise
Superficial=hair shaft, dead layer of skin
Cutaneous=epidermis, hair, nails
Opportunistic=Internal organs
What are essential and non essentail components of a bacterial cell
Essential: cell wall, plasma membrane, ribosome, nucleoid
Non essential: capsule, flagella, pili, plasmid, spore
What is peptidoglycan comprised of
Is a polymer composed of hexose sugars (N-acetylglucosamine and N-acetylmuramic acid) and amino acids
Gram staining procedure
primary stain: crystal violet (blue)->mordant fixes the dye: iodine->decolourising agent alcohol/acetone->counter stain: safranin (red)
Why does gram positive and negative stain differently
Negative doesn’t retain primary staining due to thin peptidoglycan
Compare gram positive and negative in terms of: peptidoglycan layer, outer membrane, LPS, lipoprotein content, teichoic acid, porin
ref. notes
Why can’t some bacteria be gram stained
thick outer layer of complex waxy lipids mean that gram stain don’t penetrate the walls. These are acid-fast because they resist decolourisation with acid-alcohol after being stained. Ziehl-Neelsen stain used to stain acid-fast bacteria
Describe properties of the bacterial capsule
gleatinaous layer outside cell wall mainly comprised of polysaccharides. Determinants of virulence, helps bacterial adherence, antigenic (can be vaccine component)
Describe properties of the flagella
organ of motility, role in pathogenesis, identification+lab diagnosis
What are fibriae and what do they do
hair-like filaments that extend from cell surface. Thinner and shorter thean flagella
Function: attachment, conjugation
What are properties of plasmids and what are they transmissable by
mostly circular dsDNA, capable of self replication, can contain antibiotic resistance genes,
Transmission: conjugation, transduction, transformation
What are the properties of spores
only produced by some gram positive bacteria, highly resistant structures formed in response to adverse conditions, contain bacterial DNA surrounded by thick keratin-like coat that confers resistance to: heat (resistance to boiling, killed by autoclaving)
chemical (only sporicidal kills it)
drying, can survive long time (wound contaminated with soil can be infected by spores)
What is required for viral propagation
Machinery for translation of viral mRNA
Enzymes for replication of genome and assembly of new virions.
Transport parthways to reach site of replication, viral assembly
energy source
Virus essential and nonessential components
Essential-DNA or RNA genome, capside core, polymerase protein
Nonessential-envelope
What are capsids and what are its properties
Constructed from small number of virally encoded protein subunits=capsomeres. Viral genome enclosed by capsid protein coat is called nucleocapsid
symmetry shown by virus particles: icosahedral (20 triangles arranged around sphere), helical, complex (neither helical nor icosahedral.
What are the properties of viral envelopes and its functions
lipid bilayer containing viral glycoproteins that project from membrane
Function: determines the stability of virions outside the host and correlates with mode of transmission.(nonenveloped=stable in environment, transmitted by food/water, enveloped=only survive transiently outside host and infectious viruses do not persist in environment)
Importance of viral surface protein
attach to receptors - determinant of tropism
target for antibodies-neutralisation
determinant of antibody specificity (serotype)
What are the steps for viral replication
Surface proteins of virus interact with receptor on target cell. Whilst enveloped viruses bind to their receptor via spikes in their envelope, naked viruses recognise receptors directly by coat->Many barriers to entry into host overcome by fusion of envelope onto host membrane or translocation of virion across the host cell membrane or receptor mediated endocytosis->uncoating so nucleic acid available for transcription->production of viral proteins and replication of viral genome->bringing together newly formed viral nucleic acid and the structural proteins to form the nucleocapsid of virus->release+dissemination/transmission
