IAI - intro to microbiology Flashcards
What are the 5 different types of microbes?
- Parasites: Helminths and Protozoa
- Fungi
- Bacteria
- Viruses
- Prions
what 3 things determine how the organisms of infectious diseases interact with their hosts and how they cause disease
- Structural and molecular make-up
- Biochemical and metabolic strategies
- Reproductive processes
which one of these can be classified as a ‘cell’
viruses
bacteria
fungi
protozoa and helminths
viruses - no
bacteria - yes
fungi - yes
protozoa and helminths - yes
which of the following has DNA or RNA or both
viruses
bacteria
fungi
protozoa and helminths
viruses - either DNA or RNA
bacteria - both
fungi - both
protozoa and helminths - both
what kind of nucleus do the following microbes have
viruses
bacteria
fungi
protozoa and helminths
viruses - none
bacteria - prokaryotic
fungi - eukaryotic
protozoa and helminths - eukaryotic
what kind of ribosomes do the following microbes have:
viruses
bacteria
fungi
protozoa and helminths
viruses - none
bacteria - 70s
fungi - 80s
protozoa and helminths - 80s
whats the nature of the outer surface of the following microbes
viruses
bacteria
fungi
protozoa and helminths
viruses - Protein Capsid
+/- lipoprotein
envelope
bacteria - Rigid Cell wall
containing
peptidoglycan
fungi - Rigid Cell wall
containing chitin
protozoa and helminths - Flexible
membrane
what is the method of replication for the following microbes
viruses
bacteria
fungi
protozoa and helminths
viruses - Require host cell
machinery
bacteria - Binary fission
fungi - Budding or Mitosis
protozoa and helminths - Mitosis
what are the organisms of macroparasites vs microparasites
macro = helminths
micro = viruses, bacteria, protozoa, fungi
whats the difference in replication in macroparasites vs microparasites
macro = outside host
micro = inside host
whats the generation time of macroparasites vs microparasites
macro = long
micro = short
what 4 morphological characteristics of bacteria are used for classification?
- Nature of the cell wall
- Staining
- Shape (cocci, bacilli/rods and spirilla/spirochetes)
- Spore-forming abilities
what 2 biochemical characteristics of bacteria are used for classification?
- Metabolism: Bacterial growth is affected by oxygen depending on their energy-generating system (e.g. obligate aerobes, facultative anaerobes and obligate anaerobes)
- Production of specific enzymes (e.g. coagulase) or toxins (e.g. hemolysins)
what 3 characteristics of bacteria are used for classification?
- morphological
- biochemical
- DNA sequencing of their genome
What are the 5 characteristics of viruses used for classification?
- Type of nucleic acid (DNA or RNA)
- Number of strands of nucleic acid (ss/ds) & their physical construction (e.g. segmented)
- Polarity of viral genome (e.g. positive or negative strand RNA).
- Symmetry of nucleocapsid.
- Lipid envelope (presence or absence)
What are helminths (parasites)?
Helminths are multicellular worms that infest many organs of the body, most commonly the gastrointestinal tract.
Many have complex life cycles that progress from egg to larva to adult.
IE TAPEWORMS
how does helminths transmission occur?
- Transmission might be:
- Direct through swallowing infective stages or by larvae penetrating the skin.
- Indirect via intermediate non-human costs.
what is a protozoa?
- Protozoa are single cell organisms.
- Their life cycle includes a metabolically active growth stage (trophozoite) and a dormant stage (cyst).
- May be free-living or life cycle may require one or more hosts
IE MALARIA
how are protozoa transmitted?
Infections are acquired through ingestion of contaminated water or food or
via insect vectors.
what can fungi grow as? what is the cell wall composed of in fungi compared to bacteria?
Fungi grow as:
1. single cell (yeasts)
2. branched filaments (hyphae) - In filamentous fungi the mass of hyphae forms a mycelium
3. or both (dimorphic fungi).
Fungi have a thick cell wall composed primarily of chitin, bacterial cell walls composed of peptidoglycan
how is fungi transmitted?
Species causing disease may be acquired from the
environment or occur as part of the normal flora.
what are the 4 essential components of bacteria?
cell wall
plasma membrane
ribosome
nucleoid
what are the 5 non-essential components of a bacterial cell?
capsule
flagella
pilli
plasmid
spore
describe the cell wall of the bacteria?
multilayered structure mainly composed of peptidoglycan (also known as mucopeptide or murein)
what is peptidoglycan composed of?
a polymer composed of the hexose sugars N-acetylglucosamine and Nacetylmuramic acid (glycan chain) and amino acids (tetrapeptide chain).
How can bacteria be classified based on the characteristics of their cell wall?
positive = purple (remember peepee hehe)
negative = pink
Why do gram positive and negative bacteria stain differently?
Due to thin peptidoglycan layer, gram negative bacteria don’t retain primary staining.
what are 3 differences between gram positive and gram negative bacteria?
- gram positive bacteria has thicker petidoglycan layer
-In gram-negative bacteria the peptidoglycan layer is overlaid by an outer membrane which is anchored to the peptidogylcan layer by lipoprotein molecules.
- Also the outer membrane of gram-negative bacteria is rich in lipids and contains lipopolysaccharides (also called LPS or endotoxins).
does gram positive or gram negative have an outer membrane
gram positive -NO OUTER MEMBRANE
gram negative - YES OUTER MEMBRANE
does gram positive or gram negative have LPS
gram positive = NO LPS
gram negative = YES LPS
out of gram positive and gram negative bacteria, which has a high lipid/ lipoprotein content, and which one has a low lipid/ lipoprotein content?
gram positive = LOW
gram negative = HIGH
does gram positive or gram negative have techoic and lipoteichoic acids
gram positive = YES
gram negative = NO
does gram positive or gram negative have porins?
gram positive = NO
gram negative = YES
what stain technique is used to stain acid-fast bacteria when the gram stain doesnt penetrate the walls?
The Ziehl-Neelson (ZN) stain is a technique used to stain acid-fast bacteria and the myobacteria are stained bright red with a blue background.
whats the structure of the capsule in bacteria?
- Gelatinous layer outside cell wall mainly composed of polysaccharide (sugars)
- Determinant of virulence (antiphagocytic)
- Helps bacterial adherence
- Antigenic; can be component of vaccine
- Used for identification and lab diagnosis: swelling reaction
whats the structure of flagella in bacteria?
- Organ of motility
- Flagellated bacteria have a
characteristic fixed number and
location of flagella - Plays a role in pathogenesis
- Used for identification and lab
diagnosis
whats the structure of pilli in bacteria?
- Hair-like filaments that extend from cell
surface - Thinner and shorter than flagella
whats the 2 main functions of pilli in bacteria?
- Two main functions:
o Attachment (ordinary pili/fimbriae)
o Conjugation (sex pili)
What is the structure of bacterial plasmids?
- Additional extra-chromosomal genetic material
- Mostly circular dsDNA
- Capable of self-replication
- Can contain antibiotic resistance genes
- Transmissible by conjugation, transduction
What are bacterial pores produced by? What is the structure of bacterial pores?
- Only produced by some Gram positive bacteria(Bacillus and Clostridium species)
- Highly resistant structures formed in response to adverse conditions
- Contain bacterial DNA surrounded by a thick keratin-like coat that confers resistance to heat, chemicals and drying.
what are the essential components of viruses
DNA or RNA (never both)
capsid core
polymerase protein
what is a non essential components of viruses
envelope
whats the structure of a capsid?
Capsids are constructed from a small number of virally-encoded protein subunits called capsomeres.
The viral genome enclosed by the capsid protein coat is called nucleocapsid (core)
what 3 types of symmetry do virus particles show?
- Icosahedral (e.g. adeno, herpes).
- Helical (e.g. orthomyxo, paramyxo)
- Complex (e.g. poxviridae)
What is the structure of a icosahedral capsid (closed)?
The capsid is composed of 20 solid equilateral triangles arranged around the face of a sphere.
the minimum number of subunits in an icosahedral capsid is 60
What is the structure of a helical capsid (open)?
Capsomeres bound in a periodic fashion to the viral genome
helix shape
What is the structure of a complex capsid?
The capsid is neither purely helical nor purely icosahedral
The nucleocapsid is a continuous cylinder surrounded by a lipid layer and complex proteinaceous core wall (pallisade layer).
What is the structure of the viral envelope?
- Lipid bilayer derived from the host cell membrane
- Not present in all viruses.
- Contains viral glycoproteins (spikes) that project from the membrane.
- The interaction between the capsid and envelope is mediated by the viral matrix protein
- Determines the stability of virions outside the host and correlates with mode of transmission:
- Non-enveloped (naked) viruses are stable in the environment; may be transmitted by food or water
(e.g noroviruses). - Enveloped viruses often survive only transiently outside host and infectious viruses do not persist in the environment (e.g.HIV)
- Non-enveloped (naked) viruses are stable in the environment; may be transmitted by food or water
is mRNA positive or negative? how does this differ with DNA and RNA, and consequently whether they’re positive or negative?
- By convention, mRNA is defined as a positive strand because it is the template for protein synthesis.
- A strand of DNA of the equivalent sequence is also called the positive strand.
- RNA and DNA strands that are complementary to the positive strand are called negative strands.
do keats quiz on intro to microbiology
https://keats.kcl.ac.uk/mod/lesson/view.php?id=6620868
whats the smallest microorganism
virus
Bacteria and viruses are prokaryotes whilst fungi, helminths and protozoa are eukaryotes.
True or False
FALSE - Viruses are not made up of cells and, hence, are neither prokaryotes nor eukaryotes
out of gram negative and gram positive bacteria, which produces spores
Only two medically important gram-positive bacteria produce spores (Bacillus spp and Clostridium spp)
