S2) Introduction to Microbes Flashcards
Identify the 4 constituents of the ‘microbial world’
- Viruses => thread like and reproduce in a host
- Bacteria => single celled and no nucleus
- Parasites => single celled with nucleus
- Fungi => single celled with thread like filaments
Identify 8 micro-organisms and list them in order of increasing size
→ Prions
→ Proteins
→ Viruses
→ Mycoplasma / Chlamydiae / Rickettsiae
→ Mitochondria
→ Bacteria
→ Eukaryotic cells (yeasts, protozoa, etc)
→ Worms
List 4 components of a virus
- Envelope
- Protein coat
- Spikes
- Nucleic acid (DNA / RNA)
What are the different bacterial shapes?
What colour do Gram positive bacteria stain?
Stain purple
Positive = Purple
What are the components of Gram positive gram stains?
- Plasma membrane
- Periplasmic space
- Peptidoglycan
What colour do Gram negative bacteria stain?
Stain red
What are the components of Gram negative gram stains?
- Plasma membrane
- Periplasmic space
- Peptidoglycan (thinner than gram positive) more susceptible to damage
- Outer membrane (lipopolysaccharide and protein)
Identify and describe different bacteria in terms of their oxygen tolerance
- Aerobes – require oxygen in environment for survival
- Anaerobes – require oxygen-free environment for survival
Identify 3 medically important Gram Positive cocci bacteria
- Staph aureus (cellulitis)
- Streptococcus pneumoniae
- Strep pyogenes (pneumonia, scarlett fever)
Identify 2 medically important Gram Positive bacilli bacteria
- Listeria monocytogenes (sepsis, meningitis)
- Clostridium difficile (diarrehoea and collitis)
Identify 2 medically important Gram Negative cocci bacteria
- Neisseria meningitidis
- Neisseria gonorrhoeae
Identify 4 medically important Gram Negative bacilli bacteria
- E.coli
- Klebsiella pneumoniae
- Salmonella typhi
- Haemophilus influenzae
Identify two mechanisms of bacterial pathogenesis
- Virulence factors
- Toxins
Identify 4 virulence factors and provide an example for each
- Host entry e.g. polysaccharide capsule
- Adherence to host cells e.g. pili, fimbrae
- Invasiveness e.g. enzymes such as collagenase
- Iron sequestration e.g. siderophores
Identify 2 types of toxins and provide and example for each
- Exotoxins e.g. diphtheria toxin
- Endotoxins e.g. lipopolysaccharide
Identify 2 types of fungi and provide and example for each
- Yeasts (unicellular) e.g. Candida albicans
- Moulds (multicellular) e.g. Dermatophytes
Identify 2 types of parasites and provide and example for each
- Protozoa (unicellular) e.g. Plasmodium falciparum
- Helminths (multicellular) e.g. Roundworms, tapeworms
Describe the kinetics of bacterial growth in a liquid medium
describe a gram positive bacteria
thick, multi layered, walls are exterior to the cytoplasmic membrane
describe a gram negative bacteria
more complex cell wall structure ( 2 membranes seperated by periplasmic space)
comparison of sizes between bacteria, viruses, parasites and fungi
smallest = virus
largest = parasite
layers surrounding bacteria
cell envelope - consists of cytoplasmic membrane, cell wall and capsule
cell wall - peptidoglycan (determines shape of cell) target for many antiibiotics this detrmines the gram stain
capsule - sticky, viscous material forming a coat around cell (allows cells to adhere, protect from attack and diffusion barrier)
list microbes that are prokaryotic
bacteria
agar plates
- culture bacteria
- red due to addition of blood
- enriched medium as blood provides nutrients for bacteria to grow
-
chocolate agar - blood has been lysed and intracellular nutrients have been released
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benefits of normal flora
- competes for nutrients with invading pathogens and win
- produce antimicrobial substances that other microbes are suceptible to
- help educate the immmune system
eg
- lactobacilli in vagina maintain acidic environment = inhibits growth of other microbes
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harmful effects of notmal flora
- somtimes normal flora can reach other surfaces eg. staphylococcus epidermis and can breach skin
- normal bowel flora can cause colitis if misplaced
what part of body is home to the most amount of flora
intestines
