| how can bacteria be classified? | by macroscopic and microscopic appearance, characteristic growth and metabolic properties, antigenicity and genotype
biggest distinction is between gram-negative and gram-positive bacteria |
| how does the gram staining work? | 1. bacteria are heated and dried on a slide
2. they are stained with crystal violet
3. excess stain is removed by acetone-based decolorizer and water
4. a red counter stain called safranin is used |
| what is the difference between gram-positive and gram-negative bacteria? | gram-positive bacteria: thick, cross-linked cell wall composed of peptidoglycan, only consist of peptidoglycan and cytoplasmic membrane, contain many proteins and acids, stain purple
gram-negative bacteria: consist of outer membrane, periplasmic space with some peptidoglycan, cytoplasmic membrane. contain endotoxin, stain red becasue of the thin layer |
| what is serotyping? | identifying differences between bacteria species by using antibodies to detect their characteristic antigens |
| what do bacteria compose of? | cytoplasm, cytoplasmic membrane, cell wall, chromosomes, plasmids, 70S ribosomes, flagella, fimbriae
not always; capsules, outer membrane, periplasmic space |
| what proteins/structures can be found in gram-positive and gram-negative bacteria? | gram-positive bacteria: much peptidoglycan (can be degraded by lysozyme), proteins, teichoic and lipoteichoic acids, polysaccharides
gram-negative bacteria: very little peptidoglycan, transport systems for iron, proteins, surgars, enzymes, phospholipids, endotoxin (LPS) |
| what are the mechanical barriers of the body? and what are the chemical ones? | mechanical: skin (keratin), mucus membranes and nostril hairs
chemical: acid (skin), hydrochloric acid (stomach), enzymes, mucin, defensins, other chemicals e.g. dermcidin in sweat |
| what are the functions of the innate immune system? | - recruiting immune cells to the site of infection
- activation of the complement cascade to identify bacteria
- identification and removal of foreign substances
- activation of the adaptive immune system
- acting as a physical and chemical barrier to pathogens |
| what cells are involved in the innate immune system? | the non-specific cells; neutrophils, mast cells, basophils, eosinophils, macrophages |
| what do neutrophils do in response to an infection? | they fight against bacteria and fungi: their receptors (e.g. scavenger, opsonin) bind to the microbes directly, they promote phagocytosis.
their granules also contain antimicrobial proteins and can produce reactive oxygen species (ROS) |
| what do mast cells and basophils do in response to an infection and where are they present? | they are similar to each other in function; they bind IgE, complement and microbial products. they also release histamine and cytokines as part of the inflammatory response.
mast cells can be found in the skin, muco-epithelial tissue and the lining of the small blood vessels and nerves. the basophils circulate in the blood. |
| what do eosinophils do in response to an infection and where are they present? | they circulate in the blood and function in antiparasitic responses |
| what do macrophages do in response to an infection and where are they present? | they circulate in the blood, but when there's an infection they migrate into the tissues.
they can be subdivided into M1 and M2 macrophages
M2: remove debris and promote tissue repair
M1: kill phagocytosed bacteria, produce ROS, nitric oxide and enzymes, attract neutrophils, NK cells and activated T cells by producing chemokines |
| what do PAMPs and DAMPs do and how do they work? | they notify the body that there is an infection. PAMPs (pathogen associated molecular patterns) do this by a signal that is released by the pathogen and DAMPs (damage associated molecular patterns) do this by damage that is done to the tissue.
the body receives these signals through special receptors; pattern recognition receptors (PRRs) |
| what are the steps of phagocytosis? | 1. attachment; mediated by cell-surface, fibronectin and opsonin receptors
2. internalization; part of the plasma membrane around the pathogen to form a phagocytic vesicle
3. digestion; vesicle fuses with primary lysosomes and become phagolysosomes |
| what happens during an oxidative burst? | it starts during phagocytosis;
1. enzymes in the phagolysosomes are activated
2. one of them, phagocyte oxidase, converts oxygen into superoxide anion and free radicals (ROS), which are toxins
3. inducible nitric oxide synthase converts arginine into nitric oxide, which kills bacteria |
| what are the pathways of the complement cascade and where do they come together? | alternate/properdin pathway, lectin pathway and classical pathway.
they come together with the production of component C3. |
| what is the end product of the complement cascade and what does it do? | the membrane attack complex (MAC), also called lytic unit. it kills infected cells by drilling a hole in their cell membrane, which leads to apoptosis or hypotonic lysis of the cell. |
| what are the PRRs and are they intracellular or extracellular? | TLR -> intracellular and extracellular
NLR -> intracellular
CLR -> extracellular
RLR -> intracellular |
| what do TLR4, TLR5, TLR9, NOD-1 and NOD-2 and NLRP3 recognise respectively? | TLR4 and NLRP3-> LPS
TLR5 -> bacterial flagella
TLR9 -> bacterial unmethylated CpG DNA
NOD-1 and NOD-2 -> bacterial peptidoglycan
NLRP3 -> changes in cytosol and forms inflammasome |
| what are the three outcomes of the complement system and what components are involved? | opsonisation -> increases phagocytosis (C3b)
anaphylatoxin -> induce inflammation (C4a, C3a, C5a)
lytic pathway -> formation of MAC, lysis of pathogens (C5b, C6, C7, C8, C9) |
