Microbiology Exam 1 Flashcards
What are virulence factors
molecules or activities that permit the processes of pathogens, including adherence factors, toxins, inflammatory mediators, anti-host enzymes, bacterial capsules.
Pathogens are organisms with capability to do what three things
- colonize host
- overcome host immunity
- replicate within the host environment and/or cause host tissue damage
What are the 3 domains of life and some examples of each
- eukaryotes: all non-microscopic life: mammals, fungi, algae, plants as well as some microscopic life such as protozoa
- bacteria: gram+ gram-; rods, cocci, etc
- archaea: geyers at yellowstone!
What is the difference between gram+ and gram-
gram+ have thick outer cell wall and a single inner plasma membrane
gram- have a thin cell wall sandwiched between two cell membranes, the outer wall contains major virulence factor - LPS (lipopolysaccharide) which is toxic an thus termed an endotoxin
difference in gram staining between these two results from different wall sizes, both take up a crystal violet stain, but only the gram- are destained by an alcohol wash
Are viruses living?
what are their two categories and provide an example of each?
non-living
enveloped and non-enveloped
enveloped are much less hardy than non-enveloped. ex) herpes, hepatitis B, influenza, rubella, mimps, HIV
non-enveloped: Hep-A, polio, papilloma, rotaviruses
what are prions?
What is an example?
Prions are small “infectious” proteins whose modes of actions are poorly understood, also non-living
ex: mad cow disease
what are the surface molecules anchored in the cell wall of bacteria of bacteria and what do they do?
Pili aka **fimbrae: used for attachment and conjugation
Flagella: used for locomotion
capsule: used to protect from phagocytosis
LPS: major virulence factor found in the outer membrane of gram- bacteria
why do bacteria secrete digestive enzymes?
because only small molecular weight molecules can pass through the cell wall and cell membrane. The digestive enzymes break down carbs and proteins to small sugars and amino acids which can then be taken in through the pores
what is the role of the bacterial cell wall?
What is it made of?
protects the bacterial cell, wraps around the fragile-balloon like plasma membrane and protects it from osmotic pressure within cytoplasm, by preventing the bacterial cell from swelling up and breaking open
it is made of rope-like, linear, polysaccharide chains cross-linked by peptides. The polysaccharide chains are formed by repeating, modified glucose-dimers called N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM).
The wall molecule is a peptidoglycan that is constantly being synthesized and degraded by autolysins
discuss the ways that LPS can cause serious problems if present in large amounts.
in small amounts, LPS is excellent at activating the innate immune reaction
in large amounts:
-in blood vessels, large amounts of LPS can activate the clotting system, leading to disseminated intravascular coagulation. This can completely obstruct blood flow in the affected blood vessels, causing damage or death to the underlying tissues.
-Macrophages also respond to LPS in their environment by becoming activated, LPS-activated Macrophages secrete “drool” various noxious compounds onto the surrounding tissues, which includes proteases that breakdown the extracellular matrix (e.g. collagen, etc.) in the area. They also produce pro-inflammatory mediators, such as PGE2 and TNF. PGE2 can activate osteoclasts to reabsorb bone and TNF signals endothelial cells to produce more NO, which causes pre-capillary sphincters to relax (inflammation) If there are too many capillaries in the body opened at one time, this will cause the blood pressure to fall dramatically, and can lead to hypovolemic shock (septic shock)
What are the four different glucose polysaccharides in nature?
what are the major functions of large glucose polysaccharides?
1) starch (plants)/glycogen (animals)
2) cellulose (plants): structural
3) chitin (animals) : major structure that makes up the ectoskeleton of bugs/insects/fungs
4. Peptidoglycan (bacterial cell wall) modified glucose disaccharides: NAG-NAM building blocks, macrophages have lysosomes that are designed to break dimers
***amylase used by plants to breakdown starch between glucose bonds
what are antibiotics?
substances that are able to inhibit or kill another microorganism
why doesn’t penicillin harm human cells?
what is PBP?
because it blocks new bacterial cell wall synthesis and we do not make cell walls
Penicillin binding protein: takes 2 dangling side chains and covalently links them together
what three steps are required for penicillin to work effectively?
1) bacteria must be growing; requires hydrolases which cut the cell wall in order for it to expand and grow
2) penicillins & cephalosporins block the “spot-welding”; they do this by covalently binding to the transpeptidase enzyme, permanently inactivating the enzyme. If the hydrolases keep cutting up the wall, then the wall eventually falls apart.
3. the now fragile cell swells from osmotic pressure and bursts
what is meant by bactericidal and bacteriostatic?
bactericidal: penicillin is an example of a bactericidal antibiotic, which can kill bacteria directly under normal hypotonic conditions
bacteriostatic antibiotics inhibit the proliferation of bacteria, but do not generally kill them directly, and require immunity to eliminate the bacteria
what does penicillin have as part of it’s structure that allows it to covalently bond with transpeptidase?
unstable beta-lactim ring, which breaks open and renders the enzyme useless
What are the resistance mechanisms that bacteria can develop to penicillin?
1) change pore structure
2) produce penicillinase (breaks down penicillin)
3) alter transpeptidase (so penicillin won’t bind to it)
4) decrease hydrolase activity
what are immune hypersensitivities?
immune response to “harmless” things like antibiotics
how does penicillin help facilitate hypersensitivities?
when penicillin’s unstable b-lactim ring breaks open, it will quickly form a covalent bond with any nearby protein structure including host proteins, platelets, and cells (not just it’s target). When penicillin is attached to these host proteins, they take on a “foreign appearance” and our immune system can react to them to destroy them.
what is required for a bacteria to respire?
heme-proteins
what are obligate aerobes, microaerophic aerobes, facultative, aerotolerant and anaerobes?
aerobes must have oxygen to live
microaerophic aerobes compete best in environments with only very small levels of oxygen
facultative can respire if oxygen is present but can survive on fermentation if oxygen is absent
aerotolerant anaerobes are not killed by oxygen but can only ferment substrate
anaerobes are always killed by oxygen
living in an oxygen environment comes at a price - having to deal with toxic oxygen radicals. what two enzymes are the most important in neutralizing these oxygen radicals?
superoxide dismutase (SOD): produces less toxic, hydrogen peroxide (H2O2) from the very toxic O2-, making it less toxic
catalase (CAT) further converts H2O2 to water and oxygen, makes it benign
which bacteria have both SOD and CAT? Which have just one?
obligate aerobes and facultative have both
microaerophilic just have SOD
What are the two things that can happen when a bacteria is fed sugars? which is more energy efficient?
Fermentation, produce a couple of ATPs, throw out excess as acids, keytones and alcohols
Respiration, it can use oxygen to form carbon dioxide and water, 5x as energy efficient
how to bacteria replicate?
what is the bacterial chromosome like?
binary fission
it’s a circular molecule of double-stranded DNA, making it haploid (we are diploid)
what are plasmids?
extra small circular strand of DNA that can also be present in bacterial cells. They insert into bacterial host chromosome and come out again. They often carry genes that can help bacteria and harm humans; genes coding for toxins, antibiotic resistance, etc
Is a Virus DNA or RNA?
?
what are the three types of gene swapping (exchange of DNA between bacteria)?
- transformation: DNA is slurped up from nearby dead cell
- transduction: viruses transfer DNA between bacteria
- conjugation: “bacterial sex” DNA is directly passed from one bacteria to another. many of these exchanged genes give selective advantage to the recipient.
What are the 3 groups of bacterial DNA mutations
1) point mutations: one DNA base is changed which usually results in a different amino acid being placed into the protein at that site
2) base deletion: remove one DNA base, which will change the reading frame from that point on
3) base addition: adding one DNA base, which again changes the reading frame from that point on.
*the last two result in dramatic alterations, often fatal to the protein
what are the three major phagocytic cells in the body?
monocyte, neutrophil, macrophage
True or False: Is normal flora part of our innate immune system?
name some parts of our innate immune sytem
true
epithelium, water “flush” (tears, saliva), secreted anti-microbial molecules, basophils, eosinophils, monocytes, macrophages, neutrophils, platelets, RBCs
what are the three main characteristics of innate and adaptive immune system?
specificity of recognition: innate (broad) adaptive (very)
speed of action: innate (fast), adaptive (slow)
memory development: innate (nope), adaptive (yes)
Explain the pathway of inflammation
Injury –> release response molecules (histamines) from sentinel cells (mast cells) —> alerts body of problem, initiates inflammatory response
1) increase local capillary flow by relaxing pre capillary sphincters (heat and redness)
2) cause capillary endothelial to gap, allowing blood to flood into affected tissue (swelling)
3) cause capillary endothelial cells to show “stop signs” CAMs that cause certain inflammatory response cells to exit the capillaries and move to the site of injury, includes PMN, macrophages, phaocytic cells
explain the difference between primary and secondary lymphoid tissue
primary (bone marrow and thymus) are sites of lymphocyte development and education, B cells are made in bone marrow and T cells in thymus. Once their education is complete “graduation” they move to secondary lymphoid tissues, which consist of the lymph nodes, spleen, adenoid, tonsils, peyer’s patches, etc.
what do B cells do?
B cells use their Ag-specific surface receptors to bind to Ag and then they produce and release an Ab (which is an immunoglobulin) that binds to the problem, both coating and flagging it for destruction
what do T cells do?
T cell receptors only bind to processed proteins (Ag) presented to them on surface of other cells. Once the T cell receptor (TCR) binds, it releases one or more proteins called cytokines which act on their host cells.
