PLTW MI 1.2
bacterial cell parts: endotoxins
Lipopolysaccharide molecules that make up the outer leaflet of the outer membrane of Gram negative bacteria. Endotoxins are different from exotoxins, which are proteins synthesized by both Gram negative and Gram positive bacteria and function as potent toxins.
plasmid
a small ring of DNA that carries accessory genes separate from those of the bacterial chromosome
antibiotic
a substance produced by or derived from a microorganism and able in dilute solution to inhibit or kill another microorganism
efflux pump
bacteria become resistant to antibiotics using a channel that actively exports antibiotics and other compounds out of the cell
destruction/inactivation
bacteria possesses genes which produce enzymes that chemically degrade or deactivate antibiotics, so that they are ineffective against bacterium
gram negative bacteria cell wall structure
peptidoglycan (one layer). Thin compared to gram positive cell wall. Gram negative also have an outer membrane that can prevent antibiotics from coming into the cell.
bacterial cell parts: plasma membrane
cytoplasmic membrane: phospholipid bilayer responsible for diffusion and transport of materials between the cell's cytoplasm and surrounding environment outer membrane: a phospholipid bilayer in gram negative bacteria only with lipopolysaccharide (lps) on the surface
transformation process
genes are transferred between bacterium as "naked" dna. when cells die and break apart, dna is released into the environment. other bacteria scavenge this dna, which may contain advantageous genes like antibiotic resistance
is n. meningitidis gram positive or gram negative?
gram negative
bacterial cell parts: pili
hollow, hairlike structures made of protein that allow bacteria to attach to other cells. sex pilus (specialized) allows for the transfer of plasmid DNA during conjugation.
gram negative outer membrane structure
lipopolysaccharide component, which can prevent some antibiotics from entering the cell.
gram positive bacteria cell wall structure
peptidoglycan (several layers), much thicker than gram negative cell wall
conjugation process
plasmids (circular dna) replicate independently of chromosomes and carry genes resistant to antibiotics. when 2 cells are in close proximity, a hollow, bridge-like structure (pilus) forms, allowing a copy of plasmid to be transferred as it is duplicated
bacterial cell parts: ribosomes
protein synthesis takes place here. mRNA is read by the ribosome and amino acids are assembled into a complete protein chain based on the RNA sequence
gram positive gram stained cell color
purple (crystal violet dye)
gram positive outer membrane structure
none. Does not have an outer membrane
what should be prescribed to sue and why?
penicillin, because it penetrates the blood-brain barrier when the meninges are inflamed to reach the bacteria. then, it can inhibit the enzyme and stop cell wall synthesis, preventing new cells from forming and stopping the spread of disease.
gram negative gram stained cell color
red (safranin counterstain)
antibiotic resistance
resistance to one or more antibiotics, usually due to additional genetic information
nucleoid
the DNA-containing area of a bacterial cell
transformation
the genetic modification of a bacterium by incorporation of free DNA from another ruptured bacterial cell
conjugation
the one-way transfer of DNA between bacteria in cellular contact
transduction
the transfer of genetic material from one organism (such as a bacterium) to another by a genetic vector (e.g. virus)
bacterial cell parts: flagella
used for motility. long appendages which rotate by means of a "motor" in the cell envelope. may have one, a few, or many
Why are penicillins often more effective against gram positive bacteria than gram negative bacteria?
-gram positive has one layer of cytoplasmic membrane, gram negative has 2 -harder to break through -penicillin inhibits peptidoglycan cross-linking: gram pos has lots of peptidoglycan, easier to stop
Why is it important to understand the structure of a bacterial cell when developing an antibiotic?
-Knowing how to pass through structures, like cell wall, by finding flaws in the structure and composition (peptidoglycan, etc.) is how an antibiotic will work. -An antibiotic could inhibit the function of enzymes and proteins -if you know how a cell grows and performs its function, it is easier to stop
Patients forgetting to take their antibiotics are not the sole cause of antibiotic resistance. explain at least two other possible causes of the development of antibiotic resistant bacteria
-Random mutation could cause a trait that allows bacteria to survive better -Natural selection would increase the frequency of this trait -Feeding animals antibiotics, which increases the resistant population. -Conjugation, transduction, and transformation spreading resistance to other strains.
How do antibiotics work without harming the surrounding human cells?
-The structures of human cell are quite different than bacteria cells. -eukaryotic cells (human cells) do not have cell walls -antibiotics target and attack cell walls (only present in bacteria) -Bacteria cells replicate faster, so it will harm them faster.
Based on the results of the experiment as well as what you learned about the mechanism of gene transfer between bacterial cells, was the streptomycin resistant gene transferred from strain I to strain II, or was the ampicillin resistant gene transferred from strain II to strain I?
-ampicillin resistance was transferred from strain II to strain I -ampicillin resistance is found in the plasmids, which are easier to move and replicate -streptomycin resistance is found in the chromosomal DNA, which is harder to access and would not transfer during conjugation.
Why did neither strain grow on the plate containing both streptomycin and ampicillin before mixing the strains?
-both bacteria were immune to one form of antibiotic -antibiotics still usually work on other strains, just not as effectively -e. coli I's growth was prevented by ampicillin, while e. coli II's growth was prevented by streptomycin
Sue Smith wants to know why she has to continue taking her antibiotics even though she is feeling better. explain the importance of sue completing her full course of antibiotics as prescribed
-least resistant strains are the first to die from antibiotics -when these strains die, the patient feels better, but the most resistant strains are still present -resistant bacteria is free to reproduce, making the frequency of hard to kill bacteria increase -bacteria has been exposed to antibiotic, can build up resistance
Given what you know about antibiotics, what other variables, besides missing doses, might affect the success of an antibiotic?
-natural selection (less resistant strains die first) causes increasingly resistant strains of bacteria (harder to kill with antibiotics). -wrong dosages/wrong type of antibiotic for the type of bacteria (penicillin doesn't work with gram negative bacteria, etc.)
what cellular components do some bacterial cells have that make them powerful pathogens?
-pili (allows structure to attach to others) -capsule (protects against foreign invaders) -endospores (resistant to environmental stress, survive harsh conditions) -gram negatives have the outer membrane
Why did the e. coli I strain grow on both the lb agar plate and the lb agar plate with streptomycin but not grow on the lb agar plate with ampicillin?
-the e. coli I strain was resistant to streptomycin -it can grow on plates with no antibiotics or streptomycin -it is not resistant to ampicillin, so the ampicillin killed it so it couldn't grow
Explain what the results indicate about the new strain of bacteria produced when both strains of e. coli were mixed together
-the new strain inherited the other resistance in addition to its original resistance -the new strain resists both ampicillin and streptomycin
Why are antibiotics not effective against viruses?
-viruses have different structures and replicate differently than bacteria -target growth machinery in bacteria
What was the purpose of culturing bacteria on these four plates?
2 plates with 1 type of antibody each: find which strains of bacteria are immune to one type of antibody. The plate with 2 antibiotics (streptomycin and ampicillin) showed that there were no bacteria in the beginning that were resistant to both antibiotics. The plate media with no antibiotics is to show that the media is good and bacteria will grow in normal non antibiotic conditions.
bacterial cell parts: capsule
A distinct and gelatinous layer, called glycocalyx, enveloping the cell. This layer enables the bacterial cell to adhere to specific surfaces and sometimes protects bacterial cells from human immune systems.
sulfa antibiotics (sulfonamids)
Antibiotics that binds and inhibits an enzyme that controls cell growth (folic acid synthesis)
tetracyclines
Antibiotics that binds to bacterial ribosomes, inhibiting protein synthesis
fluoroquinolines
Antibiotics that effective against DNA synthesis
penicillins
Antibiotics that inhibits cell wall synthesis
transduction process
bacterial dna is transferred from 1 bacterium to another inside of a virus (bacteriophage) that infects bacteria, phage infects a bacterium and takes over its processes to produce more phage, bacterial DNA may inadvertently be incorporated into the new phage DNA, when bacteria dies and breaks apart, the new phage goes onto infect other bacteria, bringing along genes from the previously infected that may cause the spread of certain antibiotic resistance
mutation
change in the dna that sometimes causes a change in the gene product, which is the target of the antibiotic
