Lecture 1: Properties of Bacteria Flashcards
Bacterial actin and tubulin homologue
- MreB (actin)
- FtsZ (tubulin)
Because bacteria do not have a nucleus, what is uniquely coupled in these cells?
-transcription and translation
Rule of thumb: essential genes are found on the _______ and unessential genes are found on _____.
- Chromosome
- Plasmids
Theme about bacterial genome size
- Size of genome reflects lifestyle of bacterium
- Small: obligate intracellular pathogens
- Large: thrive in variety of environments
Differences between bacterial and eukaryotic membranes
- does not contain sterols
- site of energy production since they do not have mitochondria
- outside of membrane, have rigid cell wall
Peptidoglycan is what bacterial cell walls are made of and is composed of repeating pairs of what sugars?
- NAG and NAM joined by B(1,4)- linkages
- crosslinked by peptides
Peptidoglycan is sensitive to what enzyme and why?
-Lysozyme sensitive because this enzyme can cleave B(1,4) bonds
Like bacterial cell shape, _______ can be very useful in identifying bacteria
-gram stain
-Gram positive vs. gram negative
-G+: stains blue/purple, thick peptidoglycan layer outside of internal membrane
G-: stains pain, thin peptidoglycan layer sandwiched between inner and outer membrane
In a gram negative cell, what is the space between the 2 membranes called?
-Periplasm
Gram-positive surfacce
- Teichoic acid and Lipoteichoic acid (LTA)
- peptidoglycan and LTA are exposed and recognized by host immune system
- better at living in dry areas like skin
Gram-negative surface
- very asymmetric
- outer leaflet of outer membrane contains LPS (lipopolysaccharide), an endotoxin, which is trigger for immune system
- outer membrane also has porins which makes it more permeable than inner membrane
5 things bacteria use their surfaces for:
- motility via flagella
- Adherence via pili/fimbriae
- sensing the environment via Two component signal transuction system
- Acquiring nutrients
- Avoiding immune defenses: capsule,
Two-component systems
- used to sense and respond to bacteria’s surroundings
- consist of histidine kinase protein (HK) that spans bacterial membrane and a response regulator protein (RR) located in bacterial cytoplasm
- HK autophosphorylates when it binds its stimulus on outside of membrane. P-HK then phosphorylates RR which is usually a TF, to activate it
- result: change in environment results in a change in gene expression on inside of cell
T/F: only gram + cells can form capsules.
-false, + and - can
Type 3 Secretion System (TTSS)
- used only by G- cells
- crosses 3 membranes
- directly introduces bacterial effector proteins into host cell without risk of antibody interference
- effectors manipulate host cell’s behavior to usually affect actin in cytoskeleton to promote or inhibit uptake of bacterial cell
Examples of bacteria living together to form multicellular structures
- fruiting bodies (anthrax)
- biofilm
When do biofilms form?
-When planktonic cells attach to solid surface and start to secrete slime called extracellular polymeric substance (EPS)
2 mechanisms for biofilm growth and which is more prominent?
- Cell division
- recruitment **
Why are biofilms clinically important/worrisome?
-they are resistant to antibiotics and also to host antimicrobial peptides which makes them hard to treat
Why is lateral gene transfer the major way bacterial evolve into pathogens, instead of mutations?
mutations are often detrimental, lateral transfer genes have already stood the test of selection, and it allows whole sets of genes to be transferred together
T/F: most antibiotics are man-made
-false; most made by other microbes, often other bacteria
T/F: virulence genes and antibiotic resistance genes are often carried on mobile DNA elements
True
How are plasmids laterally transferred?
-conjugation
Many bacterial toxins are encoded by ________.
-temperate bacteriophages
Virulence genes found on bacterial chromosome are often clustered in what are called __________.
-Pathogenicity islands (likely from a phage)
Natural competence is also known as?
- Transformation
- mainly G+ but also done by some G- cells
- incorporate free DNA usually from lysed siblings that is in their environment
