Bacteria Flashcards
What are bacterial cell walls made of?
Peptidoglycan
What are the 3 common shapes of bacteria?
Bacillus, coccus, spiral
What are bacterial chromosomes like?
Single, circular chromosome
What is a nucleoid?
Region of condensed DNA that is anchored to the membrane, but not membrane enclosed
What 3 structures are only found in some bacteria?
Flagella, pili, capsules
What’s the difference between gram-positive and gram-negative bacteria?
Gram positive have a thick PG layer on the outside of the cell membrane, gram-negative have a thin PG layer sandwiched between two membranes
Are the outer and inner membranes in gram-negative bacteria composed of the same things?
No, the outer membrane has lipopolysaccharides in the outer leaflet
What is the structure of LPS?
Hydrophilic polysaccharide heads, hydrophobic fatty acid tails
What does LPS do?
Acts as a chemical barrier against proteins, antibiotics, toxins
Why are gram positive bacteria easier to kill?
They only have the physical protection from the PG, they don’t have the chemical protection of the LPS
How do gram-negative bacteria get nutrients across the LPS?
Selective porins in the outer membrane
How is peptidoglycan structured?
Repeating sugar units of NAG and NAM, with a tetrapeptide chain attached to the NAM sugar. The peptide chain is cross-linked to form a super strong 3D network
How is the genetic information in a bacterial cell organized?
Most species have a single circular chromosome, a few have multiple chromosomes, a few more have linear chromosomes
Why is the prokaryotic genome streamlined?
Very little DNA is non-coding compared to eukaryotes
How is the prokaryotic genome streamlined?
- No telomeres because the chromosome is circular
- No centromeres because replication happens by binary fission instead of mitosis
- Intergenic regions and regulatory elements are small
How is the bacterial chromosome condensed?
Looping and supercoiling
Do histones aid with DNA condensation in prokaryotes?
No. There are looping proteins but they aren’t histones
Why are transcription and translation able to be coupled in prokaryotes?
No membrane is separating transcription and translation, so ribosomes can attach to a binding as soon as its transcribed
Why is coupled transcription and translation advantageous?
Allows really fast gene expression
What are the 8 reasons why bacteria are good model organisms?
- Haploid
- Easy to grow
- Fast generation time
- Asexual reproduction
- Easy to count
- Easy to isolate
- Easy to store
- Easy to genetically manipulate
Why does being haploid make bacteria and phages good model organisms?
You only need one copy of a mutation to see an effect since they’re expressed immediately
Why can being haploid be disadvantageous for genetic studies?
Difficult to maintain lethal mutations, and mapping can be difficult
Why does being easy to grow make bacteria good model organisms?
Can grow really well different mediums that are easy to make, in both solid and liquid medium
When would you grow bacteria on a solid plate vs in liquid medium?
If wanting single colony isolates, use solid medium. For lots of colonies, use liquid medium
