Microbiology Flashcards
Difference between eukaryotic and prokaryotic transcription and translation
Eukaryotes
Transcription (nucleus) and translation (cytoplasm) occur separately
- Introns splicing post-transcription
Prokaryotes
Both processes take place in the cytoplasm stimultaneously
- Does not contain introns
Difference between eukaryotic and prokaryotic composition of ribosomes
Eukaryotes
- 40S and 60S subunits (larger) to yield 80S
Prokaryotes
- 30S and 50S subunits to yield 70S
The two prokaryotic domains
Archaea
Bacteria
Bacilli vs. cocci vs. spirilla
Bacilli
- Long and rod-shaped
- Strepts and staphyls
Cocci
- Spherical
- Flagellate rods (Salmonella typhi)
- Spore-former (Clastridium botulism)
Spirilla
- Helical/”spiral-shaped” (H. pylori)
- Vibrios (vibrio cholerae)
- Spirochaetes (Treponema pallidum)
Bacterial cell wall
CW is peptidoglycan
- Gram +: thick peptidoglycan (purple)
- Endospore: formed under harsh environment (mostly Gram +)
- Gram -: thin peptidoglycan with a outer membrane (pink); lipopolysaccharide
- The outer membrane may cause Gram - bacteria harder to treat with antibotics
(Fungal CW is chitin)
Flagellum
Facilitates bacterial motion
Most common form of bacterial reproduction
Binary fission
Bacterial gene transfer
Transformation
Acquiring DNA from environment (plasmid = small piece of circular DNA)
- Usually occur during crowding or starvation (aging colony); transformation can be triggered by starvation
Transduction
Being injected DNA by a bacteriophage
- May be detrimental to bacteria, but may be advantagous to the virus
Conjugation
Direct DNA transfer via contact bw bacterial cells with sex pilus
- An adaptive mechanism when resources are scarce
Transposon
A DNA sequence with the ability to excise itself from the genome and move to another location
- In both prokaryotes and eukaryotes, transposons are located in the chromosomes
Production of food of bacteria
Autotrophs
Can produce their own food
- Photoautotrophs & chemoautotrophs
Heterotrophs
Consume external organic compounds
- Photoheterotrophs & chemoheterotrophs
Bacterial ecology
Obligate anaerobes
Die in presence of oxygen
Facultative anaerobes
Can survive with or without oxygen
- E. coli
Thermophile
High temp
Mesophile
Medium temp
Psychrophile
Low temp
Symbiosis
Symbiosis: relationship between 2 species
- Mutualism
- Commensalism
- Parasitism
Characteristics of a virus
Virus can only replicate inside a host cell
(Virus are not living organisms)
Lytic cycle
- Viruses that replicate by the lytic cycle, killing their host cells, are called virulent
- If then virus does not lyse the cell, it becomes integrated into the bacterial genome in a less harmful form (provirus/prophage), lying dormant for one or more generations as a part of the lysogenic cycle (latent infection)
- Ex. HIV (also a retrovirus that infects helper T cells)
- Either spontaneously or environmental circumstances, the provirus cell enter a lytic cycle
- Superinfection: cells containing proviruses are normally resistant to further infection by similar phages
Atypical viruses
Prion
- Disease-causing protein
- Made up of only protein, no DNA
- Mad cow disease
Viroid
- Disease-causing molecule (mainly in plants)
- Made up of only a single-stranded RNA, no protein