Exam 2 Lecture 17 Flashcards
True or False: Chlamydia and Rickettsia are genetically similar
False.
The genomes most similar to rickettsia are those encoded by ______.
Mitochondria
Rickettsia are members of the ____-_________. They are able to produce their own ______.
alpha-proteobacteria
ATP
Both chlamydia and rickettsia are ______ _______ bacteria, meaning they need a _______ ____ cell and thus cannot be grown on a plate or liquid culture.
obligate intracellular
eukaryotic host
How many genera and species in the Chlamydiaceae family are pathogenic?
2 genera, 3 species
Name 3 bacteria under the Chlamydiaceae family
- Chlamydia trachomatis
- Chlamydophila pneumoniae
- Chlamydophila psittaci
What infections does Chlamydia trachomatis cause?
Ocular infections, urogenital infections
What infections does Chlamydophila pneumoniae cause?
Respiratory tract infections
What infections does Chlamydophila psittaci cause?
Respiratory tract and systemic infections
What does EB stand for? What does RB stand for?
Elementary body
Reticulate body
Name characteristics of the elementary body (5)
- infectious
- extracellular spore-like form
- metabolically inert
- non-replicating
- stabilized by disulfide crosslinking of outer membrane proteins
Name characteristics of the RB (4)
- non-infectious form
- intracellular replicating form (divide inside inclusion)
- osmotically unstable, can’t survive extracellularly
Describe the life cycle of Chlamydia
- EB binds to a host epithelial cell
- EB induces its own uptake into the cell and resides inside a membrane bound vacuole (inclusion)
- About 8 hours after, the EB differentiates into the RB form
- About 8-18 hours after, RB modifies the inclusion and brings nutrients inside the inclusion so it can replicate
- About 18-24 hours later, the inclusion has grown a lot larger and there’s a mix of Eb and Rb (b/c a signal led to differentiation of Rb back into Eb)
- The cell lyses or forms an extrusion after 48-72 hours. (Rbs do not survive, but Ebs go on to infect new host cells)
Describe the genome size of chlamydia
Small (936 genes)
Why does chlamydia have a small genome?
It has evolved to get a ton of nutrients (amino acids, lipids, nucleotides) from the host cells, so it does not require many biosynthetic pathways
Since chlamydia relies so heavily on the host for nutrients (Amino acids, nucleotides, lipids, etc), most of its genes focus on ……….
interacting and attaching to host cells
What do both EBs and RBs express?
type III secretion systems (T3SS)
More than 5% of the entire genome of Chlamydia encodes for ……..
type 3 secreted effectors
Because Chlamydia infects epithelial cells, it needs to induce its own uptake. When the EBs bind to a host cell using ____, it will inject a protein known as _____
T3SS
Tarp
Tarp is pre-formed by ___, and induces _____ _________ as well as ________ of the ___
RB
actin polymerization
phagocytosis
EB
What do RBs secrete?
- Inc proteins
- CPAF proteases
- Anti-apoptotic factors
Name the function of Inc proteins
- modify the inclusion by the following:
1. chlamydia inserts a SNARE like protein in the inclusion (normally the lysosome interacts w/ the phagosome thru their SNARE proteins). thus, this disables fusion w/ the lysosome
2. the inclusion needs to grow, so it adds membrane by fusing with Golgi vesicles
Name the function of CPAF protease
It degrades TARP. This makes sense because TARP is used to help EBs become phagocytosed. If TARP stays present on host cells, superinfection can occur.
Name the function of Anti-apoptotic factors
Keeps the host cell alive while RBs are maturing into EBs
