C7- Fungal Collaborators And Competitors Flashcards
What is ammensalism
Where one has negative effect on the other with no gain unlike parasitism
What sorts of things can bacteria modulate of fungi
Antifungal susceptibility, capsule formation, growth, biofilm, hyphal development
What sorts of things can fungi modulate on bacteria
Growth, antibiotics, virulence traits like iron acquisition, quorum sensing and biofilm
Candida albicans and pseudomonas aeruginosa - example 1
What is pa found in
Cystic fibrosis lung
What do it do to hyphae directly
Binds hyphae in response to quorum molecule homoserine lactose and kills them
What phenazines can pa release
Pyocyanin and pyorubin
What are these important according to major study on morphology effects and how do these phenazines do this
Block biofilm formation and hyphal formation
By repressing respiration in candida
Why does phenazine increasing o2 levels in biofilm important (found during experiments)
Because they’re usually anaerobic to allow colonies of anaerobes to develop
How did they find it was stopping respiration
Dye TTC which turns red by reduction by the ETC didnt happen
Lack of red in presence with phenazines
How does conversely, pa induce fluconazole resistance of candida
Homoserine lactose induces efflux pump expression
Which structure is similar to homoserine lactone which indicates its mechanism of action on hyphae (also blocks hyphal growth)
Farnesol
Which gene do pa have for iron acquisition which is compromised by fungi
Pyochelin genes
Which lung fungi can block growth and biofilm formation of pa important for virulence in Cystic fibrosis
Af through its gliotoxin
Example 2 - lactobacillus app and c. Albicans
What product of gut lactobacillus masks b glucan (immune escape) and can be used as a c source for growth of ca
Lactate
How does it remodel the cell wall
Through Gpr1 sensor of lactate and signal transduction to remodel b glucan
Which lactobacillus has chitinase activity which blocks yeast to hyphal formation which is good for us in contrast
Rhamnosis GG
In mouse model, what does scfa (also produced by commensals like lactobacillus) like butyrate help to stop overgrowth which is stopped in antiobiotic treatment (potentially important in Ibd)
Filamentation and biofilm formation
T6ss and microbial competition
Explain the structure of a t6ss
You have a sheath which contracts during firing event
Then base plate
Then a membrane complex/HCP tube which pushes effector through the vgrg and paar(needle end)
HCP-vgrg-paar structure pushes effectors into target cell
What depolymerises the sheath to decontract it after a firing event, allowing it to reset for new firing event
TssH
What do resistant bacteria have which neutralises effector proteins
Immunity proteins which bind
Give a few examples of t6ss use
Inter bacterial competition
Nutrient scavenging
Killing of fungi
Host cell invasion/killing
Which bacteroides can control other popn of bacteroides like b theta or ovatus which don’t have it through t6ss
Fragilis
What is resistant to this killing
Proteo bacteria like ecoli
Give example of a bacteria which uses its t6ss to kill fungi in inter kingdom competition
Serratia marcescens
Incubation of sm with the sach cerevisiae, c glabrata and c albicans does what compared to t6ss mutants
Kills them
Which effector previously invoked in bacterial bacterial competition was later found to only affect c albicans killing not the other 2
Tfe1
How did they later identify again tfe 1 and other like tfe2
They did a ko of tsse component of the base plate so that effectors would accumulate in fungi
Then did quantitative proteomics on wt vs tsse mutant should see toxin accumulation
and found tfe1 and tfe2 hits and proteins like hcp which validated the t6ss model
What does ko of tfe2 effector do unlike tfe1 ko
Partially Rescues ca, cg and sc not just ca
What does ko of both effectors show unlike if only 1 is ko causing partial rescue
Same phenotype as having a t6ss ko (large survival)
Doing cryo-tem of sm with yeast Candida/sach cells shows what
Necrotic cells/ lysed in presence of t6ss but not in tsse mutant and in contact
Ko of tfe1 showed rescue aswel of necrosis/lysis of Candida albicans
Loss of granules in tfe2 mutant when incubated with glabrata and sach cer
When you express a plasmid into the fungi with tfe1 or 2 into s. Cerevisae what happened. Was tfe2 found to kill the cells or jus cause growth arrest of s.cer specifically (which stopped when stopped tfe2 expression)?
Tfe1 had no toxicity effect at low levels but tfe2 always toxic
Found in liquid culture that once you stop tfe2 exp in cerevisiae then growth is rescued so it isn’t killing them.
How did studies on sach cer find the mechanism tfe1 uses is membrane transport interruption/ membrane depolarisation
Dibac4 staining which stains cells which aren’t respiring/no etc/membrane depolarisation (opposite of ttc)
Showed staining of sach cer expression of tfe1
Are hyphal tup1 ko candida also killed by sm or just yeast
Both
How is tfe1 as a membrane depolarising toxin also supported by quantitative proteomics when candida incubated with the diff effectors wt/mutant
No target proteins which are upreg or downregulated in its presence (no diff in mutants vs wt)
So suggests it targets membrane not specific proteins
How many proteins are differentially upreg or downregulated in tfe2 presence
30
What are downregulated vs upregulated
Sulfate assimilation parhway downregulated (way sulfur is acquired for growth)
Upreg of arginine synthesis
What does this indicate
Imbalance of nutrients/ depletion of nutrients leading to starvation, autophagy and death
Other fungi- bacteria interactions
Which bacteria in oral mucosa constantly found in biofilm with Candida albicans to form plaques or caries/tooth decay
Strep mutans
How is it suggested this biofilm forms
Through farnesol signalling of candida which induces glucosyltransferases by mutans to increase ecm component of biofilms
Which 2 bacterial commensals found in mouse models sufficient in stoping candida overgrowth/colonisation (eg in Ibd) - FAN 2015
Blautia producta (firmicute) and b theta
How in mice models after 2 weeks was ca undetected. The same molecule also reduced invasive disease death by 50% in mouse model
Through inducing ll37 whcih is anti-candida by hif1a tf induction
Does proteobactedia have the same effect through ll37
No- showing importance of immunomodulatory firmicute and bacteroidetes with other examples like b fragilis and clostridia/f. Prausnitzii
Why is hoarau 2016 been controversial
Because s. Marcescens shown to have a t6ss which would suggest it is not mutualistic with candida
Why are gpi anchored mannoproteins with n-mannan being on the outer cell wall very important
To hide b glucans which are very immunogenic
Which author / research study first coined the idea that l Reuteri in mouse models are critical for trp metabolism induced ilc3 which release il22- which they found to have antagonistic effects on c albicans (example of a ammensalistic relationship)
Zelante 2013
