Fungal Commensalists and Entomopathogens Flashcards
What are the three putative commensalist systems?
Labouls
Septobasidium
Fibulorhizoctonia
What are Laboulbeniales considered?
The fungal ticks of insects
What are the characteristics of Laboulbeniomycetes?
Determine growth
Lack an asexual state
Spores are sticky and attach to insect cuticles and send in a foot cell
Can be dioecious - male and female parts occur on different thalli
Spores are ejected by a trigger mechanism
Are Labouls harmful to their hosts?
Attachment is shallow; haustoria may or may not be formed
Infected insects tend not to live as long as uninfected; may be comorbidity factor with other fungal infections
Labouls are involved in which tripartite parasitism?
Bat - bat fly - laboul
What are septobasidium?
Scale insects live in pockets within the thalli and depend on the fungus for protection
The fungus has a network of tunnels connecting insect pockets
The parasitized insect individuals are immobile and sterile, and in a prolonged juvenile state
Sex differences within septobasidium?
Females are immobile and males can roam
When do the young in the septobasidium emerge?
In spring at the same time as basidiospores are formed, and disperse fungus elsewhere
What is a cuckoo fungus (fibularhizoctonia)?
A fungus that tricks termites into taking care of it
How does the cuckoo fungus trick the termite?
Not colour: termite balls and termite eggs are of a different color, but termites lack eyes anyway
Texture?
Chemical signals?
How does the cuckoo fungus use enzymes to trick termites?
They mimic termite eggs by producing the cellulose-digesting enzyme beta-glucosidase
What does the cuckoo fungus get out of the relationship?
Eggs and termite balls are groomed frequently; their saliva contains antibiotic substances that protect them from dryness and pathogens
The sclerotium is a tough ball of densely packed filaments that germinate into a fungal colony under favorable conditions
The relationship is facultative for the termites
No other fungi occur in the nest; no competitors
Is the cuckoo fungus pathogenic?
There are a small number of eggs in which the interior has been consumed and replaced by fungal hyphae
What does the termite get out of the relationship?
Under experimental conditions, the fungus improved survivorship of the eggs without native nest material
Fungal termite balls outnumber termite eggs in nests and yet are cared for, which costs energy
What are two parasitic fungal associations?
Cordyceps/Beauveria
Massospora
What does extended phenotype mean?
Architectural modifications of an organisms surrounding
Influence of a parasite on its host at a distance
Influence of a parasite on its host from within
What does the zombie fungus do?
Induces zombie behavior in insects
Around noon, based on solar cues, the insect wanders upwards and bites down on foliage or twigs, securing itself
How do zombie fungi infect their host?
The conidium forms a germ tube and appressorium that will cause hyphae to penetrate into the insect where in vivo blastospores or hyphal bodies can be produced
What are some compounds secreted by the fungus during manipulated biting behavior?
Enterotoxins
Egot
Lipocalins
Terpenoids
Tyrosinases
Non-ribosomal proteins
What are some ant processes that are affected during manipulated biting behavior?
Chemosignaling and stimuli reception
Receptor (de)activation through (ant)agonists
Abnormal serotonin/dopamine levels
Down-regulation of immune response
Circadian clock
Muscle atrophy
What did Bassi discover about Germ Theory?
He examined the death of silkworms and determined it was caused by a living agent
He recommended the separation of healthy and infected worms and disinfection
What was the living agent killing silkworms?
Beauveria bassiana
What is Beauveria?
A widespread anamorph of an Asian Cordyceps teleomorph
What are the anamorph names in Hypocreales?
Beauveria (teleomorph = Cordyceps)
Metarhizium (teleomorph = Metacordyceps)
Tolypocladium (teleomorph = Elaphocordyceps)
What does Metarhizium produce to reduce immune detection?
They produce hemolymph-induced collagen on their cell surfaces
Which genera are immune to Drosophila anti-fungal compounds?
Metarhizium and Beauveria
What do Hypocrealean fungi produce?
A wide range of secondary compounds
What do insect fungi do once they are in the hemocoel?
The fungi proliferates
What nutritional style do Hypocealean fungi follow?
Hemibiotrophic which means they parasitize the host when alive and break it down when dead (saprotrophy)
What is host death achieved by?
The secretion of secondary metabolites, some of which down-regulate the immune response of the host
What is cyclosporin?
A hypocrealean immunosuppressant
How can pathogenic fungi be used in agriculture?
Fungi adapted to killing insects slowly, so the insect helps them disperse
In agriculture, we want faster death so entomopathogens have been studied for genetic engineering
Why is transgenic beauveria/metarhizium being used in the fight against malaria?
Malaria-carrying mosquitos are becoming resistant to pesticides
We want to develop a fungus that wipes out malaria
What do we want a fungus to target in wiping out malaria?
The Plasmodium sporozoites
What proteins does the recombinant metarhizium produce in the fight against Plasmodium sporozoites?
A protein that blocks sporozoite attachment to the mosquito salivary gland
An antibody that causes sporozoites to agglutinate
A microbial toxin (scorpine)
How does Metarhizium pingshaensei target mosquitos themselves?
Researchers added genes for expression of spider and scorpion toxins that go after the CNS
Now only one spore is necessary to kill a mosquito
What is cathinone?
An amphetamine that is previously known only from plants
Massospora expresses cathinone
What is psilocybin?
A tryptamine previously only known from Psilocybe
