Guest Speaker Lecture Flashcards
Natural Selection
survival of the fittest
occurs at level of reproduction
symbiotic relationships feature multiple _________
reproductives
maxing reproduction is in the best interest of each organism
pathogenesis
mutualism
commensalism
all macroorganisms live with _______
How do these microbes interact with their host and each other?
How do these interactions change?
How does coevolution function given such complexity?
Attine Ants
Attine diversity
Gradient of evolutionary sophistication
- colony size
- nutrient source
-caste differentiation
Trachymyrmex septentrionalis
Klassen lab model system
Ranges in USA from NJ to TX
Small colonies ~ 1000 workers
Eat mostly oak catkins, catepillars frass, fresh leaves
Trachymyrmex septentrionalis body characteristics
redish brown
have wings to do a mass swarm for mating, then the males die, the women start a new colony
Trachymyrmex septentrionalis
Live in NJ pine barrens, also done work on south east coast
What do we look for in ID colony?
small mound 5-6 inches
dig a hole next to it until there is a wiggle,
then you can find the fungus garden underground which is the symbio the ants are growing underground with the plant material they harvest
What type of forest are they found?
Oak pine mix, preferably an area which has been burned
How do you take samples of ants?
Asperator, a glass rod which goes in a tube, attached to another tube attached to the mouth, to suck up the ants into the tube to the vile
Once captured, how are they stored/kept?
In a sand boxed chamber with a fungus garden, water, and airways
Leaf-cutter ants
The most highly evolved fungus-growing ant
Atta:
- millions of colony members
- dominant herbivore in neo-tropical forests
Life cycle of a leaf-cutter colony
production of sexuals -> fungus fragment -> mating flight -> colony founding -> colony growth -> production of sexuals
Clonal propogation
the queen carries the fungus to start the new garden
When the queen dies….?
The colony dies
Why is clonal propogation advantageous?
Allows co-specialization
- fungal gongylidia of the leaf-cutter cultivar
-behavioral adaptation
Fungus garden propagation by the queen
Ant nest structure to house the fungus
garden and dump
Disease management
How does the fungus contribute to clonality?
fungus-fungus antagonism increases with increasing genetic distance
fungus enzymes pass through the ant’s digestive tract and are absorbed by the grden to help leaf digestion
Mutualism of plant and fungal garden problem
Pathogen susceptibility
Pathogen susceptibility
If the pathogen gets into a healthy garden then the ant can also get sick or vice versa
Escovopsis
Shows specificity to different cultivar strains
Some prduce Shearinines that inhibit ant movement and cause ant death
Ant solution #1: Antiseptic Behavior
- Waste, old, and diseased biomass transferred from gardens to dumps
- maintained by specific castes to avoid garden contamination
Increased fungus grooming upon infection}
filter and collect spores of the contaminant to clean themselves
If you have hitchhikes, there are more spores than those not exposed to hitchhikers
Metarhizium
ant pathogen
Ant solution #2: chemical defense
Metapleural gland antimicrobial secretions
Ant solution #3: Switch cultivars
Benefit: access more diversity from the wider population
Disadvantage: limit the specialization of a tighter symbiosis
Fungus solution
Form fruiting bodies
-genetic interactions with the larger free-living population
-dispersal from site of pathogen infection
Ant solution #4 Find new friends
Pseudonocardia: antibiotic-producing actinobacteria
Pseudonocardia
Genome-guided natural product discovery
analyzing natural product biosynthetic gene help us discover new compounds
Pseudonocardia Natural Product Capacity
Problem with a 3rd symbiont #1
Potential antagonism with th cultivar fungus
Problem with a 3rd symbiont #2
Pseudonocardia compete with each other
- presumably living in ant glands is advantageous fro Pseudonocardia
- competition between pseudonocardia may select against Escovopsis defense
Bacteria in T. septentrionalis fungus gardens have very high ______
high diversity
Northern forests vary seasonally
T. septentrionalis ants are inactive in winter
- Enter torpor
Varies by geography/climate
Food availability also varies by season
Seaonsal variability of T. septentrionalis fungus garden microbes
T. septentrionalis fungus gardens collected in July are distinct
Represents peak of ant foraging activity
Transient microbes or colonists
What metabolites are produced in fungus gardens?
Wild fungus gardens are chemically diverse
Pepaibol secondary metabolites occur in wild fungus gardens
Tricoderma - A Fungus Garden Parasite
Ants prevent Trichoderma infections by “trashing”
Crude Trichoderma Extracts Induce Ant Trashing
Peptaibols induce ant trashing
Conclusion
