Microbe-Animal Symbioses

tract morphology

Evolution of herbivory in early tetrapods:

1) Changes in jaw, teeth, and digestive _______

○ Wide rib cages, blunt teeth, wide jaws

digestive tract symbionts

Evolution of herbivory in early tetrapods:

1) Acquisition of _______ with cellulolytic enzymes

○ Eating leaf-litter

○ Eating insects with endosymbionts

○ Eating or touching fecal matter

animal physiologies

Early gut microbiomes probably evolved multiple times under different environmental conditions and __________, leading to diverse feeding habits across the animal kingdom.

About 22 million years ago, grassland cover expanded leading to selective pressures for _____ based diets

This was accompanied by changes in the dental and digestive morphologies of early mammals, leading to speciation of modern day herbivorous mammals

more

Herbivores

● Jaws optimized for side-to-side movement

● High-crowned teeth and complex molars

● Larger gut chambers

● Reliance on microbial fermentation to break down plant compounds

● Generally, ______ diverse gut microbiome

less

Carnivores

● Sharp teeth for ripping and shredding

● Smaller, simpler gut

● Reliance on host and microbial enzymes for protein breakdown

● Generally, _____ diverse gut microbiome

ruminare

Rumen from Latin _____ “to chew over again”

100-150

Foregut fermentation chamber that in cows can hold _______ liters

anoxic

Rumen-

Warm (39C, 102F) and _____ with pH of 5.5-7

omasum

Rumen-

Small food particles are passed through the reticulum into the _____ , but larger particles (cud) are regurgitated and chewed again before return to the rumen

20-50

Food may remain in the rumen for ______ hours

cellulose to glucose

Inside the rumen, cellulolytic organisms hydrolyze _________

volatile fatty acids

Rumen-

Products of fermentation include _________ (acetic, propionic, and butyric acids) which the animal absorbs as nutrition

digested themselves

Microbial cells adhere tightly to food particles and end up _______ as a key source of protein and vitamins for the host

Firmicutes

Anaerobes dominate with key bacterial members including ______ and Bacteroidetes alongside archaeal methanogens

cecum

Hindgut fermentation - e.g., horses:

In hindgut fermenters, fermentation occurs after the passage of food through the stomach in the ______ and colon.

volatile fatty acids

Hindgut fermentation - e.g., horses:

Nutrition (in the form of _______ from fermentation) are absorbed through the cecum and colon walls

Hard tissue

The mammalian oral microbiome (example: canines):

Distinct niches exist within the canine mouth

1) Soft tissue

2) _______

3) Saliva

Phylogeny

Factors thought to influence the composition of the mammalian skin microbiome:

1) Geography

2) Environment

3) Physiological factors

4) ________

Photosynthesizers

Aquatic Animal-Microbe Symbioses

1. Bioluminescent bacteria

2. __________

bioluminescent Vibrio fischeri

The Hawaiian bobtail squid hosts populations of _____________ in a specialized organ

V. fischeri

______ is obtained from the environment as cilia on the light organ beat, drawing ocean water toward pore opening

Chemoattractants

Chitinous mucus containing highly specific chemical compounds is produced at the entry point

◆ ___________ to attract V. fischeri

◆ Immunity factors to ward off other organisms

70-95%

Hawaiian bobtail squid, Euprymna scolopes:

_____ of symbiont cells are released every day at dawn, and a new population is ready to go by that night.

dark

If you genetically modify V. fischeri to be “_____”, symbiosis-associated host genes are not expressed

Aliivibrio and Photobacterium

Anglerfish associate with bioluminescent bacteria in the genera ________ in organs called “lures”

female

Only _____ anglerfish exhibit this symbiosis

mates

Anglerfish:

The bioluminescent organ “lures” prey and _____ toward the host

few inches

Female anglerfish can be up to 4 feet long while males are usually only a ______ long

sexual parasitism

Males exhibit _______ wherein they attach themselves permanently to the female, providing sperm while the female provides nutrition

gene reduction

Anglerfish symbionts: a rare example of _______ in a extracellular, horizontally transmitted symbionts

photosynthetic symbionts

In clear, low nutrient waters, marine animals with large surface area relative to volume are well suited as hosts for _____________.

Symbiodinium

Reef-building corals form symbiosis with _______, a photosynthetic dinoflagellate

symbiosomes

Symbiodinium-coral symbiosis:

The symbiont is harbored within ______

vertically transmitted

In the coral symbiosis, Symbiodinium is typically ________ during reproduction but can also be horizontally transmitted

photosynthate

Symbiodinium gives most of its _______ to the coral host

In exchange, the coral host provides nitrogen and phosphorus.

calcium carbonate

The habitat provided by the coral is optimal for photosynthesis - the _________ structure of corals is very efficient at collecting solar radiation

Symbiodinium

______ also associates with jellyfish, which lay upside down to maximize light exposure for photosynthesis

Cassiopea

_______ is sometimes observed to be carried around by crabs (Dorippe frascone, ‘sea urchin crabs’), which are potentially using the jellyfish sting for defense of its own

Symbiodiniaceae

Photosynthetic dinoflagellates of the family ________ are also found in symbiosis with giant clams

rotifers and protists

Epibionts of marine zooplankton include ________

commensal or parasitic

Zooplankton protist epibionts:

This is thought to be either a __________ relationship

Dense epibionts

Zooplankton:

________ are thought to slow down the host, make reproduction harder, and make environmental sensing harder for the host.