Microbiology Lect 21

Question 1

What are the characteristics of tropical coral reefs and stony corals?

Answer 1

-Stony corals are found in tropical coral reefs
-Characterized by oligiotrophic waters
-Keystone species in these environments
-Form the basis of coral reefs through the deposition of their calcium carbonate skeleton

Question 2

What is the phylum, class, and order of stony corals?

Answer 2

-Phylum Cnidaria
-Class Hexacorallia
-Order scleractinia

Question 3

What are the basics of Stony coral biology

Answer 3

-“Simple organisms”
-Colonial organisms
-Endoderm and ectoderm seperated by mesoglea
-Tissue thickness ranges between species

Question 4

Basics of the coral microbiome

Answer 4

-Despite stony corals being basal metazoans, they have been shown to house a complex microbiome
-Most well studied is the obligate symbiont Symbiodiniceae
-Research is not focusing on the roles of the other microorganisms

Question 5

Symbiodiniceae

Answer 5

The organism (dinoflagellate) that lives in coral

Question 6

Symbiodiniceae in the coral

Answer 6

-Housed in gastrodermal cells
-Photosynthetic and provide photsynthates to the coral host
-There are a fair dew in each polyp
-Breakdown of this obligate symbioses is described as coral bleaching

Question 7

What is a classic example of what might cause coral bleaching?

Answer 7

-Classic example of what causes this is heat stress
-If heating stops, corals can recover the dinoflagellates and survive
-If heat maintains, coral will eventually die

Question 8

What are the most well study part of the coral microbiome other than dinoflagellates? What are some important roles

Answer 8

-Prokaryotes, like bacteria and archaea, are probably the next well studied
-Have important roles in coral host
-Nitrogen cycling
-Nutrient cycling (C, S, and N), influence settlement and metamorphosis of coral larvae

Question 9

How do different species of stony coral vary in bacteria and archaea?

Answer 9

-Different species have different abundances of prokaryotes
-Within species it gets complicated
-Some species show stable microbiomes over time and space
-Some show differences between genotypes
-Some show differences in geographic location

Question 10

Surface mucus layer

Answer 10

-Houses a diverse array of prokaryotes and it is different to seawater communities
-Important role in coeal health, including reduction in pathogen colonization and undergo cycling functions
-New/old mucus has different microbiome, with old not protecting as well

Question 11

Viruses in coral microbiome

Answer 11

-Proposed to be important in microbiome maintenance (bacteriophages) and in horizontal gene transfer

Question 12

Fungi in coral

Answer 12

-Possibly roles in nutrient cycling (C and N)
-Also been implicated in antimicrobial activity
-Again, more research is definitely needed in this area

Question 13

What causes microbiome to go into dysbiosis?

Answer 13

A suite of abiotic and biotic factors

Question 14

What is the diseased coral microbiome called?

Answer 14

The pathobiome

Question 15

How were Acropora palmata studied for pathobiome?

Answer 15

-Coral fragments were exposed to disease

Question 16

Microbiome of Acropora palmata healthy vs diseases?

Answer 16

-Pathobiome is far more diverse than the healthy microbiome
-Disease causes a shift from a healthy microbiome to a pathobiome

Question 17

How do corals maintain their microbiome?

Answer 17

-Microbe to microbe (microbes essentially regulate/maintain eachother)
-Host to microbe (host regulate/maintain the microbiome)
-Microbe to host (Microbes help regulate the host)

Question 18

What can disrupt the microbiome? (take home)

Answer 18

-Environmental perturbation and disrupt the microbiome and shift it to a pathobiome state
-Heat stress and dinoflagellates
-Disease and prokaryotes

Question 19

Important take homes

Answer 19

-Despite being basal metazoans, coral have a complex microbiome
-Constitutes Symbiodiniceae, prokaryotes, viruses, fungi, and others
-Microbiome is different to the surrounding marine environment
-Microbiome has key roles for coral survival, including nutrient cycling, coral immunity (defense), and others
-Corals maintain a stable microbiome
-Environmental perturbation and disrupt the microbiome and shift it to a pathobiome state
-Heat stress and dinoflagellates
-Disease and prokaryotes
-Exact mechanisms of microbiome maintenance are unknown, but it probably involves all the below processes
-Host-to-microbe
-Microbe-to-microbe
-Microbe-to-host