Question

On a coral reef there are many interactions between animals, with even more important interactions between animals and microbes. Some of these relationships are critical for the coral colony survival while others contribute to the health decline of coral reefs. reefs? What is coral bleaching and how might corals be able to adapt to avoid the destruction of coral Genome sequencing of the bacterial symbionts of animals has allowed us to compare the genomic features of several symbionts. What can you deduce about the following bacteria: l. 0.4 Mb genome, 20% G+C content, incomplete peptidoglycan and nucleotide synthesis a. b. pathways 1.8 Mb genome, 40% G+C content, complete peptidoglycan and nucleotide synthesis ll. pathways Describe the concept that is broadly used in microbiome studies today that initially developed to understand the coral as an animal with all the microbiota that support a colony's survival Lichens and corals have a similar relationship with a photosynthetic microbe. Compare and contrast lichens and corals, including the types of organisms involved, the role of each partner, the specificity of the interaction, and the method of transmission for each relationship. c. d.

Answer 1

a) CORAL BLEACHING- when corals are stressed by changes in conditions such as temperature , light, or nutrients ,they expel the symbiotic algae living in their tissues , causing them to turn completely white, without the algae the coral loses its major source of food turns white or very pale and is more susceptible to diseases. Coral can avoid its destruction because of bleaching if the stress caused bleaching is not severe coral have been known to recover.If the algae loss is prolonged and the stress continues coral eventually dies.

b)Symbiont I- is likely a vertically transferred symbiont because its genome is much smaller , and has low G+C content , and is missing many biosynthetic genes.The stable transmission of a vertically transferred symbiont means that they no longer have a free living form.Therefore, overtime functions that can be supplied by the host are no longer necessary are lost.The adenine plus thymine content increases because common mutations that convert G-C pairs to A-T pairs are not fixed in symbionts that have fewer DNA repair enzymes to fix these mutation.

Symbiont II- is most likely a more recent association that is horizontally transferred between hosts instead of vertically transferred from parent to offspring .It may also still have a free living form because most biosynthetic pathways are still complete.

c) Microorganisms are key components of all multi-cellular life due to their crucial roles in nutrient cycling and metabolism in the past few decades the important relationship between coral and its microbial symbionts have been documented , however coral- microbiome interactions are not yet fully understood due to complex interactions, which include host modulation of the physiology of symbiotic cells and the influence of symbiotic cells on their host. The response of coral associated microbial communities to shifts in coral health and environmental stressors have been extensively explored and reported.Changes in environmental conditions may modify coral physiology leading to changes in the structure spatial arrangement and abundance of the local population.Through shuffling of the dominant photosynthetic symbiodinium clades within thier tissues some corals have become more tolerant to seawater temperature increases, thereby avoiding repeated bleaching events however corals may revert to the original clade over the long term when the stress is removed .The coral bacterial communities are also be involved in coral resilience , however little is understood about the permanence of these shifts in the coral microbiome in the face of changing environmental conditions.

d)Lichen- A lichen is not a single organism, it is a stable symbiotic association between a fungus and a algae and /or cyanobacteria . Like all fungi lichen fungi require carbon as a food source, this is provided by their symbiotic algae and /or cyanobacteria that are photosynthetic. The lichens symbiosis is thought to be a mutualism since both the fungi and the photosynthetic partners called photobionts benefit.

The specificity of interaction of lichen- The photobiont may be an alga or cyanobacteria both of which can produce simple sugars by photosynthesis. In contrast fungi are heterotrophic and require an external source of food. The fungi build the structure of the lichen thallus within which they provide conditions for a long term, stable association with their photobionts on the basis of the lichen symbiosis.

Coral reefs-corals reefs owe their striking beauty to the algae living among them, whose photosynthetic pigments allow for a wide range of a colorful compositions on the ocean floor.Coral although it has the appearence of an upside down jellyfish, are actually classfied as cnidarians in animal kingdom.These are multicellular organism.The algae undergo photosynthesis and produce oxygen and energy rich nutrients like fats and carbohydrates , that the coral reef needs, because light is needed in order for their algal symbiots to achieve photosynthesis.In return for the nutrients they receive the polyps provides nitrates phosphates and carbon dioxide to the algae cells.During the time of stresses the polyp may expel the algae, this is reffered as coral bleaching due to the loss of algae pigment responsible for the corals bright colour.