Question

1. An organism is isolated from a highly acidic and hot aquatic environment. In a stepwise manner, explain how it would be identified as belonging to one of the three domains of life. Further, briefly explain the distinguishing characteristics of the three domains of life.

Answer 1

The isolated organism is a thermoacidophile.

THREE DOMAIN SYSTEM

Domain Archaea

The Archaea are prokaryotic, with no nuclear membrane and distinct biochemistry, RNA markers from bacteria. The Archaeans possess an unique, ancient evolutionary history for which they are considered some of the oldest species of organisms on Earth.

Some examples of archaeal organisms are:

methanogens – which produce the gas methane.

halophiles – which can live in very salty water.

thermoacidophiles – which thrive in acidic high-temperature water

Domain Bacteria

The Bacteria are also prokaryotic; their domain consists of cells with bacterial rRNA, no nuclear membrane, and whose membranes possess primarily diacyl glycerol diester lipids. Traditionally classified as bacteria, many thrive in the same environments favored by humans, and were the first prokaryotes discovered

Some examples of bacteria include:

• Cyanobacteria – photosynthesizing bacteria that are related to the chloroplasts of eukaryotic plants and algae
• Spirochaetes – Gram-negative bacteria that include those causing syphilis and Lyme disease
• Actinobacteria – Gram-positive bacteria including Bifidobacterium animalis which is present in the human large intestine

Domain Eukarya

The Eukarya domain includes eukaryotes or organisms that have a membrane-bound nucleus.This domain is further subdivided into the kingdoms:

• Protista
• Fungi
• Plantae
• Animalia