Chapter 18.1, Problem 4MI

Summary Introduction

To summarize:

Three general environments where archaea live and to give one example of each environment

Introduction:

There are six kingdoms of organisms; archaebacteria, eubacteria, protists, fungi, plants and animals. There are two kingdoms of prokaryotes; archaebacteria and eubacteria. There are several hundred species of known archaebacteria and most of them live in extreme environments. The lipids in the cell membranes of archaebacteria, the composition of their cell walls and the sequence of nucleic acids in their ribosomal RNA differ considerably from those of other prokaryotes.

Answer to Problem 4MI

1. Hot, acidic environment such as sulfur hot springs, thermal vents, volcanoes- thermoacidophiles
2. High salt concentration such as in Great Salt Lake, Dead Sea- halophiles
3. Oxygen free conditions such as swamps, bogs, volcanic vents

Explanation of Solution

Most archaebacteria live in extreme conditions such as swamps, deep- ocean hydrothermal vents, and seawater evaporating ponds. Most of these environments are oxygen free.

Three kinds of environments which archaebacteria predominate are:

1. Hot, acidic conditions such as sulfur hot springs, thermal vents on ocean floor and around volcanoes- Example is thermoacidophiles. They can live in temperatures above 80⁰C and a pH of 1- 2. Some of these bacteria cannot live below 55⁰C. Many are even strictly anaerobic; that is they die in the presence of oxygen.
2. High salt concentration such as Great Salt Lake, Dead Sea- Example is halophiles. Some archaebacteria live in very salty conditions. They are adapted to survive in high salt concentrations. They are mostly aerobic and some carry out unique form of photosynthesis using a protein instead of chlorophyll.
3. Oxygen free environment such as swamps, bogs, volcanic vents- example is methanogens. These are obligate anaerobes, which mean they cannot live in presence of oxygen. They use carbon dioxide during respiration and produce methane as a waste product. Methanogens are found in sewage treatment plants, bogs, swamps etc. they can even live in gastrointestinal tract of humans and other animals and are responsible for release of gases from lower digestive tract.