Halo-Ed: Extreme Microbiology and Astrobiology

Life in Extremes: Astrobiology

Recently, intense interest in halophiles has resulted from the perspective of our search for ExtraTerrestrial Life (ETL), or the search for life on other planets. Many planets have been discovered in other solar systems in the past 10 years. Are there life-forms on these planets? Where are they? What are they like? Halophiles are perfect candidates for life on our closest neighboring planet, Mars. They can withstand radiation, such as ultraviolet and ionizing radiation, desiccation, toxic chemicals, and high salinity conditions found on Mars.

In this exercise, called Life in an Extreme Environment, students use salt crystals with entrapped brine inclusions containing live Halobacterium sp. NRC-1 to grow a liquid culture. Once grown, students observe the phase-bright gas vesicle inclusions, which enable the cells to float and give the liquid culture its opaque appearance. They can also see pink coloration due to the presence of carotenoids, light absorbing molecules that protect the cells against damaging radiation, and purple hue due to bacteriorhodopsin, a pigment in the cell membrane used to obtain energy from light in an alternative fashion to that of photosynthesis called phototrophy. These features allow these cells to survive conditions that are lethal to most common microorganisms. For more information, see: Life in an Extreme Environment.

An interesting question for students to consider: 'Can life be transmitted between planets and other celestial bodies through a process known as panspermia?'

See the Webinar on astrobiology.

As a companion to this website, we have developed a comprehensive set of laboratory exercises using Halobacterium NRC-1 as the model organism for teaching a wide range of subjects, including exponential growth, colony formation, life in extreme environments, crystal formation and survival of life in salt crystals, mutation, antibiotic resistance, motility, flotation, DNA function, transformation, complementation, biotechnology, genomics, and bioinformatics.

What types of extremes are there on Earth? Who survives or thrives there? Where on Earth can you find them? Could you use Haloarchaea to search for Life Elsewhere?

Extreme / Stressor	Type of Extremophiles identified	Grow optimally	Example of conditions
Acidity	Acidophiles	pH < 3	Acid mine drainage
Alkalinity	Alkaliphile	pH >10	Lake Magadi, Kenya
Cold	Psychrophiles / Psychrotolerant	Low temperatures including < 0 °C	Deep Lake, Antarctica
Heat	Thermophiles	> 80 °C	Geothermal springs, Yellowstone, U.S.A.
Hypersalinity	Extreme Halophiles	> 3.4M (20% /198.7g /L /~200,000ppm) NaCl	Great Salt Lake, U.S.A.
Lack of oxygen	Microaerobes / Anaerobes	Very low levels or Absence of oxygen	Cow rumen
Pressure	Barophiles	High hydrostatic pressures	Mariana Trench, New Guinea

For Questions and Suggestions, contact the Halo-Ed Team

MolGenT

Microbiology

DNA Extraction

Mutations

Life in Extremes

Antibiotics

Bioinformatics

Teachers

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