Lava Tube Microbial Mats

Investigation by The Slime Team

Project description by J. Mickey Ide.

Lava tubes are a type of cave found all over the world. They are the second highest occurring cave in the world and can vary from tens of feet to several miles long.

Lava tubes form when molten rock oozes out of the Earth, as in a volcanic eruption, and slides down the side. The outer surface of the lava cools and hardensforming a tube. Lava continues to flow through the tube until the source of the lava ceases.

Ariel view of a lava tube. Photo by Kenneth Ingham.

Inside of an extinct lava tube.

Lava tubes can be active or extinct.

Active lava tubes continue to seep lava, or molten rock, from the source.

Extinct lava tubes have no active flow and they have cooled and hardened leaving a cave-like channel.

Lava tubes are home to some interesting features. One such feature is "bacterial mats", or lava wall slime, that grows in both the twilight zones and the dark zones of the cave. However, even though they grow abundantly, not much is known about these communities.

So, the Slime Team went to El Malpais National Monument in New Mexico U.S.A. to investigate the bacterial mats of Four Windows Cave.

Bacterial mats cover about 25% to 75% of the walls of the first 500 feet of Four Windows Cave.

Bacterial mats in Four Windows Cave. The walls appear silver when a light shines on the mats. Photo by Kenneth Ingham.

The bacteria covering 25% of the walls show large areas of wall through empty spaces in the mats.

While areas that cover 75% of the walls showed very small patches of wall though the mats.

These bacterial mats were thought to be made of Actinomycetes, bacteria that break down complex organic matter.

Actinomycetes are known to thrive in environments where food is meager and living conditions extreme; they are commonly found living in caves.

Missing photo
Bacterial mats in Four Windows Cave. The walls appear silver when a light shines on the mats. Photo by Kenneth Ingham.

Lights shining behind bacterial mats show the silver shine of the mats.

Water dripping into the cave. This is a possible source of food for the bacteria.

The bacteria gain their energy from organic matter that seeps in the cave in water from the surface. Microbes on the surface break down organic matters, such as leaves. The compounds then mix with water on the surface, which then drips into the cave.
Actinomycetes also come in different colors. They can be pink, silver, white, yellow, or gold.

Different pigments in the bacteria produce the colors. Scientists do not known why or how the bacteria make these pigments. These colors are seen all over the world; caves in the Azores have gorgeous gold-pigmented bacteria on the walls.

The Slime Team extracted DNA from the wall communities to determine what types of bacteria were living in these communities. The DNA was purified, the samples cloned, and later the sequences were compared to the Ribosomal Database. The data showed that the bacteria from Four Windows Cave was most closely related to Actinomycetes.

Example of a white and gold bacterial mat. Photo by Kenneth Ingham.

Example of pink bacterial mats. Photo by Kenneth Ingham.

An unknowing visitor wrote their name in one of the bacterial communities. Photo by Kenneth Ingham.

The Slime Team then investigated the amount of adaptation the Actinomycetes had gone through in order to live in the lava tubes.

In order to do this, they tested the capacity of the bacteria to endure the effects of UV radiation (i.e. simulating sunlight). The results showed that the bacteria from the lava tubes of Four Windows Cave were much more sensitive to UV light than the bacterial microbes collected from the surface. This indicates that the bacterial communities in Four Windows may be relatively cave-adapted.

The Slime Team continues to study the microbes of caves all over the world.

This web site Copyright 2007, 2011, Kenneth Ingham