"Cave biofilms are simpler than the microbes that occur in soils where there can be hundreds of thousands of species," says Dr. Jennifer L. Macalady, assistant professor of geosciences, Penn State. "Some cave biofilms have very few species, 10 to 20. The more complex ones have 100s or 1,000s."
The researchers investigated the Frasassi cave system located north of Rome and south of Venice in Italy. These limestone caves are like New Mexico's Carlsbad Caverns and Lechuguilla
Cave, but in those caves, sulfur entered the caves from oil and gas reserves, while in Italy, the sulfur source is a thick gypsum layer below. Having sulfur in the environment allows these biofilms to grow.
Most limestone caves form when rainwater and runoff permeate the caves from above. Water and carbon dioxide mix to form carbonic acid, a very weak acid, that erodes the limestone cave walls. In sulfidic caves, water enters the caves from below, carrying hydrogen sulfide. Microbes in the biofilms use the sulfur for energy and produce sulfuric acid, a very strong acid.
"One type of biofilm, called a snottite because of its appearance, has a pH of zero or one," says Daniel S. Jones, graduate student in geosciences. "This is very, very acidic."
Carbonic acid cave systems lose about a third of an inch of wall every thousand years, while sulfuric acid cave systems lose about two and a third inches or six times as much in the same time. The researchers are interested in the make-up of the biofilms and how they cycle sulfur.
Biofilms are made up of thin layers of microbe species that can be very different. All require water, but some biofilms live in the pools, lakes and streams in caves and others live on the damp walls. The layers against the rock surface use oxygen and hydrogen sulfide for energy and produce sulfuric acid. The layer on the outside does as well, but, because middle layers exist, there is an opportunity for microbes that find oxygen poisonous to thrive. These middle layers may convert the sulfuric acid to hydrogen sulfide, creating a complete sulfur cycle in a few microns.
In dental biofilms, the microbes on the teeth are the ones that produce the acids that cause cavities, while the ones on the top create the right conditions for the acid-producing microbes to survive. Cave biofilm layers also fulfill different niches in their very tiny environment.
"Stream biofilms are responsible for the majority of sulfide disappearance in streams," Jones told attendees today (Dec. 11) at the fall meeting of the American Geophysical Meeting in San Francisco.
Because the cave biofilms are relatively simple, it will be easier to connect the various microbe species to the geochemistry involved. While this work is not yet complete, the researchers are working on the problem. Dr. Greg K. Druschel, assistant professor of geology, University of Vermont, used microelectrode voltammetry to try to determine exactly which biofilm layers produce acids. The levels of hydrogen sulfide and sulfuric acid change, depending on which layer is tested.
"There is also a question about where these microbes originate," says Macalady. "We do not know if they are always in rocks or if they are transported from somewhere else to establish themselves."
No matter the answer, the biofilms probably begin growing in tiny cracks in the rock and eventually create some of the largest cave systems in the world. Cave biofilms are also the bottom of the food chain for cave ecosystems. They provide food for a variety of spiders, flat worms, pill bugs and amphipods – shrimp like crustaceans – that form a blind and pigmentless community.
"The only other place we find sulfur-based ecosystems is near the deep sea vents on the ocean floor," says Jones.
Understanding how cave biofilms dissolve calcium carbonate may help us to understand the communities around ocean floor vents, but it may also, eventually, lead to understanding how biofilms dissolve calcium phosphate on teeth and the steel hulls of ships.
Northern oceans pumped CO2 into the atmosphere
27.03.2017 | CAGE - Center for Arctic Gas Hydrate, Climate and Environment
Weather extremes: Humans likely influence giant airstreams
27.03.2017 | Potsdam-Institut für Klimafolgenforschung
Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.
The results will be published on March 22 in the journal „Astronomy & Astrophysics“.
Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...
Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.
Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...
In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...
20.03.2017 | Event News
14.03.2017 | Event News
07.03.2017 | Event News
27.03.2017 | Earth Sciences
27.03.2017 | Life Sciences
27.03.2017 | Life Sciences