Deforestation Of Amazon Threatens More Than Just Plants And Animals

June 27, 1997

WASHINGTON, DC-- June 26, 1997--The Amazon Basin, home to largest rainforest in the world, is known for its astounding variety of plants and animals. But the rainforest may be also be home to an even more overwhelming variety of previously unknown bacteria and this diversity, just as with plants and animals, may be jeopardized by deforestation, says a report in the July issue of the journal Applied and Environmental Microbiology.

The report, by James Borneman and Eric Triplett at the Agronomy Department of the University of Wisconsin, Madison, describes a study in which soil samples were taken from a mature rainforest as well as an adjacent pastureland that was the result of deforestation. The soils were sampled, using polymerase chain reaction (PCR), to isolate bacterial DNA.

The researchers identified 100 different DNA sequences, 98 from bacteria and two from another domain of microorganisms known as archea. They found no duplicate sequences and none of the sequences they did find had ever been previously reported. Eighteen percent could not be classified in any known bacterial kingdom.

"The microbial diversity found in the mature forest and pasture soils from eastern Amazonia is immense," says Dr. Triplett. "Even with all the work that has been done on biodiversity in the Amazon to date, clearly much more work is needed to understand the enormous genetic complexity of this region. This is even more true of microbial life."

The Amazon region contains the largest body of fresh water and the largest rain forest in the world. It is home to at least 15,000 documented animal species, 8,000 of which were new to biology when they were discovered. At least 40% of the world's freshwater fish and 25% of the world's bird species reside there. Over 5,000 tree species have been described there, 235 of which were found in a single hectare in central Amazonia.

Very few studies, however, have been done to examine soil microbial populations in the Amazon region, say the researchers.

"It's such a rich biological reource that we decided to go and study it," says Triplett. "In the discovery of new organisms we can find previously unknown enzymes that can help further the progress of biotechnology. In addition, there are bacteria out there producing antiobiotics that we have yet to discover."

In addition to just examining and identifying microbial populations, the researchers also compared the populations of the two soil samples in order to illustrate the potential impact of deforestation on microbial diversity of the soil in the region.

"Comparison of the DNA clones obtained from the mature forest soils and pasture soils suggests differences between the two sites," says Dr. Triplett. "A tremendous difference was found between the forest and the pasture soils."

Deforestation of tropical forests alters many soil properties, say the researchers. Analysis of the two soil samples showed distinct differences in pH, levels of certain chemicals, density and porosity. These changes in the soil properties could account for the differences in microbial populations.

Dr. Triplett can be reached by phone at: (608) 262-9824 or by email at:

Applied and Environmental Microbiology is a publication of the American Society for Microbiology (ASM). With over 40,000 members worldwide, the ASM is the oldest and largest single biological membership organization in the world.

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