By Sean Henahan, Access Excellence

Caption: Highland Andean girl in Quito, Ecuador, selling medicinal plants. Photo by Steven R. King, 1996.

The Amazon Basin is home to the largest rainforest in the world, and is known for its remarkable variety of plants and animals.  Researchers at  the Agronomy Department of the University of Wisconsin, Madison, now report that miscroscopic life forms may also be jeopardized by deforestation.

The researchers obtained soil samples 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. Eric 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 study is among the first 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.
 
The report appears in the July issue of the journal Applied and Environmental Microbiology.