Brazilian researchers organized a very peculiar type of fishing in much of the Amazon. Instead of trying to catch tucunarés and tambaquis, their target was the myriad species of aquatic microorganisms that “eat” nearly 1 billion tons of organic matter in the region each year.
The result of the “fishing” expedition is the first large catalog of genes from microbes in Amazonian waters that are located in an area that extends from the upper Solimões in the west to sections of the Atlantic Ocean at the mouth of the Amazon Substance dumped from the largest river in the world (in total they are over 2,000 km long). The mountain of data obtained in the work has the potential to stimulate biotechnological innovations and should help to understand important aspects of how the ecosystems of the Amazon work.
“It’s enough work to continue until the next incarnation,” jokes Flávio Henrique Silva, professor at the Institute for Genetics and Evolution at UFSCar (Federal University of São Carlos). Together with colleagues from other institutions in Brazil and Spain, Silva is the author of an article describing the results in the journal Microbiome.
In essence, the team’s work has been a metagenomic effort, as the area of research that seeks to obtain new data on the DNA of several species, mainly microbial species, is known and studies the entire batch of genetic material that can be taken from the samples of an environment such as the bottom, a coral reef, lakes or rivers.
Metagenomics is particularly useful when the species that live in such environments are not yet known or when they are difficult to reproduce in laboratory cultures (this is the case with the vast majority of microorganisms). Based on the crude sequence of “letters” of DNA present in the samples, it is often possible to have at least a general idea of what type of organism this genetic material belongs to and what biochemical functions it performs.
Such information can be derived by comparing new data with libraries of already known DNA. But of course, we still know very little about many of the Earth’s microbes, and the team’s results confirm this. The researchers estimate that their samples contain nearly 4 million genes (that is, pieces of DNA that contain the recipe for making proteins), but almost half of them do not bear any significant similarity to already known genes.
A comparison with other metagenomics studies also conducted in river ecosystems (in the Canada and Mississippi Rivers, the largest waterway in the United States and North America) also found that the microorganism community in the Amazon is very different from the others.
In any case, the less mysterious genes, which have similarities to others already studied, helped the researchers get a reasonably clear idea of how microbes deal with the enormous amounts of organic matter in the region’s rivers. Of the 6,516 genes that appear to be associated with this process, more than 2,000 are involved in “breaking” lignin molecules that are essential for strengthening the plant cell wall, especially in the wood and bark of trees. Another important molecule in these structures is cellulose, which is known as a raw material for paper.
“The breakdown of organic matter in the case of the Amazon is very efficient. This is important because when lignin is broken down, aromatic molecules are formed first [formadas por anéis de átomos de carbono]and these reaction products hinder the action of other substances that break down cellulose from plant residues, ”explains the UFSCar researcher. “The initial efficiency of bacterial degradation of lignin minimizes this process and also makes the subsequent process work better.”
Indeed, everything suggests that there is some kind of collaboration – not intended, of course – between different types of microorganisms and different parts of the Amazon Canal. In the samples taken upstream and further from the mouth, genes associated with lignin breakdown, the initial stage in the breakdown of organic matter, predominate, while genes that break down cellulose, the next step in the process, are most common were found downstream.
For example, more detailed information on how microbes use their gene library to “break down” organic matter can help optimize the production processes for second-generation ethanol – which is made from the “hard” part of plants, not just cane sugar. They could also help create plastic equivalents from living raw materials and replace the use of petroleum products. “It is a monstrous sea of possibilities,” summarizes Silva.