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Survival from the jungle

Analysis of genes helps to understand adaptation mechanism of bacterium common in the dark waters of Amazonia

MÁRCIA ATTIASC. violaceum and the Negro River: potential source of antibioticsMÁRCIA ATTIAS

Acid and with few nutrients, the coffee-colored waters of the Negro River, in the state of Amazonas, ought not to be the best place to live. The temperature can easily reach 40º Celsius, the ultraviolet radiation of the Sun is intense, and the concentration of toxic agents like heavy metals and free radicals is high. Even so, both the river and the soil of its banks house high quantities of a free-living bacterium, the Chromobacterium violaceum, now much better understood. On September 30, 107 researchers from the Brazilian Genome project published an article in the American magazine Proceedings of the National Academy of Sciences (PNAS), presenting the sequencing of the whole of this microorganism’s genome (set of genes). Besides the basic data, such as the dimensions of the genome (about 4.7 million nitrogenous base pairs) and the estimated number of genes (4,431), the article highlights a peculiarity of the C. violaceum that seems to be vital for its adaptation to the waters of environments as remote as Amazonia, West Africa or Australia: 11% of its genes (496) contain instructions for producing cell membrane proteins related to transporting substances into the bacterium from outside and vice-versa.

The researchers identified, for example, 35 genes linked to the use of iron, and 14 that alleviate the effects of the heat. “This set of carrier proteins allows the bacterium an efficient exploitation of low concentrations of nutrients and is responsible for its tolerance to many toxic agents”, explains Ana Tereza Vasconcelos, from the National Laboratory of Scientific Computing (LNCC), of Petrópolis, the coordinator of the project. Handled by a national network of 25 research laboratories, spread over 15 states, from Amazonas to Rio Grande do Sul, the sequencing of the microorganism’s genome cost almost R$ 12 million, funded by the National Council for Scientific and Technological Development (CNPq). Part of the budget was used in the purchase of special equipment, sequencers, for the laboratories in the national network. The first organism to be sequenced by the national consortium of laboratories, C. violaceum earned this name for producing a violet-colored pigment called violacein, which appears to present a series of properties of medical and environmental interest. Violacein is already used in dermatological treatments, and there is evidence that it may have antibacterial and antiviral action.

Found in tropical and subtropical environments, it is the only species of this genus that can possibly be pathogenic for human beings, above all children and the elderly: it does not usually cause serious problems, although there are records of cases of severe infections in the United States, France and South Korea. But it was its abundance in the Negro River that motivated its choice as an object for study, besides the prospect of generating products of an economic value. The Brazilian Genome team believes that C. violaceum may be used as a biofactory, capable of producing, for example, certain kinds of plastic. “To guarantee the intellectual protection of possible applications that may arise from the results of our work, before publishing the article in the PNAS, we requested patents covering the genes of the Chromobacterium”, says Ana Tereza. Understanding the mechanisms that the bacterium employs to adapt itself to different environments may be the first step towards exploiting its biotechnological potentialities.

The Project
Brazilian Genome Project; Coordinator Ana Tereza Vasconcelos – National Laboratory of Scientific Computing (LNCC); Investment R$ 11,990,074.84 (CNPq)