Abstract
Nocardia brasiliensis is an important etiologic agent of mycetoma. These bacteria live as a saprobe in soil or organic material and enter the tissue via minor trauma. Mycetoma is characterized by tumefaction and the production of fistula and abscesses, with no spontaneous cure. By using mass sequencing, we determined the complete genomic nucleotide sequence of the bacteria. According to our data, the genome is a circular chromosome 9,436,348-bp long with 68% G+C content that encodes 8,414 proteins. We observed orthologs for virulence factors, a higher number of genes involved in lipid biosynthesis and catabolism, and gene clusters for the synthesis of bioactive compounds, such as antibiotics, terpenes, and polyketides. An in silico analysis of the sequence supports the conclusion that the bacteria acquired diverse genes by horizontal transfer from other soil bacteria, even from eukaryotic organisms. The genome composition reflects the evolution of bacteria via the acquisition of a large amount of DNA, which allows it to survive in new ecological niches, including humans.
Highlights
Actinobacteria are gram-positive organisms that are ecologically important in nature as re-cyclers of organic matter, including cellulose from plants and chitin from insects
There is a zone of about 600,000-bp starting at about nucleotide 5,126,00 to nucleotide 5,800,000 with a lower G+C % (63–65%). When analyzing this DNA stretch by using the internet program BLAST, very little homology with any gene in the GenBank library was observed, and we observed less than 10 genes that were similar in two other complete Nocardia genomes, N. farcinica IFM102 and N. cyriacigerogica GUH-2
It is possible that this fragment was acquired by N. brasiliensis HUJEG-1 by horizontal transfer, which has been observed in soil bacteria [16], a transferred fragment this large has not been reported
Summary
Actinobacteria are gram-positive organisms that are ecologically important in nature as re-cyclers of organic matter, including cellulose from plants and chitin from insects. Many actinobacteria are branched and may produce exospores. Actinobacteria are important in medicine because they produce many biological active compounds. Corynebacterineae, is characterized by the production of mycolic acids that provide strength to the bacterial cell wall. Included in this sub-order are the families Corynebacteriaceae, Dietziaceae, Gordoniaceae, Mycobacteriaceae, Nocardiaceae, Tsukamurellaceae, and Williamsiaceae, which include specialized human pathogens, such as Mycobacterium tuberculosis, M. leprae, and Corynebacterium diphtheriae [2]. The Nocardiaceae family includes the genera Nocardia and Rhodococcus. The latter is an animal pathogen, found in horses and immunodepressed human patients [3,4]
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