RESUMO
Bacteria of the genus Azospirillum include several plant associated bacteria which often promote the growth of their host plants. Although the host range of Azospirillum brasilense Sp7 is much wider than its close relative Azospirillum lipoferum 4B, it lacks the ability to efficiently utilize D-glucose for its growth. By comparing the genomes of both the species, the genes of A. lipoferum 4B responsible for conferring D-glucose utilization ability in A. brasilese Sp7 were identified by cloning individual or a combination of genes in a broad host range expression vector, mobilizing them in A. brasilense Sp7 and examining the ability of exconjugants to use D-glucose as sole carbon source for growth. These genes also included the homologs of genes involved in N-acetyl glucosamine utilization in Pseudomonas aeruginosa PAO1. A transcriptional fusion of the 5 genes encoding glucose-6-phosphate dehydrogenase and 4 components of glucose phosphotransferase system were able to improve D-glucose utilization ability in A. brasilense Sp7. The A. brasilense Sp7 strain engineered with D-glucose utilization ability showed significantly improved root colonization of rice seedling. The improvement in the ability of A. brasilense Sp7 to colonize rice roots is expected to bring benefits to rice by promoting its growth. KEY POINTS: ⢠Genes required for glucose utilization in Azospirillum lipoferum were identified. ⢠A gene cassette encoding glucose utilization was constructed. ⢠Transfer of gene cassette in A. brasilense improves glucose utilization and rice root colonization..
Assuntos
Azospirillum brasilense , Azospirillum , Oryza , Azospirillum brasilense/genética , Azospirillum brasilense/metabolismo , Glucose/metabolismoRESUMO
Pharmaceutical compounds are designed to elicit a biological reaction in specific organisms. However, they may also elicit a biological response in non-specific organisms when exposed to ambient quantities. Therefore, the potential human health hazards and environmental effects associated with pharmaceutically active compounds presented in aquatic environments are being studied by researchers all over the world. Owing to their broad-spectrum occurrence in various environmental matrices, direct or indirect environmental hazardous impacts, and human-health related consequences, several pharmaceutically active compounds have been categorized as emerging contaminants (ECs) of top concern. ECs are often recalcitrant and resistant to abate from water matrices. In this review, we have examined the classification, occurrence, and environmental hazards of pharmaceutically active compounds. Moreover, because of their toxicity and the inefficiency of wastewater treatment plants to remove pharmaceutical pollutants, novel wastewater remediation technologies are urgently required. Thus, we have also analyzed the recent advances in microbes-assisted bioremediation as a suitable, cost-effective, and eco-friendly alternative for the decontamination of pharmaceutical pollutants. Finally, the most important factors to reach optimal bioremediation are discussed.
Assuntos
Poluentes Ambientais , Poluentes Químicos da Água , Purificação da Água , Biodegradação Ambiental , Humanos , Águas Residuárias , Água , Poluentes Químicos da Água/análiseRESUMO
Azospirillum brasilense is a plant growth-promoting bacterium that colonizes the roots of a large number of plants, including C3 and C4 grasses. Malate has been used as a preferred source of carbon for the enrichment and isolation Azospirillum spp., but the genes involved in their transport and utilization are not yet characterized. In this study, we investigated the role of the two types of dicarboxylate transporters (DctP and DctA) of A. brasilense in their ability to colonize and promote growth of the roots of a C4 grass. We found that DctP protein was distinctly upregulated in A. brasilense grown with malate as sole carbon source. Inactivation of dctP in A. brasilense led to a drastic reduction in its ability to grow on dicarboxylates and form cell aggregates. Inactivation of dctA, however, showed a marginal reduction in growth and flocculation. The growth and nitrogen fixation of a dctP and dctA double mutant of A. brasilense were severely compromised. We have shown here that DctPQM and DctA transporters play a major and a minor role in the transport of C4-dicarboxylates in A. brasilense, respectively. Studies on inoculation of the seedlings of a C4 grass, Eleusine corcana, with A. brasilense and its dicarboxylate transport mutants revealed that dicarboxylate transporters are required by A. brasilense for an efficient colonization of plant roots and their growth.