PGPRs and nitrogen-fixing legumes: a perfect team for efficient Cd phytoremediation?

Cadmium (Cd) is a toxic, biologically non-essential and highly mobile metal that has become an increasingly important environmental hazard to both wildlife and humans. In contrast to conventional remediation technologies, phytoremediation based on legume rhizobia symbiosis has emerged as an inexpensive decontamination alternative which also revitalize contaminated soils due to the role of legumes in nitrogen cycling. In recent years, there is a growing interest in understanding symbiotic legume rhizobia relationship and its interactions with Cd. The aim of the present review is to provide a comprehensive picture of the main effects of Cd in N-2-fixing leguminous plants and the benefits of exploiting this symbiosis together with plant growth promoting rhizobacteria to boost an efficient reclamation of Cd-contaminated soils.

The biosurfactant viscosin produced by Pseudomonas fluorescens SBW25 aids spreading motility and plant growth promotion

Food security depends on enhancing production and reducing loss to pests and pathogens. A promising alternative to agrochemicals is the use of plant growth-promoting rhizobacteria (PGPR), which are commonly associated with many, if not all, plant species. However, exploiting the benefits of PGPRs requires knowledge of bacterial function and an in-depth understanding of plant-bacteria associations. Motility is important for colonization efficiency and microbial fitness in the plant environment, but the mechanisms employed by bacteria on and around plants are not well understood. We describe and investigate an atypical mode of motility in Pseudomonas fluorescens SBW25 that was revealed only after flagellum production was eliminated by deletion of the master regulator fleQ. Our results suggest that this ‘spidery spreading’ is a type of surface motility. Transposon mutagenesis of SBW25ΔfleQ (SBW25Q) produced mutants, defective in viscosin production, and surface spreading was also abolished. Genetic analysis indicated growth-dependency, production of viscosin, and several potential regulatory and secretory systems involved in the spidery spreading phenotype. Moreover, viscosin both increases efficiency of surface spreading over the plant root and protects germinating seedlings in soil infected with the plant pathogen Pythium. Thus, viscosin could be a useful target for biotechnological development of plant growth promotion agents.

Prospecção de rizobactérias promotoras de crescimento em quatro espécies arbóreas nativas do Brasil

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

A COLETA SELETIVA EM UM PROJETO DE PESQUISA PARTICIPATIVA

A organização de sistemas municipais de coleta seletiva, com a inclusão de catadores(as) tem se ampliado, nas últimas décadas. Na Região Metropolitana de São Paulo, BR, a coleta seletiva tem apoiadores, mas há muito a realizar com as equipes técnicas de governo e, imprescindivelmente para a gestão participativa, com os catadores(as), seu fortalecimento, qualificação e “empoderamento”. O objetivo desta pesquisa participativa, desenvolvida no interior do Projeto Gestão Participativa de Resíduos Sólidos (PGPRS- convênio inter universidades - Brasil. Canadá) prevê ações educativas, a sistematização e análise dessas ações, com o pressuposto básico do cooperativismo, visando ampliar a autonomia, a identidade ética, saúde, auto estima e a busca de soluções concretas para a comercialização em rede dos resíduos e a inclusão dos catadores(as) nas políticas públicas. A pesquisa enfrenta desafios, pois os envolvidos são pessoas extremamente sofridas, da camada mais espoliada da pirâmide social, que têm como modelo (valores e relações interpessoais) do modo capitalista de produção, onde a hierarquia e a competição predominam, antagonicamente ao cooperativismo, exigência fundamental na construção de outra lógica. A preocupação atual do Projeto é o entendimento da Nova Lei da Coleta Seletiva, aprovada em 2010.