AbstractBiological nitrogen fixation (BNF) is carried out by representatives of various bacterial phylogeneticgroups named diazotrophs. These bacteria can live free in many ecosystems and/or establishingsymbiosis or associations with diverse plant species. These last ones are called associative diazotrophs.Associative diazotrophic bacteria can contribute to plant growth by improving N-nutrition as wellas by other processes like hormone production, phosphate solubilization, biological control, amongothers. This review presents different genera of associative diazothophs regarding their taxonomicposition, ecological features and process they mediated related to plant growth promotion. It alsoshows how modifications in ecosystems influence density and diversity of these bacteria.A fixação biológica de nitrogênio (FBN) é realizada por representantes de diversos gruposfilogenéticos bacterianos, que são denominados diazotróficos. Estas bactérias podem viver livresem diversos ecossistemas, estabelecer simbioses ou estar associados às plantas, sendo neste últimocaso denominados de diazotróficas associativas. As bactérias diazotróficas associativas podemcontribuir para o crescimento vegetal não só pelo fornecimento de nitrogênio, mas também poroutros mecanismos como produção de fitormônios, solubilização de fosfatos, antagonismo afitopatógeno, entre outros. Esta revisão aborda os diferentes gêneros de diazotróficos associativose discute aspectos relacionados à taxonomia, ecologia e processos de promoção do crescimentovegetal e ainda como as alterações dos ecossistemas atuam na diversidade e densidade destasbactérias. Diazotrophic associative bacteria: diversity, ecology and potential applicationsAbstractBiological nitrogen fixation (BNF) is carried out by representatives of various bacterial phylogeneticgroups named diazotrophs. These bacteria can live free in many ecosystems and/or establishingsymbiosis or associations with diverse plant species. These last ones are called associative diazotrophs.Associative diazotrophic bacteria can contribute to plant growth by improving N-nutrition as wellas by other processes like hormone production, phosphate solubilization, biological control, amongothers. This review presents different genera of associative diazothophs regarding their taxonomicposition, ecological features and process they mediated related to plant growth promotion. It alsoshows how modifications in ecosystems influence density and diversity of these bacteria
