Shifts in the bacterial community composition along deep soil profiles in monospecific and mixed stands of <i>Eucalyptus grandis</i> and <i>Acacia mangium</i> de Araujo PereiraArthur Prudêncio de AndradePedro Avelino Maia BiniDaniel DurrerAdemir RobinAgnès BouilletJean Pierre Dini AndreoteFernando CardosoElke Jurandy Bran Nogueira 2017 <div><p>Our knowledge of the rhizosphere bacterial communities in deep soils and the role of <i>Eucalyptus</i> and <i>Acacia</i> on the structure of these communities remains very limited. In this study, we targeted the bacterial community along a depth profile (0 to 800 cm) and compared community structure in monospecific or mixed plantations of <i>Acacia mangium</i> and <i>Eucalyptus grandis</i>. We applied quantitative PCR (qPCR) and sequence the V6 region of the 16S rRNA gene to characterize composition of bacterial communities. We identified a decrease in bacterial abundance with soil depth, and differences in community patterns between monospecific and mixed cultivations. Sequence analysis indicated a prevalent effect of soil depth on bacterial communities in the mixed plant cultivation system, and a remarkable differentiation of bacterial communities in areas solely cultivated with <i>Eucalyptus</i>. The groups most influenced by soil depth were <i>Proteobacteria</i> and <i>Acidobacteria</i> (more frequent in samples between 0 and 300 cm). The predominant bacterial groups differentially displayed in the monospecific stands of <i>Eucalyptus</i> were <i>Firmicutes</i> and <i>Proteobacteria</i>. Our results suggest that the addition of an N<sub>2</sub>-fixing tree in a monospecific cultivation system modulates bacterial community composition even at a great depth. We conclude that co-cultivation systems may represent a key strategy to improve soil resources and to establish more sustainable cultivation of <i>Eucalyptus</i> in Brazil.</p></div>