Eucalyptus plantations offer a cost-effective and renewable source of raw material. There is substantial interest in improving forestry production, especially through sustainable strategies such as the use of plant growth-promoting bacteria. However, little is known about Eucalyptus microbiology. In this study, the endophytic bacterial community was assessed in Eucalyptus urograndis roots using culture-dependent and culture-independent techniques with plants grown under different conditions. Three phyla accounted for approximately 95% of the community, with Actinobacteria corresponding to approximately 59%. This contrasts with previous studies in which Actinobacteria accounted for only 5 to 10%. Our data also revealed a high diversity of bacteria, with 359 different genera but a high level of dominance. Six genera, Mycobacterium, Bradyrhizobium, Streptomyces, Bacillus, Actinospica, and Burkholderia, accounted for more than 50% of the classified sequences. We observed a significant influence of the treatments on some genera, causing changes in the bacterial community structure. The obtained data also suggest that Eucalyptus may benefit from biological nitrogen fixation, with many abundant genera being closely related to nitrogen-fixing bacteria. Using N-depleted media, we also cultured 95 bacterial isolates, of which 24 tested positive for the nifH gene and were able to maintain growth without any N source in the medium.
Agriculture, forestry and other land uses are currently the second highest source of anthropogenic greenhouse gases (GHGs) emissions. In soil, these gases derive from microbial activity, during carbon (C) and nitrogen (N) cycling. To investigate how Eucalyptus land use and growth period impact the microbial community, GHG fluxes and inorganic N levels, and if there is a link among these variables, we monitored three adjacent areas for 9 months: a recently planted Eucalyptus area, fully developed Eucalyptus forest (final of rotation) and native forest. We assessed the microbial community using 16S rRNA gene sequencing and qPCR of key genes involved in C and N cycles. No considerable differences in GHG flux were evident among the areas, but logging considerably increased inorganic N levels. Eucalyptus areas displayed richer and more diverse communities, with selection for specific groups. Land use influenced communities more extensively than the time of sampling or growth phase, although all were significant modulators. Several microbial groups and genes shifted temporally, and inorganic N levels shaped several of these changes. No correlations among microbial groups or genes and GHG were found, suggesting no link among these variables in this short-rotation Eucalyptus study.
The original version of this article unfortunately contained mistakes in the first author's name and the running page headers. The spelling of Dr. Fonseca's first name should read BEduardo da Silva Binstead of BEduardo da Siva^. While in the running authors, it should have been BFonseca et al.î nstead of "da Silva Fonseca E. et al". The original article has been corrected.
O aço é um dos materiais metálicos mais utilizados atualmente. Em virtude da importância econômica e industrial do aço no desenvolvimento tecnológico, existe uma motivação contínua na proteção anticorrosiva destes materiais, destacando-se a importância da redução de custos e a relação custo-benefício. Este trabalho tem como objetivo realizar uma avaliação da influência do meio sobre a corrosão do aço estrutural ASTM A-36, para tanto foram utilizados meios eletrolíticos em pH neutro, contendo íons cloreto e íons sulfatos; pH básico (hidróxido de sódio) e pH ácido (ácido clorídrico). Este estudo mostrou, claramente, que na solução de NaOH 0,1 M, a taxa de corrosão foi significativamente menor em relação aos demais eletrólitos estudados, não somente nas primeiras horas, mas após períodos mais longos. Foi observado também que em meio neutro a taxa de corrosão é significativamente menor que em meio ácido mesmo na presença de íons cloretos.
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