Manganese removal from mine waters - investigating the occurrence and importance of manganese carbonates

Manganese is a common contaminant of mine water and other waste waters. Due to its high solubility over a wide pH range, it is notoriously difficult to remove from contaminated waters. Previous systems that effectively remove Mn from mine waters have involved oxidising the soluble Mn(II) species at an elevated pH using substrates such as limestone and dolomites. However it is currently unclear what effect the substrate type has upon abiotic Mn removal compared to biotic removal by in situ micro-organisms (biofilms). In order to investigate the relationship between substrate type, Mn precipitation and the biofilm community, net-alkaline Mn-contaminated mine water was treated in reactors containing one of the pure materials: dolomite, limestone, magnesite and quartzite. Mine water chemistry and Mn removal rates were monitored over a 3-month period in continuous-flow reactors. For all substrates except quartzite, Mn was removed from the mine water during this period, and Mn minerals precipitated in all cases. In addition, the plastic from which the reactor was made played a role in Mn removal. Manganese oxyhydroxides were formed in all the reactors; however, Mn carbonates (specifically kutnahorite) were only identified in the reactors containing quartzite and on the reactor plastic. Magnesium-rich calcites were identified in the dolomite and magnesite reactors, suggesting that the Mg from the substrate minerals may have inhibited Mn carbonate formation. Biofilm community development and composition on all the substrates was also monitored over the 3-month period using denaturing gradient gel electrophoresis (DGGE). The DGGE profiles in all reactors showed no change with time and no difference between substrate types, suggesting that any microbiological effects are independent of mineral substrate. The identification of Mn carbonates in these systems has important implications for the design of Mn treatment systems in that the provision of a carbonate-rich substrate may not be necessary for successful Mn precipitation

Molecular analysis of the bacterial diversity in a specialized consortium for diesel oil degradation Análise molecular da diversidade bacteriana de um consórcio degradador de óleo diesel

Diesel oil is a compound derived from petroleum, consisting primarily of hydrocarbons. Poor conditions in transportation and storage of this product can contribute significantly to accidental spills causing serious ecological problems in soil and water and affecting the diversity of the microbial environment. The cloning and sequencing of the 16S rRNA gene is one of the molecular techniques that allows estimation and comparison of the microbial diversity in different environmental samples. The aim of this work was to estimate the diversity of microorganisms from the Bacteria domain in a consortium specialized in diesel oil degradation through partial sequencing of the 16S rRNA gene. After the extraction of DNA metagenomics, the material was amplified by PCR reaction using specific oligonucleotide primers for the 16S rRNA gene. The PCR products were cloned into a pGEM-T-Easy vector (Promega), and Escherichia coli was used as the host cell for recombinant DNAs. The partial clone sequencing was obtained using universal oligonucleotide primers from the vector. The genetic library obtained generated 431 clones. All the sequenced clones presented similarity to phylum Proteobacteria, with Gammaproteobacteria the most present group (49.8 % of the clones), followed by Alphaproteobacteira (44.8 %) and Betaproteobacteria (5.4 %). The Pseudomonas genus was the most abundant in the metagenomic library, followed by the Parvibaculum and the Sphingobium genus, respectively. After partial sequencing of the 16S rRNA, the diversity of the bacterial consortium was estimated using DOTUR software. When comparing these sequences to the database from the National Center for Biotechnology Information (NCBI), a strong correlation was found between the data generated by the software used and the data deposited in NCBI.<br>O óleo diesel é um composto derivado do petróleo, constituído basicamente por hidrocarbonetos. Condições precárias no processo de transporte e armazenagem desse produto contribuem significativamente para derrames acidentais, ocasionando sérios problemas ecológicos no solo e água, alterando assim toda a diversidade microbiológica do ambiente. A estratégia de clonagem e sequenciamento do gene 16S rRNA é uma das técnicas moleculares que permitem estimar e comparar a diversidade microbiana de diferentes amostras ambientais, sejam elas impactadas ou não. O objetivo deste trabalho foi estimar a diversidade de microrganismos pertencentes ao domínio Bacteria em um consórcio degradador de óleo diesel por meio de sequenciamento parcial do gene 16S rRNA. Após extração do DNA metagenômico, o material foi amplificado por reação de PCR com oligonucleotídeos iniciadores específicos para o gene 16S rRNA. Os produtos da reação de PCR foram clonados em vetor pGEM T Easy (Promega) e transformados em células competentes de Escherichia coli. O sequenciamento parcial dos clones foi feito com oligonucleotídeos universais do vetor. A biblioteca obtida gerou 431 clones. Todos os clones mostraram similaridade com o filo Proteobacteria, onde as Gammaproteobacteria compreenderam o grupo de maior representatividade, com 49,8 % dos clones, seguida das Alphaproteobacteira, com 44,8 %, e das Betaproteobacteria, com 5,4 %. O gênero Pseudomonas destacou-se como representante com maior frequência de clones na biblioteca, seguido pelos gêneros Parvibaculum e Sphingobium. Após o sequenciamento parcial do gene 16S rRNA, a diversidade bacteriana do consórcio foi estimada utilizando-se o software DOTUR. Essas sequências, quando comparadas com as do banco do National Center for Biotechnology Information (NCBI), mostraram grande correlação entre os dados gerados pelo software utilizado e aqueles depositados no NCBI