Diversidad bacteriana en el biocátodo reductor de Cr(VI) de una Celda de Combustible Microbiana con puente salino / Bacterial diversity in the Cr(VI) reducing biocathode of a Microbial Fuel Cell with salt bridge

Although Cr(VI)-reducing and/or tolerant microorganisms have been investigated, there is no detailed information on the composition of the microbial community of the biocathode microbial fuel cell for Cr(VI) reduction. In this investigation, the bacterial diversity of a biocathode was analyzed using 454 pyrosequencing of the 16S rRNA gene. It was found that most bacteria belonged to phylum Proteobacteria (78.8%), Firmicutes (7.9%), Actinobacteria (6.6%) and Bacteroidetes (5.5%), commonly present in environments contaminated with Cr(VI). The dominance of the genus Pseudomonas (34.87%), followed by the genera Stenotrophomonas (5.8%), Shinella (4%), Papillibacter (3.96%), Brevundimonas (3.91%), Pseu-dochrobactrum (3.54%), Ochrobactrum (3.49%), Hydrogenophaga (2.88%), Rhodococcus (2.88%), Fluviicola (2.35%), and Alcaligenes (2.3%), was found. It is emphasized that some genera have not previously been associated with Cr(VI) reduction. This biocathode from waters contaminated with tannery effluents was able to remove Cr(VI) (97.83%) in the cathodic chamber. Additionally, through use of anaerobic sludge in the anodic chamber, the removal of 76.6% of organic matter (glucose) from synthetic waste water was achieved. In this study, an efficient biocathode for the reduction of Cr(VI) with future use in bioremediation, was characterized.

Aunque se ha investigado sobre los microorganismos reductores y/o tolerantes de Cr(VI), no hay información detallada sobre la composición de la comunidad microbiana del cátodo de una Celda de Combustible Microbiana para la reducción de Cr(VI). En esta investigación se analizó la diversidad bacteriana de un biocátodo usando pirosecuenciación 454 del gen 16S rRNA. Se encontró que la mayoría de las bacterias pertenecieron a los filos Proteobac-teria (78,8%), Firmicutes (7,9%), Actinobacteria (6,6%) y Bacteroidetes (5,5%), comúnmente presentes en ambientes contaminados con Cr(VI). Se encontró como género dominante a Pseudomonas (34,87%), seguido por los géneros Stenotrophomonas (5,8%), Shinella (4%), Papil-libacter (3,96%), Brevundimonas (3,91%), Pseudochrobactrum (3,54%), Ochrobactrum (3,49%), Hydrogenophaga (2,88%), Rhodococcus (2,88%), Fluviicola (2,35%) y Alcaligenes (2,3%). Se destaca que algunos géneros no han sido previamente asociados con la reducción de Cr(VI). Este biocátodo procedente de aguas contaminadas con efluentes de curtiembres fue capaz de remover Cr(VI) (97,83%) en la cámara catódica. Adicionalmente, a través del uso de lodo anaeróbico en la cámara anódica, se logró la remoción del 76,6% de materia orgánica (glucosa) a partir de agua residual sintética. En este estudio se caracterizó un eficiente biocátodo para la reducción de Cr(VI) con futuro uso en biorremediación.

A most effective method for selecting a broad range of short and medium-chain-length polyhidroxyalcanoate producing microorganisms

A molecular approach was used for selecting polyhydroxyalcanoate (PHA)-accumulating potential Gram-negative bacteria from different genera by colony polymerase chain reaction (PCR). Three degenerate primers were designed for amplifying a fragment from PHA synthase gene (phaC) (Class I), phaC1 and phaC2 (Class II) genes for detecting PHA-producing bacteria. Thirty-four out of 55 bacterial strains from the old collection selected using Sudan black B staining were phaC+. PCR was used for directly selecting 35 new collection bacterial strains; these strains were phaC+ and their ability to produce PHA was confirmed by Sudan black B staining. Four specific primers were designed on genes of Class II PHA biosynthesis operon. These primers were used for evaluating 9 strains from the old phaC+ collection; 6 showed Class II PHA synthase organisation. 34 from the old and new bacterial isolation were characterised by 16S ribosomal gene (16S rDNA) gene partial sequencing. The tool proposed here can be used for better directing PHA production based on PHA biosynthesis genes and bacterial genera. Class I or II phaC genes were detected in 9 different genera and were able to infer the type of polymer produced.