Biodegradation of polyethoxylated nonylphenols

Spatio-temporal variations in chemical pollutants found among urban deposits match changes in thiopurine S-methyltransferase-harboring bacteria tracked by the tpm metabarcoding approach

The bTPMT (bacterial thiopurine S-methyltransferase), encoded by the tpm gene, can detoxify metalloid-containing oxyanions and xenobiotics. The hypothesis of significant relationships between tpm distribution patterns and chemical pollutants found in urban deposits was investigated. The tpm gene was found conserved among eight bacterial phyla with no sign of horizontal gene transfers but a predominance among gammaproteobacteria. A DNA metabarcoding approach was designed for tracking tpm-harboring bacteria among polluted urban deposits and sediments recovered for more than six years in a detention basin (DB). This DB recovers runoff waters and sediments from a zone of high commercial activities. The PCR products from DB samples led to more than 540,000 tpm reads after DADA2 or MOTHUR bio-informatic manipulations that were allocated to more than 88 and less than 634 sequence variants per sample. The tpm community patterns were significantly different between the recent urban deposits and those that had accumulated for more than 2 years in the DB, and between those of the DB surface and the DB settling pit. These groups of samples had distinct mixture of priority pollutants. Significant relationships between tpm ordination patterns, sediment accumulation time periods and location, and concentrations in PAH, chlorpyrifos, and 4-nonylphenols (NP) were observed. These correlations matched the higher occurrences of, among others, Aeromonas, Pseudomonas, and Xanthomonas tpm-harboring bacteria in recent urban DB deposits more contaminated with chrysene and alkylphenol ethoxylates. Highly significant drops in tpm reads allocated to Aeromonas species were recorded in the oldest DB sediments accumulating naphthalene and metallic pollutants. Degraders of urban pollutants such as P. aeruginosa and P. putida showed conserved distribution patterns over time but P. syringae phytopathogens were more abundant in the oldest sediments. TPMT-harboring bacteria can be used to assess the incidence of high risk priority pollutants on environmental systems.

Bio-Removal of Methylene Blue from Aqueous Solution by Galactomyces geotrichum KL20A

The conventional treatments used to remove dyes produced as a result of different industrial activities are not completely effective. At times, some toxic by-products are generated, affecting aquatic ecosystems. In this article, an efficient use of microorganisms is presented as a biodegradation technique that is a safe environmental alternative for the benefit of aquatic life. A strain of the yeast Galactomyces geotrichum KL20A isolated from Kumis (a Colombian natural fermented milk) was used for Methylene Blue (MB) bioremoval. Two parameters of the bioremediation process were studied at three different levels: initial dye concentration and growth temperature. The maximum time of MB exposure to the yeast was 48 h. Finally, a pseudo-first-order model was used to simulate the kinetics of the process. The removal percentages of MB, by action of G. geotrichum KL20A were greater than 70% under the best operating conditions and in addition, the kinetic simulation of the experimental results indicated that the constant rate of the process was 2.2 × 10-2 h−1 with a half time for biotransformation of 31.2 h. The cytotoxicity test based on the hemolytic reaction indicated that by-products obtained after the bioremoval process reached a much lower percentage of hemolysis (22%) compared to the hemolytic activity of the negative control (100%). All of these results suggest that the strain has the capacity to remove significant amounts of MB from wastewater effluents.

Plant age and genotype affect the bacterial community composition in the tuber rhizosphere of field-grown sweet potato plants

The hypothesis that sweet potato genotypes containing different starch yields in their tuberous roots can affect the bacterial communities present in the rhizosphere (soil adhering to tubers) was tested in this study. Tuberous roots of field-grown sweet potato of genotypes IPB-149 (commercial genotype), IPB-052, and IPB-137 were sampled three and six months after planting and analyzed by denaturing gradient gel electrophoresis (DGGE) and pyrosequencing analysis of 16S rRNA genes PCR-amplified from total community DNA. The statistical analysis of the DGGE fingerprints showed that both plant age and genotypes influenced the bacterial community structure in the tuber rhizosphere. Pyrosequencing analysis showed that the IPB-149 and IPB-052 (both with high starch content) displayed similar bacterial composition in the tuber rhizosphere, while IPB-137 with the lowest starch content was distinct. In comparison with bulk soil, higher 16S rRNA gene copy numbers (qPCR) and numerous genera with significantly increased abundance in the tuber rhizosphere of IPB-137 (Sphingobium, Pseudomonas, Acinetobacter, Stenotrophomonas, Chryseobacterium) indicated a stronger rhizosphere effect. The genus Bacillus was strongly enriched in the tuber rhizosphere samples of all sweet potato genotypes studied, while other genera showed a plant genotype-dependent abundance. This is the first report on the molecular identification of bacteria being associated with the tuber rhizosphere of different sweet potato genotypes.