Microbial biology and biotechnology

Environmental Microbiology

The implementation of bioremediation strategies to restore contaminated environments requires the understanding of the factors controlling microbial growth and metabolism in challenging polluted environments. Pseudomonas sp. M1, isolated from the Rhine River sediments, is able to utilize several toxic and/or recalcitrant  compounds as sole carbon and energy source, including phenol, b-myrcene and benzene. The unique organization and co-regulation of a gene cluster required for phenol and benzene catabolism in this strain was characterized [1]. As previously described for P. putida KT2440 [2], Pseudomonas M1 is also able to adapt to deleterious concentrations of several aromatic toxicants (e.g. phenol) through a series of mechanisms, as revealed by expression proteomics [3].

b-myrcene is an acyclic monoterpene found in essential oils from plants, such as in lemongrass, hops, bay, and verbena. This monoterpene is widely used in cosmetics, detergents, soaps, food and beverages. Furthermore, this compound possesses analgesic, antimutagenic, antiviral and antimicrobial activities. It is likely that some b-myrcene derivatives may show improved therapeutic activities. However, although b-myrcene biosynthesis and catabolism in plants have been on the focus of several research works, the present knowledge of b-myrcene metabolism in bacteria is very scarce. The elucidation of the genes, enzymes, and regulatory mechanisms behind Pseudomonas sp. M1 adaptation to growth using b-myrcene as sole carbon source may provide guidance to the bioproduction of fine chemicals from essential oils components. These ongoing studies explore molecular biology and expression proteomics approaches.

Atrazine is an s-triazine herbicide used worldwide and is frequently detected in surface and groundwater mainly due to leaching and run-off phenomena. Concerns regarding impact on human health and ecosystems have incited the search for efficient bioremediation strategies for atrazine-polluted soils. In the context of the EU project [QLK3-CT-1999-00041], our group was involved in a study that has suggested that a joint bioaugmentation (with the atrazine mineralizing bacterial strain Pseudomonas sp ADP) and biostimulation (with organic acids) may be an effective approach to cleanup soil contaminated with high atrazine concentrations [4].This potential bioremediation tool has been scaled-up to open soil microcosms representative of crop soil from Central Portugal, spiked with doses of atrazine commercial formulations, mimicking over-use or spill situations. Atrazine biodegradation was greatly accelerated following one sole bacterial inoculation or several successive inoculations plus biostimulation [5]. Optimized conditions allowed soil detoxification in up to 10 days. Further optimization at larger scales (mesocosms and real field scenarios) is foreseen in collaboration with partners from Instituto do Mar (IMAR), U. Coimbra, and Agência Portuguesa do Ambiente (project POCI/AMB/56039/2004).

A simple, rapid, cost-effective yeast-based microplate susceptibility test that requires small sample volumes, was established for assessing the relative toxicity of herbicides and degradation metabolites [6].This bioassay was recently adapted to compare the toxicity of synthetic azo and antraquinone dyes and of their enzymatic degradation products, to assess the toxicological impact of enzymatic bioremediation of dyeing effluents [7], in collaboration with a partner from ITQB/UNL (project PTDC/BIO/72108/2006). In collaboration with partners from IGC and IMAR-U. Coimbra (project PTDC/AMB/64230/2006), it is also envisaged the development of bioassays for the diagnosis of pesticide toxicity in environmental samples based on the analysis of gene expression profiling in yeast cells exposed to environmentally relevant levels of selected pesticides.

References:

1- Santos PM, Sá-Correia I. (2007) Characterization of the unique organization and co-regulation of a gene cluster required for phenol and benzene catabolism in Pseudomonas sp. M1. Journal of Biotechnology 131:371-378. (abstract)

2- Santos P.M., Benndorf D., Sá-Correia I. (2004) Insights in Pseudomonas putida KT2440 response to phenol-induced stress by quantitative proteomics. Proteomics 4:2640-2652.(abstract)

3- Santos P.M. Roma V., Benndorf D., von Bergen M., Harms H., Sá-Correia I. (2007) Mechanistic insights into the global response to phenol in the phenol-biodegrading strain Pseudomonas sp. M1, revealed by quantitative proteomics. OMICS: A Journal of Integrative Biology 11:233-251. (abstract)

4 - Silva E, Fialho AM, Sá-Correia I, Burns RG, Shaw LJ (2004) Combined bioaugmentation and biostimulation to cleanup soil contamined with high concentrations of atrazine. Environ Sci Technol 5:632-637 (abstract)

5 – Lima D, Viana P, André S, Chelinho S, Costa C, Ribeiro R, Sousa JP, Fialho AM, Viegas CA (2009) Evaluating a bioremediation tool for atrazine contamination soies in open soil microcosmos: the effectiveness of bioaugmentation and biostimulation approaches. Chemosphere, 74: 187-192 (abstract)

6 - Papaefthimiou C, Cabral MG, Mixailidou C, Viegas CA, Sá-Correia I, Theophilidis G (2004) Comparison of two screening bioassays, based on the frog sciatic nerve and yeast cells, for the assessment of herbicide toxicity. Environ Toxicol Chem 23:1211-1218. (abstract)

7 – Pereira L, Coelho AV, Viegas CA, dos Santos MMC, Robalo MP, Martins, LO (2009) Enzymatic biotransformation of the azo dye Sudan Orange G with bacterial CotA-laccase. Journal of Biotechnology, 139: 68-77 (abstract)