Organic pollutants (dyes, pesticides, explosives, pharmaceuticals, etc.) are constantly released into the environment due to human activities. Many of these compounds are xenobiotics, which means that microorganisms in nature have never seen them before (please, imagine Mariah Carey's "I don't know her" meme). Luckily, some microorganisms can adapt to this major inconvenience. For example, enzymes used for naturally occurring substrates can end up degrading a new contaminant in the environment. Alternatively, microorganisms can evolve and develop new specific enzymes to do that. However, microbes are not alone in nature or engineered systems (e.g., a biological reactor treating wastewater). Instead, they are surrounded – and affected to – by other microorganisms, water, nutrients, inert or reactive minerals, natural organic matter, gases, etc. The organic contaminants and their biotransformation products (i.e., whatever the microbes transformed the contaminants to) can also react with these other components, affecting the contaminants' environmental fate and generating final products with different toxicity levels. Most of my experimental work (yes, it does involve long hours working at the lab bench) consists of breaking these complex environments into smaller pieces, which we call microcosms, to discover what chemical and biological phenomena are occurring after a new compound gets released in the environment. My research philosophy is to generate solutions to remediate environmental contamination by organic pollutants and, in the process, to find out how nature works.
This whole scientific journey started as a kid in my parents' backyard when I observed that the water with red ink that I had exhaustively extracted from a marker pencil became clear after passing it through a pot with soil (poor plants!). Years later, more formally, during my graduate studies at the Federal University of Pernambuco (Brazil), I initially worked with the treatment of azo dyes, which are largely released by the fashion industry in many aquatic environments. I optimized oxygen injection in a biological reactor to transform heavily contaminated textile wastewater into a non-toxic effluent. Next, I worked with the environmental remediation of explosive contaminants released on the soil by military activities, especially in four different topics: the ability of some reactive minerals in the soils and aquatic sediments to degrade explosives; the unusual phenomenon of soil bacteria making a living breathing an explosive; the (bio)degradation of a product of explosives compounds in contaminated wastewater; and the oligomerization reactions that lock the contaminant inside complex humic substances, which is a safe dead-end for some explosives in the environment.
During my postdoc at the University of Arizona, where I am supervised by Dr. Jim A. Field and Dr. Reyes Sierra-Alvarez, I am currently investigating the remediation of nitro-aromatics (including but not limited to explosives) using the soil natural organic matter's ability to shuttle electrons between biological and chemical systems in subsurface environments. The intense knowledge exchange with the brilliant people in the research group has made my research life fulfilling. Furthermore, it is evident to me how the new challenges and responsibilities as a postdoc are quickly preparing me for my career.
Dr. Osmar Menezes was awarded a Postdoctoral Research Development Grant (PRDG) from the University of Arizona for a project titled “Soil Organic Matter Improves the Microbial Degradation of Emerging Contaminants”.
Each month we'll feature a Postdoctoral Scholar and their research, sharing their experiences from the UA, life in Arizona and their research interests.