Project background (Week 10)

Pseudomonas aeruginosa is one of the famous Pseudomonas species. It’s known to be a gram-negative, aerobic bacterium usually found in water and soil. Pseudomonas aeruginosa is an increasing concern because it thrives in water systems and is famous for cooling towers, showers, irrigation systems, or medical devices made of plastics. When it comes to individuals, Pseudomonas aeruginosa can cause respiratory infections and lung diseases that could turn out to be chronic in individuals with Cystic Fibrosis or individuals who are immunocompromised (Jamunadevi et al. 2012; Pseudomonas Data Sheet. 2011). Like most ordinary bacteria, Pseudomonas species produce a biofilm that attaches to surfaces, which allows it to grow and persist in different environments, including plumbing systems, on medical devices such as catheters and respiratory tubing (major issues in hospitals), and on small (<5 mm) microplastics found in environmental water samples (Mena, 2009).

A study made by McCormick et al in 2014 concluded that microplastics that ascend from industrial products can serve as a distinct microbial habitat for biofilm-forming bacteria, such as Pseudomonas. Several types of research have also found that in addition to colonizing microplastics, Pseudomonas species play a role in the breaking down of plastics such as polyvinyl alcohol (PVA), polypropylene and polythene (McCormick et al,2014; Shimao, 2001; Kathiresan, 2003; Cacciari et al. 1993). Medical devices like respiratory tubing and catheters are made of plastics. The ability to identify the species of Pseudomonas present in the degradation of microplastics is a major factor in the medical field. The teams research seeks to answer the question: “What Pseudomonas species can colonize and degrade microplastics such as polyvinyl alcohol, polypropylene, and polythene?”

The team’s objective is to examine the diversity of Pseudomonas on microplastics collected from the environment, and identify which species can degrade microplastics composed of polyvinyl alcohol (PVC), polyvinyl chloride, LPDE (low-density polyethylene), and SPI plastic. These objectives will be accomplished by collecting microplastic samples from the environment, isolating and identifying Pseudomonas species from these microplastics, and examine degradation of the microplastics by these species.

So far, the team has observed the separation of microplastics from environmental water sources, isolate biofilm-forming bacteria, such as Pseudomonas using filtration found in the biomedical laboratory, and culture Pseudomonas using selective media. Most strains of the Pseudomonas produce a variety of pigments, such as pyoverdin (a fluorescent yellow-green pigment) and pyocyanin (a blue-green, non-fluorescent pigment), which can aid in their identification (Reyes et al. 1981).

For the research being conducted, the team will isolate Pseudomonas species using Pseudomonas Isolation Agar (PIA) and Pseudomonas fluorescence (PF). PIA includes a broad-spectrum antibiotic (Irgasan) that selectively inhibits gram-positive and gram-negative bacteria other than Pseudomonas, and PF helps differentiate pseudomonas pigments between the different types of Pseudomonas species. DNA will then be extracted from colonies growing on PIA and PF and samples will be analyzed by PCR for the presence of Pseudomonas aeruginosa, Pseudomonas putida, Pseudomonas fluorescens, and Pseudomonas stutzeri. DNA gel extraction and sequencing analysis will then be utilized to identify the species of Pseudomonas present in the isolated samples.

Reference

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Cacciari, I.; Quatrini, P.; Zirletta, G.; Mincione, E.; Vinciguerra, V.; Lupattelli, P.; Sermanni, G. G. Isotactic polypropylene biodegradation by a microbial community: physicochemical characterization of metabolites produced. Appl. Environ. Microbiol. 1993, 59 (11), 3695−3700.

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