Separating and characterizing functional alkane degraders from crude-oil-contaminated sites via magnetic nanoparticle-mediated isolation

Abstract

Uncultivable microorganisms account for over 99% of all species on the planet, but their functions are yet not well characterized. Though many cultivable degraders for n-alkanes have been intensively investigated, the roles of functional n-alkane degraders remain hidden in the natural environment. This study introduces the novel magnetic nanoparticle-mediated isolation (MMI) technology in Nigerian soils and successfully separates functional microbes belonging to the families Oxalobacteraceae and Moraxellaceae, which are dominant and responsible for alkane metabolism in situ. The alkR-type n-alkane monooxygenase genes, instead of alkA- or alkP-type, were the key functional genes involved in the n-alkane degradation process. Further physiological investigation via a BIOLOG PM plate revealed some carbon (Tween 20, Tween 40 and Tween 80) and nitrogen (tyramine, l-glutamine and d-aspartic acid) sources promoting microbial respiration and n-alkane degradation. With further addition of promoter carbon or nitrogen sources, the separated functional alkane degraders significantly improved n-alkane biodegradation rates. This suggests that MMI is a promising technology for separating functional microbes from complex microbiota, with deeper insight into their ecological functions and influencing factors. The technique also broadens the application of the BIOLOG PM plate for physiological research on functional yet uncultivable microorganisms.

Separating and Characterizing Functional Nitrogen Degraders via Magnetic Nanoparticle-Mediated Isolation

“…After 20 days, the degradation efficiency exceeded 90%, indicating that MNPs had no effect on the bacterial activities or the ammonia nitrogen degradation performance [26]. And this is similar to the results of separation of functional alkane degradation agents using magnetic nanoparticles by Wang et al [27]. e long-term acclimated sludge already contains a large number of target pollutant-degrading microorganisms.…”

“…e activated sludge was functionalized with MNPs according to a previously reported method [27]. Sludge and nanoparticle concentrations were determined as follows: 1.0 mL of synthetic MNPs was mixed with 0.01 to 1.099 mg of sludge samples.…”

“…e low magnetic functionalization efficiency likely resulted from the large sizes of the sludge particles or microbial cells. Also, microbial cells are functionalized by MNPs via the interaction of MNPs with functional groups, such as carboxyl groups (-COOH), thiol (-SH), and amino groups (-NH 2 ), on microbial cell membranes [27,34]. Given that all microbial cells have functional groups, magnetic functionalization is not selective, and all microbial cells can be magnetized.…”

“…Some scholars have used MNPs for the separation and screening of pollutant-degrading bacteria. For example, Wang et al [27] used Fe 3 O 4 MNP separation technology to study alkane-degrading bacteria in soil and experimentally confirmed that Oxalobacteraceae and Moraxellaceae are functional microorganisms in the degradation process. In this study, the composition and properties of the MNPs were characterized by some methods, and MMI was used for the first time in long-term domesticated activated sludge systems, adding urea as a carbon source to enhance the activity of ammonia nitrogen-degrading bacteria.…”

A whole-cell bioreporter assay for quantitative genotoxicity evaluation of environmental samples

“…Normally, whole-cell bioreporters are classified into two categories. One is responsive to specific toxicity pathways and induced in the presence of specific compounds or their analogues with similar structure, such as alkanes (e.g., alkane degradation pathway) (Sticher et al, 1997;Wang et al, 2016), naphthalene (e.g., napthalene degradation pathway) (Neilson et al, 1999), polycyclic aromatic hydrocarbons (e.g., phenanthrene mineralization) (Tecon et al, 2009) and mercury (mercuric resistant regulatory M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT 5 pathway) (Rasmussen et al, 2000). The others can be induced by general toxicity pathways, including stressful conditions such as DNA damage (Vollmer et al, 1997;Min et al, 1999;Biran et al, 2009), membrane damage (Bechor et al, 2002) and oxidative damage (Lee and Gu, 2003).…”