October 25, 2022 | Mark J. Krzmarzick (Chair, AEESP Publications Committee), Catherine A. Peters ( EES Editor-in-Chief), David A. Ladner (Member, AEESP Publications Committee)
The “Spotlight” column draws attention to selected articles in Environmental Engineering Science (EES), the official journal of the Association of Environmental Engineering and Science Professors (AEESP). Spotlight articles appear regularly in the journal as an Editor’s Note, as well as in the AEESP Newsletter. Through the publication of high-quality peer-reviewed research, the EES journal helps AEESP achieve its mission of developing and disseminating knowledge in environmental engineering and science. In this entry we shine the spotlight on selected articles from the December 2021 through March 2022 issues of EES. Congratulations to all whose work is highlighted.
Chowdhury, N. N., and Wiesner, M. R. (2021). Persistence and environmental relevance of extracellular antibiotic resistance genes: regulation by nanoparticle association. Environ. Eng. Sci. 38 (12), 1129-1139.
Antibiotic resistance poses imminent threats to human health. In the environment, antibiotic resistance can spread through the proliferation of antibiotic-resistant bacteria and the transmission of antibiotic resistance genes (ARGs). ARGs that lurk from dead and live cells become extracellular (eARGs) and they tend to remain persistent and transmissible over the long term. In an article by Chowdhury and Wiesner (2021), naturally occurring nanoparticles can extend the half-life of eARGs as they absorb the DNA fragments or reduce the degradation by nucleases. This may also increase the bioavailability of eARGs for bacterial uptake, ultimately promoting the dissemination of antibiotic resistance. Thus, the interactions between nanoparticles and eARGs have broad implications in various environments, underscoring future attention.
Lamas-Samanamud, G., Reeves, T., Tidwell, M., Bohmann, J., Lange, K., and Shipley, H. (2022). Changes in chemical structure of n-acyl homoserine lactones and their effects on microcystin expression from Microcystis aeruginosa PCC7806. Environ. Eng. Sci. 39 (1), 29-38.
Algal blooms represent another major environmental issue that threatens natural biota and human health. Cyanobacteria like Microcystis aeruginosa can secrete toxic chemicals (e.g., microcystins) that are bioaccumulative once they enter the food chain. The production of toxins can be attributed to communications among the cyanobacterial populations, which are regulated by quorum sensing chemicals, such as homoserine lactones (HSLs). Lamas-Samanamud et al. (2022) investigated the effects of 18 HSLs of different chemical structures on the biofilm formation and toxin production by Microcystis aeruginosa PCC7806. They found that HSLs with phenyl, ether, and oxo moieties are most potent in inhibiting microcystin production, achieving a reduction of 80% and higher. This study revealed that structural changes to HSLs can effectively regulate cyanobacteria physiology and toxin production, promoting the development of novel approaches to mitigate algal blooms and their impacts.
Chen, S., Wang, Y., Cheng, H., Hazen, T. C., He, C., and He, Q. (2022). Identification of propionate-degrading microbial populations in methanogenic processes for waste treatment: Methanosaeta and Methanoculleus. Environ. Eng. Sci.39 (3), 202-211.
In addition to their attention on natural environments, environmental engineers and scientists are also motivated in addressing relevant issues in engineered systems. Chen et al. (2022) focused their research on methanogenic processes in anaerobic digesters that treat animal waste. Methanogenic processes are widely adapted and provide a sustainable way to decompose organic wastes and generate methane as a renewable energy source. However, the stability of methanogenic processes is frequently affected by the fluctuating concentration of propionate and other volatile fatty acids (VFAs) in the system given their ability to alter the pH. Chen et al. investigated shifts in Archaeal populations in response to propionate dosed to continuous batch bioreactors. Using amplicon-based sequencing and quantitative PCR, Methanosaeta and Methanoculleus were reported as the two key propionate degraders considering their dominance and positive response to elevated propionate. This discovery does not only advance our understanding of fundamental microbial processes involved in propionate and VFA degradation, but also has the potential to promote the development of strategies feasible to maintain stable operations in methanogenic waste treatment.
Devine, C., Wang, F., and Edwards, M. (2021). A standardized test protocol for evaluation of scale reduction technologies. Environ. Eng. Sci. 38 (12), 1109-1119.
Scaling is a serious and prevalent problem in engineered water systems. Scaling can largely dampen energy efficiency and cause other undesirable issues, spanning from flow reduction, clogging, and corrosion damage, to the contamination of opportunistic bacteria. Scaling is caused by precipitation of calcium carbonate and can vary with temperature and chemistry changes. Devine et al. (2021) developed a standardized scaling test protocol (SSTP) for the quantitative assessment of scale deposition under varying conditions. This SSTP is designed with streamlined procedures and requires only a laboratory-scale model plumbing system and a synthetic scaling water, making it reproducible in any laboratory. This SSTP is of critical application value, improving the investigation of scaling and design of treatment. It is also applicable to natural water with high scaling potential and can be modified for systems when corrosion inhibitors are used.