Neurological disorders such as anxiety, depression, Parkinson’s disease (PD), and Alzheimer’s disease (AD) have been increasing in patient numbers. Those can be treated by inhibiting target enzymes including monoamine oxidase (MAO)-A and MAO-B, acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and β-site amyloid precursor protein (APP) cleaving enzyme 1 (BACE1) using potent inhibitors. During the lecture, leading compounds will be introduced from natural compounds and their derivatives as well as synthetic compounds. In natural compounds, 1) rhamnocitrin, hispidol, osthenol, and decursin as MAO-A inhibitors; 2) maackiain and medicarpin as MAO-B inhibitors; 3) sargachromanol I and macelignan as AChE inhibitors; 4) three BACE1 inhibitors were isolated. In synthetic compounds, 1) furanochalcones, ethyl acetohydroxamate chalcones, conjugated dienones, and oxygenated chalcones as potent MAO-B inhibitors; 2) 4-substituted benzyl-2-triazole-linked-tryptamine-paeonol derivatives as BChE inhibitors; 3) N-methyl-piperazine chalcones as dual MAO-B/AChE inhibitors; 4) sargachromanol I and decursin derivatives as improved AChE and BACE1 inhibitors, respectively, were screened. Some of the compounds showed significant effects on anti-depressant activity and/or cognitive function alleviation in the animal behavioral tests using mice, and could be served as potential candidates for the treatment of depression, PD, and AD. In this presentation, the progress of the study will be presented with the major results obtained by the lab members for about 36 years, including molecular enzymology and metagenomics for cellulases (Cel) and esterases carried out in the early research period.

The antibiotic resistome refers to the collection of all antibiotic resistance genes (ARGs) in both pathogenic and non-pathogenic bacteria. It is an important area of study as it helps in understanding how antibiotic resistance evolves and spreads, which is crucial for the effective treatment of bacterial infections. If the spread of antibiotic resistance is not halted, we could face a future where many common infections become untreatable. If no action is taken, it has been suggested that by 2050, the annual death toll could be as high as 10 million, which is predicted to be higher than that caused by cancer. To investigate the antibiotic resistome, we applied next-generation sequencing (NGS) in three ways: amplicon sequencing to perform fecal pollution source identification; metagenomic sequencing to investigate antibiotic resistome; and whole-genome sequencing (WGS) to discern the dissemination mechanisms of antibiotic resistant E. coli.
Fecal pollution is an indication of antimicrobial resistance spread as fecal bacteria often carry ARGs. Fecal source identification, also known as microbial source tracking (MST), was done using FEAST, a machine-learning model developed for MST. We performed MST for the Miho River and compared fecal pollution degree before and after heavy rain. Results showed that the Miho River was only polluted by several livestock feces after heavy rain, suggesting that surrounding environments contribute to the pollution.
We have conducted metagenomics to investigate the antibiotic resistome in effluents from wastewater treatment plants (WWTPs) and fish farms. Nearly 10 to 20 Gb of metagenomic data were obtained from each sample. The pipeline we developed estimates the abundance of ARGs, possible bacterial hosts of ARGs, and the mobility of ARGs. The results showed that WWTPs and fish farm effluents contain various ARGs, most of which are mediated by plasmids. Therefore, these environments serve as a source of ARGs to the environments.
Lastly, we conducted WGS for multidrug-resistant E. coli to discern dissemination mechanisms between pets-human and livestock-human. Long- and short-read sequencing were done to obtain WGS data for 144 ESBL-producing E. coli. WGS data were used to characterize how these antibiotic-resistant bacteria were transferred between animals and humans: clonal spread or horizontal gene transfer. Core genome MLST (cgMLST) analysis showed these ESBL-producing E. coli were shared more frequently between pets and humans compared to livestock and humans, suggesting that antibiotic-resistant bacteria can be easily transferred through physical contacts. Moreover, results showed ESBL-related genes (i.e., CTX-M-14) were frequently associated with mobile genetic elements (MGEs), and conjugative/mobilizable plasmids shared by these E. coli between humans and animals often carry various ARGs.
Results from these studies suggest that aquatic environments (i.e., rivers and seawater) are likely to contain antibiotic-resistant bacteria. Although they may not be pathogenic, there is always a chance for them to pass ARGs to pathogenic bacteria. While current research investment is mostly focused on surveillance of AMR, future research should include the prevention of AMR spread across environments as our results suggest that AMR spread seems to be persistent.

Microbial biofilms and environmental pollution are considered to be a major concern for human health worldwide. Microbial invasions cause a range of diseases such as tuberculosis, candidiasis, streptobacillary rat-bite fever, chickenpox, AIDS, COVID 19, Hepatitis, etc., on the other hand, the environmental pollutions lead the serious health impact by causing the diseases such as arthritis, cancer, diabetes, reproductive, and neurological diseases. The current interest is in understanding the biology, and biotechnology of the infectious disease related to the microbial biofilms and environmental pollution would protect the human life from deadly diseases. Therefore, our research group has worked on the development of engineered nanomaterials and natural products to cure deadly diseases as well as secure a healthy environment for human life. For the instance, our group has recently reported several inorganic and organic nanoparticles with promising anticancer, antioxidant, antibacterial, and bioremediation properties. Also, we are developing the polymers and liposomes-based drug delivery system for the improved therapeutic activity of the natural products for the treatment of several chronic diseases including diabetes, cancer, and bacterial infections.

Keywords: Nanoparticles, pollution, natural products, microbial biofilms