Specific fecal DNA markers were investigated for major pollution sources, cow, human, and pig, and occurrence of the identified markers was analyzed in river waters using Terminal Restriction Fragment Length Polymorphism (T-RFLP) techniques and sequencing of 16S rDNA of Bacteroides-Prevotella. The unique and specific DNA markers for cow and human were identified as a 222 bp and 60 bp peak in HaeIII T-RFLP profiles, respectively, and the pig-specific marker was not identified but the unique T-RFLP profile of pig could be used as a substitution. Human-specific marker was detected in most of the river waters tested (92.1%) and T-RFLP profiles of river waters were shown to be similar to those of human feces. Cluster analysis of T-RFLP data showed that the fecal sources were multiple (human plus cow and human plus dairy cow) in most of the river waters. The phylogenetic analysis for the clones recovered from the fecal and water samples showed that the clones from cow formed a discreet cluster from those of other sources. The other clones from human, pig, and river water formed two groups all together. The results of this study could be used to identify and control the fecal pollution source in the bodies of water in Korea.

Outbreaks of 2-methylisoborneol (2-MIB) contamination in drinking water sources cause inconvenient odor issues in the water distribution system. In this study, microscopy-based isolation with physiological and molecular phylogenetic characterization were performed to investigate and characterize the 2-MIB odor producers that caused an odor problem in the freshwater system of the North Han River in the autumn of 2018. A benthic cyanobacterium was isolated from 2-MIB odor-issue freshwater samples and was found to be phylogenetically affiliated with Pseudanabaena yagii (99.66% sequence similarity), which was recorded in South Korea for the first time. The 2-MIB synthesis gene sequences from the odor-issue freshwater samples showed 100% similarity with those in the P. yagii strains. Protein sequences of 2-MIB synthase observed in the genome of the isolated strain showed structural and functional characteristics similar to those observed in other Pseudanabaena species. The 2-MIB production rate increased slowly during mat formation on the vessel wall; however, it rapidly increased after the temperature dropped. The 2-MIB gene was continuously expressed regardless of the temperature changes. These results suggest that the 2-MIB odor issue in the North Han River might be caused by the release of 2-MIB from the mat-forming P. yagii species in a low-temperature freshwater environment.

The complete genome and plasmid sequences of Raphidiopsis curvispora strain GIHE-G1, a coiled filamentous heterocyst-forming cyanobacterium isolated from a drinking water reservoir in South Korea, are reported here. The genome information is expected to improve understanding of this species.

The present study aims to assess the effectiveness of eDNA metabarcoding for the analysis of fish communities in rivers. The findings suggest that the methodology attained an accuracy rate of 80% for species identification and was able to detect between 79.2% and 87.5% of the fish species recorded in the fish monitoring database for three rivers of Anseong, Bokha and Gyeongan during the period 2019 to 2021. Significantly, the eDNA metabarcoding technique enabled the successful detection of comparatively larger fish species, such as <i>Channa argus</i> and <i>Silurus asotus</i>. Furthermore, depending on the river, this method identified 12 to 14 additional species that could not be observed through traditional methodologies. However, it is worth noting that the Mifish primer used amplifies short gene segments, which can pose challenges in identifying species with identical gene sequences. Notwithstanding this limitation, the advantages of eDNA analysis over conventional methods are significant, enabling the identification of a broader range of species within a shorter timeframe, using smaller sample volumes and minimizing risks to both endangered fish and to researchers. As a result, eDNA analysis represents a valuable alternative for assessing biodiversity and for collecting data on fish species that are challenging to analyze.

Tropical and subtropical cyanobacteria have been increasingly reported in temperate regions. The genus Raphidiopsis is rarely observed in South Korea. To date, R. curvispora has been reported generally in tropical and subtropical regions, such as Africa and South-east Asia. R. curvispora strain GIHE-G1 was isolated in a drinking water reservoir in South Korea for the first time in July 2020, and its whole genome was sequenced. The complete genome sequence indicated that the strain did not contain any cyanotoxin genes. Morphologically, the GIHE-G1 strain is more similar to the African than Japanese strain, which has a closer geographical distribution. Phylogenetic analysis of several genetic markers, such as 16S rRNA, phycocyanin intergenic spacer (cpcBA-IGS), nitrogenase gene (nifH) and RNA polymerase gene (rpoC1), did not show geographical characteristics or a close relationship with the African strains, unlike the case of Raphidiopsis raciborskii. Moreover, a minimal genetic relationship with Raphidiopsis from China was found. Considering the morphological and genetic characteristics, R. curvispora strain GIHE-G1 was likely introduced a long time ago or is native to Korea and is becoming more noticeable because of recent environmental changes.