Members of the bacterial genus Thalassotalea have been isolated recently from various marine environments, including marine invertebrates. A metagenomic study of the Deepwater Horizon oil plume has identified genes involved in aromatic hydrocarbon degradation in the Thalassotalea genome, shedding light on its potential role in the degradation of crude oils. However, the genomic traits of the genus are not well-characterized, despite the ability of the species to degrade complex natural compounds, such as agar, gelatin, chitin, or starch. Here, we obtained a complete genome of a new member of the genus, designated PS06, isolated from marine sediments containing dead marine benthic macroalgae. Unexpectedly, strain PS06 was unable to grow using most carbohydrates as sole carbon sources, which is consistent with the finding of few ABC transporters in the PS06 genome. A comparative analysis of 12 Thalassotalea genomes provided insights into their metabolic potential (e.g., microaerobic respiration and carbohydrate utilization) and evolutionary stability [including a low abundance of clustered regularly interspaced short palindromic repeats (CRISPR) loci and prophages]. The diversity and frequency of genes encoding extracellular enzymes for carbohydrate metabolism in the 12 genomes suggest that members of Thalassotalea contribute to nutrient cycling by the redistribution of dissolved organic matter in marine environments. Our study improves our understanding of the ecological and genomic properties of the genus Thalassotalea.

Desmarestia japonica (Phaeophyceae, Desmarestiales) was recently established from the Japanese ligulate Desmarestia and is morphologically similar to D. ligulata. This species has been reported only from Japan. However, the taxonomic reports based on additional regional distributions are needed to clarify this taxonomic entity and its species boundaries. Because Desmarestia species have restricted distributions in Korea, we reexamined herbarium specimens of D. ligulata deposited at the National Institute of Biological Resources (South Korea). To improve the amplification efficiency of the polymerase chain reaction and avoid contamination by the DNA of other organisms, we developed taxon-specific molecular markers suitable for DNA barcoding of Desmarestia species. Nuclear ribosomal small subunit RNA (18S rDNA) and mitochondrial cytochrome c oxidase 1 (cox1) regions were selected as target DNA. As a result, both were successfully isolated from herbarium specimens of D. japonica acquired over 10 years. These molecular markers provide useful genetic information for herbarium specimens for which conventional molecular analysis is challenging.

Three species of the genus Ishige (Phaeophyceae, Ishigeaceae) are known from Korea, Japan and Mexico; they include Ishige foliacea Okamura, I. okamurae Yendo and I. sinicola (Setchell and N.L. Gardner) Chihara. Two species, I. foliacea and I. okamurae, are present in the algal flora of Korea and Japan. The original description of I. okamurae defined two forms of branches, filiform and foliose, but later the foliose branch was recognized as a new species I. foliacea, which is epiphytic on I. okamurae but can also be free-living. The currently proposed lectotype for I. foliacea is based on a free-living form and does not reflect the intent of the original description of the species. In this study, we conducted the DNA barcoding for herbarium specimens to identify Ishige species. Additionally, the variation in cox3 sequences obtained from I. okamurae specimens with two morphological forms collected from waters around the Korean Peninsula was sufficient to separate two species, I. okamurae and its epiphyte I. foliacea. The epiphytic I. foliacea on the lectotype specimen of I. okamurae is designated as lectotype I. foliacea.

Desmarestia japonica H. Kawai, T. Hanyuda, D. G. Müller, E. C. Yang, A. F. Peters, & F.C. Küpper (2014: 161) was recently reported in Japan, Korea, and China. In this study, we found intraspecific morphogenetic variation in D. japonica. Morphologically, the new taxonomic entity was characterized by narrow filamentous primary and secondary branches (morphotype 2), which was distinct from the broad (ligulate) branches in the original description of D. japonica (morphotype 1). Korean individuals with morphotype 2 were clearly separated from D. japonica with morphotype 1 in the molecular phylogenetic tree using the mitochondrial cytochrome c oxidase 1 (cox1) gene. Therefore, we propose that this new taxonomic entity be established as Desmarestia japonica subsp. angustifolia subsp. nov. (Phaeophyceae, Desmarestiales) based on its morphological and molecular characteristics.

The genus Meristotheca (Gigartinales, Solieriaceae) comprises edible red algae that are economically important food ingredients in Korea, Japan, and China. In Korea, two species, Meristotheca coacta and Meristotheca papulosa, have been identified, with the latter being predominantly reported. Recently, molecular phylogenetic analysis enabled the identification of Meristotheca pilulaora (Gigartinales; Solieriaceae) on Jeju Island (Korea). In this study, we used a DNA barcoding method to re-examine M. papulosa herbarium specimens deposited at the National Institute of Biological Resources (Incheon, Korea). Specimens were collected from Korean coastal regions between 2009 and 2019. Molecular analyses based on the rbcL and cox1 sequences of the “M. papulosa” herbarium specimens revealed that the specimens were of two other species, M. pilulaora and Gracilaria textorii (Gracilariales; Gracilariaceae). Our work represents a case study for establishing a misidentification at the inter-ordinal level among herbarium specimens without DNA sequence verification. Moreover, we developed a molecular marker for the effective species-level identification of M. pilulaora and G. textorii specimens. The DNA barcoding method provides useful information regarding M. pilulaora distribution and taxonomy.

The taxonomic position of the green alga Capsosiphon fulvescens was first reported from Northern Europe and has since been reported from all over the world, including Korea. In Korea, C. fulvescens has been used as an essential edible economic alga for approximately 570 years, from the time of the Joseon Dynasty to the present, and is currently under development as a new aquaculture strain. Therefore, examining the taxonomic relationships between the European and Korean C. fulvescens is important. In this study, we analyzed nuclear 18S rDNA and ITS regions and compared them with the DNA sequences of authentic materials of North Atlantic C. fulvescens. Additionally, rbcL and tufA genes were sequenced to analyze genetic variations among populations. The results showed that the Korean and European C. fulvescens were different species. Moreover, the Korean C. fulvescens was distantly related to the North Atlantic C. fulvescens at the order level. Moreover, the Korean C. fulvescens formed a sister group with the North Pacific Pseudothrix borealis. Cryptic genetic diversity was observed at the intraspecific level among the Korean populations. These findings will help in tracing the origin of the Korean C. fulvescens and provide new genetic insights into this species.