Journal of Microbiology

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Genomic profiling of soil nitrifying microorganisms enriched on floating membrane filter: Christiana Abiola, Joo-Han Gwak, Ui-Ju Lee, Aderonke Odunayo Adigun, Sung-Keun Rhee; J. Microbiol. 2025;63(4):e2502002. Published online April 29, 2025; DOI: https://doi.org/10.71150/jm.2502002

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Abstract PDF Supplementary Material: Recently, floating membrane filter cultivation was adopted to simulate solid surface and enrich surface-adapted soil ammonia-oxidizing archaea (AOA) communities from agricultural soil, as opposed to the conventional liquid medium. Here, we conducted metagenomic sequencing to recover nitrifier bins from the floating membrane filter cultures and reveal their genomic properties. Phylogenomic analysis showed that AOA bins recovered from this study, designated FF_bin01 and FF_bin02, are affiliated with the Nitrososphaeraceae family, while the third bin, FF_bin03, is a nitrite-oxidizing bacterium affiliated with the Nitrospiraceae family. Based on the ANI/AAI analysis, FF_bin01 and FF_bin02 are identified as novel species within the genera “Candidatus Nitrosocosmicus” and Nitrososphaera, respectively, while FF_bin03 represents a novel species within the genus Nitrospira. The pan and core genome analysis for the 29 AOA genomes considered in this study revealed 5,784 orthologous clusters, out of which 653 were core orthologous clusters. Additionally, 90 unique orthologous clusters were conserved among the Nitrososphaeraceae family, suggesting their potential role in enhancing culturability and adaptation to diverse environmental conditions. Intriguingly, FF_bin01 and FF_bin02 harbor a gene encoding manganese catalase and FF_bin03 also possesses a heme catalase gene, which might enhance their growth on the floating membrane filter. Overall, the floating membrane filter cultivation has proven to be a promising approach for isolating distinct soil AOA, and further modifications to this technique could stimulate the growth of a broader range of uncultivated nitrifiers from diverse soil environments.

Journal Article

Transcriptomic Insights into Archaeal Nitrification in the Amundsen Sea Polynya, Antarctica: Joo-Han Gwak , Samuel Imisi Awala , So-Jeong Kim , Sang-Hoon Lee , Eun-Jin Yang , Jisoo Park , Jinyoung Jung , Sung-Keun Rhee; J. Microbiol. 2023;61(11):967-980. Published online December 7, 2023; DOI: https://doi.org/10.1007/s12275-023-00090-0

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Antarctic polynyas have the highest Southern Ocean summer primary productivity, and due to anthropogenic climate change, these areas have formed faster recently. Ammonia-oxidizing archaea (AOA) are among the most ubiquitous and abundant microorganisms in the ocean and play a primary role in the global nitrogen cycle. We utilized metagenomics and metatranscriptomics to gain insights into the physiology and metabolism of AOA in polar oceans, which are associated with ecosystem functioning. A polar-specific ecotype of AOA, from the “Candidatus Nitrosomarinus”-like group, was observed to be dominant in the Amundsen Sea Polynya (ASP), West Antarctica, during a succession of summer phytoplankton blooms. AOA had the highest transcriptional activity among prokaryotes during the bloom decline phase (DC). Metatranscriptomic analysis of key genes involved in ammonia oxidation, carbon fixation, transport, and cell division indicated that this polar AOA ecotype was actively involved in nitrification in the bloom DC in the ASP. This study revealed the physiological and metabolic traits of this key polar-type AOA in response to phytoplankton blooms in the ASP and provided insights into AOA functions in polar oceans.

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Alleviated photoinhibition on nitrification in the Indian Sector of the Southern Ocean
Lingfang Fan, Min Chen, Zifei Yang, Minfang Zheng, Yusheng Qiu
Acta Oceanologica Sinica.2024; 43(7): 52. CrossRef

Review

Ammonia-oxidizing archaea in biological interactions: Jong-Geol Kim , Khaled S. Gazi , Samuel Imisi Awala , Man-Young Jung , Sung-Keun Rhee; J. Microbiol. 2021;59(3):298-310. Published online February 23, 2021; DOI: https://doi.org/10.1007/s12275-021-1005-z

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Abstract

The third domain Archaea was known to thrive in extreme or anoxic environments based on cultivation studies. Recent metagenomics- based approaches revealed a widespread abundance of archaea, including ammonia-oxidizing archaea (AOA) of Thaumarchaeota in non-extreme and oxic environments. AOA alter nitrogen species availability by mediating the first step of chemolithoautotrophic nitrification, ammonia oxidation to nitrite, and are important primary producers in ecosystems, which affects the distribution and activity of other organisms in ecosystems. Thus, information on the interactions of AOA with other cohabiting organisms is a crucial element in understanding nitrogen and carbon cycles in ecosystems as well as the functioning of whole ecosystems. AOA are self-nourishing, and thus interactions of AOA with other organisms can often be indirect and broad. Besides, there are possibilities of specific and obligate interactions. Mechanisms of interaction are often not clearly identified but only inferred due to limited knowledge on the interaction factors analyzed by current technologies. Here, we overviewed different types of AOA interactions with other cohabiting organisms, which contribute to understanding AOA functions in ecosystems.

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Journal Articles

Comparative genomic analysis of Geosporobacter ferrireducens and its versatility of anaerobic energy metabolism: Man-Young Jung , So-Jeong Kim , Jong-Geol Kim , Heeji Hong , Joo-Han Gwak , Soo-Je Park , Yang-Hoon Kim , Sung-Keun Rhee; J. Microbiol. 2018;56(5):365-371. Published online May 2, 2018; DOI: https://doi.org/10.1007/s12275-018-7451-6

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Abstract

Members of the family Clostridiaceae within phylum Firmicutes are ubiquitous in various iron-reducing environments. However, genomic data on iron-reducing bacteria of the family Clostridiaceae, particularly regarding their environmental distribution, are limited. Here, we report the analysis and comparison of the genomic properties of Geosporobacter ferrireducens IRF9, a strict anaerobe that ferments sugars and degrades toluene under iron-reducing conditions, with those of the closely related species, Geosporobacter subterraneus DSM 17957. Putative alkyl succinate synthase-encoding genes were observed in the genome of strain IRF9 instead of the typical benzyl succinate synthase-encoding genes. Canonical genes associated with iron reduction were not observed in either genome. The genomes of strains IRF9 and DMS 17957 harbored genes for acetogenesis, that encode two types of Rnf complexes mediating the translocation of H+ and Na+ ions, respectively. Strain IRF9 harbored two different types of ATPases (Na+-dependent F-type ATPase and H+- dependent V-type ATPase), which enable full exploitation of ion gradients. The versatile energy conservation potential of strain IRF9 promotes its survival in various environmental conditions.

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A novel methanotroph in the genus Methylomonas that contains a distinct clade of soluble methane monooxygenase: Ngoc-Loi Nguyen , Woon-Jong Yu , Hye-Young Yang , Jong-Geol Kim , Man-Young Jung , Soo-Je Park , Seong-Woon Roh , Sung-Keun Rhee; J. Microbiol. 2017;55(10):775-782. Published online September 28, 2017; DOI: https://doi.org/10.1007/s12275-017-7317-3

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Abstract

Aerobic methane oxidation is a key process in the global carbon cycle that acts as a major sink of methane. In this study, we describe a novel methanotroph designated EMGL16-1 that was isolated from a freshwater lake using the floating filter culture technique. Based on a phylogenetic analysis of 16S rRNA gene sequences, the isolate was found to be closely related to the genus Methylomonas in the family Methylococcaceae of the class Gammaproteobacteria with 94.2–97.4% 16S rRNA gene similarity to Methylomonas type strains. Comparison of chemotaxonomic and physiological properties further suggested that strain EMGL16-1 was taxonomically distinct from other species in the genus Methylomonas. The isolate was versatile in utilizing nitrogen sources such as molecular nitrogen, nitrate, nitrite, urea, and ammonium. The genes coding for subunit of the particulate form methane monooxygenase (pmoA), soluble methane monooxygenase (mmoX), and methanol dehydrogenase (mxaF) were detected in strain EMGL16-1. Phylogenetic analysis of mmoX indicated that mmoX of strain EMGL16-1 is distinct from those of other strains in the genus Methylomonas. This isolate probably represents a novel species in the genus. Our study provides new insights into the diversity of species in the genus Methylomonas and their environmental adaptations.

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Calculibacillus koreensis gen. nov., sp. nov., an anaerobic Fe(III)-reducing bacterium isolated from sediment of mine tailings: Ui-Gi Min , So-Jeong Kim , Heeji Hong , Song-Gun Kim , Joo-Han Gwak , Man-Young Jung , Jong-Geol Kim , Jeong-Geol Na , Sung-Keun Rhee; J. Microbiol. 2016;54(6):413-419. Published online May 27, 2016; DOI: https://doi.org/10.1007/s12275-016-6086-8

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Abstract

A strictly anaerobic bacterium, strain B5T, was isolated from sediment of an abandoned coal mine in Taebaek, Republic of Korea. Cells of strain B5T were non-spore-forming, straight, Gram-positive rods. The optimum pH and temperature for growth were pH 7.0 and 30°C, respectively, while the strain was able to grow within pH and temperature ranges of 5.5– 7.5 and 25–45°C, respectively. Growth of strain B5T was observed at NaCl concentrations of 0 to 6.0% (w/v) with an optimum at 3.0–4.0% (w/v). The polar lipids consisted of phosphatidylethanolamine, phosphatidylglycerol, an unknown phospholipid and three unknown polar lipids. Strain B5T grew anaerobically by reducing nitrate, nitrite, ferric-citrate, ferric-nitrilotriacetate, elemental sulfur, thiosulfate, and anthraquinone- 2-sulfonate in the presence of proteinaceous compounds, organic acids, and carbohydrates as electron donors. The isolate was not able to grow by fermentation. Strain B5T did not grow under aerobic or microaerobic conditions. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain B5T is most closely related to the genus Tepidibacillus (T. fermentans STGHT; 96.3%) and Vulcanibacillus (V. modesticaldus BRT; 94.6%). The genomic DNA G+C content (36.9 mol%) of strain B5T was higher than those of T. fermentans STGHT (34.8 mol%) and V. modesticaldus BRT (34.5 mol%). Based on its phenotypic, chemotaxonomic, and phylogenetic properties, we describe a new species of a novel genus Calculibacillus, represented by strain B5T (=KCTC 15397T =JCM 19989T), for which we propose the name Calculibacillus koreensis gen. nov., sp. nov.

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Research Support, Non-U.S. Gov'ts

NOTE] Evaluation of a Fosmid-Clone-Based Microarray for Comparative Analysis of Swine Fecal Metagenomes: Soo-Je Park , Dong-Hwan Kim , Man-Young Jung , So-Jeong Kim , Hongik Kim , Yang-Hoon Kim , Jong-Chan Chae , Sung-Keun Rhee; J. Microbiol. 2012;50(4):684-688. Published online July 21, 2012; DOI: https://doi.org/10.1007/s12275-012-2115-4

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Abstract: Glass slide arrayed with fosmid clone DNAs generated from swine feces as probes were fabricated and used as a metagenome microarray (MGA). MGA appeared to be specific to their corresponding target genomic fragments. The detection limit was 10 ng of genomic DNA (ca. 106 bacterial cells) in the presence of 1000 ng of background DNA. Linear relationships between the signal intensity and the target DNA (20–100 ng) were observed (r2=0.98). Application of MGA to the comparison of swine fecal metagenomes suggested that the microbial community composition of swine intestine could be dependent on the health state of swine.

Molecular Analysis of Spatial Variation of Iron-Reducing Bacteria in Riverine Alluvial Aquifers of the Mankyeong River: So-Jeong Kim , Dong-Chan Koh , Soo-Je Park , In-Tae Cha , Joong-Wook Park , Jong-Hwa Na , Yul Roh , Kyung-Seok Ko , Kangjoo Kim , Sung-Keun Rhee; J. Microbiol. 2012;50(2):207-217. Published online April 27, 2012; DOI: https://doi.org/10.1007/s12275-012-1342-z

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Abstract: Alluvial aquifers are one of the mainwater resources in many countries. Iron reduction in alluvial aquifers is often a major anaerobic process involved in bioremediation or causing problems, including the release of As trapped in Fe(III) oxide. We investigated the distribution of potential iron-reducing bacteria (IRB) in riverine alluvial aquifers (B1, B3, and B6 sites) at the Mankyeong River, Republic of Korea. Inactive iron reduction zones, the diversity and abundance of IRB can be examined using a clone library and quantitative PCR analysis of 16S rRNA genes. Geobacter spp. are potential IRB in the iron-reducing zone at the B6 (9 m) site, where high Fe(II) and arsenic (As) concentrations were observed. At the B3 (16 m) site, where low iron reduction activity was predicted, a dominant clone (10.6%) was 99% identical in 16S rRNA gene sequence with Rhodoferax ferrireducens. Although a major clone belonging to Clostridium spp. was found, possible IRB candidates could not be unambiguously determined at the B1 (18 m) site. Acanonical correspondence analysis demonstrated that, among potential IRB, only the Geobacteraceae were well correlated with Fe(II) and As concentrations. Our results indicate high environmental heterogeneity, and thus high spatial variability, in thedistribution of potential IRB in the riverine alluvial aquifersnear the Mankyeong River.

Metagenomic Assessment of a Sulfur-Oxidizing Enrichment Culture Derived from Marine Sediment: Man-Young Jung , VinhHoa Pham , Soo-Je Park , So-Jeong Kim , Jong-Chan Chae , Yul Roh , Sung-Keun Rhee; J. Microbiol. 2010;48(6):739-747. Published online January 9, 2011; DOI: https://doi.org/10.1007/s12275-010-0257-9

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Abstract: The biological oxidation of reduced sulfur compounds is a critically important process in global sulfur biogeochemistry. In this study, we enriched from marine sediments under denitrifying conditions, chemolithotrophic sulfur oxidizers that could oxidize a variety of reduced sulfur compounds: thiosulfate, tetrathionate, sulfide, and polysulfide. Two major phylotypes of 16S rRNA gene (>99% identity in each phylotype) were detected in this enrichment culture. In order to characterize sulfide oxidation, we sequenced and characterized one fosmid clone (43.6 kb) containing the group I sulfide-quinone reductase (sqr) gene. Interestingly, four putative rhodanese genes were found in this clone. Furthermore, comparative alignment with the closest genome of Thiomicrospira crunogena XCL2 revealed that three homologous genes were located within the vicinity of the sqr gene. Fosmid clones harboring carbon fixation (cbbL and cbbM) and denitrification (narG) genes were screened, and the phylogeny of the functional genes was analyzed. Along with the comparison between the sqr-containing fosmid clones and the relevant gamma-proteobacteria, our phylogenetic study based on the 16S rRNA gene and carbon fixation genes suggest the prevalence of chemolithotrophic gamma-proteobacteria in the denitrifying cultures. The findings of this study imply that a combination of cultivation and metagenomic approaches might provide us with a glimpse into the characteristics of sulfur oxidizers in marine sediments.

Detection of Representative Enteropathogenic Bacteria, Vibrio spp., Pathogenic Escherichia coli, Salmonella spp., Shigella spp., and Yersinia enterocolitica, Using a Virulence Factor Gene-Based Oligonucleotide Microarray§: Dong-Hun Kim , Bok-Kwon Lee , Yong-Dae Kim , Sung-Keun Rhee , Young-Chang Kim; J. Microbiol. 2010;48(5):682-688. Published online November 3, 2010; DOI: https://doi.org/10.1007/s12275-010-0119-5

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Abstract: Rapid identification of enteropathogenic bacteria in stool samples is critical for clinical diagnosis and antimicrobial therapy. In this study, we describe the development of an approach that couples multiplex PCR with hybridization to a DNA microarray, to allow the simultaneous detection of the 10 pathogens. The microarray was synthesized with 20-mer oligonucleotide probes that were designed to be specific for virulencefactor genes of each strain. The detection limit for genomic DNA from a single strain was approximately 10 fg. In the presence of heterogeneous non-target DNA, the detection sensitivity of the array decreased to approximately 100 fg. We did not observe any non-specific hybridization. In addition, we successfully used this oligonucleotide-based DNA microarray to identify the causative agents in clinical stool samples from patients with food-borne enteritis.

Isolation, Characterization, and Abundance of Filamentous Members of Caldilineae in Activated Sludge: Dae-No Yoon , Soo-Je Park , So-Jeong Kim , Che Ok Jeon , Jong-Chan Chae , Sung-Keun Rhee; J. Microbiol. 2010;48(3):275-283. Published online June 23, 2010; DOI: https://doi.org/10.1007/s12275-010-9366-8

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Abstract: Chloroflexi are currently believed to serve as backbone forming agents in the activated sludge of wastewater treatment plants (WWTPs). In this study, we isolated and characterized filamentous bacteria in the class Caldilineae of the phylum Chloroflexi in municipal WWTPs. Diversity analysis using Chloroflexi-specific 16S rRNA gene clone libraries showed that 97% of the clones belonged to the subdivision Anaerolineae comprising the two classes Anaerolineae (95%) and Caldilineae (2%). Clones of Caldilineae were related to a thermophilic filament Caldilinea aerophila with 93% 16S rRNA gene sequence similarity. We obtained filamentous isolates classified into the class Caldilineae showing the best match to C. aerophila with 89% 16S rRNA gene sequence similarity. Isolates showed no ability to assimilate glucose or N-acetylglucosamine or to degrade biopolymers which were observed in filamentous Chloroflexi of WWTPs. The assessment of relative abundance based on quantitative PCR of the 16S rRNA gene indicated that members of the class Caldilineae comprised 12-19% of the Chloroflexi in the activated sludge. Additionally, fluorescence in situ hybridization experiments showed that diverse filamentous Caldilineae inhabit the activated sludge of municipal WWTPs. These findings yield insight into the role of filamentous mesophilic Caldilinea in stabilizing flocs of activated sludge in a wide range of WWTPs.

Microeukaryotic Diversity in Marine Environments, an Analysis of Surface Layer Sediments from the East Sea: Soo-Je Park , Byoung-Joon Park , Vinh Hoa Pham , Dae-No Yoon , Si-Kwan Kim , Sung-Keun Rhee; J. Microbiol. 2008;46(3):244-249. Published online July 5, 2008; DOI: https://doi.org/10.1007/s12275-007-0237-x

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Abstract: Molecular techniques, based on clone library of 18S rRNA gene, were employed to ascertain the diversity of microeukaryotic organisms in sediments from the East Sea. A total of 261 clones were recovered from surface sediments. Most of the clone sequences (90%) were affiliated with protists, dominated by Ciliates (18%) and Dinoflagellates (19%) of Alveolates, phototrophic Stramenopiles (11%), and Cercozoa (20%). Many of the clones were related to uncultivated eukaryotes clones retrieved from anoxic environments with several highly divergent 18S rRNA gene sequences. However, no clones were related to cultivated obligate anaerobic protists. Protistan communities between subsurface layers of 1 and 9 cm shared 23% of total phylotypes which comprised 64% of total clones retrieved. Analysis of diversity indices and rarefaction curve showed that the protistan community within the 1 cm layer exhibited higher diversity than the 9 cm layer. Our results imply that diverse protists remain to be uncovered within marine benthic environments.

Characterization of the Depth-Related Changes in the Microbial Communities in Lake Hovsgol Sediment by 16S rRNA Gene-Based Approaches: Young-Do Nam , Youlboong Sung , Ho-Won Chang , Seong Woon Roh , Kyoung-Ho Kim , Sung-Keun Rhee , Jung-Chan Kim , Joo-Yong Kim , Jung-Hoon Yoon , Jin-Woo Bae; J. Microbiol. 2008;46(2):125-136. Published online June 11, 2008; DOI: https://doi.org/10.1007/s12275-007-0189-1

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Abstract: The undisturbed sediment of Lake Hovsgol (Mongolia) is scientifically important because it represents a record of the environmental changes that took place between the Holocene (the present age) and Pleistocene (the last ice age; 12,000 14C years before present day). Here, we investigated how the current microbial <br>communities change as the depth increases by PCR-denaturing gradient gel electrophoresis (DGGE) analysis of the 16S rRNA genes of the microbial communities. The microbial diversity, as estimated by the Shannon index, decreased as the depth increased. In particular, significant changes in archaeal diversity were observed in the middle depth (at 39~42 cm depth of total 60 cm depth) that marks the border between the Holocene and Pleistocene. Phylotype belonging to Beta- and Gamma-Proteobacteria were the predominant bacteria and most of these persisted throughout the depth examined. However, as the depth increased, some bacteria <br>(some genera belonging to Beta-Proteobacteria, Nitrospira, and OP8-9) were not detectable while others (some genera belonging to Alpha-, Beta-, Gamma-Proteobacteria) newly deteced by DGGE. Crenarchaea were the predominant archaea and only one phylotype belonging to Euryarchaea was found. Both the <br>archaeal and bacterial profiles revealed by the DGGE band patterns could be grouped into four and three subsets, respectively, subsets that were largely divided by the border between the Holocene and Pleistocene. Thus, the diversity of the current microbial communities in Lake Hovsgol sediments decreases with increasing <br>depth. These changes probably relate to the environmental conditions in the sediments, which were shaped by the paleoclimatic events taking place between the Holocene and Pleistocene.

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