Journal of Microbiology

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

Research Support, Non-U.S. Gov't

Prediction of Bacterial Proteins Carrying A Nuclear Localization Signal and Nuclear Targeting of HsdM from Klebsiella pneumoniae: Je Chul Lee , Dong Sun Kim , Dong Chan Moon , Jung-Hwa Lee , Mi Jin Kim , Su Man Lee , Yong Seok Lee , Se-Won Kang , Eun Jung Lee , Sang Sun Kang , Eunpyo Lee , Sung Hee Hyun; J. Microbiol. 2009;47(5):641-645. Published online October 24, 2009; DOI: https://doi.org/10.1007/s12275-009-0217-4

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Abstract: Nuclear targeting of bacterial proteins is an emerging pathogenic mechanism whereby bacterial proteins can interact with nuclear molecules and alter the physiology of host cells. The fully sequenced bacterial genome can predict proteins that target the nuclei of host cells based on the presence of nuclear localization signal (NLS). In the present study, we predicted bacterial proteins with the NLS sequences from Klebsiella pneumoniae by bioinformatic analysis, and 13 proteins were identified as carrying putative NLS sequences. Among them, HsdM, a subunit of KpnAI that is a type I restriction-modification system found in K. pneumoniae, was selected for the experimental proof of nuclear targeting in host cells. HsdM carried the NLS sequences, 7KKAKAKK13, in the N-terminus. A transient expression of HsdM-EGFP in COS-1 cells exhibited exclusively a nuclear localization of the fusion proteins, whereas the fusion proteins of HsdM with substitutions in residues lysine to alanine in the NLS sequences, 7AAAKAAA13, were localized in the cytoplasm. HsdM was co-localized with importin α in the nuclei of host cells. Recombinant HsdM alone methylated the eukaryotic DNA in vitro assay. Although HsdM tested in this study has not been considered to be a virulence factor, the prediction of NLS motifs from the full sequenced genome of bacteria extends our knowledge of functional genomics to understand subcellular targeting of bacterial proteins.

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