Journal of Microbiology

Reviews

Temperature Matters: Bacterial Response to Temperature Change: Seongjoon Moon , Soojeong Ham , Juwon Jeong , Heechan Ku , Hyunhee Kim , Changhan Lee; J. Microbiol. 2023;61(3):343-357. Published online April 3, 2023; DOI: https://doi.org/10.1007/s12275-023-00031-x

Abstract: Temperature is one of the most important factors in all living organisms for survival. Being a unicellular organism, bacterium requires sensitive sensing and defense mechanisms to tolerate changes in temperature. During a temperature shift, the structure and composition of various cellular molecules including nucleic acids, proteins, and membranes are affected. In addition, numerous genes are induced during heat or cold shocks to overcome the cellular stresses, which are known as heat- and cold-shock proteins. In this review, we describe the cellular phenomena that occur with temperature change and bacterial responses from a molecular perspective, mainly in Escherichia coli.

[Minireview]Cytoplasmic molecular chaperones in Pseudomonas species: Hyunhee Kim , Seongjoon Moon , Soojeong Ham , Kihyun Lee , Ute Römling , Changhan Lee; J. Microbiol. 2022;60(11):1049-1060. Published online November 1, 2022; DOI: https://doi.org/10.1007/s12275-022-2425-0

Abstract: Pseudomonas is widespread in various environmental and host niches. To promote rejuvenation, cellular protein homeostasis must be finely tuned in response to diverse stresses, such as extremely high and low temperatures, oxidative stress, and desiccation, which can result in protein homeostasis imbalance. Molecular chaperones function as key components that aid protein folding and prevent protein denaturation. Pseudomonas, an ecologically important bacterial genus, includes human and plant pathogens as well as growth-promoting symbionts and species useful for bioremediation. In this review, we focus on protein quality control systems, particularly molecular chaperones, in ecologically diverse species of Pseudomonas, including the opportunistic human pathogen Pseudomonas aeruginosa, the plant pathogen Pseudomonas syringae, the soil species Pseudomonas putida, and the psychrophilic Pseudomonas antarctica.

Journal Articles

Effects of tryptophan and phenylalanine on tryptophol production in Saccharomyces cerevisiae revealed by transcriptomic and metabolomic analyses: Xiaowei Gong , Huajun Luo , Liu Hong , Jun Wu , Heng Wu , Chunxia Song , Wei Zhao , Yi Han , Ya Dao , Xia Zhang , Donglai Zhu , Yiyong Luo; J. Microbiol. 2022;60(8):832-842. Published online May 27, 2022; DOI: https://doi.org/10.1007/s12275-022-2059-2

Abstract: Tryptophol (TOL) is a metabolic derivative of tryptophan (Trp) and shows pleiotropic effects in humans, plants and microbes. In this study, the effect of Trp and phenylalanine (Phe) on TOL production in Saccharomyces cerevisiae was determined, and a systematic interpretation of TOL accumulation was offered by transcriptomic and metabolomic analyses. Trp significantly promoted TOL production, but the output plateaued (231.02−266.31 mg/L) at Trp concentrations ≥ 0.6 g/L. In contrast, Phe reduced the stimulatory effect of Trp, which was strongly dependent on the Phe concentration. An integrated genomic, transcriptomic, and metabolomic analysis revealed that the effect of Trp and Phe on TOL production was mainly related to the transamination and decarboxylation of the Ehrlich pathway. Additionally, other genes, including thiamine regulon genes (this), the allantoin catabolic genes dal1, dal2, dal4, and the transcriptional activator gene aro80, may play important roles. These findings were partly supported by the fact that the thi4 gene was involved in TOL production, as shown by heterologous expression analysis. To the best of our knowledge, this novel biological function of thi4 in S. cerevisiae is reported here for the first time. Overall, our findings provide insights into the mechanism of TOL production, which will contribute to TOL production using metabolic engineering strategies.

Assessing the microcystins concentration through optimized protein phosphatase inhibition assay in environmental samples: Kyoung-Hee Oh , Kung-Min Beak , Yuna Shin , Young-Cheol Cho; J. Microbiol. 2022;60(6):602-609. Published online April 30, 2022; DOI: https://doi.org/10.1007/s12275-022-2020-4

Abstract: Protein phosphatase (PPase) inhibition assay (PPIA) is widely used to analyze the concentration of microcystins (MCs) because it is comparatively less expensive and faster than other assays. This study aimed to optimize the PPIA by determining a suitable reaction terminator and an optimal methanol concentration in the sample. The most suitable reaction time was 90 min, with the corresponding methanol concentration in the sample being 15% or less. When p-nitrophenyl phosphate (pNPP) was used as a substrate, copper chloride solution was suitably used as a reaction terminator, and when 4- methylumbelliferyl phosphate (MUP) was used, a glycine buffer not only increased the measurement sensitivity of the reaction product but also terminated the enzymatic reaction. When PPase 1 and MUP were used as an enzyme and a substrate, respectively, the limit of quantitation for MC-leucine/ arginine (LR) was 0.02 μg/L, whereas it was 0.1 μg/L when pNPP was used as a substrate. The proposed method facilitated the measurement of MC-LR concentration without additional pretreatments, such as concentration or purification; therefore, this method was suitable and feasible for the continuous monitoring of MCs in drinking water.

The C-22 sterol desaturase Erg5 is responsible for ergosterol biosynthesis and conidiation in Aspergillus fumigatus: Nanbiao Long , Guowei Zhong; J. Microbiol. 2022;60(6):620-626. Published online April 18, 2022; DOI: https://doi.org/10.1007/s12275-022-1564-7

Abstract: Aspergillus fumigatus is the most prevalent saprophytic fungi and can cause severe invasive aspergillosis in immunocompromised individuals. For infection of A. fumigatus, the small hydrophobic conidia have been shown to play a dominant role. In this study, we found that deletion of erg5, a C-22 sterol desaturase gene which function in the last two steps of ergosterol biosynthesis, was sufficient to block ergosterol biosynthesis and conidiation. The deletion phenotype was further verified by a conditional expression strain of erg5 using the inducible tet-on system. Strikingly, erg5 mutant displays increased susceptibility to antifungal azoles itraconazole. RNA sequencing analysis showed that erg5 deficiency resulted in changes in transcription mainly related to lipid, carbohydrate, and amino acid metabolism. Genes encoding ergosterol biosynthesis- related enzymes were found to be up-regulated in erg5 null mutants. However, genes involved in asexual development, including upstream regulators, melanin biosynthesis enzymes, heterotrimeric G proteins, and MAPK signaling, were down-regulated to various degrees. Furthermore, metabolomic study revealed that erg5 deficiency also resulted in altered lipid and amino acid metabolism, which was consistent with our transcriptomics analysis. Collectively, our study established a link between ergosterol biosynthesis and asexual development at the transcriptomics and metabolomics level in A. fumigatus.

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