Journal of Microbiology

Review

Mycobacterial Regulatory Systems Involved in the Regulation of Gene Expression Under Respiration‑Inhibitory Conditions: Yuna Oh , Ha-Na Lee , Eon-Min Ko , Ji-A Jeong , Sae Woong Park , Jeong-Il Oh; J. Microbiol. 2023;61(3):297-315. Published online February 27, 2023; DOI: https://doi.org/10.1007/s12275-023-00026-8

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Abstract: Mycobacterium tuberculosis is the causative agent of tuberculosis. M. tuberculosis can survive in a dormant state within the granuloma, avoiding the host-mounting immune attack. M. tuberculosis bacilli in this state show increased tolerance to antibiotics and stress conditions, and thus the transition of M. tuberculosis to the nonreplicating dormant state acts as an obstacle to tuberculosis treatment. M. tuberculosis in the granuloma encounters hostile environments such as hypoxia, nitric oxide, reactive oxygen species, low pH, and nutrient deprivation, etc., which are expected to inhibit respiration of M. tuberculosis. To adapt to and survive in respiration-inhibitory conditions, it is required for M. tuberculosis to reprogram its metabolism and physiology. In order to get clues to the mechanism underlying the entry of M. tuberculosis to the dormant state, it is important to understand the mycobacterial regulatory systems that are involved in the regulation of gene expression in response to respiration inhibition. In this review, we briefly summarize the information regarding the regulatory systems implicated in upregulation of gene expression in mycobacteria exposed to respiration-inhibitory conditions. The regulatory systems covered in this review encompass the DosSR (DevSR) two-component system, SigF partner switching system, MprBA-SigE-SigB signaling pathway, cAMP receptor protein, and stringent response.

Journal Articles

Propionate, together with triple antibiotics, inhibits the growth of Enterococci: Soyoung Jeong , Yunjae Lee , Cheol-Heui Yun , Ok-Jin Park , Seung Hyun Han; J. Microbiol. 2019;57(11):1019-1024. Published online October 28, 2019; DOI: https://doi.org/10.1007/s12275-019-9434-7

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Abstract: Enterococci are Gram-positive facultative anaerobic bacteria that colonize the oral cavity and gastrointestinal tract. Enterococcal infections, mainly caused by Enterococcus faecalis and Enterococcus faecium, include apical periodontitis, endocarditis, and bloodstream infections. Recently, vancomycinresistant Enterococci are considered major pathogens that are common but difficult to treat, especially in nosocomial settings. Moreover, E. faecalis is closely associated with recurrent endodontic infections and failed endodontic treatment. In this study, we investigated the effects of short-chain fatty acids (SCFAs), acetate, propionate, and butyrate, which are metabolites fermented by gut microbiota, on the growth of Enterococci. Enterococci were cultured in the presence or absence of acetate, propionate, or butyrate, and the optical density at 600 nm was measured to determine bacterial growth. The minimum inhibitory concentration/minimum bactericidal concentration test was conducted. Bacteria were treated with a SCFA, together with clinically used endodontic treatment methods such as triple antibiotics (metronidazole, minocycline, and ciprofloxacin) and chlorhexidine gluconate (CHX) to determine the effects of combination treatment. Of the SCFAs, propionate had a bacteriostatic effect, inhibiting the growth of E. faecalis in a dose-dependent manner and also that of clinical strains of E. faecalis isolated from dental plaques. Meanwhile, acetate and butyrate had minimal effects on E. faecalis growth. Moreover, propionate inhibited the growth of other Enterococci including E. faecium. In addition, combination treatment of propionate and triple antibiotics led to further growth inhibition, whereas no cooperative effect was observed at propionate plus CHX. These results indicate that propionate attenuates the growth of Enterococci, suggesting propionate as a potential agent to control Enterococcal infections, especially when combined with triple antibiotics.

Isolation, cultivation, and genome analysis of proteorhodopsincontaining SAR116-clade strain Candidatus Puniceispirillum marinum IMCC1322: Junhak Lee , Kae Kyoung Kwon , Seung-Il Lim , Jaeho Song , Ah Reum Choi , Sung-Hyun Yang , Kwang-Hwan Jung , Jung-Hyun Lee , Sung Gyun Kang , Hyun-Myung Oh , Jang-Cheon Cho; J. Microbiol. 2019;57(8):676-687. Published online June 14, 2019; DOI: https://doi.org/10.1007/s12275-019-9001-2

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Abstract: Strain IMCC1322 was isolated from a surface water sample from the East Sea of Korea. Based on 16S rRNA analysis, IMCC1322 was found to belong to the OCS28 sub-clade of SAR116. The cells appeared as short vibrioids in logarithmicphase culture, and elongated spirals during incubation with mitomycin or in aged culture. Growth characteristics of strain IMCC1322 were further evaluated based on genomic information; proteorhodopsin (PR), carbon monoxide dehydrogenase, and dimethylsulfoniopropionate (DMSP)-utilizing enzymes. IMCC1322 PR was characterized as a functional retinylidene protein that acts as a light-driven proton pump in the cytoplasmic membrane. However, the PR-dependent phototrophic potential of strain IMCC1322 was only observed under CO-inhibited and nutrient-limited culture conditions. A DMSP-enhanced growth response was observed in addition to cultures grown on C1 compounds like methanol, formate, and methane sulfonate. Strain IMCC1322 cultivation analysis revealed biogeochemical processes characteristic of the SAR116 group, a dominant member of the microbial community in euphotic regions of the ocean. The polyphasic taxonomy of strain IMCC1322 is given as Candidatus Puniceispirillum marinum, and was confirmed by chemotaxonomic tests, in addition to 16S rRNA phylogeny and cultivation analyses.

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

Crystal structure and modeling of the tetrahedral intermediate state of methylmalonate-semialdehyde dehydrogenase (MMSDH) from Oceanimonas doudoroffii: Hackwon Do , Chang Woo Lee , Sung Gu Lee , Hara Kang , Chul Min Park , Hak Jun Kim , Hyun Park , HaJeung Park , Jun Hyuck Lee; J. Microbiol. 2016;54(2):114-121. Published online February 2, 2016; DOI: https://doi.org/10.1007/s12275-016-5549-2

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Abstract: The gene product of dddC (Uniprot code G5CZI2), from the Gram-negative marine bacterium Oceanimonas doudoroffii, is a methylmalonate-semialdehyde dehydrogenase (OdoMMSDH) enzyme. MMSDH is a member of the aldehyde dehydrogenase superfamily, and it catalyzes the NADdependent decarboxylation of methylmalonate semialdehyde to propionyl-CoA. We determined the crystal structure of OdoMMSDH at 2.9 Å resolution. Among the twelve molecules in the asymmetric unit, six subunits complexed with NAD, which was carried along the protein purification steps. OdoMMSDH exists as a stable homodimer in solution; each subunit consists of three distinct domains: an NAD-binding domain, a catalytic domain, and an oligomerization domain. Computational modeling studies of the OdoMMSDH structure revealed key residues important for substrate recognition and tetrahedral intermediate stabilization. Two basic residues (Arg103 and Arg279) and six hydrophobic residues (Phe150, Met153, Val154, Trp157, Met281, and Phe449) were found to be important for tetrahedral intermediate binding. Modeling data also suggested that the backbone amide of Cys280 and the side chain amine of Asn149 function as the oxyanion hole during the enzymatic reaction. Our results provide useful insights into the substrate recognition site residues and catalytic mechanism of OdoMMSDH.

NOTE] Biosynthetic Pathway for Poly(3-Hydroxypropionate) in Recombinant Escherichia coli: Qi Wang , Changshui Liu , Mo Xian , Yongguang Zhang , Guang Zhao; J. Microbiol. 2012;50(4):693-697. Published online August 25, 2012; DOI: https://doi.org/10.1007/s12275-012-2234-y

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38 Citations

Abstract: Poly(3-hydroxypropionate) (P3HP) is a biodegradable and biocompatible thermoplastic. In this study, we engineered a P3HP biosynthetic pathway in recombinant Escherichia coli. The genes for malonyl-CoA reductase (mcr, from Chloroflexus aurantiacus), propionyl-CoA synthetase (prpE, from E. coli), and polyhydroxyalkanoate synthase (phaC1, from Ralstonia eutropha) were cloned and expressed in E. coli. The E. coli genes accABCD encoding acetyl-CoA carboxylase were used to channel the carbon into the P3HP pathway. Using glucose as a sole carbon source, the cell yield and P3HP content were 1.32 g/L and 0.98% (wt/wt [cell dry weight]), respectively. Although the yield is relatively low, our study shows the feasibility of engineering a P3HP biosynthetic pathway using a structurally unrelated carbon source in bacteria.

Published Erratum

Erratum] The transcription factor Cas5 suppresses hyphal morphogenesis during yeast-form growth in Candida albicans: Jong-Myeong Kim , Hye Yun Moon , Dong Wook Lee , Hyun Ah Kang , Jeong-Yoon Kim; J. Microbiol. 2021;59(11):1063-1063.; DOI: https://doi.org/10.1007/s12275-021-0326-2

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