Journal of Microbiology

Review

Membrane Proteins as a Regulator for Antibiotic Persistence in Gram‑Negative Bacteria: Jia Xin Yee , Juhyun Kim , Jinki Yeom; J. Microbiol. 2023;61(3):331-341. Published online February 17, 2023; DOI: https://doi.org/10.1007/s12275-023-00024-w

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Abstract: Antibiotic treatment failure threatens our ability to control bacterial infections that can cause chronic diseases. Persister bacteria are a subpopulation of physiological variants that becomes highly tolerant to antibiotics. Membrane proteins play crucial roles in all living organisms to regulate cellular physiology. Although a diverse membrane component involved in persistence can result in antibiotic treatment failure, the regulations of antibiotic persistence by membrane proteins has not been fully understood. In this review, we summarize the recent advances in our understanding with regards to membrane proteins in Gram-negative bacteria as a regulator for antibiotic persistence, highlighting various physiological mechanisms in bacteria.

Journal Articles

Lactobacillus plantarum-derived metabolites sensitize the tumorsuppressive effects of butyrate by regulating the functional expression of SMCT1 in 5-FU-resistant colorectal cancer cells: Hye-Ju Kim , JaeJin An , Eun-Mi Ha; J. Microbiol. 2022;60(1):100-117. Published online December 29, 2021; DOI: https://doi.org/10.1007/s12275-022-1533-1

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26 Citations

Abstract: A critical obstacle to the successful treatment of colorectal cancer (CRC) is chemoresistance. Chemoresistant CRC cells contribute to treatment failure by providing a mechanism of drug lethargy and modifying chemoresistance-associated molecules. The gut microbiota provide prophylactic and therapeutic effects by targeting CRC through anticancer mechanisms. Among them, Lactobacillus plantarum contributes to the health of the host and is clinically effective in treating CRC. This study confirmed that 5-fluorouracil (5-FU)-resistant CRC HCT116 (HCT116/5FUR) cells acquired butyrateinsensitive properties. To date, the relationship between 5- FU-resistant CRC and butyrate resistance has not been elucidated. Here, we demonstrated that the acquisition of butyrate resistance in HCT116/5FUR cells was strongly correlated with the inhibition of the expression and function of SMCT1, a major transporter of butyrate in colonocytes. L. plantarum-cultured cell-free supernatant (LP) restored the functional expression of SMCT1 in HCT116/5FUR cells, leading to butyrate-induced antiproliferative effect and apoptosis. These results suggest that LP has a synergistic effect on the SMCT1/butyrate-mediated tumor suppressor function and is a potential chemosensitizer to overcome dual 5-FU and butyrate resistance in HCT116 cells.

Short-chain fatty acids inhibit the biofilm formation of Streptococcus gordonii through negative regulation of competence-stimulating peptide signaling pathway: Taehwan Park , Jintaek Im , A Reum Kim , Dongwook Lee , Sungho Jeong , Cheol-Heui Yun , Seung Hyun Han; J. Microbiol. 2021;59(12):1142-1149. Published online December 4, 2021; DOI: https://doi.org/10.1007/s12275-021-1576-8

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Abstract: Streptococcus gordonii, a Gram-positive commensal bacterium, is an opportunistic pathogen closely related to initiation and progression of various oral diseases, such as periodontitis and dental caries. Its biofilm formation is linked with the development of such diseases by enhanced resistance against antimicrobial treatment or host immunity. In the present study, we investigated the effect of short-chain fatty acids (SCFAs) on the biofilm formation of S. gordonii. SCFAs, including sodium acetate (NaA), sodium propionate (NaP), and sodium butyrate (NaB), showed an effective inhibitory activity on the biofilm formation of S. gordonii without reduction in bacterial growth. SCFAs suppressed S. gordonii biofilm formation at early time points whereas SCFAs did not affect its preformed biofilm. A quorum-sensing system mediated by competence-stimulating peptide (CSP) is known to regulate biofilm formation of streptococci. Interestingly, SCFAs substantially decreased mRNA expression of comD and comE, which are CSP-sensor and its response regulator responsible for CSP pathway, respectively. Although S. gordonii biofilm formation was enhanced by exogenous synthetic CSP treatment, such effect was not observed in the presence of SCFAs. Collectively, these results suggest that SCFAs have an anti-biofilm activity on S. gordonii through inhibiting comD and comE expression which results in negative regulation of CSP quorum-sensing system. SCFAs could be an effective anti-biofilm agent against S. gordonii for the prevention of oral diseases.

[PROTOCOL] Flow cytometric monitoring of the bacterial phenotypic diversity in aquatic ecosystems: Jin-Kyung Hong , Soo Bin Kim , Seok Hyun Ahn , Yongjoo Choi , Tae Kwon Lee; J. Microbiol. 2021;59(10):879-885. Published online September 23, 2021; DOI: https://doi.org/10.1007/s12275-021-1443-7

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Abstract: Flow cytometry is a promising tool used to identify the phenotypic features of bacterial communities in aquatic ecosystems by measuring the physical and chemical properties of cells based on their light scattering behavior and fluorescence. Compared to molecular or culture-based approaches, flow cytometry is suitable for the online monitoring of microbial water quality because of its relatively simple sample preparation process, rapid analysis time, and high-resolution phenotypic data. Advanced statistical techniques (e.g., denoising and binning) can be utilized to successfully calculate phenotypic diversity by processing the scatter data obtained from flow cytometry. These phenotypic diversities were well correlated with taxonomic-based diversity computed using nextgeneration 16S RNA gene sequencing. The protocol provided in this paper should be a useful guide for a fast and reliable flow cytometric monitoring of bacterial phenotypic diversity in aquatic ecosystems.

Full-repertoire comparison of the microscopic objects composing the human gut microbiome with sequenced and cultured communities: Edmond Kuete Yimagou , Jean-Pierre Baudoin , Rita Abou Abdallah , Fabrizio Di Pinto , Jacques Yaacoub Bou Khalil , Didier Raoult; J. Microbiol. 2020;58(5):377-386. Published online April 11, 2020; DOI: https://doi.org/10.1007/s12275-020-9365-3

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Abstract: The study of the human gut microbiome is essential in microbiology and infectious diseases as specific alterations in the gut microbiome might be associated with various pathologies, such as chronic inflammatory disease, intestinal infection and colorectal cancer. To identify such dysregulations, several strategies are being used to create a repertoire of the microorganisms composing the human gut microbiome. In this study, we used the “microscomics” approach, which consists of creating an ultrastructural repertoire of all the cell-like objects composing stool samples from healthy donors using transmission electron microscopy (TEM). We used TEM to screen ultrathin sections of 8 resin-embedded stool samples. After exploring hundreds of micrographs, we managed to elaborate ultrastructural categories based on morphological criteria or features. This approach explained many inconsistencies observed with other techniques, such as metagenomics and culturomics. We highlighted the value of our cultureindependent approach by comparing our microscopic images to those of cultured bacteria and those reported in the literature. This study helped to detect “minimicrobes” Candidate Phyla Radiation (CPR) for the first time in human stool samples. This “microscomics” approach is non-exhaustive but complements already existing approaches and adds important data to the puzzle of the microbiota.

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