Journal of Microbiology

Review

Signification and Application of Mutator and Antimutator Phenotype‑Induced Genetic Variations in Evolutionary Adaptation and Cancer Therapeutics: Woo-Hyun Chung; J. Microbiol. 2023;61(12):1013-1024. Published online December 15, 2023; DOI: https://doi.org/10.1007/s12275-023-00091-z

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Abstract: Mutations present a dichotomy in their implications for cellular processes. They primarily arise from DNA replication errors or damage repair processes induced by environmental challenges. Cumulative mutations underlie genetic variations and drive evolution, yet also contribute to degenerative diseases such as cancer and aging. The mutator phenotype elucidates the heightened mutation rates observed in malignant tumors. Evolutionary adaptation, analogous to bacterial and eukaryotic systems, manifests through mutator phenotypes during changing environmental conditions, highlighting the delicate balance between advantageous mutations and their potentially detrimental consequences. Leveraging the genetic tractability of Saccharomyces cerevisiae offers unique insights into mutator phenotypes and genome instability akin to human cancers. Innovative reporter assays in yeast model organisms enable the detection of diverse genome alterations, aiding a comprehensive analysis of mutator phenotypes. Despite significant advancements, our understanding of the intricate mechanisms governing spontaneous mutation rates and preserving genetic integrity remains incomplete. This review outlines various cellular pathways affecting mutation rates and explores the role of mutator genes and mutation-derived phenotypes, particularly prevalent in malignant tumor cells. An in-depth comprehension of mutator and antimutator activities in yeast and higher eukaryotes holds promise for effective cancer control strategies.

Journal Article

Characterization of Marinilongibacter aquaticus gen. nov., sp. nov., a unique marine bacterium harboring four CRISPR-Cas systems in the phylum Bacteroidota: Dao-Feng Zhang , Yu-Fang Yao , Hua-Peng Xue , Zi-Yue Fu , Xiao-Mei Zhang , Zongze Shao; J. Microbiol. 2022;60(9):905-915. Published online August 1, 2022; DOI: https://doi.org/10.1007/s12275-022-2102-3

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5 Citations

Abstract: A novel bacterium, designated YYF0007T, was isolated from an agar-degrading co-culture. The strain was found harboring four CRISPR-Cas systems of two classes in the chromosome and subsequently subjected to a study on polyphasic taxonomy. Pairwise analyses of the 16S rRNA gene sequences indicated that strain YYF0007T had highest 16S rRNA gene sequence similarity (92.2%) to Jiulongibacter sediminis JN- 14-9T. The phylogenomic trees based on the 16S rRNA gene and 269 single-copy orthologous gene clusters (OCs) indicated that strain YYF0007T should be recognized as a novel genus of the family Spirosomaceae. The cells were Gramstain- negative, nonmotile, strictly aerobic, and straight long rods with no flagellum. Optimum growth occurred at 28°C and pH 7.0 with the presence of NaCl concentration 1.0–3.0% (w/v). The strain showed oxidase and catalase activities. The major fatty acids were C16:1ω5c, iso-C15:0 and summed feature 3 (C16:1 ω7c and/or C16:1 ω6c). The predominant isoprenoid quinone was MK-7. The complete genome size was 4.64 Mb with a DNA G + C content of 44.4%. Further typing of CRISPR-Cas systems in the family Spirosomaceae and the phylum Bacteroidota indicated that it was remarkable for strain YYF0007T featured by such a set of CRISPR-Cas systems. This trait highlights the applications of strain YYF- 0007T in studies on the evolutionary dynamics and bacterial autoimmunity of CRISPR-Cas system as a potential model. The name Marinilongibacter aquaticus gen. nov., sp. nov. is proposed, and the type strain is YYF0007T (= MCCC 1K06017T = GDMCC 1.2428T = JCM 34683T).

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

Catabolite Control Protein A of Streptococcus suis Type 2 Contributes to Sugar Metabolism and Virulence: Yulong Tang , Wei Wu , Xiaoyan Zhang , Zhongyan Lu , Jianshun Chen , Weihuan Fang; J. Microbiol. 2012;50(6):994-1002. Published online December 30, 2012; DOI: https://doi.org/10.1007/s12275-012-2035-3

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22 Citations

Abstract: Catabolite control protein A (CcpA) is the major transcriptional regulator in carbon catabolite repression in several Gram-positive bacteria. We attempted to characterize the role of a CcpA homologue of Streptococcus suis type 2 in sugar metabolism and virulence. Addition of glucose or sucrose to the defined medium significantly reduced the activity of raffinose-inducible α-galactosidase, cellobiose-inducible β-glucosidase, and maltose-inducible α-glucosidase of the wildtype strain by about 9, 4, and 2-3 fold, respectively. Deletion of ccpA substantially derepressed the effects of repressing sugars on α-galactosidase or β-glucosidase activity. The ccpA deletion mutant showed reduced expression of virulence genes sly and eno (P<0.05), decreased adhesion to and invasion into endothelial cells (P<0.05), and attenuated virulence to mice with significant reduction of death rate and bacterial burden in organs, as compared to the wild-type strain. Both the in vitro and in vivo defect phenotypes were reversible by ccpA complementation. Thus, this study shows that CcpA of S. suis type 2 plays an important role in carbon catabolite repression and virulence.

Differential Expression of citA Gene Encoding the Mitochondrial Citrate Synthase of Aspergillus nidulans in Response to Developmental Status and Carbon Sources: In Sook Min , Ji Young Bang , Soon Won Seo , Cheong Ho Lee , Pil Jae Maeng; J. Microbiol. 2010;48(2):188-198. Published online May 1, 2010; DOI: https://doi.org/10.1007/s12275-010-0096-8

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6 Citations

Abstract: As an extension of our previous studies on the mitochondrial citrate synthase of Aspergillus nidulans and cloning of its coding gene (citA), we analyzed differential expression of citA in response to the progress of development and change of carbon source. The cDNA consisted of 1,700 nucleotides and was predicted to encode a 474-amino acid protein. By comparing the cDNA sequence with the corresponding genomic sequence, we confirmed that citA gene contains 7 introns and that its transcription starts at position -26 (26-nucleotide upstream from the initiation codon). Four putative CreA binding motifs and three putative stress-response elements (STREs) were found within the 1.45-kb citA promoter region. The mode of citA expression was examined by both Northern blot and confocal microscopy using green fluorescent protein (sGFP) as a vital reporter. During vegetative growth and asexual development, the expression of citA was ubiqiutous throughout the whole fungal body including mycelia and conidiophores. During sexual development, the expression of citA was quite strong in cleistothecial shells, but significantly weak in the content of cleistothecia including ascospores. Acetate showed a strong inductive effect on citA expression, which is subjected to carbon catabolite repression (CCR) caused by glucose. The recombinant fusion protein CitA40::sGFP (sGFP containing the 40-amino acid N-terminal segment of CitA) was localized into mitochondria, which supports that a mitochondrial targeting signal is included within the 40-amino acid N-terminal segment of CitA.

Expression of the Promoter for the Maltogenic Amylase Gene in Bacillus subtilis 168: Do-Yeon Kim , Choon-Hwan Cha , Wan-Seok Oh , Young-Jun Yoon , Jung-Wan Kim; J. Microbiol. 2004;42(4):319-327.; DOI: https://doi.org/2104 [pii]

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Abstract: An additional amylase, besides the typical a-amylase, was detected for the first time in the cytoplasm of B. subtilis SUH4-2, an isolate from Korean soil. The corresponding gene (bbmA) encoded a maltogenic amylase (MAase) and its sequence was almost identical to the yvdF gene of B. subtilis 168, whose function was unknown. Southern blot analysis using bbmA as the probe indicated that this gene was ubiquitous among various B. subtilis strains. In an effort to understand the physiological function of the bbmA gene in B. subtilis, the expression pattern of the gene was monitored by measuring the [beta]-galactosidase activity produced from the bbmA promoter fused to the amino terminus of the lacZ structural gene, which was then integrated into the amyE locus on the B. subtilis 168 chromosome. The promoter was induced during the mid-log phase and fully expressed at the early stationary phase in defined media containing [beta]-cyclodextrin ([beta]-CD), maltose, or starch. On the other hand, it was kept repressed in the presence of glucose, fructose, sucrose, or glycerol, suggesting that catabolite repression might be involved in the expression of the gene. Production of the [beta]-CD hydrolyzing activity was impaired by the spo0A mutation in B. subtilis 168, indicating the involvement of an additional regulatory system exerting control on the promoter. Inactivation of yvdF resulted in a significant decrease of the [beta]-CD hydrolyzing activity, if not all. This result implied the presence of an additional enzyme(s) that is capable of hydrolyzing [beta]-CD in B. subtilis 168. Based on the results, MAase encoded by bbmA is likely to be involved in maltose and [beta]-CD utilization when other sugars, which are readily usable as an energy source, are not available during the stationary phase.

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