Journal of Microbiology

Journal Articles

Salicibibacter cibarius sp. nov. and Salicibibacter cibi sp. nov., two novel species of the family Bacillaceae isolated from kimchi: Young Joon Oh , Joon Yong Kim , Seul Ki Lim , Min-Sung Kwon , Hak-Jong Choi; J. Microbiol. 2021;59(5):460-466. Published online April 28, 2021; DOI: https://doi.org/10.1007/s12275-021-0513-1

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Abstract: To date, all species in the genus Salicibibacter have been isolated in Korean commercial kimchi. We aimed to describe the taxonomic characteristics of two strains, NKC5-3T and NKC21-4T, isolated from commercial kimchi collected from various regions in the Republic of Korea. Cells of these strains were rod-shaped, Gram-positive, aerobic, oxidase- and catalase- positive, non-motile, halophilic, and alkalitolerant. Both strains, unlike other species of the genus Salicibibacter, could not grow without NaCl. Strains NKC5-3T and NKC21-4T could tolerate up to 25.0% (w/v) NaCl (optimum 10%) and grow at pH 7.0–10.0 (optimum 8.5) and 8.0–9.0 (optimum 8.5), respectively; they showed 97.1% 16S rRNA gene sequence similarity to each other and were most closely related to S. kimchii NKC1-1T (97.0% and 96.8% similarity, respectively). The genome of strain NKC5-3T was nearly 4.6 Mb in size, with 4,456 protein-coding sequences (CDSs), whereas NKC21-4T genome was nearly 3.9 Mb in size, with 3,717 CDSs. OrthoANI values between the novel strains and S. kimchii NKC1-1T were far lower than the species demarcation threshold. NKC5-3T and NKC21-4T clustered together to form branches that were distinct from the other Salicibibacter species. The major fatty acids in these strains were anteiso-C15:0 and anteiso-C17:0, and the predominant menaquinone was menaquinone-7. The polar lipids of NKC5-3T included diphosphatidylglycerol (DPG), phosphatidylglycerol (PG), and five unidentified phospholipids (PL), and those of NKC21-4T included DPG, PG, seven unidentified PLs, and an unidentified lipid. Both isolates had DPG, which is the first case in the genus Salicibibacter. The genomic G + C content of strains NKC5-3T and NKC21-4T was 44.7 and 44.9 mol%, respectively. Based on phenotypic, genomic, phylogenetic, and chemotaxonomic analyses, strains NKC5-3T (= KACC 22040T = DSM 111417T) and NKC21-4T (= KACC 22041T = DSM 111418T) represent two novel species of the genus Salicibibacter, for which the names Salicibibacter cibarius sp. nov. and Salicibibacter cibi sp. nov. are proposed.

Spot 42 RNA regulates putrescine catabolism in Escherichia coli by controlling the expression of puuE at the post-transcription level: Xin Sun , Ruyan Li , Guochen Wan , Wanli Peng , Shuangjun Lin , Zixin Deng , Rubing Liang; J. Microbiol. 2021;59(2):175-185. Published online February 1, 2021; DOI: https://doi.org/10.1007/s12275-021-0421-4

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Abstract: Putrescine, a typical polyamine compound important for cell growth and stress resistance, can be utilized as an energy source. However, the regulation of its catabolism is unclear. Here the small RNA (sRNA) Spot 42, an essential regulator of carbon catabolite repression (CCR), was confirmed to participate in the post-transcriptional regulation of putrescine catabolism in Escherichia coli. Its encoding gene spf exclusively exists in the γ-proteobacteria and contains specific binding sites to the 5􍿁-untranslated regions of the puuE gene, which encodes transaminase in the glutamylated putrescine pathway of putrescine catabolism converting γ-aminobutyrate (GABA) into succinate semialdehyde (SSA). The transcription of the spf gene was induced by glucose, inhibited by putrescine, and unaffected by PuuR, the repressor of puu genes. Excess Spot 42 repressed the expression of PuuE significantly in an antisense mechanism through the direct and specific base-pairing between the 51–57 nt of Spot 42 and the 5􍿁- UTR of puuE. Interestingly, Spot 42 mainly influenced the stability of the puuCBE transcript. This work revealed the regulatory role of Spot 42 in putrescine catabolism, in the switch between favorable and non-favorable carbon source utilization, and in the balance of metabolism of carbon and nitrogen sources.

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

NOTE] Biological and Genetic Properties of SA14-14-2, a Live-Attenuated Japanese Encephalitis Vaccine That Is Currently Available for Humans: Byung-Hak Song , Gil-Nam Yun , Jin-Kyoung Kim , Sang-Im Yun , Young-Min Lee; J. Microbiol. 2012;50(4):698-706. Published online August 25, 2012; DOI: https://doi.org/10.1007/s12275-012-2336-6

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Abstract: Japanese encephalitis virus (JEV), a mosquito-borne flavivirus, is a major cause of acute encephalitis, a disease of significance for global public health. In the absence of antiviral therapy to treat JEV infection, vaccination is the most effective method of preventing the disease. In JE-endemic areas, the most widely used vaccine to date is SA14-14-2, a live-attenuated virus derived from its virulent parent SA14. In this study, we describe the biological properties of SA14-14-2, both in vitro and in vivo, and report the genetic characteristics of its genomic RNA. In BHK-21 (hamster kidney) cells, SA14-14-2 displayed a slight delay in plaque formation and growth kinetics when compared to a virulent JEV strain, CNU/LP2, with no decrease in maximum virus production. The delay in viral growth was also observed in two other cell lines, SH-SY5Y (human neuroblastoma) and C6/36 (mosquito larva), which are potentially relevant to JEV pathogenesis and transmission. In 3-week-old ICR mice, SA14-14-2 did not cause any symptoms or death after either intracerebral or peripheral inoculation with a maximum dose of up to 1.5×103 plaqueforming units (PFU) per mouse. The SA14-14-2 genome consisted of 10977 nucleotides, one nucleotide longer than all the previously reported genomes of SA14-14-2, SA14 and two other SA14-derived attenuated viruses. This difference was due to an insertion of one G nucleotide at position 10701 in the 3' noncoding region. Also, we noted a significant number of nucleotide and/or amino acid substitutions throughout the genome of SA14-14-2, except for the prM protein-coding region, that differed from SA14 and/or the other two attenuated viruses. Our results, together with others’, provide a foundation not only for the study of JEV virulence but also for the development of new and improved vaccines for JEV.

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