Journal of Microbiology

Journal Article

Flavihumibacter fluminis sp. nov. and Flavihumibacter rivuli sp. nov., isolated from a freshwater stream: Miri S. Park , Hyeonuk Sa , Ilnam Kang , Jang-Cheon Cho; J. Microbiol. 2022;60(8):806-813. Published online July 29, 2022; DOI: https://doi.org/10.1007/s12275-022-2298-2

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Abstract: Two Gram-stain-positive, aerobic, chemoheterotrophic, nonmotile, rod-shaped, and yellow-pigmented bacterial strains, designated IMCC34837T and IMCC34838T, were isolated from a freshwater stream. Results of 16S rRNA gene-based phylogenetic analyses showed that strains IMCC34837T and IMCC- 34838T shared 96.3% sequence similarity and were most closely related to Flavihumibacter profundi Chu64-6-1T (99.6%) and Flavihumibacter cheonanensis WS16T (96.4%), respectively. Complete whole-genome sequences of strains IMCC- 34837T and IMCC34838T were 5.0 Mbp and 4.3 Mbp of genome size with 44.5% and 47.9% of DNA G + C contents, respectively. Average nucleotide identity (ANI) and digital DNA- DNA hybridization (dDDH) values between the two strains were 70.0% and 17.9%, repectively, revealing that they are independent species. The two strains showed ≤ 75.2% ANI and ≤ 19.3% dDDH values to each closely related species of the genus Flavihumibacter, indicating that the two strains represent each novel species. Major fatty acid constituents of strain IMCC34837T were iso-C15:0, iso-C15:1 G and anteiso-C15:0 and those of strain IMCC34838T were iso-C15:0 and iso-C15:1 G. The predominant isoprenoid quinone detected in both strains was menaquinone-7 (MK-7). Major polar lipids of both strains were phosphatidylethanolamine, aminolipids, and glycolipids. Based on the phylogenetic and phenotypic characterization, strains IMCC34837T and IMCC34838T were considered to represent two novel species within the genus Flavihumibacter, for which the names Flavihumibacter fluminis sp. nov. and Flavihumibacter rivuli sp. nov. are proposed with IMCC34837T (= KACC 21752T = NBRC 115292T) and IMCC34838T (= KACC 21753T = NBRC 115293T) as the type strains, respectively.

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

Isolation and Characterization of Cold-adapted Strains Producing β-Galactosidase: Jeong-Won Park , Yong-Sik Oh , Jai-Yun Lim , Dong-Hyun Roh; J. Microbiol. 2006;44(4):396-402.; DOI: https://doi.org/2414 [pii]

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Abstract: β-Galactosidase is extensively employed in the manufacture of dairy products, including lactose-reduced milk. Here, we have isolated two gram-negative and rod-shaped coldadapted bacteria, BS 1 and HS 39. These strains were able to break down lactose at low temperatures. Although two isolates were found to grow well at 10°C, the BS 1 strain was unable to grow at 37°C. Another strain, HS-39, evidenced retarded growth at 37°C. The biochemical characteristics and the results of 16S rDNA sequencing identified the BS 1 isolate as Rahnella aquatilis, and showed that the HS 39 strain belonged to genus Buttiauxella. Whereas the R. aquatilis BS 1 strain generated maximal quantities of β-galactosidase when incubated for 60 h at 10°C, Buttiauxella sp. HS-39 generated β-galactosidase earlier, and at slightly lower levels, than R. aquatilis BS 1. The optimum temperature for β-galactosidase was 30°C for R. aquatilis BS-1, and was 45°C for Buttiauxella sp. HS-39, thereby indicating that R. aquatilis BS-1 was able to generate a cold-adaptive enzyme. These two cold-adapted strains, and most notably the β-galactosidase from each isolate, might prove useful in some biotechnological applications.

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