Journal of Microbiology

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Functional Characterization of DNA N‑Glycosylase Ogg1 and Ntg1 in DNA Damage Stress of Cryptococcus neoformans: Kwang-Woo Jung , Sunhak Kwon , Jong-Hyun Jung , Sangyong Lim , Yong-Sun Bahn; J. Microbiol. 2023;61(11):981-992. Published online December 6, 2023; DOI: https://doi.org/10.1007/s12275-023-00092-y

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Abstract: Reactive oxygen species induce DNA strand breaks and DNA oxidation. DNA oxidation leads to DNA mismatches, resulting in mutations in the genome if not properly repaired. Homologous recombination (HR) and non-homologous end-joining (NHEJ) are required for DNA strand breaks, whereas the base excision repair system mainly repairs oxidized DNAs, such as 8-oxoguanine and thymine glycol, by cleaving the glycosidic bond, inserting correct nucleotides, and sealing the gap. Our previous studies revealed that the Rad53-Bdr1 pathway mainly controls DNA strand breaks through the regulation of HRand NHEJ-related genes. However, the functional roles of genes involved in the base excision repair system remain elusive in Cryptococcus neoformans. In the present study, we identified OGG1 and NTG1 genes in the base excision repair system of C. neoformans, which are involved in DNA oxidation repair. The expression of OGG1 was induced in a Hog1-dependent manner under oxidative stress. On the other hand, the expression of NTG1 was strongly induced by DNA damage stress in a Rad53-independent manner. We demonstrated that the deletion of NTG1, but not OGG1, resulted in elevated susceptibility to DNA damage agents and oxidative stress inducers. Notably, the ntg1Δ mutant showed growth defects upon antifungal drug treatment. Although deletion of OGG1 or NTG1 did not increase mutation rates, the mutation profile of each ogg1Δ and ntg1Δ mutant was different from that of the wild-type strain. Taken together, we found that DNA N-glycosylase Ntg1 is required for oxidative DNA damage stress and antifungal drug resistance in C. neoformans.

Comparative genomics of Lactobacillus species as bee symbionts and description of Lactobacillus bombintestini sp. nov., isolated from the gut of Bombus ignitus: Jun Heo , Soo-Jin Kim , Jeong-Seon Kim , Seung-Beom Hong , Soon-Wo Kwon; J. Microbiol. 2020;58(6):445-455. Published online March 28, 2020; DOI: https://doi.org/10.1007/s12275-020-9596-3

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Abstract: The Lactobacillus genus is widely used for fermentation of plant materials and dairy products. These species are typically found in highly specialized environments, with the bee gut serving as one of the niche locations in which Lactobacillus is detected. Lactobacillus species isolated from the bee gut and bee-related habitats were phylogenetically classified into three distinct groups, Lactobacillus kunkeei, Firm-4, and Firm-5. The L. kunkeei group was clearly differentiated from other members of the Lactobacillus buchneri group isolated from non-bee habitats. In comparison with non-bee members of the L. buchneri group, three bee-symbiotic Lactobacillus groups had a small-sized genome with low G + C content and showed a sharp reduction in the number of genes involved in energy production, carbohydrate transport and metabolism, and amino acid transport and metabolism. In addition, all three groups lacked the mutY gene, which encodes A/G-specific adenine glycosylase. The phylogenetic dendrogram based on the presence or absence of 1,199 functional genes indicated that these bee-symbiotic groups experienced convergent evolution. The occurrence of convergent evolution is thought to stem from the three bee-symbiotic groups sharing a similar habitat, i.e., the bee gut. The causative factor underlying genomic reduction was postulated to be mutY, which was absent in all three groups. Here, a novel strain, BHWM-4T, isolated from the gut of Bombus ignites was studied using polyphasic taxonomy and classified as a new member of the L. kunkeei group. The strain was Gram-positive, facultative anaerobic, and rod-shaped. The 16S ribosomal RNA gene sequence and genome analysis revealed that strain BHWM-4T was clustered into the L. kunkeei group, forming a compact cluster with L. kunkeei and Lactobacillus apinorum. Biochemical, chemotaxonomic, and genotypic data of strain BHWM-4T supports the proposal of a novel species, Lactobacillus bombintestini sp. nov., whose type strain is BHWM-4T (= KACC 19317T = NBRC 113067T).

Published Erratum

Erratum] Brevibacterium limosum sp. nov., Brevibacterium pigmenatum sp. nov., and Brevibacterium atlanticum sp. nov., three novel dye decolorizing actinobacteria isolated from ocean sediments: Shengxiang Pei , Siwen Niu , Fuquan Xie , Wenjing Wang , Shuang Zhang , Gaiyun Zhang; J. Microbiol. 2021;59(11):1064-1065.; DOI: https://doi.org/10.1007/s12275-021-0235-4

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