• Asian-Australasian Journal of Animal Sciences
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• 제31권9호
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• pp.1464-1473
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• 2018

Objective: To describe in-depth sequencing, the bacterial community diversity and its succession during ensiling of whole-plant maize and subsequent exposure to air. Methods: The microbial community dynamics of fermented whole-plant maize for 60 days (sampled on day 5, 10, 20, 40, 60) and subsequent aerobic exposure (sampled on day 63 after exposure to air for 3 days) were explored using Illumina Miseq sequence platform. Results: A total of 227,220 effective reads were obtained. At the genus level, there were 12 genera with relative abundance >1%, Lactobacillus, Klebsiella, Sporolactobacillus, Norank-c-cyanobacteria, Pantoea, Pediococcus, Rahnella, Sphingomonas, Serratia, Chryseobacterium, Sphingobacterium, and Lactococcus. Lactobacillus consistently dominated the bacterial communities with relative abundance from 49.56% to 64.17% during the ensiling process. Klebsiella was also an important succession bacterium with a decrease tendency from 15.20% to 6.41% during the ensiling process. The genus Sporolactobacillus appeared in late-ensiling stages with 7.70% abundance on day 40 and 5.32% on day 60. After aerobic exposure, the Lactobacillus decreased its abundance from 63.2% on day 60 to 45.03% on d 63, and Klebsiella from 5.51% to 5.64%, while Sporolactobacillus greatly increased its abundance to 28.15%. These bacterial genera belong to 5 phyla: Firmicutes (relative abundance: 56.38% to 78.43%) was dominant, others were Proteobacteria, Bacteroidetes, Cyanobacteria, and Actinobacteria. The bacterial communities clearly clustered into early-ensiling (d 5), medium-ensiling (d 10, d 20), late-ensiling (d 40, d 60), and aerobic exposure (d 63) clusters, with early- and late-ensiling communities more like each other than to the aerobic exposure communities. Conclusion: High-throughput sequencing based on 16S rRNA genes proved to be a useful method to explore bacterial communities of silage. The results indicated that the bacterial communities varied during fermentation and more dramatically during aerobic exposure. The study is valuable for understanding the mechanism of population change and the relationship between bacteria and ensilage characteristics.

• Journal of Microbiology and Biotechnology
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• 제18권6호
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• pp.1024-1032
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• 2008

Efficient expression of the Salmonella Typhimurium tdc ABCDEG operon involved in the degradation of L-serine and L-threonine requires TdcA, the transcriptional activator of the tdc operon. We found that the tdcA gene was transiently activated when the bacterial growth condition was changed from aerobic to anaerobic, but this was not observed if Salmonella was grown anaerobically from the beginning of the culture. Expression kinetics of six tdc genes after anaerobic shock demonstrated by a real-time PCR assay showed that the tdc CDEG genes were not induced in the tdcA mutant but tdcB maintained its inducibility by anaerobic shock even in the absence of tdcA, suggesting that an additional unknown transcriptional regulation may be working for the tdcB expression. We also investigated the effects of nucleoid-associated proteins by primer extension analysis and found that H-NS repressed tdcA under anaerobic shock conditions, and fis mutation delayed the peak expression time of the tdc operon. DNA microarray analysis of genes regulated by TdcA revealed that the genes involved in N-acetylmannosamine, maltose, and propanediol utilization were significantly induced in a tdcA mutant. These findings suggest that Tdc enzymes may playa pivotal role in energy metabolism under a sudden change of oxygen tension.

• Journal of Microbiology and Biotechnology
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• 제25권8호
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• pp.1380-1389
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• 2015

Prx1, an AhpF-dependent 2-Cys peroxiredoxin (Prx), was previously identified in Vibrio vulnificus, a facultative aerobic pathogen. In the present study, transcription of the V. vulnificus prx1ahpF genes, which are adjacently located on the chromosome, was evaluated by analyzing the promoter and intergenic region of the two genes. Northern blot analyses revealed that transcription of prx1ahpF results in two transcripts, the prx1 and prx1ahpF transcripts. Primer extension analysis and a point mutational analysis of the promoter region showed that the two transcripts are generated from a single promoter. In addition, the 3' end of the prx1 transcript at the prx1ahpF intergenic region was determined by a 3'RACE assay. These results suggested that the prx1ahpF genes are transcribed as an operon, and the prx1 transcript was produced by transcriptional termination in the intergenic region. RNA secondary structure prediction of the prx1ahpF intergenic region singled out a stem-loop structure without poly(U) tract, and a deletion analysis of the intergenic region showed that the atypical stem-loop structure acts as the transcriptional attenuator to result in the prx1 and prx1ahpF transcripts. The combined results demonstrate that the differential expression of prx1 and ahpF is accomplished by the cis-acting transcriptional attenuator located between the two genes and thereby leads to the production of a high level of Prx1 and a low level of AhpF.

• 대한임상검사과학회지
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• 제43권2호
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• pp.68-74
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• 2011

Pseudomonas aeruginosa is an aerobic, Gram-negative, glucose-nonfermenting bacterium, which has emerged as a serious opportunistic pathogen. Recently, outbreaks of carbapenem resistant P. aeruginosa give rise to significant therapeutic challenges for treating nosocomial infections. The genes of metallo-${\beta}$-lactamase (MBL), a powerful carbapenemase, are carried as a part of the mobile gene cassettes inserted into integrons playing an important role in rapid dissemination of antibiotic resistance genes among bacterial isolates. In this study, we investigated the prevalence of integron in imipenem resistant P. aeruginosa isolates. A total of 61 consecutive, non-duplicate, and imipenem resistant P. aeruginosa strains were isolated from a university hospital in the Chungcheong province of Korea. We employed repetitive extragenic palindromic sequence-based PCR (rep-PCR) method for the selection of clonally different P. aerusinosa strains. PCR and DNA sequencing were conducted for the detection of integrons. Twenty-one clonally different P. aeruginosa strains were isolated. Only one (P28) of the strains harbored $bla_{VIM-2}$ that was found as gene cassettes in class 1 integrons. Four of 21 carbapenem resistant P. aeruginosa strains harbored class 1 integron containing aminoglycoside resistance determinant. All of the integrons detected in the study contained more than one resistance gene cassette, which can mediate resistance to multiple antibiotics. To prevent further spreading of the multi-drug resistant P. aeruginosa, conseguent monitoring and clinical polices are required.

• Journal of Microbiology and Biotechnology
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• 제28권4호
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• pp.652-662
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• 2018

Diarrhea is a global disease with a high morbidity and mortality rate in children. In this study, 25 fecal samples were collected from children under 5 years old. Seven samples had been taken from healthy children without diarrhea and marked as the healthy control group; eight samples had been sampled from children with diarrhea caused by dyspepsia and defined as the non-infectious group; and ten samples had been taken from children with diarrhea induced by intestinal infections and identified as the infectious group. We detected the microbial communities of samples by using high-throughput sequencing of 16S rRNA genes. The proportion of aerobic and facultative anaerobic microbes in samples of the infectious group was much higher than in the non-infectious group. In addition, the relative abundance of Enterococcus in the healthy control group was significantly higher than in the non-infectious group and infectious group. This can be used as a potential diagnostic biomarker for diarrhea.

• 생명과학회지
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• 제28권10호
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• pp.1186-1192
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• 2018

비만에 의한 근형질세망 스트레스(Endoplasmic stress, ER stress) 발생은 비접힙 단백질의 축적으로 근육내 대사와 근기능 저하를 초래한다. 유산소 운동과 폴리페놀은 비만에 유도된 염증성 사이토카인과 ER stress를 감소시키는 것으로 잘 알려졌다. 그러나 신체활동과 약물에 의한 염증성 사이토카인과 ER stress 변인들의 변화에 선택적인 반응이 있는지에 대한 연구는 이루어지지 않았다. 따라서, 이 연구의 목적은 유산소 운동과 폴리페놀섭취에 따른 골격근내 ER stress 관련 변인에 우선적인 효과가 있는지 비교분석하고자 하였다. 이 연구의 목적을 위해 (1) 정상식이 그룹, (2) 60% 고지방식이 그룹, (3) 고지방식와 레스베라트롤 25 mg/kg 그룹, (4) 고지방식이와 크리신 50 mg/kg 투여 그룹, (5) 고지방식이와 운동 그룹으로 나누어 실시하였다. 레스베라트롤과 크리신 그룹은 16주간 경구 투여 하였고, 운동 그룹은 1일 40-60분간 10-14 m/min의 속도로 주 4일, 총 16주간 트레드밀 운동을 수행하였다. 운동그룹에서 $IRE1{\alpha}$, BIP/GRP78는 고지방 식이 그룹과 비교하여 유의하게 낮아졌다(p<0.05). 고지방식이와 레스베라트롤 투여 그룹에서 ATF6, $IRE1{\alpha}$, BIP/GRP78는 고지방식이 그룹과 비교하여 유의하게 낮아졌다(p<0.05). 고지방식이와 크리신 투여 그룹은 고지방식이 그룹과 비교하여 ATF6가 유의하게 낮아졌다(p<0.05). 이러한 결과는 유산소 운동과 레스베라트롤, 크리신 섭취에 의해 ER stress 관련 변인을 조절할 수 있다. 그러나 유산소 운동은 고지방 식이에 의해 유도되는 ER stress 개선이 더욱 효과적인 것으로 나타났다.

• 미생물과산업
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• 제12권2호
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• pp.30-35
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• 1986

Almost all of the aerobic organisms contain citric acid cycle (or, tricarboxylic acid cycle). This cycle is involved both in energy metabolism and biosynthetic reactions; generation of NADH which derives the synthesis of chemical energy, ATP, and provision of intermediates needed for the biosynthesis. Because of its importance in the cellular metabolism, the regulation of the TCA cycle and its component enzymes has been extensively studied by many biologists (7,28). Citrate synthase is resposible for the initial step of the cycle and has been recognized as the rate limiting step (14,121,26). Understanding of the mechanism of the expression of citrate synthase should be a key step for the elucidation of the regulation of the TCA cycle in the cell metabolism.

• Journal of Microbiology
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• 제44권3호
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• pp.284-292
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• 2006

The cbb3 cytochrome c oxidase has the dual function as a terminal oxidase and oxygen sensor in the photosynthetic bacterium, Rhodobacter sphaeroides. The cbb3 oxidase forms a signal transduction pathway together with the PrrBA two-component system that controls photosynthesis gene expression in response to changes in oxygen tension in the environment. Under aerobic conditions the cbb3 oxidase generates an inhibitory signal, which shifts the equilibrium of PrrB kinase/phosphatase activities towards the phosphatase mode. Photosynthesis genes are thereby turned off under aerobic conditions. The catalytic subunit (CcoN) of the R. sphaeroides cbb3 oxidase contains five histidine residues (H2l4, B233, H303, H320, and H444) that are conserved in all CcoN subunits of the cbb3 oxidase, but not in the catalytic subunits of other members of copper-heme superfamily oxidases. H214A mutation of CcoN affected neither catalytic activity nor sensory (signaling) function of the cbb3 oxidase, whereas H320A mutation led to almost complete loss of both catalytic activity and sensory function of the cbb3 oxidase. H233V and H444A mutations brought about the partial loss of catalytic activity and sensory function of the cbb3 oxidase. Interestingly, the H303A mutant form of the cbb3 oxidase retains the catalytic function as a cytochrome c oxidase as compared to the wild-type oxidase, while it is defective in signaling function as an oxygen sensor. H303 appears to be implicated in either signal sensing or generation of the inhibitory signal to the PrrBA two-component system.

• Journal of Microbiology and Biotechnology
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• 제30권9호
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• pp.1367-1378
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• 2020

The polyphagous eri silk moth, Samia ricini, is associated with various symbiotic gut bacteria believed to provide several benefits to the host. The larvae of S. ricini were subjected to isolation of gut bacteria using culture-dependent 16S rRNA generic characterization, metagenomics analysis and qualitative enzymatic assays. Sixty culturable aerobic gut bacterial isolates comprising Firmicutes (54%) and Proteobacteria (46%); and twelve culturable facultative anaerobic bacteria comprising Proteobacteria (92%) and Firmicutes (8%) were identified inhabiting the gut of S. ricini. The results of metagenomics analysis revealed the presence of a diverse community of both culturable and un-culturable gut bacteria belonging to Proteobacteria (60%) and Firmicutes (20%) associated with seven orders. An analysis of the results of culturable isolation indicates that these bacterial isolates inhabited all the three compartments of the gut. Investigation on persistence of bacteria coupled with metagenomics analysis of the fifth instar suggested that bacteria persist in the gut across the different instar stages. In addition, enzymatic assays indicated that 48 and 75% of culturable aerobic, and 75% of anaerobic gut bacterial isolates had cellulolytic, lipolytic and nitrate reductase activities, thus suggesting that they may be involved in food digestion and nutritional provision to the host. These bacterial isolates may be good sources for profiling novel genes and biomolecules for biotechnological application.

• 생명과학회지
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• 제21권9호
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• pp.1259-1265
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• 2011

본 연구의 목적은 일회성 유산소 운동이 TLR4, IL-6, TNF-${\alpha}$, SOCS-3 유전자 발현에 미치는 영향을 쥐의 골격근에서 살펴보는데 있었다. 또한 이러한 일회성 운동의 영향이 근섬유 형태 특이적으로 나타나는 지에 대한 연구도 수행되었다. 실험은 Balb/c 수컷 쥐(male: 7주령, 몸무게 $22.78{\pm}0.27g$) 13마리 대상으로 하였으며, 대조군과 운동군으로 무선배정되었다. 운동은 일회성으로 지칠 때까지 트레드밀 운동(경사도 $10^{\circ}$, speed 17 cm/sec 10 min, 33 cm/sec 10 min, 50 cm/sec)을 실시하였으며, 운동 후 24시간이 지난 시점에서 가자미근과 족저근을 적출하였다. 가자미근과 족저근의 TLR4, IL-6, TNF-${\alpha}$, SOCS-3 mRNA 수준 변화는 real-time PCR을 이용하여 측정하였다. 일회성 유산소 트레드밀 운동은 가자미근에서 TLR4 mRNA 발현을 유의하게 증가시켰지만, 족저근의 TLR4 mRNA 발현에는 유의한 영향을 미치지 않았다. 또한 IL-6, TNF-${\alpha}$, SOCS-3 mRNA 발현은 가자미근에서 일회성트레드밀 운동에 의해 유의하게 증가되었다. 하지만 족저근에서 이들 유전자의 mRNA 발현은 일회성 운동에 의해 영향을 받지 않았다. 결론적으로 TLR4, IL-6, TNF-${\alpha}$, SOCS-3와 같은 면역관련 유전자의 발현 수준은 일회성트레드밀 운동에 의해 근섬유 형태 특이적으로 조절됨을 알 수 있었다.