• Journal of Microbiology and Biotechnology
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• 제27권2호
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• pp.342-349
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• 2017

Polylactic acid (PLA) has been highlighted as an alternative renewable polymer for the replacement of petroleum-based plastic materials, and is considered to be biodegradable. On the other hand, the biodegradation of PLA by terminal degraders, such as microorganisms, requires a lengthy period in the natural environment, and its mechanism is not completely understood. PLA biodegradation studies have been conducted using mainly undefined mixed cultures, but only a few bacterial strains have been isolated and examined. For further characterization of PLA biodegradation, in this study, the PLA-degrading bacteria from digester sludge were isolated and identified using a polymer film-based screening method. The enrichment of sludge on PLA granules was conducted with the serial transference of a subculture into fresh media for 40 days, and the attached biofilm was inoculated on a PLA film on an agar plate. 3D optical microscopy showed that the isolates physically degraded the PLA film due to bacterial degradation. 16S rRNA gene sequencing identified the microbial colonies to be Pseudomonas sp. MYK1 and Bacillus sp. MYK2. The two isolates exhibited significantly higher specific gas production rates from PLA biodegradation compared with that of the initial sludge inoculum.

• Journal of Microbiology and Biotechnology
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• 제32권11호
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• pp.1427-1434
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• 2022

Two novel, halotolerant strains of Martelella soudanensis, NC18^T and NC20, were isolated from deep subsurface sediment, deeply sequenced, and comparatively analyzed with related strains. Based on a phylogenetic analysis using 16S rRNA gene sequences, the two strains grouped with members of the genus Martelella. Here, we sequenced the complete genomes of NC18^T and NC20 to understand the mechanisms of their halotolerance. The genome sizes and G+C content of the strains were 6.1 Mb and 61.8 mol%, respectively. Moreover, NC18^T and NC20 were predicted to contain 5,849 and 5,830 genes, and 5,502 and 5,585 protein-coding genes, respectively. Both strains contain the identically predicted 6 rRNAs and 48 tRNAs. The harboring of halotolerant-associated genes revealed that strains NC18^T and NC20 might tolerate high salinity through the accumulation of potassium ions in a "salt-in" strategy induced by K⁺ uptake protein (kup) and the K⁺ transport system (trkAH and kdpFABC). These two strains also use the ectoine transport system (dctPQM), the glycine betaine transport system (proVWX), and glycine betaine uptake protein (opu) to accumulate "compatible solutes," such as ectoine and glycine betaine, to protect cells from salt stress. This study reveals the halotolerance mechanism of strains NC18^T and NC20 in high salt environments and suggests potential applications for these halotolerant and halophilic strains in environmental biotechnology.

• Journal of Ecology and Environment
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• 제48권2호
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• pp.120-127
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• 2024

Bats serve as vectors and natural reservoir hosts for various infectious viruses, bacteria, and fungi. These pathogens have also been detected in bat feces and can cause severe illnesses in hosts, other animals, and humans. Because pathogens can easily spread into the environment through bat feces, determining the bacterial communities in bat guano is crucial to mitigate potential disease transmission and outbreaks. This study primarily aimed to examine bacterial communities in the feces of insectivorous bats living in South Korea. Fecal samples were collected after capturing 84 individuals of four different bat species in two regions of South Korea, and the bacterial microbiota was assessed through next generation sequencing of the 16S rRNA gene. The results revealed that, with respect to the relative abundance at the phylum level, Myotis bombinus was dominated by Firmicutes (47.24%) and Proteobacteria (42.66%) whereas Miniopterus fuliginosus (82.78%), Rhinolophus ferrumequinum (63.46%), and Myotis macrodactylus (78.04%) were dominated by Proteobacteria. Alpha diversity analysis showed no difference in abundance between species and a significant difference (p < 0.05) between M. bombinus and M. fuliginosus. Beta-diversity analysis revealed that Clostridium, Asaia, and Enterobacteriaceae_g were clustered as major factors at the genus level using principal component analysis. Additionally, linear discriminant analysis effect size was conducted based on relative expression information to select bacterial markers for each bat species. Clostridium was relatively abundant in M. bombinus, whereas Mycoplasma_g10 was relatively abundant in R. ferrumequinum. Our results provide an overview of bat guano microbiota diversity and the significance of pathogenic taxa for humans and the environment, highlighting a better understanding of preventing emerging diseases. We anticipate that this research will yield bioinformatic data to advance our knowledge of overall microbial genetic diversity and clustering characteristics in insectivorous bat feces in South Korea.

• The Plant Pathology Journal
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• 제27권4호
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• pp.333-341
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• 2011

Two antifungal bacteria were selected from forest soils during the screening of microorganisms antagonistic to Cylindrocarpon destructans, a cause of ginseng root rot. The antifungal bacteria were identified as Bacillus subtilis (I4) and B. amyloliquefaciens (yD16) based on physiological and cultural characteristics, the Biolog program, and 16S rRNA gene sequencing analyses. Antagonistic activity of both bacterial isolates to C. destructans increased with increasing temperature. More rapid starch hydrolytic activity of the bacteria was seen on starch agar at higher temperatures than at lower temperatures, and in the higher density inoculum treatment than in the lower density inoculum treatment. The bacterial isolates failed to colonize ginseng root the root tissues inoculated with the bacteria alone at an inoculum density of $1{\times}10^6$ cfu/ml, but succeeded in colonizing the root tissues co-inoculated with the bacteria and C. destructans. Scanning electron microscopy showed that the pathogen was damaged by the low-density inoculum treatment with the bacterial isolates as much as by the high-density inoculum treatment. Both bacterial isolates were more effective in reducing root rot when they were treated at a concentration of $1{\times}10^6$ cfu/ml than at $1{\times}10^8$ cfu/ml. Also, only the former treatment induced prominent wound periderm formation, related to structural defense against pathogen infection. The results suggest that the bacterial antagonists may have high potential as biocontrol agents against ginseng root rot at relatively low-inoculum concentrations.

• Journal of Microbiology and Biotechnology
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• 제24권8호
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• pp.1105-1108
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• 2014

We investigated whether Bacillus spp., newly isolated from Korean traditional food resources, influence the resistance of hosts to foodborne pathogens, by using Caenorhabditis elegans as a surrogate host model. Initially, we selected 20 Bacillus spp. that possess antimicrobial activity against various foodborne pathogens, including Staphylococcus aureus. Among the selected strains, six strains of Bacillus spp. used in preconditioning significantly prolonged the survival of nematodes exposed to S. aureus. Based on 16S rRNA gene sequencing, all six strains were identified as B. licheniformis. Our findings suggest that preconditioning with B. licheniformis may modulate the host defense response against S. aureus.

• The Plant Pathology Journal
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• 제34권2호
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• pp.126-138
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• 2018

Rice blast caused by Magnaporthe oryzae is a major disease. In the present study, we aimed to identify and evaluate the novel bacterial isolates from rice rhizosphere for biocontrol of M. oryzae pathogen. Sixty bacterial strains from the rice plant's rhizosphere were tested for their biocontrol activity against M. oryzae under in vitro and in vivo. Among them, B. amyloliquefaciens had significant high activity against the pathogen. The least disease severity and highest germination were recorded in seeds treated with B. amyloliquefaciens UASBR9 (0.96 and 98.00%) compared to untreated control (3.43 and 95.00%, respectively) under in vivo condition. These isolates had high activity of enzymes in relation to growth promoting activity upon challenge inoculation of the pathogen. The potential strains were identified based on 16S rRNA gene sequencing and dominance of these particular genes were associated in Bacillus strains. These strains were also confirmed for the presence of antimicrobial peptide biosynthetic genes viz., srfAA (surfactin), fenD (fengycin), spaS (subtilin), and ituC (iturin) related to secondary metabolite production (e.g., AMPs). Overall, the results suggested that application of potential bacterial strains like B. amyloliquefaciens UASBR9 not only helps in control of the biological suppression of one of the most devastating rice pathogens, M. grisea but also increases plant growth along with a reduction in application of toxic chemical pesticides.

• 대한임상검사과학회지
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• 제52권3호
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• pp.202-213
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• 2020

미생물 연구에서 대량의 마이크로바이옴 데이터를 효율적으로 얻는 기술이 발전해왔지만, 마이크로바이옴 빅 데이터를 적절하게 분석하는 도구는 여전히 부족하다. 또한 빈약한 데이터베이스를 사용하여 미생물 군집을 분석하면 잘못된 결과를 초래할 수 있다. 따라서 본 연구는 대량의 미생물 데이터베이스 분석을 위한 적절한 방법을 설계하고자 하였다. 박테리아는 개인의 손끝과 개인 소지품(휴대 전화 및 랩탑 키보드)에서 수집되었다. 박테리아로부터 게놈 DNA를 추출하고 16S rRNA 유전자를 표적으로 하여 차세대 시퀀싱을 실시하였다. 손끝과 개인 소지품 간의 박테리아 매칭 비율의 정확성은 공식과 함께 환경 및 인간관련 데이터베이스를 사용하여 확인하였다. 적절한 분석을 설계하기 위해 다음 세가지 범주를 기준으로: 정성적 분석과 정량적 분석 비교, 성별에 관계없이 모든 참여자뿐만 아니라 동일 성별 참여자 내 비교, 환경(eDB) 및 인간 관련 데이터 베이스(hDB)를 이용하여 샘플간 비교하였다. 결과는 정성적 분석과 동일 성별 참가자 내에서의 비교 및 hDB의 사용이 비교적 정확한 결과를 제공하였다. 우리의 연구는 인간 유래 미생물을 사용하여 대량의 미생물학적 데이터를 포함하는 연구를 수행할 때 정확한 결과를 얻을 수 있는 분석 방법을 제공한다.

• 생명과학회지
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• 제29권2호
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• pp.248-255
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• 2019

국내 삼천포 및 서천에서 채집한 갯장어(Muraenesox cinereus)의 장내기관으로부터 분리된 미생물들의 다양성 및 특성에 관하여 조사하였다. 장내 미생물의 순수 분리를 위하여 marine agar 배지를 사용하였으며 $37^{\circ}C$에서 호기적으로 배양하였다. 순수 분리 후, 49 균주를 분리하였으며 16S rRNA 염기서열 분석 결과를 바탕으로 계통학적 분석을 실시한 결과, 3문, 13과, 14속, 34종으로 구성되어 있는 것을 확인하였다. 특히, Proteobacteria 문은 83.7%의 분포를 나타내었으며 8과, 8속, 26종으로 Aeromonadaceae, Pseudoalteromonadaceae, Shewanellaceae, Enterobacteriaceae, Morganellaceae, Moraxellaceae, Pseudomonadaceae와 Vibrionaceae로 분포하는 것을 확인하였다. 그리고 분리한 균주들이 amylase, lipase, protease와 같은 산업적으로 유용한 효소를 생산하는지 확인하기 위하여 효소 활성 평가를 실시하였으며, 39 균주가 최소 한 종류 이상의 효소 활성을 가지고 있는 것을 확인하였다. 특히 Aeromonas 속의 균주들은 테스트한 모든 효소의 활성을 나타내는 것을 확인하였다. 이러한 결과는 본 연구를 통하여 분리한 미생물들의 산업적 활용 가능성을 나타내었다. 그러므로 이번 연구는 국내 유전자원 확보 및 갯장어의 장내마이크로비옴의 과학적 지식 확장에 도움이 될 것으로 생각된다.

• 한국미생물·생명공학회지
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• 제49권2호
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• pp.192-200
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• 2021

Kunun-zaki, produced by submerged fermentation of a combination of millet and sorghum, is a popular beverage in Northern Nigeria. Owing to the nature of the process involved in its production, kunun-zaki is highly susceptible to contamination by food spoilage microorganisms, leading to inconsistent quality and short shelf-life. In this study, we investigated various food spices, including cinnamon, garlic, and nutmeg, as potential preservatives that could be used to extend kunun-zaki shelf-life. Kunun-zaki varieties were fermented with each of these spices mentioned above and subjected to bacterial, nutritional, sensory, and quality maintenance assessments (using a twelve-member sensory panel to evaluate the organoleptic properties of kunun-zaki). Bacterial counts in the final products ranged between 10^5-7 CFU/ml. We identified two bacterial genera, Weissella and Enterococcus, based on partial 16S rRNA gene amplicon sequencing. Three amino acids, namely leucine, aspartate, and glutamate, were abundant in all kunun-zaki varieties, while the total essential amino acid content was above 39%, suggesting that kunun-zaki could potentially be considered as a protein-rich food source both for infants and adults. The kunun-zaki products were also rich in carbohydrates, crude proteins, ash, crude fiber, and fat, with contents estimated as 81-84, 8-11, 0.8-4.0, 2.9-3.58, and 5.1-6.3%, respectively. However, this nutritional content depreciated rapidly after 24 h of storage, except for kunun-zaki fermented with garlic, which its crude protein and fat content was maintained for up to 48 h. Our results revealed that organic spices increased the nutritional content of the kunun-zaki varieties and could be potentially be used as natural preservatives for enhancing the kunun-zaki shelf-life. However, garlic might be considered a better alternative based on our preliminary investigation. The presence of the isolated microorganisms in the analyzed kunun-zaki samples should be highlighted to raise awareness on the possible health hazards that could arise from poor handling and processing techniques.