Journal of Microbiology

Volume 54(8); August 2016

Review

MINIREVIEW] On the study of microbial transcriptomes using second- and third-generation sequencing technologies: Sang Chul Choi; J. Microbiol. 2016;54(8):527-536. Published online August 2, 2016; DOI: https://doi.org/10.1007/s12275-016-6233-2

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Abstract: Second-generation sequencing technologies transformed the study of microbial transcriptomes. They helped reveal the transcription start sites and antisense transcripts of microbial species, improving the microbial genome annotation. Quantification of genome-wide gene expression levels allowed for functional studies of microbial research. Ever-evolving sequencing technologies are reshaping approaches to studying microbial transcriptomes. Recently, Oxford Nanopore Technologies delivered a sequencing platform called MinION, a third-generation sequencing technology, to the research community. We expect it to be the next sequencing technology that enables breakthroughs in life science fields. The studies of microbial transcriptomes will be no exception. In this paper, we review microbial transcriptomics studies using second- generation sequencing technology. We also discuss the prospect of microbial transcriptomics studies with thirdgeneration sequencing.

Journal Articles

Deinococcus seoulensis sp. nov., a bacterium isolated from sediment at Han River in Seoul, Republic of Korea: Jae-Jin Lee , Yeon-Hee Lee , Su-Jin Park , Sangyong Lim , Sun-Wook Jeong , Seung-Yeol Lee , Young-Je Cho , Myung Kyum Kim , Hee-Young Jung; J. Microbiol. 2016;54(8):537-542. Published online August 2, 2016; DOI: https://doi.org/10.1007/s12275-016-6253-y

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Abstract: Strain 16F1ET was isolated from a 3-kGy-irradiated sediment sample collected at Han River in Seoul, Republic of Korea. Cells of this strain were observed to be Gram-positive, pililike structure, and short rod shape, and colonies were red in color. The strain showed the highest degree of 16S rRNA gene sequence similarity to Deinococcus aquaticus PB314T (98.8%), Deinococcus depolymerans TDMA-24T (98.1%), Deinococcus caeni Ho-08T (98.0%), and Deinococcus grandis DSM 3963T (97.0%). 16S rRNA gene sequence analysis identified this strain as a member of the genus Deinococcus (Family: Deinococcaceae). The genomic DNA G+C content of strain 16F1ET was 66.9 mol%. The low levels of DNA-DNA hybridization (< 56.2%) with the species mentioned above identified strain 16F1ET as a novel Deinococcus species. Its oxidase and catalase activities as well as the production of acid from glucose were positive. Growth of the strain was observed at 10–37°C (optimum: 20–30°C) and pH 4–10 (optimum: pH 7–8). The cells tolerated less than 5% NaCl and had low resistance to gamma radiation (D10 < 4 kGy). Strain 16F1ET possessed the following chemotaxonomic characteristics: C16:0, C15:1 ω6c, and C16:1 ω7c as the major fatty acids; phosphoglycolipid as the predominant polar lipid; and menaquinone-8 as the predominant respiratory isoprenoid quinone. Based on the polyphasic evidence, as well as the phylogenetic, genotypic, phenotypic, and chemotaxonomic characterization results, strain 16F1ET (=KCTC 33793T =JCM 31404T) is proposed to represent the type strain of a novel species, Deinococcus seoulensis sp. nov.

Dynamic variation of toxic and non-toxic Microcystis proportion in the eutrophic Daechung Reservoir in Korea: Seung-Hyun Joung , Hee-Mock Oh , Kyung-A You; J. Microbiol. 2016;54(8):543-550. Published online August 2, 2016; DOI: https://doi.org/10.1007/s12275-016-6141-5

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Abstract: This study was conducted to determine the environmental factors affecting the level of potentially toxic Microcystis. The long-term tendencies of temperature, precipitation, and water quality factors were analyzed to determine the environmental characteristics of the Daechung Reservoir in Korea, and water samples were directly collected to analyze the dynamics of toxic and non-toxic Microcystis at weekly intervals from May to October 2012. Microcystis was the dominant genus during the study period, and it was composed of potentially toxic and non-toxic Microcystis. The fraction of potentially toxic Microcystis ranged from 6.0% to 61.1%. The amount of toxic Microcystis was highly related to the intracellular microcystin concentration (r = 0.760, P < 0.01). Therefore, the fraction of potentially toxic Microcystis is an important concern in Microcystis blooming because the intracellular microcystin concentration may reflect microcystin levels in the water. The prevalence of potentially toxic Microcystis was highly related to water temperature in Daechung Reservoir (r = 0.585, P < 0.01). Thus, temperature increase during Microcystis blooming may lead to more frequent toxic Microcystis blooms in eutrophic water bodies.

Epidemiology and resistance features of Acinetobacter baumannii isolates from the ward environment and patients in the burn ICU of a Chinese hospital: Yali Gong , Xiaodong Shen , Guangtao Huang , Cheng Zhang , Xiaoqiang Luo , Supeng Yin , Jing Wang , Fuquan Hu , Yizhi Peng , Ming Li; J. Microbiol. 2016;54(8):551-558. Published online August 2, 2016; DOI: https://doi.org/10.1007/s12275-016-6146-0

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26 Citations

Abstract: Acinetobacter baumannii is an important opportunistic pathogen that causes severe nosocomial infections, especially in intensive care units (ICUs). Over the past decades, an everincreasing number of hospital outbreaks caused by A. baumannii have been reported worldwide. However, little attention has been directed toward the relationship between A. baumannii isolates from the ward environment and patients in the burn ICU. In this study, 88 A. baumannii isolates (26 from the ward environment and 62 from patients) were collected from the burn ICU of the Southwest Hospital in Chongqing, China, from July through December 2013. Antimicrobial susceptibility testing results showed that drug resistance was more severe in isolates from patients than from the ward environment, with all of the patient isolates being fully resistant to 10 out of 19 antimicrobials tested. Isolations from both the ward environment and patients possessed the β-lactamase genes blaOXA-51, blaOXA-23, blaAmpC, blaVIM, and blaPER. Using pulsed-field gel electrophoresis (PFGE) and multi-locus sequence typing (MLST), these isolates could be clustered into 4 major PFGE types and 4 main sequence types (ST368, ST369, ST195, and ST191) among which, ST368 was the dominant genotype. Epidemiologic and molecular typing data also revealed that a small-scale outbreak of A. baumannii infection was underway in the burn ICU of our hospital during the sampling period. These results suggest that dissemination of β-lactamase genes in the burn ICU might be closely associated with the high-level resistance of A. baumannii, and the ICU environment places these patients at a high risk for nosocomial infection. Cross-contamination should be an important concern in clinical activities to reduce hospital acquired infections caused by A. baumannii.

Amino acid residues in the Ler protein critical for derepression of the LEE5 promoter in enteropathogenic E. coli: Su-Mi Choi , Jae-Ho Jeong , Hyon E. Choy , Minsang Shin; J. Microbiol. 2016;54(8):559-564. Published online August 2, 2016; DOI: https://doi.org/10.1007/s12275-016-6027-6

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Abstract: Enteropathogenic E. coli causes attaching and effacing (A/E) intestinal lesions. The genes involved in the formation of A/E lesions are encoded within a chromosomal island comprising of five major operons, LEE1-5. The global regulator H-NS represses the expression of these operons. Ler, a H-NS homologue, counteracts the H-NS–mediated repression. Using a novel genetic approach, we identified the amino acid residues in Ler that are involved in the interaction with H-NS: I20 and L23 in the C-terminal portion of α-helix 3, and I42 in the following unstructured linker region.

Mycobacterium tuberculosis gene expression at different stages of hypoxia-induced dormancy and upon resuscitation: Elisabetta Iona , Manuela Pardini , Alessandro Mustazzolu , Giovanni Piccaro , Roberto Nisini , Lanfranco Fattorini , Federico Giannoni; J. Microbiol. 2016;54(8):565-572. Published online August 2, 2016; DOI: https://doi.org/10.1007/s12275-016-6150-4

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Abstract: The physiology of dormant Mycobacterium tuberculosis was studied in detail by examining the gene expression of 51 genes using quantitative Reverse-Transcription Polymerase Chain Reaction. A forty-day period of dormancy in the Wayne culture model depicted four major transcription patterns. Some sigma factors and many metabolic genes were constant, whereas genes belonging to the dormancy regulon were activated on day 9. In particular, alpha-crystallin mRNA showed more than a 1,000-fold increase compared to replicating bacilli. Genes belonging to the enduring hypoxic response were up-regulated at day 16, notably, transcription factors sigma B and E. Early genes typical of log-phase bacilli, esat-6 and fbpB, were uniformly down-regulated during dormancy. Late stages of dormancy showed a drop in gene expression likely due to a lack of substrates in anaerobic respiration as demonstrated by the transcriptional activation observed following nitrates addition. Among genes involved in nitrate metabolism, narG was strongly up-regulated by nitrates addition. Dormant bacilli responded very rapidly when exposed to oxygen and fresh medium, showing a transcriptional activation of many genes, including resuscitation-promoting factors, within one hour. Our observations extend the current knowledge on dormant M. tuberculosis gene expression and its response to nutrients and to aerobic and anaerobic respiration.

The Pseudomonas aeruginosa extracellular secondary metabolite, Paerucumarin, chelates iron and is not localized to extracellular membrane vesicles: Uzma Qaisar , Cassandra J. Kruczek , Muhammed Azeem , Nasir Javaid , Jane A. Colmer-Hamood , Abdul N. Hamood; J. Microbiol. 2016;54(8):573-581. Published online August 2, 2016; DOI: https://doi.org/10.1007/s12275-016-5645-3

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Abstract: Proteins encoded by the Pseudomonas aeruginosa pvcA-D operon synthesize a novel isonitrile functionalized cumarin termed paerucumarin. The pvcA-D operon enhances the expression of the P. aeruginosa fimbrial chaperone/usher pathway (cup) genes and this effect is mediated through paerucumarin. Whether pvcA-D and/or paerucumarin affect the expression of other P. aeruginosa genes is not known. In this study, we examined the effect of a mutation in pvcA-D operon the global transcriptome of the P. aeruginosa strain PAO1- UW. The mutation reduced the expression of several ironcontrolled genes including pvdS, which is essential for the expression of the pyoverdine genes. Additional transcriptional studies showed that the pvcA-D operon is not regulated by iron. Exogenously added paerucumarin enhanced pyoverdine production and pvdS expression in PAO1-UW. Iron-chelation experiments revealed that purified paerucumarin chelates iron. However, exogenously added paerucumarin significantly reduced the growth of a P. aeruginosa mutant defective in pyoverdine and pyochelin production. In contrast to other secondary metabolite, Pseudomonas quinolone signal (PQS), paerucumarin is not localized to the P. aeruginosa membrane vesicles. These results suggest that paerucumarin enhances the expression of iron-controlled genes by chelating iron within the P. aeruginosa extracellular environment. Although paerucumarin chelates iron, it does not function as a siderophore. Unlike PQS, paerucumarin is not associated with the P. aeruginosa cell envelope.

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