Journal of Microbiology

Journal Articles

Unexpected Requirement of Small Amino Acids at Position 183 for DNA Binding in the Escherichia coli cAMP Receptor Protein.: Marcus Carranza, Amanda Rea, Daisy Pacheco, Christian Montiel, Jin Park, Hwan Youn; J. Microbiol. 2024;62(10):871-882. Published online September 6, 2024; DOI: https://doi.org/10.1007/s12275-024-00169-2

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Abstract: The Escherichia coli cAMP receptor protein (CRP) relies on the F-helix, the recognition helix of the helix-turn-helix motif, for DNA binding. The importance of the CRP F-helix in DNA binding is well-established, yet there is little information on the roles of its non-base-contacting residues. Here, we show that a CRP F-helix position occupied by a non-base-contacting residue Val183 bears an unexpected importance in DNA binding. Codon randomization and successive in vivo screening selected six amino acids (alanine, cysteine, glycine, serine, threonine, and valine) at CRP position 183 to be compatible with DNA binding. These amino acids are quite different in their amino acid properties (polar, non-polar, hydrophobicity), but one commonality is that they are all relatively small. Larger amino acid substitutions such as histidine, methionine, and tyrosine were made site-directedly and showed to have no detectable DNA binding, further supporting the requirement of small amino acids at CRP position 183. Bioinformatics analysis revealed that small amino acids (92.15% valine and 7.75% alanine) exclusively occupy the position analogous to CRP Val183 in 1,007 core CRP homologs, consistent with our mutant data. However, in extended CRP homologs comprising 3700 proteins, larger amino acids could also occupy the position analogous to CRP Val183 albeit with low occurrence. Another bioinformatics analysis suggested that large amino acids could be tolerated by compensatory small-sized amino acids at their neighboring positions. A full understanding of the unexpected requirement of small amino acids at CRP position 183 for DNA binding entails the verification of the hypothesized compensatory change(s) in CRP.

A PadR family transcriptional repressor regulates the transcription of chromate efflux transporter in Enterobacter sp. Z1.: Xueqi Huo, Zijie Zhou, Hongliang Liu, Gejiao Wang, Kaixiang Shi; J. Microbiol. 2024;62(5):355-365. Published online April 8, 2024; DOI: https://doi.org/10.1007/s12275-024-00117-0

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Abstract: Chromium is a prevalent toxic heavy metal, and chromate [Cr(VI)] exhibits high mutagenicity and carcinogenicity. The presence of the Cr(VI) efflux protein ChrA has been identified in strains exhibiting resistance to Cr(VI). Nevertheless, certain strains of bacteria that are resistant to Cr(VI) lack the presence of ChrB, a known regulatory factor. Here, a PadR family transcriptional repressor, ChrN, has been identified as a regulator in the response of Enterobacter sp. Z1(CCTCC NO: M 2019147) to Cr(VI). The chrN gene is cotranscribed with the chrA gene, and the transcriptional expression of this operon is induced by Cr(VI). The binding capacity of the ChrN protein to Cr(VI) was demonstrated by both the tryptophan fluorescence assay and Ni-NTA purification assay. The interaction between ChrN and the chrAN operon promoter was validated by reporter gene assay and electrophoretic mobility shift assay. Mutation of the conserved histidine residues His14 and His50 resulted in loss of ChrN binding with the promoter of the chrAN operon. This observation implies that these residues are crucial for establishing a DNA-binding site. These findings demonstrate that ChrN functions as a transcriptional repressor, modulating the cellular response of strain Z1 to Cr(VI) exposure.

Development of a Novel Korean H9‑Specific rRT‑PCR Assay and Its Application for Avian Influenza Virus Surveillance in Korea: Mingeun Sagong , Yong-Myung Kang , Na Yeong Kim , Eun Bi Noh , Gyeong-Beom Heo , Se-Hee An , Youn-Jeong Lee , Young Ki Choi , Kwang-Nyeong Lee; J. Microbiol. 2023;61(10):929-936. Published online November 27, 2023; DOI: https://doi.org/10.1007/s12275-023-00088-8

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Abstract: Since the 2000s, the Y439 lineage of H9N2 avian influenza virus (AIV) has been the predominant strain circulating in poultry in Korea; however, in 2020, the Y280 lineage emerged and spread rapidly nationwide, causing large economic losses. To prevent further spread and circulation of such viruses, rapid detection and diagnosis through active surveillance programs are crucial. Here, we developed a novel H9 rRT-PCR assay that can detect a broad range of H9Nx viruses in situations in which multiple lineages of H9 AIVs are co-circulating. We then evaluated its efficacy using a large number of clinical samples. The assay, named the Uni Kor-H9 assay, showed high sensitivity for Y280 lineage viruses, as well as for the Y439 lineage originating in Korean poultry and wild birds. In addition, the assay showed no cross-reactivity with other subtypes of AIV or other avian pathogens. Furthermore, the Uni Kor-H9 assay was more sensitive, and had higher detection rates, than reference H9 rRT-PCR methods when tested against a panel of domestically isolated H9 AIVs. In conclusion, the novel Uni Kor-H9 assay enables more rapid and efficient diagnosis than the “traditional” method of virus isolation followed by subtyping RT-PCR. Application of the new H9 rRT-PCR assay to AI active surveillance programs will help to control and manage Korean H9 AIVs more efficiently.

Identification and Characterization of HEPN‑MNT Type II TA System from Methanothermobacter thermautotrophicus ΔH: Wonho Choi , Anoth Maharjan , Hae Gang Im , Ji-Young Park , Jong-Tae Park , Jung-Ho Park; J. Microbiol. 2023;61(4):411-421. Published online April 18, 2023; DOI: https://doi.org/10.1007/s12275-023-00041-9

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Abstract: Toxin-antitoxin (TA) systems are widespread in bacteria and archaea plasmids and genomes to regulate DNA replication, gene transcr!ption, or protein translation. Higher eukaryotic and prokaryotic nucleotide-binding (HEPN) and minimal nucleotidyltransferase (MNT) domains are prevalent in prokaryotic genomes and constitute TA pairs. However, three gene pairs (MTH304/305, 408/409, and 463/464) of Methanothermobacter thermautotropicus ΔH HEPN-MNT family have not been studied as TA systems. Among these candidates, our study characterizes the MTH463/MTH464 TA system. MTH463 expression inhibited Escherichia coli growth, whereas MTH464 did not and blocked MTH463 instead. Using site-directed MTH463 mutagenesis, we determined that amino acids R99G, H104A, and Y106A from the R[ɸX]4-6H motif are involved with MTH463 cell toxicity. Furthermore, we established that purified MTH463 could degrade MS2 phage RNA, whereas purified MTH464 neutralized MTH463 activity in vitro. Our results indicate that the endonuclease toxin MTH463 (encoding a HEPN domain) and its cognate antitoxin MTH464 (encoding the MNT domain) may act as a type II TA system in M. thermautotropicus ΔH. This study provides initial and essential information studying TA system functions, primarily archaea HEPN-MNT family.

Review

cAMP Activation of the cAMP Receptor Protein, a Model Bacterial Transcription Factor: Hwan Youn , Marcus Carranza; J. Microbiol. 2023;61(3):277-287. Published online March 9, 2023; DOI: https://doi.org/10.1007/s12275-023-00028-6

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4 Citations

Abstract: The active and inactive structures of the Escherichia coli cAMP receptor protein (CRP), a model bacterial transcr!ption factor, are compared to generate a paradigm in the cAMP-induced activation of CRP. The resulting paradigm is shown to be consistent with numerous biochemical studies of CRP and CRP*, a group of CRP mutants displaying cAMP-free activity. The cAMP affinity of CRP is dictated by two factors: (i) the effectiveness of the cAMP pocket and (ii) the protein equilibrium of apo-CRP. How these two factors interplay in determining the cAMP affinity and cAMP specificity of CRP and CRP* mutants are discussed. Both the current understanding and knowledge gaps of CRP-DNA interactions are also described. This review ends with a list of several important CRP issues that need to be addressed in the future.

Journal Articles

Characteristic alterations of gut microbiota in uncontrolled gout: Asad ul-Haq , Kyung-Ann Lee , Hoonhee Seo , Sukyung Kim , Sujin Jo , Kyung Min Ko , Su-Jin Moon , Yun Sung Kim , Jung Ran Choi , Ho-Yeon Song , Hyun-Sook Kim; J. Microbiol. 2022;60(12):1178-1190. Published online November 24, 2022; DOI: https://doi.org/10.1007/s12275-022-2416-1

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12 Citations

Abstract: Microbiome research has been on the rise recently for a more in-depth understanding of gout. Meanwhile, there is a need to understand the gut microbiome related to uric acid-lowering drug resistance. In this study, 16S rRNA gene-based microbiota analysis was performed for a total of 65 stool samples from 17 healthy controls and 48 febuxostat-treated gout patients (including 28 controlled subjects with decreased uric acid levels and 20 uncontrolled subjects with non-reduced uric acid levels). Alpha diversity of bacterial community decreased in the healthy control, controlled, and uncontrolled groups. In the case of beta diversity, the bacterial community was significantly different among groups (healthy control, controlled, and uncontrolled groups). Taxonomic biomarker analysis revealed the increased population of g-Bifidobacterium in healthy controls and g-Prevotella in uncontrolled patients. PCR further confirmed this result at the species level. Additionally, functional metagenomics predictions led to the exploration of various functional biomarkers, including purine metabolism. The results of this study can serve as a basis for developing potential new strategies for diagnosing and treating gout from microbiome prospects.

Phenotypic and genomic characteristics of Brevibacterium zhoupengii sp. nov., a novel halotolerant actinomycete isolated from bat feces: Yuyuan Huang , Lingzhi Dong , Jian Gong , Jing Yang , Shan Lu , Xin-He Lai , Dong Jin , Qianni Huang , Ji Pu , Liyun Liu , Jianguo Xu; J. Microbiol. 2022;60(10):977-985. Published online August 19, 2022; DOI: https://doi.org/10.1007/s12275-022-2134-8

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3 Citations

Abstract: Two strictly aerobic, Gram-staining-positive, non-spore-forming, regular rod-shaped (approximately 0.7 × 1.9 mm) bacteria (HY170T and HY001) were isolated from bat feces collected from Chongzuo city, Guangxi province (22°20􍿁54􍿂N, 106°49􍿁20􍿂E, July 2011) and Chuxiong Yi Autonomous Prefecture, Yunnan province (25°09􍿁10􍿂N, 102°04􍿁39􍿂E, October 2013) of South China, respectively. Optimal growth is obtained at 25–28°C (range, 4–32°C) on BHI-5% sheep blood plate with pH 7.5 (range, 5.0–10.0) in the presence of 0.5– 1.0% NaCl (w/v) (range, 0–15% NaCl [w/v]). The phylogenetic and phylogenomic trees based respectively on the 16S rRNA gene and 845 core gene sequences revealed that the two strains formed a distinct lineage within the genus Brevibacterium, most closely related to B. aurantiacum NCDO 739T (16S rRNA similarity, both 98.5%; dDDH, 46.7–46.8%; ANI, 91.9–92.1%). Strain HY170T contained MK-8(H2), diphosphatidylglycerol (DPG) and phosphatidylglycerol (PG), galactose and ribose as the predominant menaquinone, major polar lipids, and main sugars in the cell wall teichoic acids, respectively. The meso-diaminopimelic acid (meso-DAP) was the diagnostic diamino acid of the peptidoglycan found in strain HY170T. Anteiso-C15:0 and anteiso-C17:0 were the major fatty acids (> 10%) of strains HY170T and HY001, with anteiso-C17:1A predominant in strain HY170T but absent in strain HY001. Mining the genomes revealed the presence of secondary metabolite biosynthesis gene clusters encoding for non-alpha poly-amino acids (NAPAA), ectoine, siderophore, and terpene. Based on results from the phylogenetic, chemotaxonomic and phenotypic analyses, the two strains could be classified as a novel species of the genus Brevibacterium, for which the name Brevibacterium zhoupengii sp. nov. is proposed (type strain HY170T = CGMCC 1.18600T = JCM 34230T).

Review

Insights into the immune responses of SARS-CoV-2 in relation to COVID-19 vaccines: Heedo Park , Mee Sook Park , Jong Hyeon Seok , Jaehwan You , Jineui Kim , Jeonghun Kim , Man-Seong Park; J. Microbiol. 2022;60(3):308-320. Published online March 2, 2022; DOI: https://doi.org/10.1007/s12275-022-1598-x

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6 Citations

Abstract: The three types of approved coronavirus disease 2019 (COVID- 19) vaccines that have been emergency-use listed (EUL) by the World Health Organization are mRNA vaccines, adenovirus- vectored vaccines, and inactivated vaccines. Canonical vaccine developments usually take years or decades to be completed to commercialization; however, the EUL vaccines being used in the current situation comprise several COVID- 19 vaccine candidates applied in studies and clinical settings across the world. The extraordinary circumstances of the COVID-19 pandemic have necessitated the emergency authorization of these EUL vaccines, which have been rapidly developed. Although the benefits of the EUL vaccines outweigh their adverse effects, there have been reports of rare but fatal cases directly associated with COVID-19 vaccinations. Thus, a reassessment of the immunological rationale underlying EUL vaccines in relation to COVID-19 caused by SARSCOV- 2 virus infection is now required. In this review, we discuss the manifestations of COVID-19, immunologically projected effects of EUL vaccines, reported immune responses, informed issues related to COVID-19 vaccination, and the potential strategies for future vaccine use against antigenic variants.

Journal Articles

Constantimarinum furrinae gen. nov., sp. nov., a marine bacterium isolated from saline volcanic rock aquifer (lava seawater) at Jeju Island, Republic of Korea: Sung-Hyun Yang , Hyun-Myung Oh , Mi-Jeong Park , Dongil Jang , Kae Kyoung Kwon; J. Microbiol. 2022;60(1):11-17. Published online December 29, 2021; DOI: https://doi.org/10.1007/s12275-022-1468-6

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Abstract: A Gram-stain-negative, aerobic, rod-shaped (0.3–0.5 × 1.0– 1.9 μm), non-motile marine bacterium designated as ALE3EIT was isolated from a saline volcanic rock aquifer (lava seawater) on Jeju Island, Republic of Korea. The 16S rRNA gene sequence analysis revealed that strain ALE3EIT showed high similarity to ‘Altibacter lentus’ JLT2010T (97.2%), followed by Marixanthomonas ophiurae KMM 3046T (94.5%). Growth was observed at 10–41°C (optimum, 30°C), at pH 6.0–8.5 (optimum, pH 7.5) and at 0.5–8% (optimum, 4.0%) NaCl. The predominant cellular fatty acids were iso-C15:0 (23.5%), iso-C16:0 (10.2%), iso-C16:0 3OH (10.5%), and iso-C17:0 3OH (16.8%). The DNA G + C contents was 40.4 mol%. The major respiratory quinone was MK-6. The major polar lipids were determined to be phosphatidylethanolamine, two unidentified glycolipids, and two unidentified aminolipids. Several phenotypic characteristics such as production of acetoin, activities of arginine dihydrolase and acid phosphatase, and utilization pattern of carbon sources differentiate strain ALE3EIT from ‘A. lentus’ JLT2010T. Activities of the lipase, trypsin, α- chymotrypsin and gelatinase and utilization pattern of carbon sources differentiate strain ALE3EIT from M. ophiurae KMM 3046T. The genome of strain ALE3EIT is 3.0 Mbp long and its ANI and AAI values against ‘A. lentus’ JLT2010T were 76.58 and 72.76, respectively, however, AAI values against members in other genera were lower than 72%. The phylogenomic tree inferred by PhyloPhlAn clearly differentiated the strain ALE3EIT together with strain JLT2010T from other genera in the Falvobacteriaceae. This polyphasic taxonomic data indicates that strain ALE3EIT should be identified as a novel species in the genus ‘Altibacter’, however, the name has not been validated. Therefore, the strain is classified as a novel genus and is proposed as Constantimarinum furrinae gen. nov., sp. nov. The type strain is ALE3EIT (= KCCM 43303T = JCM 33022T).

Discovery of novel glycoside hydrolases from C-glycoside-degrading bacteria using sequence similarity network analysis: Bin Wei , Ya-Kun Wang , Jin-Biao Yu , Si-Jia Wang , Yan-Lei Yu , Xue-Wei Xu , Hong Wang; J. Microbiol. 2021;59(10):931-940. Published online September 23, 2021; DOI: https://doi.org/10.1007/s12275-021-1292-4

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Abstract: C-Glycosides are an important type of natural product with significant bioactivities, and the C-glycosidic bonds of C-glycosides can be cleaved by several intestinal bacteria, as exemplified by the human faeces-derived puerarin-degrading bacterium Dorea strain PUE. However, glycoside hydrolases in these bacteria, which may be involved in the C-glycosidic bond cleavage of C-glycosides, remain largely unknown. In this study, the genomes of the closest phylogenetic neighbours of five puerarin-degrading intestinal bacteria (including Dorea strain PUE) were retrieved, and the protein-coding genes in the genomes were subjected to sequence similarity network (SSN) analysis. Only four clusters of genes were annotated as glycoside hydrolases and observed in the genome of D. longicatena DSM 13814T (the closest phylogenetic neighbour of Dorea strain PUE); therefore, genes from D. longicatena DSM 13814T belonging to these clusters were selected to overexpress recombinant proteins (CG1, CG2, CG3, and CG4) in Escherichia coli BL21(DE3). In vitro assays indicated that CG4 efficiently cleaved the O-glycosidic bond of daidzin and showed moderate β-D-glucosidase and β-D-xylosidase activity. CG2 showed weak activity in hydrolyzing daidzin and pNP- β-D-fucopyranoside, while CG3 was identified as a highly selective and efficient α-glycosidase. Interestingly, CG3 and CG4 could be selectively inhibited by daidzein, explaining their different performance in kinetic studies. Molecular docking studies predicted the molecular determinants of CG2, CG3, and CG4 in substrate selectivity and inhibition propensity. The present study identified three novel and distinctive glycoside hydrolases, highlighting the potential of SSN in the discovery of novel enzymes from genomic data.

Molecular characterization of the Saccharomycopsis fibuligera ATF genes, encoding alcohol acetyltransferase for volatile acetate ester formation: Hye Yun Moon , Hyeon Jin Kim , Ki Seung Kim , Su Jin Yoo , Dong Wook Lee , Hee Je Shin , Jeong Ah Seo , Hyun Ah Kang; J. Microbiol. 2021;59(6):598-608. Published online May 29, 2021; DOI: https://doi.org/10.1007/s12275-021-1159-8

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Abstract: Aroma ester components produced by fermenting yeast cells via alcohol acetyltransferase (AATase)-catalyzed intracellular reactions are responsible for the fruity character of fermented alcoholic beverages, such as beer and wine. Acetate esters are reportedly produced at relatively high concentrations by non-Saccharomyces species. Here, we identified 12 ATF orthologues (SfATFs) encoding putative AATases, in the diploid genome of Saccharomycopsis fibuligera KJJ81, an isolate from wheat-based Nuruk in Korea. The identified SfATF proteins (SfAtfp) display low sequence identities with S. cerevisiae Atf1p (between 13.3 and 27.0%). All SfAtfp identified, except SfAtf(A)4p and SfAtf(B)4p, contained the activation domain (HXXXD) conserved in other Atf proteins. Culture supernatant analysis using headspace gas chromatography mass spectrometry confirmed that the recombinant S. cerevisiae strains expressing SfAtf(A)2p, SfAtf(B)2p, and SfAtf(B)6p produced high levels of isoamyl and phenethyl acetates. The volatile aroma profiles generated by the SfAtf proteins were distinctive from that of S. cerevisiae Atf1p, implying difference in the substrate preference. Cellular localization analysis using GFP fusion revealed the localization of SfAtf proteins proximal to the lipid particles, consistent with the presence of amphipathic helices at their N- and C-termini. This is the first report that systematically characterizes the S. fibuligera ATF genes encoding functional AATases responsible for acetate ester formation using higher alcohols as substrate, demonstrating their biotechnological potential for volatile ester production.

Comparative analysis of type 2 diabetes-associated gut microbiota between Han and Mongolian people: Shu-chun Li , Yao Xiao , Ri-tu Wu , Dan Xie , Huan-hu Zhao , Gang-yi Shen , En-qi Wu; J. Microbiol. 2021;59(7):693-701. Published online May 15, 2021; DOI: https://doi.org/10.1007/s12275-021-0454-8

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14 Citations

Abstract: Due to the different rates of diabetes in different ethnic groups and the structural differences in intestinal microbiota, this study evaluated the changes in diabetes-related intestinal microbiota in two ethnic groups. Fifty-six stool samples were collected from subjects from the Han and Mongolian ethnic groups in China, including participants without diabetes (non-diabetic, ND) and with type 2 diabetes (T2D). The 16S rDNA gene V3 + V4 area was extracted from microbiota, amplified by PCR, and used to perform high-throughput sequencing and screen differential microbiota associated with ethnicity. The results showed that there were 44 T2D-related bacterial markers in the Han subjects, of which Flavonifractor, Alistipes, Prevotella, Oscillibacter, Clostridium XlVa, and Lachnospiracea_incertae_sedis were most closely related to diabetes. There were 20 T2D-related bacterial markers in the Mongolian subjects, of which Fastidiosipila and Barnesiella were most closely related to diabetes. The common markers of T2D bacteria in the two ethnic groups were Papillibacter and Bifidobacterium. There were 17 metabolic pathways with significant differences between the ND and T2D groups in the Han group, and 29 metabolic pathways in the Mongolian group. The glutamatergic metabolic pathway was the only common metabolic pathway in two ethnic groups. The composition and function of diabetes-related bacteria were significantly different among the different ethnic groups, which suggested that the influence of ethnic differences should be fully considered when studying the association between diabetes and bacteria. In addition, the common bacterial markers found in diabetic patients of different ethnic groups in this study can be used as potential targets to study the pathogenesis and treatment of diabetes.

Effects of digested Cheonggukjang on human microbiota assessed by in vitro fecal fermentation: Vineet Singh , Nakwon Hwang , Gwangpyo Ko , Unno Tatsuya; J. Microbiol. 2021;59(2):217-227. Published online February 1, 2021; DOI: https://doi.org/10.1007/s12275-021-0525-x

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Abstract: In vitro fecal fermentation is an assay that uses fecal microbes to ferment foods, the results of which can be used to evaluate the potential of prebiotic candidates. To date, there have been various protocols used for in vitro fecal fermentation- based assessments of food substances. In this study, we investigated how personal gut microbiota differences and external factors affect the results of in vitro fecal fermentation assays. We used Cheonggukjang (CGJ), a Korean traditional fermented soybean soup that is acknowledged as healthy functional diet. CGJ was digested in vitro using acids and enzymes, and then fermented with human feces anaerobically. After fecal fermentation, the microbiota was analyzed using MiSeq, and the amount of short chain fatty acids (SCFAs) were measured using GC-MS. Our results suggest that CGJ was effectively metabolized by fecal bacteria to produce SCFAs, and this process resulted in an increase in the abundance of Coprococcus, Ruminococcus, and Bifidobacterium and a reduction in the growth of Sutterella, an opportunistic pathogen. The metabolic activities predicted from the microbiota shifts indicated enhanced metabolism linked to methionine biosynthesis and depleted chondroitin sulfate degradation. Moreover, the amount of SCFAs and microbiota shifts varied depending on personal microbiota differences. Our findings also suggest that in vitro fecal fermentation of CGJ for longer durations may partially affect certain fecal microbes. Overall, the study discusses the usability of in vitro gastrointestinal digestion and fecal fermentation (GIDFF) to imitate the effects of diet-induced microbiome modulation and its impact on the host.

Development of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) thermal inactivation method with preservation of diagnostic sensitivity: Young-Il Kim , Mark Anthony B. Casel , Se-Mi Kim , Seong-Gyu Kim , Su-Jin Park , Eun-Ha Kim , Hye Won Jeong , Haryoung Poo , Young Ki Choi; J. Microbiol. 2020;58(10):886-891. Published online September 29, 2020; DOI: https://doi.org/10.1007/s12275-020-0335-6

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21 Citations

Abstract: Various treatments and agents had been reported to inactivate RNA viruses. Of these, thermal inactivation is generally considered an effective and cheap method of sample preparation for downstream assays. The purpose of this study is to establish a safe inactivation method for SARS-CoV-2 without compromising the amount of amplifiable viral genome necessary for clinical diagnoses. In this study, we demonstrate the infectivity and genomic stability of SARSCoV- 2 by thermal inactivation at both 56°C and 65°C. The
results
substantiate that viable SARS-CoV-2 is readily inactivated when incubated at 56°C for 30 min or at 65°C for 10 min. qRT-PCR of specimens heat-inactivated at 56°C for 30 min or 65°C for 15 min revealed similar genomic RNA stability compared with non-heat inactivated specimens. Further, we demonstrate that 30 min of thermal inactivation at 56°C could inactivate viable viruses from clinical COVID-19 specimens without attenuating the qRT-PCR diagnostic sensitivity. Heat treatment of clinical specimens from COVID-19 patients at 56°C for 30 min or 65°C for 15 min could be a useful
method
for the inactivation of a highly contagious agent, SARS-CoV-2. Use of this method would reduce the potential for secondary infections in BSL2 conditions during diagnostic procedures. Importantly, infectious virus can be inactivated in clinical specimens without compromising the sensitivity of the diagnostic RT-PCR assay.

Retracted Publication

Cryptic prophages in a blaNDM-1-bearing plasmid increase bacterial survival against high NaCl concentration, high and low temperatures, and oxidative and immunological stressors: So Yeon Kim , Kwan Soo Ko; J. Microbiol. 2020;58(6):483-488. Published online March 28, 2020; DOI: https://doi.org/10.1007/s12275-020-9605-6

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Abstract: In this study, we investigated the effect of cryptic prophage regions in a blaNDM-1-bearing plasmid, which was identified in a patient from South Korea, on the survival of bacteria against adverse environmental conditions. First, we conjugated the intact plasmid and plasmids with deleted cryptic prophages into Escherichia coli DH5α. The E. coli transconjugants carrying the plasmid with intact cryptic prophages showed increased survival during treatment with a high concentration of NaCl, high and low temperatures, an oxidative stressor (H2O2), and an immunological stressor (human serum). By contrast, the transconjugants carrying the plasmid with a single-cryptic prophage knockout did not show any change in survival rates. mRNA expression analyses revealed that the genes encoding sigma factor proteins were highly upregulated by the tested stressors and affected the expression of various proteins (antioxidant, cell osmosis-related, heat shock, cold shock, and universal stress proteins) associated with the specific defense against each stress. These findings indicate that a bacterial strain carrying a plasmid with intact carbapenemase gene and cryptic prophage regions exhibited an increased resistance against simulated environmental stresses, and cryptic prophages in the plasmid might contribute to this enhanced stress resistance. Our study indicated that the coselection of antibiotic resistance and resistance to other stresses may help bacteria to increase survival rates against adverse environments and disseminate.

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