Journal of Microbiology

Volume 54(5); May 2016

Review

MINIREVIEW] Transcriptional control of sexual development in Cryptococcus neoformans: Matthew E. Mead , Christina M. Hull; J. Microbiol. 2016;54(5):339-346. Published online April 20, 2016; DOI: https://doi.org/10.1007/s12275-016-6080-1

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Abstract: Developmental processes are essential for the normal life cycles of many pathogenic fungi, and they can facilitate survival in challenging environments, including the human host. Sexual development of the human fungal pathogen Cryptococcus neoformans not only produces infectious particles (spores) but has also enabled the evolution of new disease-related traits such as drug resistance. Transcription factor networks are essential to the development and pathogenesis of C. neoformans, and a variety of sequence-specific DNA-binding proteins control both key developmental transitions and virulence by regulating the expression of their target genes. In this review we discuss the roles of known transcription factors that harbor important connections to both development and virulence. Recent studies of these transcription factors have identified a common theme in which metabolic, stress, and other responses that are required for sexual development appear to have been co-opted for survival in the human host, thus facilitating pathogenesis. Future work elucidating the connection between development and pathogenesis will provide vital insights into the evolution of complex traits in eukaryotes as well as mechanisms that may be used to combat fungal pathogens.

Research Support, Non-U.S. Gov'ts

Abyssisolibacter fermentans gen. nov. sp. nov., isolated from deep sub-seafloor sediment: Wonduck Kim , Jung-Hyun Lee , Kae Kyoung Kwon; J. Microbiol. 2016;54(5):347-352. Published online April 20, 2016; DOI: https://doi.org/10.1007/s12275-016-6048-1

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Abstract: A Gram-staining-negative, thin rod-shaped, anaerobic bacterium designated MCWD3T was isolated from sediment of the deep sea in Ulleung Basin, East Sea, Korea. The ranges of temperature, pH and NaCl for growth of this strain were 15– 40°C (optimum 29°C), 5.0–10.0 (optimum pH 6.5), and 1–5%, respectively. The major fatty acids were iso-C15:0 (30%) and iso-C15:0 dimethyl acetal (17%). The major polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, and unidentified aminophospholipids, phospholipids, and aminolipids. The fermentation product from yeast extract was acetate. Phylogenetic analysis based on 16S rRNA genes indicated that the isolate was related to Sporosalibacterium faouarense (92.8% sequence identity), Clostridiisalibacter paucivorans (92.6%), and Brassicibacter mesophilus (92.4%). However, the isolate was differentiated from these genera by both physiological and chemotaxonomical properties. On the basis of a polyphasic taxonomic analysis, we propose that MCWD3T represents a novel taxon with the name Abyssisolibacter fermentans gen. nov. sp. nov.

Diversity of indigenous endophytic bacteria associated with the roots of Chinese cabbage (Brassica campestris L.) cultivars and their antagonism towards pathogens: Md. Azizul Haque , Han Dae Yun , Kye Man Cho; J. Microbiol. 2016;54(5):353-363. Published online April 20, 2016; DOI: https://doi.org/10.1007/s12275-016-5641-7

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Abstract: The study aimed to reveal the diversity of endophytic bacteria in the roots of Chinese cabbage (CC) cultivated in two areas in Korea, namely, Seosang-gun (SS) and Haenam-gun (HN), and also in a transgenic plant (TP) from the laboratory. A total of 653 colonies were isolated from the interior of CC roots, comprising 118, 302, and 233 isolates from SS, HN, and TP samples, respectively. Based on 16S rRNA gene sequence analysis, the isolates belonged to four major phylogenetic groups: high-G+C Gram-positive bacteria (HGC-GPB), low-G+C Gram-positive bacteria (LGC-GPB), Proteobacteria, and Bacteriodetes. The most dominant groups in the roots of the SS, HN, and TP cultivars were LGC-GPB (48.3%), Proteobacteria (50.2%), and HGC-GPB (38.2%), respectively. Importantly, most of the isolates that produced cell-walldegrading enzymes belonged to the genus Bacillus. Bacillus sp. (HNR03, TPR06), Bacillus pumilus (SSR07, HNR11, TPR07), and Bacillus subtilis (TPR03) showed high antagonism against the tested food-borne pathogenic bacteria. In addition, Bacillus sp. (HNR03, TPR06), Bacillus pumilus (SSR07, HNR11, HNR17, TPR11), Microbacterium oxidans (SSR09, TPR04), Bacillus cereus HNR10, Pseudomonas sp. HNR13, and Bacillus subtilis (TPR02, TPR03) showed strong antagonistic activity against the fungi Phythium ultimum, Phytophthora capsici, Fusarium oxysporum, and Rhizoctonia solani. The endophytes isolated from the TP cultivar showed the strongest antagonistic reactions against pathogens. This study is the first report on endophytic bacteria from Chinese cabbage roots.

Photosynthetic inhibition and oxidative stress to the toxic Phaeocystis globosa caused by a diketopiperazine isolated from products of algicidal bacterium metabolism: Shuo Tan , Xiaoli Hu , Pinghe Yin , Ling Zhao; J. Microbiol. 2016;54(5):364-375. Published online April 20, 2016; DOI: https://doi.org/10.1007/s12275-016-6012-0

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50 Citations

Abstract: Algicidal bacteria have been turned out to be available for inhibiting Phaeocystis globosa which frequently caused harmful algal blooms and threatened to economic development and ecological balance. A marine bacterium Bacillus sp. Ts-12 exhibited significant algicidal activity against P. globosa by indirect attack. In present study, an algicidal compound was isolated by silica gel column, Sephadex G-15 column and HPLC, further identified as hexahydropyrrolo[1,2-a]pyrazine- 1,4-dione, cyclo-(Pro-Gly), by GC-MS and 1H-NMR. Cyclo-(Pro-Gly) significantly increased the level of reactive oxygen species (ROS) within P. globosa cells, further activating the enzymatic and non-enzymatic antioxidant systems, including superoxide dismutase (SOD), catalase (CAT), glutathione (GSH) and ascorbic acid (AsA). The increase in methane dicarboxylic aldehyde (MDA) content showed that the surplus ROS induced lipid peroxidation on membrane system. Transmission electron microscope (TEM) and flow cytometry (FCM) analysis revealed that cyclo-(Pro-Gly) caused reduction of Chl-a content, destruction of cell membrane integrity, chloroplasts and nuclear structure. Real-time PCR assay showed that the transcriptions of photosynthesis related genes (psbA, psbD, rbcL) were significantly inhibited. This study indicated that cyclo-(Pro-Gly) from marine Bacillus sp. Ts-12 exerted photosynthetic inhibition and oxidative stress to P. globosa and eventually led to the algal cells lysis. This algicidal compound might be potential bio-agent for controlling P. globosa red tide.

Journal Article

Inverse PCR for subtyping of Acinetobacter baumannii carrying ISAba1: Shukho Kim , Yun-Ju Park , Jungmin Kim; J. Microbiol. 2016;54(5):376-380. Published online April 20, 2016; DOI: https://doi.org/10.1007/s12275-016-6038-3

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Abstract: Acinetobacter baumannii has been prevalent in nosocomial infections, often causing outbreaks in intensive care units. ISAba1 is an insertion sequence that has been identified only in A. baumannii and its copy number varies among strains. It has been reported that ISAba1 provides a promoter for blaOXA-51-like, blaOXA-23-like, and blaampC, which are associated with the resistance of A. baumannii to carbapenems and cephalosporins. The main purpose of this study was to develop a novel inverse PCR method capable of typing A. baumannii strains. The method involves three major steps: cutting of genomic DNA with a restriction enzyme, ligation, and PCR. In the first step, bacterial genomic DNA was digested with DpnI. In the second step, the digested genomic DNAs were ligated to form intramolecular circular DNAs. In the last step, the ligated circular DNAs were amplified by PCR with primers specific for ISAba1 and the amplified PCR products were electrophoresed. Twenty-two clinical isolates of A. baumannii were used for the evaluation of the inverse PCR (iPCR) typing method. Dendrogram analysis revealed two major clusters, similar to pulsed-field gel electrophoresis (PFGE) results. Three ISAba1-associated genes – blaampC, blaOXA-66-like, and csuD – were amplified and detected in the clinical isolates. This novel iPCR typing method is comparable to PFGE in its ability to discriminate A. baumannii strains, and is a promising molecular epidemiological tool for investigating A. baumannii carrying ISAba1.

Research Support, Non-U.S. Gov'ts

Comparing the sugar profiles and primary structures of alkali-extracted water-soluble polysaccharides in cell wall between the yeast and mycelial phases from Tremella fuciformis: Hanyu Zhu , Yuan Yuan , Juan Liu , Liesheng Zheng , Liguo Chen , Aimin Ma; J. Microbiol. 2016;54(5):381-386. Published online April 20, 2016; DOI: https://doi.org/10.1007/s12275-016-5533-x

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27 Citations

Abstract: To gain insights into dimorphism, cell wall polysaccharides from Tremella fuciformis strains were obtained from alkaliextracted water-soluble fractions PTF-M38 (from the mycelial form), PTF-Y3 and PTF-Y8 (from the yeast form) of T. fuciformis strains were used to gain some insights into dimorphism study. Their chemical properties and structural features were investigated using gel permeation chromatography, gas chromatography, UV and IR spectrophotometry and Congo red binding reactions. The results indicated that the backbones of PTF-M38, PTF-Y3 and PTF-Y8 were configured with α-linkages with average molecular weights of 1.24, 1.08, and 1.19 kDa, respectively. PTF-M38 was mainly composed of xylose, mannose, glucose, and galactose in a ratio of 1:1.47:0.48:0.34, while PTF-Y3 and PTF-Y8 were mainly composed of xylose, mannose and glucose in a ratio of 1:1.65:4.06 and 1:1.21:0.44, respectively. The sugar profiles of PTF-M38, PTF-Y3 and PTF-Y8 were also established for further comparison. These profiles showed that all three polysaccharides contained the same sugars but in different ratios, and the carbon sources (xylose, mannose, glucose, and galactose) affected the sugar ratios within the polysaccharides.

Novel nuclear targeting coiled-coil protein of Helicobacter pylori showing Ca2+-independent, Mg2+-dependent DNase I activity: Young Chul Kwon , Sinil Kim , Yong Seok Lee , Je Chul Lee , Myung-Je Cho , Woo-Kon Lee , Hyung-Lyun Kang , Jae-Young Song , Seung Chul Baik , Hyeon Su Ro; J. Microbiol. 2016;54(5):387-395. Published online April 20, 2016; DOI: https://doi.org/10.1007/s12275-016-5631-9

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Abstract: HP0059, an uncharacterized gene of Helicobacter pylori, encodes a 284-aa-long protein containing a nuclear localization sequence (NLS) and multiple leucine-rich heptad repeats. Effects of HP0059 proteins in human stomach cells were assessed by incubation of recombinant HP0059 proteins with the AGS human gastric carcinoma cell line. Wild-type HP0059 proteins showed cytotoxicity in AGS cells in a concentrationdependent manner, whereas NLS mutant protein showed no effect, suggesting that the cytotoxicity is attributed to host nuclear localization. AGS cells transfected with pEGFP-HP0059 plasmid showed strong GFP signal merged to the chromosomal DNA region. The chromosome was fragmented into multiple distinct dots merged with the GFP signal after 12 h of incubation. The chromosome fragmentation was further explored by incubation of AGS chromosomal DNA with recombinant HP0059 proteins, which leaded to complete degradation of the chromosomal DNA. HP0059 protein also degraded circular plasmid DNA without consensus, being an indication of DNase I activity. The DNase was activated by MgCl2, but not by CaCl2. The activity was completely blocked by EDTA. The optimal pH and temperature for DNase activity were 7.0–8.0 and 55°C, respectively. These results indicate that HP0059 possesses a novel DNase I activity along with a role in the genomic instability of human gastric cells, which may result in the transformation of gastric cells.

Role of bacterial γ-glutamyltranspeptidase as a novel virulence factor in bone-resorbing pathogenesis: Jinmoon Kim , Sungil Jang , Aeryun Kim , Hanfu Su , Niluka Gunawardhana , Yeong-Eui Jeon , Eun Jung Bak , Ji-Hye Kim , Jeong-Heon Cha; J. Microbiol. 2016;54(5):396-402. Published online April 20, 2016; DOI: https://doi.org/10.1007/s12275-016-6137-1

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Abstract: Mammalian γ-glutamyltranspeptidase (GGT) has been identified as a bone-resorbing factor. Since GGT of Bacillus subtilis exhibits similarity in their primary structure and enzymatic characteristics with mammalian GGTs, the bone-resorbing activity of bacterial GGT was examined in this study. Osteoclastogenesis was performed in a co-culture system of mouse calvaria-derived osteoblasts and bone marrow cells. A conditioned medium from GGT-overproducing B. subtilis culture showed significantly higher activity of osteoclast formation than a conditioned medium from wild-type B. subtilis culture. Recombinant GGT (rGGT) of wild-type B. subtilis and an enzymatic activity-defected rGGT of B. subtilis 2288 mutant were expressed in Escherichia coli and purified using His tag. Both purified rGGTs induced similar levels of osteoclastogenesis, suggesting that B. subtilis GGT possesses virulent boneresorbing activity and its activity is probably independent of its enzymatic activity. Furthermore, a recombinant protein of B. subtilis GGT heavy subunit (Bs rGGT/H) showed strong activity of osteoclastogenesis while the light subunit failed to show strong activity, suggesting that the bone-resorbing activity is mainly located at the heavy subunit. More importantly, the GGT enzymatic activity may not be required for this virulence activity since the light subunit contains the catalytic pocket. In addition, B. subtilis rGGT stimulated mRNA expressions of receptor activator of nuclear factor kappa-B ligand (RANKL) and cyclooxygenase-2 (COX-2), while an osteoprotegerin inhibited the osteoclast formation induced by Bs rGGT/H. This is the first demonstration that bacterial GGT itself is sufficient to act as a bone-resorbing virulence factor via RANKL-dependent pathway. Therefore, it can be hypothesized that GGT of periodontopathic bacteria may play an important role as a virulence factor in bone destruction.

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