Journal of Microbiology

Volume 43(6); December 2005

Review

Genomics Reveals Traces of Fungal Phenylpropanoid-flavonoid Metabolic Pathway in the F ilamentous Fungus Aspergillus oryzae: Praveen Rao Juvvadi , Yasuyo Seshime , Katsuhiko Kitamoto; J. Microbiol. 2005;43(6):475-486.; DOI: https://doi.org/2302 [pii]

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Abstract: Fungal secondary metabolites constitute a wide variety of compounds which either play a vital role in agricultural, pharmaceutical and industrial contexts, or have devastating effects on agriculture, animal and human affairs by virtue of their toxigenicity. Owing to their beneficial and deleterious characteristics, these complex compounds and the genes responsible for their synthesis have been the subjects of extensive investigation by microbiologists and pharmacologists. A majority of the fungal secondary metabolic genes are classified as type I polyketide synthases (PKS) which are often clustered with other secondary metabolism related genes. In this review we discuss on the significance of our recent discovery of chalcone synthase (CHS) genes belonging to the type III PKS superfamily in an industrially important fungus, Aspergillus oryzae. CHS genes are known to play a vital role in the biosynthesis of flavonoids in plants. A comparative genome analyses revealed the unique character of A. oryzae with four CHS-like genes (csyA, csyB, csyC and csyD) amongst other Aspergilli (Aspergillus nidulans and Aspergillus fumigatus) which contained none of the CHS-like genes. Some other fungi such as Neurospora crassa, Fusarium graminearum, Magnaporthe grisea, Podospora anserina and Phanerochaete chrysosporium also contained putative type III PKSs, with a phylogenic distinction from bacteria and plants. The enzymatically active nature of these newly discovered homologues is expected owing to the conservation in the catalytic residues across the different species of plants and fungi, and also by the fact that a majority of these genes (csyA, csyB and csyD) were expressed in A. oryzae. While this finding brings filamentous fungi closer to plants and bacteria which until recently were the only ones considered to possess the type III PKSs, the presence of putative genes encoding other principal enzymes involved in the phenylpropanoid and flavonoid biosynthesis (viz., phenylalanine ammonia-lyase, cinnamic acid hydroxylase and p-coumarate CoA ligase) in the A. oryzae genome undoubtedly prove the extent of its metabolic diversity. Since many of these genes have not been identified earlier, knowledge on their corresponding products or activities remain undeciphered. In future, it is anticipated that these enzymes may be reasonable targets for metabolic engineering in fungi to produce agriculturally and nutritionally important metabolites.

Research Support, Non-U.S. Gov't

Degradation of Crystalline Cellulose by the Brown-rot Basidiomycete Fomitopsis palustris: Jeong-Jun Yoon , Young-Kyoon Kim; J. Microbiol. 2005;43(6):487-492.; DOI: https://doi.org/2301 [pii]

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Abstract: This study demonstrated that the brown rot basidiomycete Fomitopsis palustris was able to degrade crystalline cellulose (Avicel). This fungus could also produce the three major cellulases (exoglucanases, endoglucanases, and -glucosidase) when the cells were grown on 2.0% Avicel. Avicel degraded by F. palustris showed a decrease in relative crystallinity from 83% to 78.5% after 14 days of incubation. The characterization study indicated that optimum pH was 4.5 and optimum temperature was 70oC for exoglucanase (cellobiohydrolase) activity. Hydrolysis of Avicel by the crude enzyme from F. palustris yielded 1.6 mg/ml of glucose after 43 h, which corresponded to a cellulose conversion degree of 3.2%. Therefore, this study revealed for the first time that the brown rot basidiomycete F. palustris produces cellulases capable of yielding soluble sugars from crystalline cellulose.

Journal Article

Safety Assessment of Potential Lactic Acid Bacteria Bifidobacterium longum SPM1205 Isolated from Healthy Koreans: Sung Sook Choi , Byung Yong Kang , Myung Jun Chung , Soo Dong Kim , So Hee Park , Jung Soo Kim , Chin Yang Kang , Nam Joo Ha; J. Microbiol. 2005;43(6):493-498.; DOI: https://doi.org/2300 [pii]

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Abstract: The safety assessment of Bifidobacterium longum SPM1205 isolated from healthy Koreans and this strain''''''''s inhibitory effects on fecal harmful enzymes of intestinal microflora were investigated. The overall safety of this strain was investigated during a feeding trial. Groups of SD rats were orally administered a test strain or commercial reference strain B. longum 1?109 CFU/kg body weight/day for four weeks. Throughout this time, their feed intake, water intake and live body weight were monitored. Fecal samples were periodically collected to test harmful enzyme activities of intestinal microflora. At the end of the four-week observation period, samples of blood, liver, spleen, kidney, and gut tissues were collected to determine for hematological parameters and histological differences. The results obtained in this experiment demonstrated that four weeks of consumption of this Bifidobacterium strain had no adverse effects on rat''''''''s general health status, blood biochemical parameters or histology. Therefore, it is likely to be safe for human use. Fecal harmful enzymes such as -glucosidase, -glucuronidase, tryptophanase and urease, were effectively inhibited during the administration of the B. longum SPM1205. These results suggested that this B. longum SPM 1205 could be used for humans as a probiotic strain.

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

Characterization of Methylophaga sp. strain SK1 Cytochrome cL Expressed in Escherichia coli: Hee Gon Kim , Trong Nhat Phan , Tae Sa Jang , Moonjoo Koh , Si Wouk Kim; J. Microbiol. 2005;43(6):499-502.; DOI: https://doi.org/2299 [pii]

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Abstract: Methylophaga sp. strain SK1 is a new restricted facultative methanol-oxidizing bacterium that was isolated from seawater. The aim of this study was to characterize the electron carriers involved in the methanol oxidation process in Methylophaga sp. strain SK1. The gene encoding cytochrome cL (mxaG) was cloned and the recombinant gene was expressed in Escherichia coli DH5 under strict anaerobic conditions. The recombinant cytochrome cL had the same molecular weight and absorption spectra as the wild-type cytochrome cL both in the reduced and oxidized forms. The electron flow rate from methanol dehydrogenase (MDH) to the recombinant cytochrome cL was similar to that from MDH to the wild-type cytochrome cL. These results suggest that recombinant cytochrome cL acts as a physiological primary electron acceptor for MDH.

Purification and Characterization of Manganese Peroxidase of the White-Rot Fungus Irpex lacteus: Kwang-Soo Shin , Young Hwan Kim , Jong-Soon Lim; J. Microbiol. 2005;43(6):503-509.; DOI: https://doi.org/2298 [pii]

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Abstract: The production of manganese peroxidase (MnP) by Irpex lacteus, purified to electrophoretic homogeneity by acetone precipitation, HiPrep Q and HiPrep Sephacryl S-200 chromatography, was shown to correlate with the decolorization of textile industry wastewater. The MnP was purified 11.0-fold, with an overall yield of 24.3%. The molecular mass of the native enzyme, as determined by gel filtration chromatography, was about 53 kDa. The enzyme was shown to have a molecular mass of 53.2 and 38.3 kDa on SDS-PAGE and MALDI-TOF mass spectrometry, respectively, and an isoelectric point of about 3.7. The enzyme was optimally active at pH 6.0 and between 30 and 40oC. The enzyme efficiently catalyzed the decolorization of various artificial dyes and oxidized Mn (II) to Mn (III) in the presence of H2O2. The absorption spectrum of the enzyme exhibited maxima at 407, 500, and 640 nm. The amino acid sequence of the three tryptic peptides was analyzed by ESI Q-TOF MS/MS spectrometry, and showed low similarity to those of the extracellular peroxidases of other white-rot basidiomycetes.

Gibberellins-Producing Rhizobacteria Increase Endogenous Gibberellins Content and Promote Growth of Red Peppers: Gil-Jae Joo , Young-Mog Kim , Jung-Tae Kim , In-Koo Rhee , Jin-Ho Kim , In-Jung Lee; J. Microbiol. 2005;43(6):510-515.; DOI: https://doi.org/2297 [pii]

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Abstract: The growth of red pepper plants was enhanced by treatment with the rhizobacterium, Bacillus cereus MJ-1. Red pepper shoots showed a 1.38-fold increase in fresh weight (fw) and roots showed a 1.28-fold fw gain. This plant growth-promoting rhizobacterium (PGPR) has been reported to produce gibberellins (GAs). Other GAs-producing rhizobacteria, Bacillus macroides CJ-29 and Bacillus pumilus CJ-69, also enhanced the fw of the plants. They were less effective than B. cereus MJ-1, though. The endogenous GAs content of pepper shoots inoculated with MJ-1 was also higher than in shoots inoculated with CJ-29 or CJ-69. When inoculated with MJ-1, bacterial colonization rate of the roots was higher than that of roots inoculated with CJ-29 or CJ-69. These results support the idea that the plant growth-promoting effect of the bacteria also positively related with the efficiency of root colonization by the bacteria. In addition, we identified the major endogenous GAs of the red pepper as originating from both the early C-13 hydroxylation and the early non C-13 hydroxylation pathways, with the latter being the predominant pathway of GA biosynthesis in red pepper shoots.

Role of RNA Polymerase II Carboxy Terminal Domain Phosphorylation in DNA Damage Response: Su-Jin Jeong , Hye-Jin Kim , Yong-Jin Yang , Ja-Hwan Seol , Bo-Young Jung , Jeong-Whan Han , Hyang-Woo Lee , Eun-Jung Cho; J. Microbiol. 2005;43(6):516-522.; DOI: https://doi.org/2296 [pii]

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Abstract: The phosphorylation of C-terminal domain (CTD) of Rpb1p, the largest subunit of RNA polymerase II plays an important role in transcription and the coupling of various cellular events to transcription. In this study, its role in DNA damage response is closely examined in Saccharomyces cerevisiae, focusing specifically on several transcription factors that mediate or respond to the phosphorylation of the CTD. CTDK-1, the pol II CTD kinase, FCP1, the CTD phosphatase, ESS1, the CTD phosphorylation dependent cis-trans isomerase, and RSP5, the phosphorylation dependent pol II ubiquitinating enzyme, were chosen for the study. We determined that the CTD phosphorylation of CTD, which occurred predominantly at serine 2 within a heptapeptide repeat, was enhanced in response to a variety of sources of DNA damage. This modification was shown to be mediated by CTDK-1. Although mutations in ESS1 or FCP1 caused cells to become quite sensitive to DNA damage, the characteristic pattern of CTD phosphorylation remained unaltered, thereby implying that ESS1 and FCP1 play roles downstream of CTD phosphorylation in response to DNA damage. Our data suggest that the location or extent of CTD phosphorylation might be altered in response to DNA damage, and that the modified CTD, ESS1, and FCP1 all contribute to cellular survival in such conditions.

Screening of Growth- or Development-related Genes by Using Genomic Library with Inducible Promoter in Aspergillus nidulans: Bang-Yong Lee , Sang-Yong Han , Han Gil Choi , Jee Hyun Kim , Kap-Hoon Han , Dong-Min Han; J. Microbiol. 2005;43(6):523-528.; DOI: https://doi.org/2295 [pii]

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Abstract: Using the genomic library constructed at the downstream of the niiA promoter, which induces the over-expression of an inserted DNA fragment, we have attempted to screen the genes affecting growth or development by over-expression. The wild-type strain was transformed using the AMA-niiA(p) library and cultured on 1.2 M sorbitol media, in which asexual sporulation is induced, but sexual development is repressed. Over 100,000 strains transformed to pyrG+ were analyzed with regard to any changes in phenotype. Consequently, seven strains were isolated for further analyses. These strains were designated NOT [niiA(p) over-expression transformants] stains. Four of the strains were of the inducible type, and the remaining strains were of the multi-copy suppression type. Two of the inducible-type strains, NOT1 and NOT40, harbored genes which had been inserted in reverse direction, suggesting that the mutant phenotypes had been derived from an excess amount of anti-sense mRNA. Domain analyses of the deduced polypeptides from the DNA fragments rescued from the transformants revealed that NOT1, NOT40 and NOT6 harbored a LisH motif, a forkhead domain, and a Zn(II)2Cys6 binuclear zinc cluster, respectively.

Journal Articles

Hepatitis C Virus Non-structural Protein NS4B Can Modulate an Unfolded Protein Response: Yi Zheng , Bo Gao , Li Ye , Lingbao Kong , Wei Jing , Xiaojun Yang , Zhenghui Wu , Linbai Ye; J. Microbiol. 2005;43(6):529-536.; DOI: https://doi.org/2294 [pii]

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Abstract: Viral infection causes stress to the endoplasmic reticulum (ER). The response to endoplasmic reticulum stress, known as the unfolded protein response (UPR), is designed to eliminate misfolded proteins and allow the cell to recover. The role of hepatitis C virus (HCV) non-structural protein NS4B, a component of the HCV replicons that induce UPR, is incompletely understood. We demonstrate that HCV NS4B could induce activating transcription factor (ATF6) and inositol-requiring enzyme 1 (IRE1), to favor the HCV subreplicon and HCV viral replication. HCV NS4B activated the IRE1 pathway, as indicated by splicing of X box-binding protein (Xbp-1) mRNA. However, transcriptional activation of the XBP-1 target gene, EDEM (ER degradation-enhancing a-mannosidase-like protein, a protein degradation factor), was inhibited. These results imply that NS4B might induce UPR through ATF6 and IRE1-XBP1 pathways, but might also modify the outcome to benefit HCV or HCV subreplicon replication.

Analysis of Immune Responses Against Nucleocapsid Protein of the Hantaan Virus Elicited by Virus Infection or DNA Vaccination: Gyu-Jin Woo , Eun-Young Chun , Keun Hee Kim , Wankee Kim; J. Microbiol. 2005;43(6):537-545.; DOI: https://doi.org/2292 [pii]

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Abstract: Even though neutralizing antibodies against the Hantaan virus (HTNV) has been proven to be critical against viral infections, the cellular immune responses to HTNV are also assumed to be important for viral clearance. In this report, we have examined the cellular and humoral immune responses against the HTNV nucleocapsid protein (NP) elicited by virus infection or DNA vaccination. To examine the cellular immune response against HTNV NP, we used H-2Kb restricted T-cell epitopes of NP. The NP-specific CD8+ T cell response was analyzed using a 51Cr-release assay, intracellular cytokine staining assay, enzyme-linked immunospot assay and tetramer binding assay in C57BL/6 mice infected with HTNV. Using these methods, we found that HTNV infection elicited a strong NP-specific CD8+ T cell response at eight days after infection. We also found that several different methods to check the NP-specific CD8+ T cell response showed a very high correlation among analysis. In the case of DNA vaccination by plasmid encoding nucleocapsid gene, the NP-specific antibody response was elicited 2 ~ 4 weeks after immunization and maximized at 6~8 weeks. NP-specific CD8+ T cell response reached its peak 3 weeks after immunization. In a challenge test with the recombinant vaccinia virus expressing NP (rVV-HTNV-N), the rVV-HTNV-N titers in DNA vaccinated mice were decreased about 100-fold compared to the negative control mice.

Molecular Epidemiological Analysis of Bloodstream Isolates of Candida albicans from a University Hospital over a Five-Year Period: Jong Hee Shin , Yu Gyung Og , Duck Cho , Seung Jung Kee , Myung Geun Shin , Soon Pal Suh , Dong Wook Ryang; J. Microbiol. 2005;43(6):546-554.; DOI: https://doi.org/2291 [pii]

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Abstract: We assessed the genetic relations and epidemiological links among bloodstream isolates of Candida albicans, which were obtained from a university hospital over a period of five years. The 54 bloodstream isolates from the 38 patients yielded 14 different karyotypes, 29 different patterns after digestion with SfiI (REAG-S), and 31 different patterns after digestion with BssHII (REAG-B) when analyzed using three different pulsed-field gel electrophoresis (PFGE) typing methods. In 11 patients with serial bloodstream isolates, all strains from each patient had the same PFGE pattern. The dendrograms for all of the strains revealed that the distribution of similarity values ranged from 0.70 to 1.0 in the REAG-S patterns, and from 0.35 to 1.0 in the REAG-B patterns. Overall, the combination of the three different PFGE methods identified 31 distinct types, reflecting the results obtained using the REAG-B alone different. different Five PFGE types were shared among 22 isolates from 12 patients. These types of strains were more frequently associated with central venous catheter-related fungemia than the other 26 type strains (92% versus 31%; P < 0.005). Of five PFGE types, four isolates were determined to be epidemiologically related: each of these types was primarily from two or three patients who had been hospitalized concurrently within the same intensive care unit. Our results suggest that the REAG-B constitutes perhaps the most useful PFGE method for investigating C. albicans candidemia and also shows that a relatively high proportion of C. albicans candidemia may be associated with exogenous acquisition of clonal strains.

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

Purification and Characterization of Laccase from the White Rot Fungus Trametes versicolor: Moon-Jeong Han , Hyoung-Tae Choi , Hong-Gyu Song; J. Microbiol. 2005;43(6):555-560.; DOI: https://doi.org/2290 [pii]

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Abstract: Laccase is one of the ligninolytic enzymes of white rot fungus Trametes versicolor 951022, a strain first isolated in Korea. This laccase was purified 209-fold from culture fluid with a yield of 6.2% using ethanol precipitation, DEAE-Sepharose, Phenyl-Sepharose, and Sephadex G-100 chromatography. T. versicolor 951022 excretes a single monomeric laccase showing a high specific activity of 91,443 U/mg for 2,2''-azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) as a substrate. The enzyme has a molecular mass of approximately 97 kDa as determined by SDS-PAGE, which is larger than those of other laccases reported. It exhibits high enzyme activity over broad pH and temperature ranges with optimum activity at pH 3.0 and a temperature of 50oC. The Km value of the enzyme for substrate ABTS is 12.8 M and its corresponding Vmax value is 8125.4 U/mg. The specific activity and substrate affinity of this laccase are higher than those of other white rot fungi, therefore, it may be potentially useful for industrial purposes.

Production of Saccharogenic and Dextrinogenic Amylases by Rhizomucor pusillus A 13.36: Tony M. Silva , Derlene Attili-Angelis , Ana Flavia Azevedo Carvalho , Roberto Da Silva , Mauricio Boscolo , Eleni Gomes; J. Microbiol. 2005;43(6):561-568.; DOI: https://doi.org/2289 [pii]

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Abstract: A newly-isolated thermophilic strain of the zygomycete fungus Rhizomucor pusillus 13.36 produced highly active dextrinogenic and saccharogenic enzymes. Cassava pulp was a good alternative substrate for amylase production. Dextrinogenic and saccharogenic amylases exhibited optimum activities at a pH of 4.0-4.5 and 5.0 respectively and at a temperature of 75oC. The enzymes were highly thermostable, with no detectable loss of saccharogenic or dextrinogenic activity after 1 h and 6 h at 60oC, respectively. The saccharogenic activity was inhibited by Ca2+ while the dextrinogenic was indifferent to this ion. Both activities were inhibited by Fe2+ and Cu2+ Hydrolysis of soluble starch by the crude enzyme yielded 66% glucose, 19.5% maltose, 7.7% maltotriose and 6.6% oligosaccharides.

Cloning of a Manganese Peroxidase cDNA Gene Repressed by Manganese in Trametes versicolor: Yongho Kim , Sumin Yeo , Joohee Kum , Hong-Gyu Song , Hyoung T. Choi; J. Microbiol. 2005;43(6):569-571.; DOI: https://doi.org/2288 [pii]

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Abstract: White-rot fungi have the following enzyme systems for lignin degradation: laccase, lignin peroxidase and manganese peroxidase. There are other types of peroxidases related to lignin degradation, one of which we have cloned a cDNA gene of manganese-repressed peroxidase (MrP) in Trametes versicolor isolated in South Korea. The mrp transcript level has been decreased by 1 M of Mn2+.

Molecular Detection of Catabolic Genes for Polycyclic Aromatic Hydrocarbons in the Reed Rhizosphere of Sunchon Bay: Hyung-Yeel Kahng , Kye-Heon Oh; J. Microbiol. 2005;43(6):572-576.; DOI: https://doi.org/2287 [pii]

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Abstract: This study focused on detecting catabolic genes for polycyclic aromatic hydrocarbons (PAHs) distributed in the reed rhizosphere of Sunchon Bay, Korea. These marsh and mud environments were severely affected by human activities, including agriculture and fisheries. Our previous study on microbial roles in natural decontamination displayed the possibility that PAH-degrading bacteria, such as Achromobacter sp., Alcaligenes sp., Burkholderia sp. and Pseudomonas sp. play an important decontamination role in a reed rhizosphere. In order to gain further fundamental knowledge on the natural decontamination process, catabolic genes for PAH metabolism were investigated through PCR amplification of dioxygenase genes using soil genomic DNA and sequencing. Comparative analysis of predicted amino acid sequences from 50 randomly selected dioxygenase clones capable of hydroxylating inactivated aromatic nuclei indicated that these were divided into three groups, two of which might be originated from PAH-degrading bacteria. Amino acid sequences of each dioxygenase clone were a part of the genes encoding enzymes for initial catabolism of naphthalene, phenanthrene, or pyrene that might be originated from bacteria in the reed rhizosphere of Sunchon Bay.

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