Journal of Microbiology

Journal Articles

The Regulation of Phosphorus Release by Penicillium chrysogenum in Different Phosphate via the TCA Cycle and Mycelial Morphology: Liyan Wang , Da Tian , Xiaoru Zhang , Mingxue Han , Xiaohui Cheng , Xinxin Ye , Chaochun Zhang , Hongjian Gao , Zhen Li; J. Microbiol. 2023;61(8):765-775. Published online September 4, 2023; DOI: https://doi.org/10.1007/s12275-023-00072-2

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Abstract: Phosphate-solubilizing fungi (PSF) efficiently dissolve insoluble phosphates through the production of organic acids. This study investigates the mechanisms of organic acid secretion by PSF, specifically Penicillium chrysogenum, under tricalcium phosphate ( Ca3(PO4)2, Ca–P) and ferric phosphate ( FePO4, Fe–P) conditions. Penicillium chrysogenum exhibited higher phosphorus (P) release efficiency from Ca-P (693.6 mg/L) than from Fe–P (162.6 mg/L). However, Fe–P significantly enhanced oxalic acid (1193.7 mg/L) and citric acid (227.7 mg/L) production by Penicillium chrysogenum compared with Ca–P (905.7 and 3.5 mg/L, respectively). The presence of Fe–P upregulated the expression of genes and activity of enzymes related to the tricarboxylic acid cycle, including pyruvate dehydrogenase and citrate synthase. Additionally, Fe–P upregulated the expression of chitinase and endoglucanase genes, inducing a transformation of Penicillium chrysogenum mycelial morphology from pellet to filamentous. The filamentous morphology exhibited higher efficiency in oxalic acid secretion and P release from Fe–P and Ca–P. Compared with pellet morphology, filamentous morphology enhanced P release capacity by > 40% and > 18% in Ca–P and Fe–P, respectively. This study explored the strategies employed by PSF to improve the dissolution of different insoluble phosphates.

Rhizosphere Microbial Community and Metabolites of Susceptible and Resistant Tobacco Cultivars to Bacterial Wilt: Wan Zhao , Yanyan Li , Chunlei Yang , Yong Yang , Yun Hu; J. Microbiol. 2023;61(4):389-402. Published online March 7, 2023; DOI: https://doi.org/10.1007/s12275-023-00012-0

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Abstract: Soil-borne diseases are closely related to rhizosphere microecosystem. While, plant species and genotypes are important factors affected rhizosphere microecosystem. In this study, the rhizosphere soil microbial community and metabolites of susceptible and resistant tobacco cultivars were investigated. The results showed that there were significant differences in the rhizosphere microbial community and metabolites between susceptible cultivar Yunyan87 and resistant cultivar Fandi3. Furthermore, the rhizosphere soil of Fandi3 showed a higher microbial diversity than that of Yunyan87. The abundance of R. solanacearum was much higher in the rhizosphere soil of Yunyan87 than in the rhizosphere soil of Fandi3, resulting in a higher disease incidence and index. While the abundance of beneficial bacteria in the rhizosphere soil of Fandi3 were higher than that of Yunyan87. Additionally, there were significant differences in metabolites between Yunyan87 and Fandi3 cultivars, and 4-hydroxybenzaldehyde, 3-hydroxy-4-methoxybenzoic acid, vamillic aldehyde, benzoic acid, 4-hydroxybenzyl alcohol, p-hydroxybenzoic acid and phthalic acid were notably high in Yunyan87. Redundancy analysis (RDA) indicated that the rhizosphere microbial community of Fandi3 and Yunyan87 were highly correlated with various environmental factors and metabolites. Overall, susceptible and resistant tobacco cultivars had different impact on rhizosphere microbial community and metabolites. The results expand our understanding of the roles of tobacco cultivars in plant-micro-ecosystem interactions, and provide a basis for the control of tobacco bacterial wilt.

Whole genome and RNA sequencing of oral commensal bacterium Streptococcus anginosus subsp. anginosus with vancomycin tolerance: Kyu Hwan Kwack , Jae-Hyung Lee , Ji-Hoi Moon; J. Microbiol. 2022;60(2):167-176. Published online January 7, 2022; DOI: https://doi.org/10.1007/s12275-022-1425-4

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Abstract: “Antibiotic tolerance” promotes the rapid subsequent evolution of “antibiotic resistance,” however, it is often overlooked because it is difficult to distinguish between tolerant and susceptible organisms. A commensal bacterium S. anginosus subsp. anginosus strain KHUD_S1, isolated from dental biofilm was found to exhibit a high MBC/MIC ratio of 32 against vancomycin. We observed KHUD_S1 cells exposed to vancomycin did not grow but maintained viability. Transmission electron microscope showed KHUD_S1 cells possessed a dense, thick capsule and maintained the cell wall integrity upon vancomycin exposure. To infer the underlying mechanisms of the vancomycin tolerance in KHUD_S1, we performed whole genome sequencing and RNA sequencing. The KHUD_S1 genome carried three genes encoding branching enzymes that can affect peptidoglycan structure through interpeptide bridge formation. Global gene expression profiling revealed that the vancomycin-induced downregulation of carbohydrate and inorganic ion transport/metabolism as well as translation is less prominent in KHUD_S1 than in the vancomycin susceptible strain KHUD_S3. Based on the transcriptional levels of genes related to peptidoglycan synthesis, KHUD_S1 was determined to have a 3D peptidoglycan architecture distinct from KHUD_S3. It was found that, under vancomycin exposure, the peptidoglycan was remodeled through changes in the interpeptide bridge and transpeptidation reactions. Collectively, these features of S. anginosus KHUD_S1, including a dense capsule and differential gene expression in peptidoglycan synthesis, may contribute to vancomycin tolerance. Our results showing the occurrence of vancomycin tolerance amongst oral commensal bacteria highlight the need for considering future strategies for screening of antibiotic tolerance as an effort to reduce antibiotic resistance.

Structure of bacterial and eukaryote communities reflect in situ controls on community assembly in a high-alpine lake: Eli Michael S. Gendron , John L. Darcy , Katherinia Hell , Steven K. Schmidt; J. Microbiol. 2019;57(10):852-864. Published online August 3, 2019; DOI: https://doi.org/10.1007/s12275-019-8668-8

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9 Citations

Abstract: Recent work suggests that microbial community composition in high-elevation lakes is significantly influenced by microbes entering from upstream terrestrial and aquatic habitats. To test this idea, we conducted 18S and 16S rDNA surveys of microbial communities in a high-alpine lake in the Colorado Rocky Mountains. We compared the microbial community of the lake to water entering the lake and to uphill soils that drain into the lake. Utilizing hydrological and abiotic data, we identified potential factors controlling microbial diversity and community composition. Results show a diverse community entering the lake at the inlet with a strong resemblance to uphill terrestrial and aquatic communities. In contrast, the lake communities (water column and outlet) showed significantly lower diversity and were significantly different from the inlet communities. Assumptions of neutral community assembly poorly predicted community differences between the inlet and lake, whereas “variable selection” and “dispersal limitation” were predicted to dominate. Similarly, the lake communities were correlated with discharge rate, indicating that longer hydraulic residence times limit dispersal, allowing selective pressures within the lake to structure communities. Sulfate and inorganic nitrogen and phosphorus concentrations correlated with community composition, indicating “bottom up” controls on lake community assembly. Furthermore, bacterial community composition was correlated with both zooplankton density and eukaryotic community composition, indicating biotic controls such as “top-down” interactions also contribute to community assembly in the lake. Taken together, these community analyses suggest that deterministic biotic and abiotic selection within the lake coupled with dispersal limitation structures the microbial communities in Green Lake 4.

Development of recombinant Yarrowia lipolytica producing virus-like particles of a fish nervous necrosis virus: Van-Trinh Luu , Hye Yun Moon , Jee Youn Hwang , Bo-Kyu Kang , Hyun Ah Kang; J. Microbiol. 2017;55(8):655-664. Published online July 28, 2017; DOI: https://doi.org/10.1007/s12275-017-7218-5

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20 Citations

Abstract: Nervous necrosis virus (NNV) causes viral encephalopathy and retinopathy, a devastating disease of many species of cultured marine fish worldwide. In this study, we used the dimorphic non-pathogenic yeast Yarrowia lipolytica as a host to express the capsid protein of red-spotted grouper nervous necrosis virus (RGNNV-CP) and evaluated its potential as a platform for vaccine production. An initial attempt was made to express the codon-optimized synthetic genes encoding intact and N-terminal truncated forms of RGNNV-CP under the strong constitutive TEF1 promoter using autonomously replicating sequence (ARS)-based vectors. The full-length recombinant capsid proteins expressed in Y. lipolytica were detected not only as monomers and but also as trimers, which is a basic unit for formation of NNV virus-like particles (VLPs). Oral immunization of mice with whole recombinant Y. lipolytica harboring the ARSbased plasmids was shown to efficiently induce the formation of IgG against RGNNV-CP. To increase the number of integrated copies of the RGNNV-CP expression cassette, a set of 26S ribosomal DNA-based multiple integrative vectors was constructed in combination with a series of defective Ylura3 with truncated promoters as selection markers, resulting in integrants harboring up to eight copies of the RGNNVCP cassette. Sucrose gradient centrifugation and transmission electron microscopy of this high-copy integrant were carried out to confirm the expression of RGNNV-CPs as VLPs. This is the first report on efficient expression of viral capsid proteins as VLPs in Y. lipolytica, demonstrating high potential for the Y. lipolytica expression system as a platform for recombinant vaccine production based on VLPs.

Dominant genera of cyanobacteria in Lake Taihu and their relationships with environmental factors: Lijun Feng , Shiyou Liu , Wenxian Wu , Jiawen Ma , Pei Li , Hailing Xu , Na Li , Yaoyu Feng; J. Microbiol. 2016;54(7):468-476. Published online June 28, 2016; DOI: https://doi.org/10.1007/s12275-016-6037-4

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18 Citations

Abstract: Cyanobacterial blooms in freshwaters have become one of the most widespread of environmental problems and threaten water resources worldwide. Previous studies on cyanobacteria in Lake Taihu often collected samples from one site (like Meiliang Bay or Zhushan Bay) and focused on the variation in patterns or abundance of Microcystis during the blooming season. However, the distribution of cyanobacteria in Lake Taihu shows differing pattern in various seasons. In this study, water samples were collected monthly for one year at five sites in Lake Taihu with different trophic status and a physicochemical analysis and denaturing gradient gel electrophoresis (DGGE) were conducted. DGGE fingerprint analysis showed that Microcystis (7/35 bands) and Synechococcus (12/35 bands) were the two most dominant genera present during the study period at all five sites. Cyanobium (3/35 bands) was the third most common genus which has seldom been previously reported in Lake Taihu. Redundancy analysis (RDA) indicated that the cyanobacterial community structure was significantly correlated with NO3 --N, CODMn, and NH4 +-N in the winter and spring, whereas it was correlated with water temperature in the summer and autumn. Limiting the nutrient input (especially of N and C loading) in Lake Taihu would be a key factor in controlling the growth of different genera of cyanobacteria.

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

Dimethyl sulfoxide reduction by a hyperhermophilic archaeon Thermococcus onnurineus NA1 via a cysteine-cystine redox shuttle: Ae Ran Choi , Min-Sik Kim , Sung Gyun Kang , Hyun Sook Lee; J. Microbiol. 2016;54(1):31-38. Published online January 5, 2016; DOI: https://doi.org/10.1007/s12275-016-5574-1

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Abstract: A variety of microbes grow by respiration with dimethyl sulfoxide (DMSO) as an electron acceptor, and several distinct DMSO respiratory systems, consisting of electron carriers and a terminal DMSO reductase, have been characterized. The heterotrophic growth of a hyperthermophilic archaeon Thermococcus onnurineus NA1 was enhanced by the addition of DMSO, but the archaeon was not capable of reducing DMSO to DMS directly using a DMSO reductase. Instead, the archaeon reduced DMSO via a cysteine-cystine redox shuttle through a mechanism whereby cystine is microbially reduced to cysteine, which is then reoxidized by DMSO reduction. A thioredoxin reductase-protein disulfide oxidoreductase redox couple was identified to have intracellular cystine-reducing activity, permitting recycle of cysteine. This study presents the first example of DMSO reduction via an electron shuttle. Several Thermococcales species also exhibited enhanced growth coupled with DMSO reduction, probably by disposing of excess reducing power rather than conserving energy.

The N3 Subdomain in A Domain of Fibronectin-Binding Protein B Isotype I Is an Independent Risk Determinant Predictive for Biofilm Formation of Staphylococcus aureus Clinical Isolates: An Sung Kwon , Dong Hoon Lim , Hyo Jung Shin , Geon Park , Jong H. Reu , Hyo Jin Park , Jungmin Kim , Yong Lim; J. Microbiol. 2013;51(4):499-505. Published online August 30, 2013; DOI: https://doi.org/10.1007/s12275-013-3319-y

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Abstract: Fibronectin-binding proteins (FnBP), FnBPA and FnBPB, are purported to be involved in biofilm formation of Staphylococcus aureus. This study was performed to find which of three consecutive N subdomains of the A domain in the FnBP is the key domain in FnBP. A total of 465 clinical isolates of S. aureus were examined for the biofilm forming capacity and the presence of N subdomains of FnBP. In the biofilm-positive strains, N2 and N3 subdomains of FnBPA, and N1 and N3 subdomains of FnBPB were significantly more prevalent. Multivariate logistic regression analysis of 246 biofilm-positive and 123 biofilm-negative strains identified only the FnBPB-N3 subdomain as an independent risk determinant predictive for biofilm-positive strains of S. aureus (Odds ratio [OR], 13.174; P<0.001). We also attempted to delete each of the fnbA-N2 and -N3 and fnbB-N1 and -N3 from S. aureus strain 8325-4 and examined the biofilm forming capacity in the derivative mutants. In agreement with the results of the multivariate regression analysis, deletion of either the fnbA-N2 or -N3, or fnbB-N1 did not significantly diminish the capacity of strain 8325-4 to develop a biofilm, while deletion of the fnbB-N3 did. Therefore, it is suggested that the FnBPB-N3 subdomain of isotype I may be a key domain in FnBP which is responsible for the causing biofilm formation in S. aureus clinical isolates.

The Pectate Lyase Encoded by the pecCl1 Gene Is an Important Determinant for the Aggressiveness of Colletotrichum lindemuthianum: Andréia Cnossen-Fassoni , Denise Mara Soares Bazzolli , Sérgio Hermínio Brommonschenkel , Elza Fernandes de Araújo , Marisa Vieira de Queiroz; J. Microbiol. 2013;51(4):461-470. Published online August 30, 2013; DOI: https://doi.org/10.1007/s12275-013-3078-9

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14 Citations

Abstract: Colletotrichum lindemuthianum is the causal agent of anthracnose in the common bean, and the genes that encode its cell-wall-degrading enzymes are crucial for the development of the disease. Pectinases are the most important group of cell wall-degrading enzymes produced by phytopathogenic fungi. The pecC1l gene, which encodes a pectate lyase in C. lindemuthianum, was isolated and characterized. Possible cis-regulatory elements and transcription factor binding sites that may be involved in the regulation of genetic expression were detected in the promoter region of the gene. pecCl1 is represented by a single copy in the genome of C. lindemuthianum, though in silico analyses of the genomes of Colletotrichum graminicola and Colletotrichum higginsianum suggest that the genome of C. lindemuthianum includes other genes that encode pectate lyases. Phylogenetic analysis detected two groups that clustered based on different members of the pectate lyase family. Analysis of the differential expression of pecCl1 during different stages of infection showed a significant increase in pecCl1 expression five days after infection, at the onset of the necrotrophic phase. The split-maker technique proved to be an efficient method for inactivation of the pecCl1 gene, which allowed functional study of a mutant with a site-specific integration. Though gene inactivation did not result in complete loss of pectate lyase activity, the symptoms of anthracnose were reduced. Analysis of pectate lyases might not only contribute to the understanding of anthracnose in the common bean but might also lead to the discovery of an additional target for controlling anthracnose.

Establishment and Characterization of the Epithelioma Papulosum Cyprini (EPC) Cell Line Persistently Infected with Infectious Pancreatic Necrosis Virus (IPNV), an Aquabirnavirus: Hyoung Jun Kim , Jae-Kwon Cho , Hyung-Kyu Hwang , Myung-Joo Oh , Toyohiko Nishizawa; J. Microbiol. 2012;50(5):821-826. Published online November 4, 2012; DOI: https://doi.org/10.1007/s12275-012-2364-2

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Abstract: Infectious pancreatic necrosis virus (IPNV), a type species of aquabirnaviruses in the family Birnaviridae, is an etiological agent of infectious pancreatic necrosis and has been isolated from epizootics of cultured salmonids. In the present study, an epithelioma papulosum cyprini (EPC) cell line persistently infected with IPNV (PI-EPC) was experimentally established by subculturing EPC cells surviving IPNV infection, and was characterized. PI-EPC cells were morphologically indistinguishable from EPC, but continued to grow and yield IPNV. PI-EPC cells showed no cytopathic effect due to IPNV inoculation, and susceptibility of PI-EPC cells against heterologous viruses was not different from that of EPC cells. Only one cell of 103.5 PI-EPC cells produced IPNV at approximately 100.5 50% tissue culture infectious dose (TCID50)/cell/day, which was approximately 1,000 times lower than that of normal EPC cells. PI-EPC cells that did not yield IPNV (N-PI-EPC) were screened. The IPNV genome was detected from both PI-EPC and N-PI-EPC cells, and the IPNV VP2 structural protein was detected from both cell lines, but no other IPNV proteins were observed by Western blot analysis with anti-IPNV serum. Thus, multiplication of IPNV in PI-EPC cells was regulated by some host cell factors, except interferon.

Antiviral Activities of Flavonoids Isolated from the Bark of Rhus verniciflua Stokes against Fish Pathogenic Viruses In Vitro: So Young Kang , Ji-Young Kang , Myung-Joo Oh; J. Microbiol. 2012;50(2):293-300. Published online April 27, 2012; DOI: https://doi.org/10.1007/s12275-012-2068-7

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91 Citations

Abstract: An 80% methanolic extract of Rhus verniciflua Stokes bark showed significant anti-viral activity against fish pathogenic infectious hematopoietic necrosis virus (IHNV) and viral hemorrhagic septicemia virus (VHSV) in a cell-based assay measuring virus-induced cytopathic effect (CPE). Activity-guided fractionation and isolation for the 80% methanolic extract of R. verniciflua yielded the most active ethyl acetate fraction, and methyl gallate (1) and four flavonoids: fustin (2), fisetin (3), butin (4) and sulfuretin (5). Among them, fisetin (3) exhibited high antiviral activities against both IHNV and VHSV showing EC50 values of 27.1 and 33.3 μM with selective indices (SI = CC50/EC50) more than 15, respectively. Fustin (2) and sulfuretin (5) displayed significant antiviral activities showing EC50 values of 91.2– 197.3 μM against IHNV and VHSV. In addition, the antiviral activity of fisetin against IHNV and VHSV occurred up to 5 hr post-infection and was not associated with direct virucidal effects in a timed addition study using a plaque reduction assay. These results suggested that the bark of R. verniciflua and isolated flavonoids have significant anti-viral activity against IHNV and VHSV, and also have potential to be used as anti-viral therapeutics against fish viral diseases.

Molecular Diversity of Chrysoviruses in Korean Isolates of A New Fungal Species, Cryphonectria nitschkei: Jung-Mi Kim , Jung-Ae Kim , Jin-Ah Park , Seung-Moon Park , Byeong-Jin Cha , Moon-Sik Yang , Dae-Hyuk Kim; J. Microbiol. 2009;47(4):441-447. Published online September 9, 2009; DOI: https://doi.org/10.1007/s12275-009-0206-7

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Abstract: Genetic diversity of the chrysovirus within the four fungal strains was analyzed by comparing the full- length sequences of cloned chrysoviral genes encoding the RNA-dependent RNA polymerase (RdRp) and capsid protein (CP). Because the morphological characteristics of four chrysovirus-infected Cryphonectria spp. strains were different, strain identification was conducted via sequence comparison of the internal transcribed spacers (ITSs) of the fungal rRNA gene. Phylogenic analysis of the ITS regions revealed that the four strains were closely clustered with the reference strain of Cryphonectria nitschkei, while they were more distantly related to other common Cryphonectria species, indicating that they were likely C. nitschkei. Sequence comparison among chrysoviruses from Korean C. nitschkei strains revealed that similarities of the RdRp and CP genes ranged from 98% to 100% and from 95% to 100%, respectively, at the protein level. Their corresponding nucleotide sequences showed 97% to 100% and 84% to 100% identities, respectively. Compared to RdRp, the CP gene had more divergence, suggesting the presence of genes possessing different evolutionary rates within the chrysovirus genome. Sequence comparisons with other known chrysoviruses showed that the four Korean chrysoviruses were clustered together at the next lineage level. Discovering why two strains (bs131 and bs132) containing identical ITS sequences and chrysoviruses display different phenotypes should prove interesting.

Translocation of Green Fluorescent Protein to Cyanobacterial Periplasm Using Ice Nucleation Protein: Wipa Chungjatupornchai , Sirirat Fa-aroonsawat; J. Microbiol. 2009;47(2):187-192. Published online May 2, 2009; DOI: https://doi.org/10.1007/s12275-008-0188-x

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Abstract: The translocation of proteins to cyanobacterial cell envelope is made complex by the presence of a highly differentiated membrane system. To investigate the protein translocation in cyanobacterium Synechococcus PCC 7942 using the truncated ice nucleation protein (InpNC) from Pseudomonas syringae KCTC 1832, the green fluorescent protein (GFP) was fused in frame to the carboxyl-terminus of InpNC. The fluorescence of GFP was found almost entirely as a halo in the outer regions of cells which appeared to correspond to the periplasm as demonstrated by confocal laser scanning microscopy, however, GFP was not displayed on the outermost cell surface. Western blotting analysis revealed that InpNC-GFP fusion protein was partially degraded. The N-terminal domain of InpNC may be susceptible to protease attack; the remaining C-terminal domain conjugated with GFP lost the ability to direct translocation across outer membrane and to act as a surface display motif. The fluorescence intensity of cells with periplasmic GFP was approximately 6-fold lower than that of cells with cytoplasmic GFP. The successful translocation of the active GFP to the periplasm may provide a potential means to study the property of cyanobacterial periplasmic substances in response to environmental changes in a non-invasive manner.

Genus-Specific Distribution and Pathovar-Specific Variation of the Glycinecin R Gene Homologs in Xanthomonas genomes: Eunjung Roh , Sunggi Heu , Eunpyo Moon; J. Microbiol. 2008;46(6):681-686. Published online December 24, 2008; DOI: https://doi.org/10.1007/s12275-008-0209-9

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Abstract: Xanthomonas axonopodis pv. glycines produces bacteriocins called glycinecin, and two glycinecin genes, glyA and glyR, were reported previously. In this paper, we describe genomic distribution and variation of the glyR gene revealed by extensive Southern hybridization analysis. In contrast to the glyA gene present only in X. axonopodis pv. glycines, the glyR gene was found to be distributed widely in all the pathovars of Xanthomas genus. It was also found that the glyR gene is a multigene family while the glyA is a single copy gene. Moreover, the copy number and the variation of the glyR multigene are unique to each pathovar of Xanthomonas. The uniqueness can be easily detected by the patterns resulted from Southern hybridization using the genomic digests. Thus, we suggest the glyR gene can serve as a useful genus-specific and pathovarspecific DNA marker for Xanthomonas. One of the glyR homologs was further isolated from X. axonopodis pv. glycines, and analyzed to be functional with strong inhibitory activity against several members of Xanthomonas.

Functional Analysis of pilQ Gene in Xanthomanas oryzae pv. oryzae, Bacterial Blight Pathogen of Rice: Seon-Hwa Lim , Byoung-Ho So , Ji-Chun Wang , Eun-Seong Song , Young-Jin Park , Byoung-Moo Lee , Hee-Wan Kang; J. Microbiol. 2008;46(2):214-220. Published online June 11, 2008; DOI: https://doi.org/10.1007/s12275-007-0173-9

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Abstract: Bacterial blight (BB) of rice, caused by Xanthomonas oryzae pv. oryzae (Xoo), is the most devastating bacterial disease in rice. A virulence-attenuated mutant strain HNU89K9 of X. oryzae pv. oryzae (KACC10331), with a transposon insertion in the pilQ gene was used for this study. The pilQ was involved in the gene cluster pilMNOPQ of the Xoo genome. Growth rate of the pilQ mutant was similar to that of wild-type. At level of amino acids, PilQ of Xoo showed that a high sequence identities more than 94% and 70% to Xanthomonas species and to Xyllela fastidiosa, respectively but a low sequence homology less than 30% to other bacterial species. The twitching motility forming a marginal fringe on PSA media was observed on colony of the wild-type strain KACC10331, but not in mutant HNU89K9. Wild-type Xoo cells formed a biofilm on the surface of the PVC plastic test tube, while the mutant strain HNU89K9 did not form a biofilm. The results suggest that the pilQ gene of X. oryzae pv. oryzae plays a critical role in pathogenicity, twitching motility, and biofilm formation.

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