• The Plant Pathology Journal
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• v.24 no.2
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• pp.101-111
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• 2008

The fungal genus Alternaria is comprised of many saprophytic and endophytic species, but is most well known as containing many notoriously destructive plant pathogens. There are over 4,000 Alternaria/host associations recorded in the USDA Fungal Host Index ranking the genus 10th among nearly 2,000 fungal genera based on the total number of host records. While few Alternaria species appear to have a sexual stage to their life cycles, the majority lack sexuality altogether. Many pathogenic species of Alternaria are prolific toxin producers, which facilitates their necrotrophic lifestyle. Necrotrophs must kill host cells prior to colonization, and thus these toxins are secreted to facilitate host cell death often by triggering genetically programmed apoptotic pathways or by directly causing cell damage resulting in necrosis. While many species of Alternaria produce toxins with rather broad host ranges, a closely-related group of agronomically important Alternaria species produce selective toxins with a very narrow range often to the cultivar level. Genes that code for and direct the biosynthesis of these host-specific toxins for the Alternaria alternata sensu lato lineages are often contained on small, mostly conditionally dispensable, chromosomes. Besides the role of toxins in Alternaria pathogenesis, relatively few genes and/or gene products have been identified that contribute to or are required for pathogenicity. Recently, the completion of the A. brassicicola genome sequencing project has facilitated the examination of a substantial subset of genes for their role in pathogenicity. In this review, we will highlight the role of toxins in Alternaria pathogenesis and the use of A. brassicicola as a model representative for basic virulence studies for the genus as a whole. The current status of these research efforts will be discussed.

• Journal of Microbiology and Biotechnology
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• v.19 no.8
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• pp.749-759
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• 2009

A survey of Bacillus thuringiensis (Berliner) strains isolated from Spanish citrus orchards has been performed, and the strains were tested for insecticidal activity against the Mediterranean fruit fly Ceratitis capitata (Wiedemann), a key citrus pest in Spain. From a total of 150 environmental samples, 376 isolates were selected, recording a total B. thuringiensis index of 0.52. The collection was characterized by means of phase-contrast microscopy, SDS-PAGE, and PCR analysis with primer pairs detecting toxin genes cry1, cry2, cry3, cry4, cry5, cry7, cry8, cry9, cry10, cry11, cry12, cry14, cry17, cry19, cry21, cry27, cry39, cry44, cyt1, and cyt2. Diverse crystal inclusion morphologies were identified: bipyramidal (45%), round (40%), adhered to the spore (7%), small (5%), and irregular (3%). SDS-PAGE of spore-crystal preparations revealed 39 different electrophoresis patterns. All primer pairs used in PCR tests gave positive amplifications in strains of our collection, except for primers for detection of cry3, cry19, cry39, or cry44 genes. Strains containing cry1, cry2, cry4, and cry27 genes were the most abundant (48.7%, 46%, 11.2%, and 8.2% of the strains, respectively). Ten different genetic profiles were found, although a total of 109 strains did not amplify with the set of primers used. Screening for toxicity against C. capitata adults was performed using both spore-crystal and soluble fractions. Mortality levels were less than 30%. We have developed a large and diverse B. thuringiensis strain collection with huge potential to control several agricultural pests; however, further research is needed to find out Bt strains active against C. capitata.

• Proceedings of the Microbiological Society of Korea Conference
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• 2005.05a
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• pp.231.4-231
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• 2005

• Research in Plant Disease
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• v.7 no.3
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• pp.123-133
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• 2001

Many pathovars of the species Pseudomonas syringae are known to produce different phytotoxins as secondary metabolites. Although phytotoxins generally enhance the virulence of P. syringae, they are not required for pathogenesis. Among the phytotoxins produced by P. syringae, lipodepsipeptides, coronatine, phaseolotoxin, and tabtoxin are the most well-known toxins which have been intensively studied for their structure, mode of action, biosynthesis, and regulation. A polymerase chain reaction (PCR) technique that amplifies a segment of the phytotoxin gene cluster using a primer set has been developed in recent years. This method offers the advantages of speed and sensitivity compared to the approaches based on physiological and biochemical methods. PCR detection of genes involved in the production of toxins could be exploited for early diagnosis of plant diseases caused by P. syringae pathovars.

• Korean Journal of Veterinary Research
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• v.60 no.4
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• pp.225-228
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• 2020

Apx toxins are a virulent factor of Actinobacillus pleuropneumoniae (App). At least four genes, apxC, apxA, apxB, and apxD, are involved in the release of Apx toxins from App. apxA encodes Apx toxins, whereas apxB and apxD encode exporters. Some serotypes of App such as serotype 2 retain apxIBD, apxIICA, and apxIIICABD. Although the specificity of the ApxIB/ApxID exporter to ApxII has been established in those serotypes, that to ApxIII is under-studied. We constructed an apxIB- and apxID-lacking mutant strain of the App serotype 2 to study whether the ApxIB/ApxID exporter is capable of secreting both ApxII and ApxIII toxins.

• Journal of Microbiology and Biotechnology
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• v.19 no.10
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• pp.1238-1243
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• 2009

The susceptibilities of major enterohemorrhagic Escherichia coli (EHEC) strains to antimicrobial agents and the cytotoxicity of these agents were examined using a total of 38 strains of E. coli O26, O111, and O157, which are the major serogroups of EHEC. Among the 38 strains, 35, 36, and 36 were susceptible to amikacin, imipenem, and norfloxacin, respectively. These antimicrobial agents were further examined to determine their cytotoxicity on Vero cells as well as their effect on the release of Shiga toxins along with trimethoprim/sulfamethoxazole. Each of the E. coli O26, O111, and O157 strains containing both the stx1 and stx2 genes were grown in the absence or presence of these agents at 1/4 minimal inhibitory concentration for 6 h, 12 h, and 18 h. At the concentrations used in this study, none of the agents significantly altered cell count compared with the control group. The level of cytotoxicity in the imipenem group was lower at 12 hand 18 h than their respective controls. In contrast, the level of cytotoxicity in cultures treated with trimethoprim/sulfamethoxazole, norfloxacin, and amikacin was increased. The strains were also examined for the release of Shiga toxins 1 and 2 following treatment with the agents, which were measured by the reversed passive latex agglutination (RPLA) method. The RPLA assay showed a suppression of release of Shiga toxin 2 in the strain cultures containing imipenem. These results indicate that imipenem may be a safe and effective agent for inhibition of these bacteria, which has clinical implications for the treatment of EHEC infections.

• Journal of Microbiology and Biotechnology
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• v.14 no.3
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• pp.490-497
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• 2004

Although the E. coli heat-labile enterotoxin B subunit (LTB) is known to be a potent mucosal adjuvant towards co-administrated unrelated antigens and immunoregulator in T-helper 1-type-mediated autoimmune diseases, a more efficient and useful LTB is still required for prospective vaccine adjuvants. To determine whether a novel chimeric LTB subunit would produce an enhanced mucosal adjuvant activity and immune response, a number of LTB subunits were genetically fused with chimeric proteins using the epitope genes of the envelope glycoprotein E2 (gp51-54) from the classical swine fever virus (CSFV). It was found that the total serum immunoglobulin (Ig) levels of BALB/c mice orally immunized with chimeric proteins containing an N-terminal linked LTB subunit (LE1, LE2, and LE3) were higher than those of mice immunized with LTB, E2 epitope, and chimeric proteins that contained a C-terminal linked LTB subunit. In particular, immunization with LE1 markedly increased both the total serum Ig and fecal IgA level compared to immunization with LTB or the E2 epitope. Accordingly, the current results demonstrated that the LTB subunit in a chimeric protein exhibited a strong mucosal adjuvant effect as a carrier molecule, while the chimeric protein containing the LTB subunit stimulated the mucosal immune system by mediating the induction of antigen-specific serum Ig and mucosal IgA. Consequently, an LE1-mediated mucosal response may contribute to the development of effective antidiarrhea vaccine adjuvants.

• The Plant Pathology Journal
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• v.39 no.1
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• pp.88-107
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• 2023

In the present investigation, bacterial isolates from infected apple trees causing apple canker during winter were studied in the northern Gyeongbuk Province, Korea. The pathogen was identified as Pseudomonas syringae pv. syringae (Pss) through various physiological and biochemical characterization assays such as BIOLOG, gas chromatography of fatty acid methyl esters, and 16S rRNA. Bioassays for the production of phytotoxins were positive for syringopeptin and syringomycin against Bacillus megaterium and Geotrichum candidum, respectively. The polymerase chain reaction (PCR) method enabled the detection of toxin-producing genes, syrB1, and sypB in Pss. The differentiation of strains was performed using LOPAT and GATTa tests. Pss further exhibited ice nucleation activity (INA) at a temperature of -0.7℃, indicating an INA⁺ bacterium. The ice-nucleating temperature was -4.7℃ for a non-treated control (sterilized distilled water), whereas it was -9.6℃ for an INA^- bacterium Escherichia coli TOP10. These methods detected pathogenic strains from apple orchards. Pss might exist in an apple tree during ice injury, and it secretes a toxin that makes leaves yellow and cause canker symptoms. Until now, Korea has not developed antibiotics targeting Pss. Therefore, it is necessary to develop effective disease control to combat Pss in apple orchards. Pathogenicity test on apple leaves and stems showed canker symptoms. The pathogenic bacterium was re-isolated from symptomatic plant tissue and confirmed as original isolates by 16S rRNA. Repetitive element sequence-based PCR and enterobacterial repetitive intergenic consensus PCR primers revealed different genetic profiles within P. syringae pathovars. High antibiotic susceptibility results showed the misreading of mRNA caused by streptomycin and oxytetracycline.

• Journal of the Korea Institute of Military Science and Technology
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• v.27 no.4
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• pp.516-527
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• 2024

Rapid, early, accurate detection and identification of the various pathogenic agents associated with the development of biological weapons is critical in preventing loss of life and limiting the impact of these organisms when used against civilian or military targets. The aim of this study was to produce a system for the simple, rapid, accurate and simultaneous detection and identification of Ricin, Botulinum toxin B and Staphylococcal enterotoxin B as a proof of principle for developing field appropriate reverse transcription loop-mediated isothermal amplification systems for the accurate identification of potential biological threats. These systems were designed to facilitate the identification of potential threats even in remote or resource-limited locations.

• Journal of Food Hygiene and Safety
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• v.32 no.1
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• pp.50-56
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• 2017

The purpose of this study was to investigate the microbiological contamination of water and drinking cups in springs and to estimate the toxin gene, enterotoxin production ability and antibiotic susceptibility of foodborne pathogens. Ten spring water and 34 drinking cups were tested. The average number of total aerobic bacteria and coliform bacteria in spring water were 1.8 log CFU/mL and 1.2 log CFU/mL, and in drinking cups were $4.7log\;CFU/100cm^2$ and $1.7log\;CFU/100cm^2$. Salmonella spp., Staphylococcus aureus, E. coli O157:H7, Listeria monocytogenes, Vibrio parahaemolyticus, Yersinia enterocolitica were not isolated from all of samples but Bacillus cereus was detected in 5 (14.7%) of 34 drinking cups. The nheA and entFM genes were major enterotoxin genes in B. cereus isolated from drinking cups. All of B. cereus tested in this study produce non-heamolytic enterotoxin but only 2 isolates possessed heamolysin BL enterotoxin producing ability. B. cereus was resistant to ${\beta}-lactam$ antibiotics. These results revealed that the sanitary conditions of drinking cups in spring should be improved promptly. The substitution carrying a personal drinking cup for the public drinking cups equipped in springs is suggested to prevent food-borne illness.