• Research in Plant Disease
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• v.23 no.3
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• pp.212-227
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• 2017

Pseudomonas chlororaphis O6, isolated from the roots of dryland, field-grown commercial wheat in the USA, enhances plant health and therefore it is used in agriculture as a biofertilizer and biocontrol agent. The metabolites produced by this pseudomonad stimulate plant growth through direct antagonism of pathogens and by inducing systemic resistance in the plant. Studies upon P. chlororaphis O6 identify the pathways through which defined bacterial metabolites generate protection against pathogenic microbes, insects, and nematodes. P. chlororaphis O6 also triggers plant resistance to drought and salinity stresses. The beneficial determinants are produced from bacterial cells as they form biofilms during root colonization. Molecular control these processes in P. chlororaphis O6 involves the global regulatory Gac/Rsm signaling cascade with cross-talk between other global regulatory pathways. The Gac/Rsm regulon allows for coordinate phasing of expression of the genes that encode these beneficial traits among a community of cells. This review provides insights on the Gac/Rsm regulon in expression of beneficial traits of the P. chlororaphis O6 which can contribute to help yield enhancement and quality in agricultural production.

• Journal of Microbiology and Biotechnology
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• v.20 no.4
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• pp.779-781
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• 2010

After preliminary tests indicated an increased number of heterotrophic bacteria, we investigated possible sources of contamination in a neonatal intensive care unit (NICU) water distribution system. Scanning electron microscopic examination of flexible metallic hoses associated with the system revealed the presence of a biofilm; partial 16S rDNA sequencing revealed that the biofilm contained Blastomonas natatoria. Purgation of the water system three times a day, reinforced faucet cleaning, decreasing the cold water temperature to $12^{\circ}C$, and six repeated chlorinations at concentrations as high as 2 mg/l were not sufficient to eradicate the bacterial contamination. Replacing all of the rubber-interior flexible metallic hoses with teflon-lined hoses, followed by heating the water to $70^{\circ}C$, successfully controlled the bacteria.

• Journal of Microbiology and Biotechnology
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• v.20 no.4
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• pp.782-788
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• 2010

Microbiological calcium carbonate precipitation (MCP) has been investigated for its ability to improve the compressive strength of mortar. However, very few studies have been conducted on the use of calcite-forming bacteria (CFB) to improve compressive strength. In this study, we discovered new bacterial genera that are capable of improving the compressive strength of mortar. We isolated 4 CFB from 7 environmental concrete structures. Using sequence analysis of the 16S rRNA genes, the CFB could be partially identified as Sporosarcina soli KNUC401, Bacillus massiliensis KNUC402, Arthrobacter crystallopoietes KNUC403, and Lysinibacillus fusiformis KNUC404. Crystal aggregates were apparent in the bacterial colonies grown on an agar medium. Stereomicroscopy, scanning electron microscopy, and X-ray diffraction analyses illustrated both the crystal growth and the crystalline structure of the $CaCO_3$ crystals. We used the isolates to improve the compressive strength of cement-sand mortar cubes and found that KNUC403 offered the best improvement in compressive strength.

• International Journal of Industrial Entomology and Biomaterials
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• v.37 no.1
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• pp.9-14
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• 2018

Bacterial species, Bacillus amyloliquefaciens and Lactobacillus species (L. sp.5-1), are known to inhibit the growth of pathogenic bacteria and fungi. Metarhizium anisopliae is a pathogenic fungal species which causes fatal damage to P. brevitarsis populations. Therefore, we investigated the inhibitory effect of B. amyloliquefaciens and L. sp. 5-1 on M. anisopliae induced fatality rates in P. brevitarsis. Samples of M. anisopliae-infected sawdust were treated with strain B. amyloliquefaciens KACC10116, strain L. sp. 5-1 KACC19351, and a combination of the two. P. brevitarsis were fed treated sawdust samples, and their subsequent fatality rate was monitored. The fatality rate fell below 1.5% after 10 days and decreased by approximately 40% after 15 days. On average, the fatality rate decreased by 20%, compared to the control. The difference in the decrease in fatality rate between B. amyloliquefaciens treatment and L. sp. 5-1 treatment was not significant. Results indicate that both strains exhibit high anti-fungal activity, which may be useful in environmental purification efforts. These strains may be used for effective prevention of fungal infection in P. brevitarsis.

• Journal of Microbiology and Biotechnology
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• v.26 no.5
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• pp.953-958
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• 2016

Chitosan-based film-forming gel is regarded as a promising vehicle for topical delivery of antimicrobial agents to skin wounds, since it protects from microbial infection and the cationic polymer itself possesses antibacterial activity. In this study, possible synergistic interaction against common skin pathogens between the cationic polymer and tyrothricin (TRC), a cyclic polypeptide antibiotic, was investigated, by determining the concentration to inhibit 90% of bacterial isolates (MIC). The addition of the polysaccharide to TRC dramatically reduced the MIC values of TRC by 1/33 and 1/4 against both methicillin-resistant and methicillin-susceptible Staphylococcus aureus, respectively. The synergism of TRC and chitosan combination against both strains was demonstrated by the checkerboard method, with a fractional inhibitory concentration index below 0.5. Moreover, co-treatment of TRC and chitosan exhibited antibacterial activity against Pseudomonas aeruginosa, due to the antibacterial activity of chitosan, whereas TRC itself did not inhibit the gram-negative bacterial growth. These findings suggested that the use of chitosan-based film for topical delivery of TRC could be an alternative to improve TRC antimicrobial activity against strains that are abundant in skin wounds.

• Journal of Microbiology and Biotechnology
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• v.13 no.3
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• pp.444-450
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• 2003

In order to develop an effective means to treat P. aeruginosa infections, we have purified P. aeruginosa outer membrane proteins (OMPs)-specific human IgG antibody. In this study, we investigated the protective activity of the purified anti-OMPs IgC against P. aeruginosa infection in a rabbit endophthalmitis model. Rabbits were inoculated by an intravitreal injection with P. aeruginosa, and treated with a single dose of 1 mg anti-P. aeruginosa OMPs IgG. All the control rabbits predominantly developed edematous responses and opacity in the eyes, but the rabbits treated with the antibody showed only very limited degree of edema. Aliquots of the vitreous humor were extracted and analyzed for the number of viable bacteria and endotoxin level. The results showed that the anti-OMPs IgC significantly reduced the bacterial count compared with the control group, and that the endotoxin level of the vitreous from the IgG-treated rabbits was more than 70-fold lower 6 h after the administration than the control animals. These data suggested that the anti-P. aeruginosa OMPs IgG is effective in inhibiting the bacterial growth and thereby in reducing endotoxin levels in the vitreous, warranting further development of the anti-P. aeruginosa OMPs IgG as a therapeutic means for treating Pseudomonas endophthalmitis.

• Journal of Microbiology and Biotechnology
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• v.17 no.6
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• pp.968-978
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• 2007

A pathogenic nematode, Butlerius sp., was isolated from Oriental beetle, Blitopertha orientalis. The infective juveniles exhibited dose-as well as time-dependent entomopathogenicity on the larvae of B. orientalis. Two bacterial species, Providencia vermicola (KACC 91278) and Flavobacterium sp. (KACC 91279), were isolated from the infective juveniles and identified. P. vermicola outnumbered Flavobacterium sp. in the nematode host, in which the colony density of P. vermicola was found to be 21 times higher than that of Flavobacterium sp. However, when the two bacterial species were cocultured in culture media without the nematode host, they showed similar growth rates. Both bacteria induced significant entomopathogenicity against Spodoptera exigua larvae infesting economically important vegetable crops, where P. vermicola was more potent than Flavobacterium sp.

• Journal of Microbiology and Biotechnology
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• v.19 no.12
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• pp.1582-1589
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• 2009

Bacterial UDP-N-acetylglucosamine enolpyruvyl transferase (MurA) catalyzes the transfer of enolpyruvate from phosphoenolpyruvate (PEP) to uridine diphospho-N-acetylglucosamine (UNAG), which is the first step of bacterial cell wall synthesis. We identified thimerosal, thiram, and ebselen as effective inhibitors of Haemophilus influenzae MurA by screening a chemical library that consisted of a wide range of bioactive compounds. When MurA was preincubated with these inhibitors, their 50% inhibitory concentrations ($IC_{50}s$) were found to range from 0.1 to $0.7\;{\mu}M$. In particular, thimerosal suppressed the growth of several different Gram-negative bacteria such as Escherichia coli, Pseudomonas aeruginosa, and Salmonella typhimurium at a concentration range of $1-2\;{\mu}g/ml$. These inhibitors covalently modified the cysteine residue near the active site of MurA. This modification changed the open conformation of MurA to a more closed configuration, which may have prevented the necessary conformational change from occurring during the enzyme reaction.

• Journal of Microbiology and Biotechnology
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• v.21 no.8
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• pp.869-873
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• 2011

Most medium formulations for improving culture of entomopathogenic nematodes (EPN) based on protein sources have used enriched media like animal feed such as dried egg yolk, lactalbumin, and liver extract, among other ingredients. Most results, however, showed unstable yields and longer production time. Many of the results do not show the detailed parameters of fermentation. Soy flour, cotton seed flour, corn gluten meal, casein powder, soytone, peptone, casein hydrolysates, and lactalbumin hydrolysate as protein sources were tested to determine the source to support optimal symbiotic bacteria and nematode growth. The protein hydrolysates selected did not improve bacterial cell mass compared with the yeast extract control, but soy flour was the best, showing 75.1% recovery and producing more bacterial cell number ($1.4{\times}10^9$/ml) than all other sources. The highest yield ($1.85{\times}10^5$ IJs/ml), yield coefficient ($1.67{\times}10^6$ IJs/g medium), and productivity ($1.32{\times}10^7$ IJs/l/day) were also achieved at enriched medium with soybean protein.

• Journal of Microbiology and Biotechnology
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• v.20 no.7
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• pp.1156-1162
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• 2010

During ethanol fermentation, bacterial strains may encounter various stresses, such as ethanol and acid shock, which adversely affect cell viability and the production of ethanol. Therefore, ethanologenic strains that tolerate abiotic stresses are highly desirable. Bacteria of the genus Deinococcus are extremely resistant to ionizing radiation, ultraviolet light, and desiccation, and therefore constitute an important pool of extreme resistance genes. The irrE gene encodes a general switch responsible for the extreme radioresistance of D. radiodurans. Here, we present evidence that IrrE, acting as a global regulator, confers high stress tolerance to a Zymomonas mobilis strain. Expression of the gene protected Z. mobilis cells against ethanol, acid, osmotic, and thermal shocks. It also markedly improved cell viability, the expression levels and enzyme activities of pyruvate decarboxylase and alcohol dehydrogenase, and the production of ethanol under both ethanol and acid stresses. These data suggest that irrE is a potentially promising gene for improving the abiotic stress tolerance of ethanologenic bacterial strains.