• The Plant Pathology Journal
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• v.36 no.4
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• pp.355-363
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• 2020

Bacterial traits for virulence of Ralstonia solanacearum causing lethal wilt in plants were extensively studied but are not yet fully understood. Other than the known virulence factors of Ralstonia solanacearum, this study aimed to identify the novel gene(s) contributing to bacterial virulence of R. solanacearum. Among the transposon-inserted mutants that were previously generated, we selected mutant SL341F12 strain produced exopolysaccharide equivalent to wild type strain but showed reduced virulence compared to wild type. In this mutant, a transposon was found to disrupt the murI gene encoding glutamate racemase which converts L-glutamate to D-glutamate. SL341F12 lost its motility, and its virulence in the tomato plant was markedly diminished compared to that of the wild type. The altered phenotypes of SL341F12 were restored by introducing a full-length murI gene. The expression of genes required for flagella assembly was significantly reduced in SL341F12 compared to that of the wild type or complemented strain, indicating that the loss of bacterial motility in the mutant was due to reduced flagella assembly. A dramatic reduction of the mutant population compared to its wild type was apparent in planta (i.e., root) than its wild type but not in soil and rhizosphere. This may contribute to the impaired virulence in the mutant strain. Accordingly, we concluded that murI in R. solanacearum may be involved in controlling flagella assembly and consequently, the mutation affects bacterial motility and virulence.

• The Plant Pathology Journal
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• v.32 no.3
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• pp.190-200
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• 2016

Xanthomonas oryzae pv. oryzae (Xoo) causes bacterial leaf blight (BLB) in rice (Oryza sativa L.). In this study, we investigated the effect of a mutation in opsX (XOO1056), which encodes a saccharide biosynthesis regulatory protein, on the virulence and bacterial chemotaxis of Xoo. We performed DNA micro-array analysis, which showed that 63 of 2,678 genes, including genes related to bacterial motility (flagellar and chemotaxis proteins) were significantly downregulated ($<\;-2\;log_2$ fold changes) by the mutation in opsX. Indeed, motility assays showed that the mutant strain was nonmotile on semisolid agar swarm plates. In addition, a mutant strain (opsX::Tn5) showed decreased virulence against the susceptible rice cultivar, IR24. Quantitative real-time RT-PCR reaction was performed to confirm the expression levels of these genes, including those related to flagella and chemotaxis, in the opsX mutant. Our findings revealed that mutation of opsX affects both virulence and bacterial motility. These results will help to improve our understanding of Xoo and provide insight into Xoo-rice interactions.

• KSBB Journal
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• v.13 no.4
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• pp.449-455
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• 1998

The bacterial motility in sand was studied with Alcaligenes xylosoxidans Y234 which is known as a strong decomposer of aromatic chemicals, especially toluene. Apparent motility coefficient (${\mu}$c,app) and apparent chemotaxis coefficient (${\mu}$c,app) for toluene were measured in the sands which have four different porosities. Adsorption ratio of Alcaligenes xylosoxidans Y234 on the sands was measured as 17%. The ramdom motility coefficients were 0.85∼1.68${\times}$10-3$\textrm{cm}^2$/sec, and decreased as the porosity of sands decreased. Apparent chemotaxis coefficients were measured as 1.1∼6.8${\times}$10-5$\textrm{cm}^2$/sec, and decreased as the porosity decreased and with time. The tendency of alcaligenes xylosoxidans Y234 movement towards toluene seemed very weak and showed little chemotaxis.

• Microbiology and Biotechnology Letters
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• v.30 no.3
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• pp.199-205
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• 2002

Gliding motility is defined as the movement of nonflagellated cells in the direction of its long axis on a solid surface and found in many phylogenetically diverse bacteria. Genetic, biochemical, ultrastructural, and behavioral studies have provided a wealth of information related to the mechanism of possible gliding apparatuses. Social motility of Myxococcus xanthus and the gliding of Synechocystis appear to rely on the function of type IV pili, similar to twitching motility of pseudomonas aeruginosa and Neisseria gonorrhoeae. In contrast, adventurous motility of M. xanthus and the gliding of filamentous cyanobacteria and Flavobacterium are not dependent on the pili. Instead, they appear to employ novel motility mechanisms that are currently being unveiled.

• Reproductive and Developmental Biology
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• v.37 no.4
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• pp.213-217
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• 2013

The objective of this study was to investigate the effect of bacterial contamination on elapsed time after preservation on boar semen. Known numbers of Escherichia coli (E. coli) were inoculated to freshly ejaculated semen and sperm parameters such as viability, motility, agglutination, acrosome integrity and hypo-osmotic swelling test were performed during 7 days of liquid preservation. Semen samples were prepared using antibiotic free BTS extender and 4 different levels of E. coli were treated to semen with following concentrations; 3,000, 5,000, 7,000, 10,000 CFU/ml of sperms. Semen samples were preserved at $17^{\circ}C$ for 7 days in semen storage until analyzed. Aliquots were subjected to measure the sperm viability, motility and agglutination using computer assisted sperm analysis (CASA) system, acrosome integrity was performed using chlortetracycline (CTC) staining method and hypo-osmotic swelling test was performed using hypotonic solution from day 1 (day of semen collection) to 7. Detrimental effects on sperm motility and viability were observed 3 days after preservation at the level of 5,000 CFU/ml (p<0.05). Percentage of sperm abnormality was higher (p<0.05) in over 5,000 CFU/ml groups. Sperm agglutination rate was also significantly higher (p<0.05) in groups of 5,000 and 7,000 CFU/ml. The rate of acrosome reacted sperm was higher as preservation time goes in all the samples but the pattern was clearly higher among E. coli contaminated groups (p<0.05). The sperm membrane integrity in terms of hypo-osmotic test, E. coli affects little compared to other sperm parameters. The deleterious effects observed due to the bacterial contamination in semen suggest that importance of hygiene protocol to minimize the bacterial contamination during semen collection and processing.

• Clinical and Experimental Reproductive Medicine
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• v.18 no.1
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• pp.95-99
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• 1991

Swim-up and Wang's tube system are known methods of motile sperm selection and aerobic bacterial removal from the raw semen. This study was designed to evaluate the recovery rate of motile sperm, % normal morphology of sperm, the efficiency of bacterial removal after sperm preparation by the above two methods. The results were as follows. 1. There was more significant increase of sperm concentration in preparation by swim-up than Wang's tube (p<0.05). The concentration of sperm by swim up was changed from $82.5{\times}10^6/ml$ to $6836{\times}10^6/ml$, and Wang's tube was changed from $82.5{\times}10^6/ml$ to $36.0{\times}10^6/ml$. 2. There was significant increase in sperm motility after preparation by two methods in comparison with initial sperm motility (p<0.05), but no statistical difference between two methods was noted. The % motility of sperm by swim-up was increased from 66.1% to 95.7% and Wang's tube from 66.1% to 98.1%. 3. There was significant increase of % normal morphology of sperm in the samples prepared by two methods (p<0.05), from 49.2% to 85.3% in swim-up and from 49.2% to 92.1% in Wang's tube, but there was no statistical significance between them. 4. There was no bacterial growth in aerobic culture after preparation by two methods.

• Korean Chemical Engineering Research
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• v.50 no.4
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• pp.743-748
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• 2012

This study presents the effects of micro-geometries on the swimming behavior of Pseudomonas aeruginosa. First, we have measured parameters of single-cell motility including cell speed, run duration time, and tumble angle under two dimensional space. The results are used to calculate motility coefficients in the width of microchannels ranging from 10 to $100{\mu}m$. Since the single-cell motility parameters measured depend on the interaction of flagella with the microchannel wall, the duration time of the running cell in restricted geometries is distinctively different. Therefore, the motility of bacteria is decreased by restricted geometries. This study suggests that microfluidic approach is useful tool for the analysis of bacterial motility under the restricted space and rapid analytical tool.

• Microbiology and Biotechnology Letters
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• v.48 no.2
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• pp.185-192
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• 2020

The global carbon storage regulator (Csr) system is conserved in bacteria and functions as a regulator in the exponential and stationary phases of growth in batch culture. The Csr system plays a role in the central carbon metabolism, virulence, motility, resistance to oxidative stress, and biofilm formation. Although the Csr was extensively studied in Gram negative bacteria, it has been reported only in the control of motility in Bacillus subtilis among Gram positive bacteria. The goal of this study was to explore the role of the csrA gene of Bacillus licheniformis M2-7 on motility and the bacterial ability to use hydrocarbons as carbon source. We deleted the csrA gene of B. licheniformis M2-7 using the plasmid pCsr-L, harboring the spectinomycin cassette obtained from the plasmid pHP45-omega2. Mutants were grown on culture medium supplemented with 2% glucose or 0.1% gasoline and motility was assessed by electron microscopy. We observed that CsrA negatively regulates motility by controlling the expression of the hag gene and the synthesis of flagellin. Notably, we showed the ability of B. licheniformis to use gasoline as a unique carbon source. Our results demonstrated that CsrA is an indispensable regulator for the growth of B. licheniformis M2-7 on gasoline.

• Journal of Microbiology and Biotechnology
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• v.25 no.8
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• pp.1390-1400
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• 2015

Quorum sensing is a process of cell-to-cell communication in which bacteria produce autoinducers as signaling molecules to sense cell density and coordinate gene expression. In the present study, a LuxI-type synthase, AnoI, and a LuxR-type regulator, AnoR, were identified in Acinetobacter nosocomialis, an important nosocomial pathogen, by sequence analysis of the bacterial genome. We found that N-(3-hydroxy-dodecanoyl)- _L -homoserine lactone (OH-dDHL) is a quorum-sensing signal in A. nosocomialis. The anoI gene deletion was responsible for the impairment in the production of OH-dDHL. The expression of anoI was almost abolished in the anoR mutant. These results indicate that AnoI is essential for the production of OH-dDHL in A. nosocomialis, and its expression is positively regulated by AnoR. Moreover, the anoR mutant exhibited deficiency in biofilm formation. In particular, motility of the anoR mutant was consistently and significantly abolished compared with that of the wild type. The deficiency in the biofilm formation and motility of the anoR mutant was significantly restored by a functional anoR, indicating that AnoR plays important roles in the biofilm formation and motility. Furthermore, the present study showed that virstatin exerts its effects on the reduction of biofilm formation and motility by inhibiting the expression of anoR. Consequently, the combined results suggest that AnoIR is a quorum-sensing system that plays important roles in the biofilm formation and motility of A. nosocomialis, and virstatin is an inhibitor of the expression of anoR.

• Journal of Microbiology and Biotechnology
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• v.28 no.5
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• pp.816-820
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• 2018

The stringent response (SR), which is activated by accumulation of (p)ppGpp under conditions of growth-inhibiting stresses, plays an important role on growth and virulence in Vibrio cholerae. Herein, we carried out a genome-wide screen using transposon random mutagenesis to identify genes controlled by SR in a (p)ppGpp-overproducing mutant strain. One of the identified SR target genes was flaC encoding flagellin. Genetic studies using flaC and SR mutants demonstrated that FlaC was involved in bacterial growth, toxin production, and normal flagellum function under conditions of high (p)ppGpp levels, suggesting FlaC plays an important role in SR-induced pathogenicity in V. cholerae.