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At least 19 recordsLinked to original sources
PubMed2026

Microdroplet-based high-throughput screening for antagonistic bacteria targeting penaeid shrimp pathogenic Vibrio harveyi.

Antagonistic bacteria that suppress the growth of specific bacteria have attracted attention as an antibiotics-independent strategy for infectious disease control in aquaculture. Microfluidics-based water-in-oil droplets (microdroplets) enable high-throughput screening of antagonistic bacteria in the field of medicine or agriculture. However, the use of this screening system in aquaculture has not yet been reported. In particular, penaeid shrimp aquaculture, one of the largest sectors of global aquaculture, has a strong demand for alternative disease control strategies because vaccination is ineffective. Here, we demonstrated a proof-of-concept study of microdroplet-based high-throughput screening system for antagonistic bacteria targeting penaeid shrimp pathogenic Vibrio harveyi. Using this screening system, we successfully isolated 18 bacterial candidates with potential growth-inhibitory activity, representing three genera (Pseudoalteromonas, Shewanella, and Tenacibaculum), from the bacterial community of kuruma shrimp Penaeus japonicus rearing water. 16S rRNA gene-based bacterial community analysis revealed that these isolates included several low-abundance, rare taxa. Although these isolates showed no inhibitory activity on agar plates, one out of four tested strains showed a trend toward improved survival during co-infection tests using kuruma shrimp. Overall, our study highlights both the potential and limitation of microdroplet-based antagonistic bacterial screening to accelerate the development of biological control strategies in shrimp aquaculture.

Animals↗
PubMed2004

Biological control of chickpea Fusarium wilt by antagonistic bacteria under greenhouse condition.

In this survey, Fusarium oxysporum was isolated from roots infected plants and was shown to be pathogenic. Experiment were carried out with seven antagonistic bacteria. Based on biochemical, Physiological and morphological tests, isolates B-120, B-32, B-28 and B-22 were identified as Bacillus subtilis and isolates Pf-100, Pf-10 and CHAO as Pseudomonas fluorescens. In greenhouse studies, only isolate B-120 (Less than benomyl) reduced Fusarium wilt of chickpea in both seed and soil treatments. The application of antagonistic bacteria had no different effects on plant growth factors. Soil treatment of bacteria had a better effects on plant growth than that of bacterial seed treatment. The use of antagonists (B-120, B-28, B-120 and CHAO) in combination had no significant effect on plant growth factors and reduction wilt disease than that each isolate was applied individually.

Bacillus subtilis↗
PubMed2004

Strategy to select and assess antagonistic bacteria for biological control of Rhizoctonia solani Kühn.

A screening strategy was developed to assess the potential of plant-associated bacteria to control diseases caused by Rhizoctonia solani Kühn. About 434 already characterized antagonistic bacterial strains isolated from diverse plant species and microenvironments were evaluated for biocontrol and plant growth promotion by a hierarchical combination of assays. Analyzing in vitro antagonism towards different Rhizoctonia isolates resulted in a selection of 20 potential biocontrol agents. The strains were characterized by their antagonistic mechanisms in vitro as well as their production of the plant growth hormone indole-3-acetic acid. The plant growth promoting effect by antagonistic bacteria was determined using a microtiter plate assay on the basis of lettuce seedlings. Lettuce and sugar beet as host plant were included in the biocontrol experiments in which the antagonistic effect of 17 bacterial isolates could be confirmed in vivo. Sequencing of the 16S rDNA gene and (or) fatty acid methyl ester gas chromatography was used to identify the antagonistic isolates. Molecular fingerprints of isolates obtained by BOX-polymerase chain reaction were compared to avoid further investigation with genetically very similar strains and to obtain unique molecular fingerprints for quality control and patent licensing. According to our strategy, an assessment scheme was developed and four interesting biological control agents, Pseudomonas reactans B3, Pseudomonas fluorescens B1, Serratia plymuthica B4, and Serratia odorifera B6, were found. While S. plymuthica B4 was the best candidate to biologically control Rhizoctonia in lettuce, P. reactans B3 was the best candidate to suppress the pathogen in sugar beet.

Antibiosis↗
PubMed2003

Isolation and evaluation of antagonistic bacteria towards the cucurbit powdery mildew fungus Podosphaera fusca.

Powdery mildew is one of the most important limiting factors for cucurbits production in Spain, its management being strongly dependent on chemicals. The aim of this work was to evaluate the possibility of exploiting antagonistic bacteria in the biological control of the cucurbit powdery mildew fungus Podosphaera fusca (syn. Sphaerotheca fusca). Among a collection of bacterial strains isolated from distinct cucurbit powdery mildew diseased plants and rhizospheric soils, four isolates were selected, by means of a screening method based on antibiotic production, and identified as Bacillus spp. These isolates proved to be efficacious in the control of cucurbit powdery mildew in in vitro detached leaves and seedling biocontrol assays, where reductions of disease severity of up to 80% were obtained. Furthermore, bacterial populations on melon leaves remained at similar levels (10(5) cfu cm(-2)) over the 16-day period studied and, as observed by scanning electron microscopy analysis, they were able to establish microcolonies associated with an extracellular matrix, which reveals that these isolates efficiently colonize melon phylloplane. These results indicate that the bacterial isolates selected are promising candidates for biological control agents of cucurbit powdery mildew in southern Spain.

Antibiosis↗
PubMed1993

[Influence of antagonistic bacteria on quantity of staphylococci in the oral cavity].

The study was aimed at establishment whether antagonistic influence between physiological oral cavity bacterial flora and staphylococci do exist and whether they influence on quantity of staphylococci in oral cavity environment. In samples of saliva taken from group of 11-13 year old children and a group of adults of both sexes, determinations were performed regarding total number of bacteria, number and percentage of bacteria inhibiting in vitro growth of standard indicator strain Staphylococcus aureus Oxford 209P and total number and percentage of staphylococci (together coagulase-positive and/or coagulase-negative). It was found that in each saliva sample bacteria inhibiting the indicator strain are present and their mean percentage is significantly higher in children than in adults and amounts respectively 47.1 +/- 28.5 and 35.0 +/- 20.3 (p = 0.0316). Higher percentage of antagonistic bacteria in children is associated with lower percentage of staphylococci in bacterial flora of saliva. Statistical analysis has confirmed existence of negative correlation, both linear and ranking, between the number of antagonistic bacteria and percentage of staphylococci in the saliva. This correlation is more strongly expressed and significant in children than in adults and linear correlation coefficient of Pearson amounts respectively to r = 0.7521 (p < 0.0005) and r = 0.3325 (p < 0.05). These results indicate that antagonistic bacterial flora is a significant factor limiting quantity of staphylococcal population in human oral cavity, especially in children.

Adolescent↗
PubMed2005

[Population fluctuation of main pathogens and their antagonistic bacteria in cucumber rhizosphere].

The investigation on the population fluctuation of main pathogens Pythium spp. and Fusarium oxysporum f. cucumerinum in the rhizosphere of four cucumber varieties showed that there was a significant difference in population number of pathogens for different cucumber varieties and for different growth stages of the same variety, which was in accordance with the regular disease incidence pattern. The population number of Pythium spp. was significantly higher at cucumber creeping stage than at its other growth stages, while that of Fusarium oxysporum f. sp. cucumerinum was the highest at cucumber principal-fruiting stage. There was a closer positive relationship between two test pathogens and their antagonistic bacteria, with the correlation coefficient being 0.95 and 0.81, respectively.

Antibiosis↗
PubMed2006

The rhizosphere effect on bacteria antagonistic towards the pathogenic fungus Verticillium differs depending on plant species and site.

Rhizobacteria with antagonistic activity towards plant pathogens play an essential role in root growth and plant health and are influenced by plant species in their abundance and composition. To determine the extent of the effect of the plant species and of the site on the abundance and composition of bacteria with antagonistic activity towards Verticillium dahliae, bacteria isolated from the rhizosphere of two Verticillium host plants, oilseed rape and strawberry, and from bulk soil were analysed at three different locations in Germany over two growing seasons. A total of 6732 bacterial isolates screened for in vitro antagonism towards Verticillium resulted in 560 active isolates, among which Pseudomonas (77%) and Serratia (6%) were the most dominant genera. The rhizosphere effect on the antagonistic bacterial community was shown by an enhanced proportion of antagonistic isolates, by enrichment of specific amplified ribosomal DNA restriction analysis types, species and genotypes, and by a reduced diversity in the rhizosphere in comparison to bulk soil. Such an effect was influenced by the plant species and by the site of its cultivation. Altogether, 16S rRNA gene sequencing of 66 isolates resulted in the identification of 22 different species. Antagonists of the genus Serratia were preferentially isolated from oilseed rape rhizosphere, with the exception of one site. For isolates of Pseudomonas and Serratia, plant-specific and site-specific genotypes were found.

Antibiosis↗
PubMed1992

On-line visualization of the competitive behavior of antagonistic bacteria.

To study the interaction between cocultured Listeria monocytogenes and an antagonistic Leuconostoc strain producing an anti-Listeria bacteriocin, flow cytometry, a technique allowing on-line and real-time analysis, was used along with classical microbiological methods. Culture methods and flow cytometric measurements of the mixed culture over time point to a bactericidal action of the lactic acid-producing bacterial strain against L. monocytogenes cells.

Bacteriocins↗
PubMed2000

Establishment of introduced antagonistic bacteria in the rhizosphere of transgenic potatoes and their effect on the bacterial community.

In a field release experiment, rifampicin resistant mutants of two antagonistic plant-associated bacteria were used for seed tuber inoculation of transgenic T4 lysozyme expressing potatoes, transgenic control potatoes and non-transgenic parental potatoes. The T4 lysozyme tolerant Pseudomonas putida QC14-3-8 was originally isolated from the tuber surface (geocaulosphere) of T4 lysozyme producing plants and showed in vitro antibacterial activity to the bacterial pathogen Erwinia carotovora ssp. atroseptica. The T4 lysozyme sensitive Serratia grimesii L16-3-3 was originally isolated from the rhizosphere of parental potatoes and showed in vitro antagonism toward the plant pathogenic fungus Verticillium dahliae. The establishment of the inoculated bacteria in the rhizosphere and geocaulosphere of the different plant lines was monitored over one growing season to assess the effect of T4 lysozyme produced by transgenic potato plants on the survival of both inoculants. Both introduced isolates were able to colonize the rhizo- and geocaulosphere of transgenic plants and non-transgenic parental plants, and established in the rhizosphere at levels of ca. log(10) 5 colony forming units g(-1) fresh weight of root. During flowering of plants, significantly more colony counts of the T4 lysozyme tolerant P. putida were recovered from transgenic T4 lysozyme plants than from the transgenic control and the parental line. At this time, the highest level of T4 lysozyme (% of total soluble protein) was detected. Effects of the inoculants on the indigenous microbial community were monitored by analysis of PCR-amplified fragments of the 16S rRNA genes of the whole bacterial community after separation by denaturing gradient gel electrophoresis (DGGE). At any sampling time, the DGGE pattern of rhizosphere and geocaulosphere communities did not show differences between the inoculated and non-inoculated potatoes. Neither of the introduced strains became a dominant member of the bacterial community. This work was the first approach to assess the establishment of plant growth promoting rhizobacteria and potential biocontrol agents on transgenic plants.

Journal Article↗
PubMed2003

Screening of antagonistic bacteria for biological control of nursery wilt of black pepper (Piper nigrum).

Bacterial antagonists of Phytophthora capsici were isolated from underground shoot portions of rooted cuttings of black pepper. Initially isolates were screened by dual culture on potato dextrose agar and carrot agar. Further, a screening was done on black pepper shoots for supression of lesion caused by the pathogen. Most of the antagonists showed varying levels of antagonism in the dual culture and the shoot assay. Isolate PN-026, showing the highest suppression of lesion development in the shoot assay was found to be the most efficient antagonist in reducing Phytophthora capsici induced nursery wilt of black pepper. This screening involving the host, pathogen, and the antagonist, performed on black pepper shoot (the planting material for this vegetatively propagated crop), could be used as a rapid and reliable method for the isolation of efficient bacterial antagonists of P. capsici.

Antibiosis↗
PubMedDate not supplied

Diversity of Gram negative bacteria antagonistic against major pathogens of rice from rice seed in the tropic environment.

With the use of a seed washing technique, more than 4000 Gram negative bacteria were isolated by two improved isolation methods from 446 batches of 1 kg rice seed samples obtained from 22 provinces in the Philippines. They were initially characterized on the basis of colony morphology and results of biochemical and pathogenicity tests. Six hundred and fifty-two strains were further identified by Biolog, from which 133 were selected for fatty acid methylester (FAME) analysis together with 80 standard reference strains. Sixteen species or types of Pseudomonas and 17 genera of non-pseudomonads were identified, more than one third of which have not been recorded in rice. The most predominant species observed were P.putida and P. fulva. About 17% of the strains of Pseudomonas and 2% of the non pseudomonads were antagonistic to one or more fungal or bacterial pathogens of rice. Rice seed is an important source of biological control agents.

Antibiosis↗
PubMed1987

Intestinal bacteria antagonistic to Clostridium difficile in mice.

Overgrowth by Clostridium difficile has been reported in conventional mice injected intraperitoneally with ampicillin. In this study, we aimed to determine which types of indigenous intestinal bacteria were eliminated by ampicillin to allow overgrowth by C. difficile. C. difficile overgrowth was associated with a decrease in the numbers of lactobacilli, an increase in bacteroidaceae and a slight decrease in the frequency of isolation of fusiform-shaped bacteria (clostridia). C. difficile cytotoxin was detected in caeca from mice in which the numbers of C. difficile were greater than 10(5) per gram of faeces. Gnotobiotic mice were inoculated with various groups of intestinal anaerobes to determine which members of the indigenous flora would antagonize C. difficile. Gnotobiotic mice inoculated with three strains of lactobacilli, 37 strains of bacteroides or 46 strains of clostridia isolated from limited-flora mice were unable to eliminate C. difficile. C. difficile was eliminated, however, from the gastrointestinal tracts of gnotobiotic mice inoculated with whole faeces or chloroform-treated faeces from conventional mice or whole faeces from limited-flora mice containing only clostridia.

Ampicillin↗
PubMed2003

Biological control of Fusarium oxysporum, the causal agent of onion wilt by antagonistic bacteria.

Fusarium wilt caused by Fusarium oxysporum Sch. is one of the most important diseases of onion in Iran. Application of chemicals especially as soil drench, increased cost of onion production and may be dangerous for environment. One of the effective techniques to suppress soil-born diseases in biological control with antagonistic rhizobacteria. Experiment were carried out with 120 bacterial isolates that were collected from onion rhizosphere. Six highly effective isolates were selected from these antagonists for subsequent studies. These strains were used to investigate their biocontrol traits in vitro and their ability to suppress the onion wilt in vivo (soil and seed treatments). According to the biochemical, physiological and morphological test, the isolates 22, 38, 46 and 52 were identified as Bacillus spp. The isolates 16 and 48 were identified as Pseudomonas fluorescens. The isolates of Bacillus spp. produced volatile metabolites that inhibited mycelia growth of Fusarium oxysporum. In soil treatment, the isolates 22 and 52 with 56% and 51% had the highest effect in reducing the Fusarium wilt of onion. The mixture of two isolates reduced 60% the disease. In seed treatment the isolate 22 with 41% had the greatest effect on reducing the onion Fusarium wilt.

Antibiosis↗
PubMed2006

Survival of gfp-tagged antagonistic bacteria in the rhizosphere of tomato plants and their effects on the indigenous bacterial community.

The survival and colonization patterns of Pseudomonas putida PRD16 and Enterobacter cowanii PRF116 in the rhizosphere of greenhouse-grown tomato plants and the effects of their inoculation on the indigenous bacterial community were followed by selective plating, molecular fingerprinting, and confocal laser scanning microscopy (CLSM) over 3 weeks. Both strains, which showed in vitro antagonistic activity against Ralstonia solanacearum, were previously tagged with gfp. Seed and root inoculation were compared. Although plate counts decreased for both gfp-tagged antagonists, PRD16 showed a better survival in the rhizosphere of tomato roots independent of the inoculation method. Analysis of 16S rRNA gene fragments amplified from total community DNA by denaturing gradient gel electrophoresis and CLSM confirmed the decrease in the relative abundance of the inoculant strains. Pronounced differences in the Pseudomonas community patterns for plants inoculated with PRD16 compared to the control were detected 3 weeks after root inoculation, indicating a longer-lasting effect. Analysis by CLSM showed rather heterogeneous colonization patterns for both inoculant strains. In comparison with seed inoculation, root inoculation led to a much better colonization as evidenced by all three methods. The colonization patterns observed by CLSM provide important information on the sampling strategy required for monitoring inoculant strains in the rhizosphere.

Antibiosis↗