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Frontiers in Microbiology 2022Rhizosphere colonizing plant growth promoting bacteria (PGPB) increase their competitiveness by producing diffusible toxic secondary metabolites, which inhibit...
Rhizosphere colonizing plant growth promoting bacteria (PGPB) increase their competitiveness by producing diffusible toxic secondary metabolites, which inhibit competitors and deter predators. Many PGPB also have one or more Type VI Secretion System (T6SS), for the delivery of weapons directly into prokaryotic and eukaryotic cells. Studied predominantly in human and plant pathogens as a virulence mechanism for the delivery of effector proteins, the function of T6SS for PGPB in the rhizosphere niche is poorly understood. We utilized a collection of 30-84 mutants deficient in one or both of its two T6SS and/or secondary metabolite production to examine the relative importance of each T6SS in rhizosphere competence, bacterial competition, and protection from bacterivores. A mutant deficient in both T6SS was less persistent than wild type in the rhizosphere. Both T6SS contributed to competitiveness against other PGPB or plant pathogenic strains not affected by secondary metabolite production, but only T6SS-2 was effective against strains lacking their own T6SS. Having at least one T6SS was also essential for protection from predation by several eukaryotic bacterivores. In contrast to diffusible weapons that may not be produced at low cell density, T6SS afford rhizobacteria an additional, more immediate line of defense against competitors and predators.
PubMed: 35464916
DOI: 10.3389/fmicb.2022.843092 -
Plant Disease Jun 2020infects most major greenhouse crops worldwide. With its increasing resistance to conventional fungicides and the movement of the greenhouse industry toward more...
infects most major greenhouse crops worldwide. With its increasing resistance to conventional fungicides and the movement of the greenhouse industry toward more sustainable production practices, alternative methods of control are needed. The objective of this study was to evaluate a collection of 60 bacterial strains through both a dual-culture assay and greenhouse trials to identify strains with biocontrol activity against . For the dual-culture assay, each bacterial strain was streaked on potato dextrose agar medium with . The growth reduction and the zone of inhibition were measured. Thirty-five strains reduced the growth of . All strains were also tested in an initial greenhouse trial in which 'Carpet Red Bright' was sprayed and drenched with the bacteria biweekly for 6 weeks. All open flowers were tagged, and plants were inoculated with (1 × 10 conidia per 1 ml). Disease severity indices calculated from the daily flower gray mold severity ratings of all tagged flowers were used to identify the seven top-performing strains. These seven strains were then evaluated in a greenhouse validation trial. The methods were similar to those of the initial greenhouse trials except that replicate numbers were increased. Three strains ( AP54, 14B11, and 89F1) were selected for the ability to reduce infection in a greenhouse production setting. These strains can be used in future studies to develop additional biocontrol products for the management of in floriculture crops.
Topics: Botrytis; Fungicides, Industrial; Petunia; Plant Diseases; Spores, Fungal
PubMed: 32289248
DOI: 10.1094/PDIS-10-19-2276-RE -
Polymers Nov 2023The use of biocidal agents is a common practice for protection against biofouling in biomass-rich environments. In this paper, oligohexamethyleneguanidine (OHMG)...
The use of biocidal agents is a common practice for protection against biofouling in biomass-rich environments. In this paper, oligohexamethyleneguanidine (OHMG) polymer, known for its biocidal properties, was further modified with para-aminosalicylic acid (PAS) to enhance its properties against microorganisms coated with a lipid membrane. The structure of the product was confirmed by H NMR, C NMR, and FTIR spectroscopy. The values of the minimum inhibitory concentration (MIC) against ATCC 607 and 449 were found to be 1.40 and 1.05 μg/mL, respectively. The synthesized substance was used as an additive to the polymer matrix of the composite optical oxygen sensor material. A series of samples with different contents of OHMG-PAS was prepared using a co-dissolution method implying the fabrication of a coating from a solution containing both polymers. It turned out that the mutual influence of the components significantly affects the distribution of the indicator in the matrix, surface morphology, and contact angle. The optimal polymer content turned out to be wt.3%, at which point the water contact angle reaches almost 122°, and the fouling rate decreases by almost five times, which is confirmed by both the respiratory MTT assay and confocal microscopy with staining. This opens up prospects for creating stable and biofouling-resistant sensor elements for use in air tanks or seawater.
PubMed: 38231936
DOI: 10.3390/polym15234508 -
Microorganisms Jul 2020Plants face many biotic and abiotic challenges in nature; one of them is attack by disease-causing microbes. , the causal agent of late blight is one of the most...
Plants face many biotic and abiotic challenges in nature; one of them is attack by disease-causing microbes. , the causal agent of late blight is one of the most prominent pathogens of the potato responsible for multi-billion-dollar losses every year. We have previously reported that potato-associated strains inhibited at various developmental stages. A comparative genomics approach identified several factors putatively involved in this anti-oomycete activity, among which was the production of hydrogen cyanide (HCN). Here, we report the relative contribution of HCN emission to the overall anti- activity of two cyanogenic strains, R32 and R47. To quantify this contribution, we generated HCN-negative mutants (Δhcn) and compared their activities to those of their respective wild types in different experiments assessing mycelial growth, zoospore germination, and infection of potato leaf disks. Using in vitro experiments allowing only volatile-mediated interactions, we observed that HCN accounted for most of the mycelial growth inhibition (57% in R47 and 80% in R32). However, when allowing both volatile and diffusible compound-mediated interactions, HCN only accounted for 1% (R47) and 18% (R32) of mycelial growth inhibition. Likewise, both mutants inhibited zoospore germination in a similar way as their respective wild types. More importantly, leaf disk experiments showed that both wild-type and Δhcn strains of R47 and R32 were able to limit infection to a similar extent. Our results suggest that while HCN is a major contributor to the in vitro volatile-mediated restriction of mycelial growth, it does not play a major role in the inhibition of other disease-related features such as zoospore germination or infection of plant tissues.
PubMed: 32731625
DOI: 10.3390/microorganisms8081144 -
Microbial Ecology Oct 2023Combining different biocontrol agents (BCA) is an approach to increase efficacy and reliability of biological control. If several BCA are applied together, they have to...
Combining different biocontrol agents (BCA) is an approach to increase efficacy and reliability of biological control. If several BCA are applied together, they have to be compatible and ideally work together. We studied the interaction of a previously selected BCA consortium of entomopathogenic pseudomonads (Pseudomonas chlororaphis), nematodes (Steinernema feltiae associated with Xenorhabdus bovienii), and fungi (Metarhizium brunneum). We monitored the infection course in a leaf- (Pieris brassicae) and a root-feeding (Diabrotica balteata) pest insect after simultaneous application of the three BCA as well as their interactions inside the larvae in a laboratory setting. The triple combination caused the highest mortality and increased killing speed compared to single applications against both pests. Improved efficacy against P. brassicae was mainly caused by the pseudomonad-nematode combination, whereas the nematode-fungus combination accelerated killing of D. balteata. Co-monitoring of the three BCA and the nematode-associated Xenorhabdus symbionts revealed that the four organisms are able to co-infect the same larva. However, with advancing decay of the cadaver there is increasing competition and cadaver colonization is clearly dominated by the pseudomonads, which are known for their high competitivity in the plant rhizosphere. Altogether, the combination of the three BCA increased killing efficacy against a Coleopteran and a Lepidopteran pest which indicates that this consortium could be applied successfully against a variety of insect pests.
Topics: Animals; Reproducibility of Results; Pest Control, Biological; Insecta; Larva; Rhabditida; Plant Leaves
PubMed: 36849610
DOI: 10.1007/s00248-023-02191-0 -
Infection, Genetics and Evolution :... Dec 2021We report the isolation and genomic characterization of a VIM-2 producing Pseudomonas chlororaphis causing bloodstream infection in a newborn in Brazil. A new integron,...
We report the isolation and genomic characterization of a VIM-2 producing Pseudomonas chlororaphis causing bloodstream infection in a newborn in Brazil. A new integron, In2088 (intI1-bla-aacA7-aacA27-gcu241), was identified and the first P. chlororaphis genome from a clinical isolate was deposited in public databases.
Topics: Brazil; Humans; Infant, Newborn; Integrons; Pseudomonas Infections; Pseudomonas chlororaphis; Sepsis; beta-Lactamases
PubMed: 34619390
DOI: 10.1016/j.meegid.2021.105104 -
BMC Plant Biology Feb 2024Crown gall disease caused by Agrobacterium tumefaciens is a very destructive affliction that affects grapevines. Endophytic bacteria have been discovered to control...
Antivirulence effects of cell-free culture supernatant of endophytic bacteria against grapevine crown gall agent, Agrobacterium tumefaciens, and induction of defense responses in plantlets via intact bacterial cells.
BACKGROUND
Crown gall disease caused by Agrobacterium tumefaciens is a very destructive affliction that affects grapevines. Endophytic bacteria have been discovered to control plant diseases via the use of several mechanisms. This research examined the potential for controlling crown gall by three endophytic bacteria that were previously isolated from healthy cultivated and wild grapevines including Pseudomonas kilonensis Ba35, Pseudomonas chlororaphis Ba47, and Serratia liquefaciens Ou55.
RESULT
At various degrees, three endophytic bacteria suppressed the populations of A. tumefaciens Gh1 and greatly decreased the symptoms of crown gall. Furthermore, biofilm production and motility behaviors of A. tumefaciens Gh1were greatly inhibited by the Cell-free Culture Supernatant (CFCS) of endophytic bacteria. According to our findings, CFCS may reduce the adhesion of A. tumefaciens Gh1 cells to grapevine cv. Rashe root tissues as well as their chemotaxis motility toward the extract of the roots. When compared to the untreated control, statistical analysis showed that CFCS significantly reduced the swimming, twitching, and swarming motility of A. tumefaciens Gh1. The findings demonstrated that the endophytic bacteria effectively stimulated the production of plant defensive enzymes including superoxide dismutase (SOD), polyphenol oxidase (PPO), peroxidase (POD), phenylalanine ammonia lyase (PAL), and total soluble phenols at different time intervals in grapevine inoculated with A. tumefaciens Gh1. The Ba47 strain markedly increased the expression levels of defense genes associated with plant resistance. The up-regulation of PR1, PR2, VvACO1, and GAD1 genes in grapevine leaves indicates the activation of SA and JA pathways, which play a role in enhancing resistance to pathogen invasion. The results showed that treating grapevine with Ba47 increased antioxidant defense activities and defense-related gene expression, which reduced oxidative damage caused by A. tumefaciens and decreased the incidence of crown gall disease.
CONCLUSION
This is the first study on how A. tumefaciens, the grapevine crown gall agent, is affected by CFCS generated by endophytic bacteria in terms of growth and virulence features. To create safer plant disease management techniques, knowledge of the biocontrol processes mediated by CFCS during microbial interactions is crucial.
Topics: Plant Tumors; Agrobacterium tumefaciens; Plant Diseases; Bacteria
PubMed: 38336608
DOI: 10.1186/s12870-024-04779-1 -
International Journal of Molecular... Jan 2020The mechanisms of action of the complex including entomopathogenic nematodes of the genera and and their mutualistic partners, i.e., bacteria and , have been well...
Bacteria from the Midgut of Common Cockchafer ( L.) Larvae Exhibiting Antagonistic Activity Against Bacterial Symbionts of Entomopathogenic Nematodes: Isolation and Molecular Identification.
The mechanisms of action of the complex including entomopathogenic nematodes of the genera and and their mutualistic partners, i.e., bacteria and , have been well explained, and the nematodes have been commercialized as biological control agents against many soil insect pests. However, little is known regarding the nature of the relationships between these bacteria and the gut microbiota of infected insects. In the present study, 900 bacterial isolates that were obtained from the midgut samples of larvae were screened for their antagonistic activity against the selected species of the genera and . Twelve strains exhibited significant antibacterial activity in the applied tests. They were identified based on 16S rRNA and , , or gene sequences as , , , , sp., , and sp. The culture filtrate of the isolate MMC3 L3 04 exerted the strongest inhibitory effect on the tested bacteria. The results of the preliminary study that are presented here, which focused on interactions between the insect gut microbiota and mutualistic bacteria of entomopathogenic nematodes, show that bacteria inhabiting the gut of insects might play a key role in insect resistance to entomopathogenic nematode pressure.
Topics: Acinetobacter calcoaceticus; Animals; Chryseobacterium; Citrobacter; Gastrointestinal Microbiome; Larva; Photorhabdus; Pseudomonas chlororaphis; RNA, Ribosomal, 16S; Serratia liquefaciens; Symbiosis; Xenorhabdus
PubMed: 31963214
DOI: 10.3390/ijms21020580 -
The Plant Pathology Journal Aug 2019In our previous study, pyrrolnitrin produced in G05 plays more critical role in suppression of mycelial growth of some fungal pathogens that cause plant diseases in...
In our previous study, pyrrolnitrin produced in G05 plays more critical role in suppression of mycelial growth of some fungal pathogens that cause plant diseases in agriculture. Although some regulators for pyrrolnitrin biosynthesis were identified, the pyrrolnitrin regulation pathway was not fully constructed. During our screening novel regulator candidates, we obtained a white conjugant G05W02 while transposon mutagenesis was carried out between a fusion mutant G05ΔΔ:: and S17-1 (pUT/mini-Tn5Kan). By cloning and sequencing of the transposon-flanking DNA fragment, we found that a gene in the conjugant G05W02 was disrupted with mini-Tn5Kan. In one other previous study on , however, it was reported that the deletion of the caused increased production of pyrrolnitrin and other antifungal metabolites. To confirm its regulatory function, we constructed the -knockout mutant G05Δ and G05ΔΔ::Δ. By quantifying β-galactosidase activities, we found that deletion of the decreased the operon expression dramatically. Meanwhile, by quantifying pyrrolnitrin production in the mutant G05Δ, we found that deficiency of the Vfr caused decreased pyrrolnitrin production. However, production of phenazine-1-carboxylic acid was same to that in the wild-type strain G05. Taken together, Vfr is required for pyrrolnitrin but not for phenazine-1-carboxylic acid biosynthesis in G05.
PubMed: 31481858
DOI: 10.5423/PPJ.OA.01.2019.0011 -
Heliyon Feb 2024This study aimed to isolate and characterize plant growth-promoting rhizobacteria from the faba bean rhizosphere for future inoculum production. For this purpose,127...
This study aimed to isolate and characterize plant growth-promoting rhizobacteria from the faba bean rhizosphere for future inoculum production. For this purpose,127 dissimilar rhizobacterial colonies were isolated. All isolated colonies were tested for plant growth-promoting traits. Based on their multiple plant growth-promoting traits, eight potential isolates were selected and identified GY01, GY03, and GY08 are affiliated with Acinetobacter sp. GY04 and GY05 are affiliated with Chryseobacterium sp. GY06 and GY07 are affiliated with Pseudomonas costantinii and Pseudomonas chlororaphis, respectively; and GY02 is affiliated with the Bacterium strain. All eight isolates were evaluated for their effects on seed germination and vigor index and potential antagonism against Botrytis fabae. Selected isolates showed positive effects on seed germination and vigor index with different potentials. Isolate GY04 resulted in the highest vigor index (501), while isolate GY08 achieved the lowest (218). B. fabae radial growth inhibition was found in all eight isolates. The isolates inhibited the radial growth of the test pathogen with an inhibition efficacy of 72.38 % in GY04 to 25.57 % in GY-03. Generally, the results of this study indicated the potential of these isolates as a microbial inoculant with multiple functions for faba beans.
PubMed: 38318010
DOI: 10.1016/j.heliyon.2024.e25334