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Heliyon Nov 2022The application of soil beneficial bacteria (SBB) in agriculture is steadily increasing as it provides a promising way to replace chemical fertilisers and other...
The application of soil beneficial bacteria (SBB) in agriculture is steadily increasing as it provides a promising way to replace chemical fertilisers and other supplements. Although the role of SBB as a biofertiliser is well understood, little is known about the response of soil physiochemical properties via the change in soil enzymatic activities with SBB growth. In this study, sterilised bulk soil was inoculated with (BS) and (PF), which exhibit excellent characteristics for potentially improving soil quality. It is found that the contents of bioavailable nitrogen and ammonium in soil inoculated with SBB increased significantly, up to 34% and 57% relative to a control. This resulted from the enhancement of soil urease activity with BS and PF treatments by approximately 90% and 70%, respectively. The increased soil urease activity can be explained by the increased microorganism activity evident from the larger population size of BS (0.78-0.97 CFU mL/CFU mL) than PF (0.55-0.79 CFU mL/CFU mL) ( < 0.05). Results of principal component analysis also reinforce the interaction apparent in the significant relationship between soil urease activity and microbial biomass carbon ( < 0.05). Therefore, it can be concluded that the enhancement of soil enzymatic activities induced bulk soil fertility upregulation because of bacterial growth. These results demonstrate the application of SBB to be a promising strategy for bulk soil amendment, particularly nutrient restoration.
PubMed: 36439778
DOI: 10.1016/j.heliyon.2022.e11674 -
Frontiers in Microbiology 2021In this study, linalool, one of the principal components of essential oils, was used as an antibacterial agent to investigate the antibacterial activity and mechanism of...
In this study, linalool, one of the principal components of essential oils, was used as an antibacterial agent to investigate the antibacterial activity and mechanism of linalool against The reduction in membrane potential (MP), leakage of alkaline phosphatase (AKP) and the release of macromolecules, including DNA, RNA and protein confirmed that damage to cell wall membrane structure and leakage of cytoplasmic contents were due to the linalool treatment. Furthermore, the decrease of enzyme activity, including the succinate dehydrogenase (SDH), malate dehydrogenase (MDH), pyruvate kinase (PK), and ATPase indicated that linalool could lead to metabolic dysfunction and inhibit energy synthesis. In addition, the activity of respiratory chain dehydrogenase and metabolic activity of respiration indicated that linalool inhibits cellular respiration. These results revealed that linalool had strong antibacterial activity against via membrane damage, bacterial metabolic and oxidative respiratory perturbations, interfering in cellular functions and even causing cell death. It was suggested that linalool may be a new potential source as food antiseptics in food systems.
PubMed: 33584604
DOI: 10.3389/fmicb.2021.562094 -
Frontiers in Cellular and Infection... 2022Antagonistic coevolution between hosts and parasites, the reciprocal evolution of host resistance and parasite infectivity, has important implications in ecology and...
Antagonistic coevolution between hosts and parasites, the reciprocal evolution of host resistance and parasite infectivity, has important implications in ecology and evolution. The dynamics of coevolution-notably whether host or parasite has an evolutionary advantage-is greatly affected by the relative amount of genetic variation in host resistance and parasite infectivity traits. While studies have manipulated genetic diversity during coevolution, such as by increasing mutation rates, it is unclear how starting genetic diversity affects host-parasite coevolution. Here, we (co)evolved the bacterium SBW25 and two bacteriophage genotypes of its lytic phage SBW25ɸ2 in isolation (one phage genotype) and together (two phage genotypes). Bacterial populations rapidly evolved phage resistance, and phage reciprocally increased their infectivity in response. When phage populations were evolved with bacteria in isolation, bacterial resistance and phage infectivity increased through time, indicative of arms-race coevolution. In contrast, when both phage genotypes were together, bacteria did not increase their resistance in response to increasing phage infectivity. This was likely due to bacteria being unable to evolve resistance to both phage the same mutations. These results suggest that increasing initial parasite genotypic diversity can give parasites an evolutionary advantage that arrests long-term coevolution. This study has important implications for the applied use of phage in phage therapy and in understanding host-parasite dynamics in broader ecological and evolutionary theory.
Topics: Bacteriophages; Biological Evolution; Genotype; Host-Parasite Interactions; Pseudomonas Phages; Pseudomonas fluorescens
PubMed: 35310856
DOI: 10.3389/fcimb.2022.834406 -
3 Biotech Jun 2022Maize ( L.) is a major cereal crop grown in a large number of countries. Loss in maize yield due to biotic stresses including fungal phytopathogens is a matter of...
UNLABELLED
Maize ( L.) is a major cereal crop grown in a large number of countries. Loss in maize yield due to biotic stresses including fungal phytopathogens is a matter of immense concern. Control measures applied for eradication of fungal phytopathogens in maize are not up to the mark and more often involve harsh chemical(s)/pesticide(s) that cause deleterious effects both in humans and soil biota. Greener alternatives, such as the use of rhizosphere microbes in the form of bioinoculants, have proven to be very successful in terms of enhancing crop yield and suppressing fungal phytopathogens. In the present study, fluorescent pseudomonads were isolated from the maize rhizosphere and monitored for their plant growth-promoting (PGP) and biocontrol activities against . Based on various PGP traits and biocontrol potential, isolate JM-1 was found to be most effective and as per 16S rRNA gene sequencing analysis was identified as . Further experiments showed that the biocontrol potential of JM-1 against ear rot fungus involved the production of antifungal compound 2,4-diacetylphloroglucinol (DAPG). When examined for antagonistic interaction under scanning electron microscopy (SEM), structural abnormality, hyphal lysis, and deformity in fungal mycelium were observed. In the pot experiment, application of talc-based JM-1 containing bioformulation (in pot trials) showed significant enhancement in maize growth parameters (including the seed number and weight) in comparison to control even in presence of the phytopathogen. Ear fresh weight, dry weight, number of seeds per plant, and 100-grain weight were found to increase significantly by 34, 34, 52, and 18% respectively, in comparison to control. JM-1 can therefore be used as a bioinoculant for ear rot disease control and sustainably enhancing maize yield.
SUPPLEMENTARY INFORMATION
The online version contains supplementary material available at 10.1007/s13205-022-03201-7.
PubMed: 35646503
DOI: 10.1007/s13205-022-03201-7 -
Revista Argentina de Microbiologia 2022Biocontrol of the nematode Meloidogyne javanica was studied using the Argentinean strains Pseudomonas fluorescens MME3, TAE4, TAR5 and ZME4 and Bacillus sp. B7S, B9T and...
Biocontrol of the nematode Meloidogyne javanica was studied using the Argentinean strains Pseudomonas fluorescens MME3, TAE4, TAR5 and ZME4 and Bacillus sp. B7S, B9T and B19S. Pseudomonas protegens CHA0 was used as a positive control. Egg hatching and juvenile mortality were evaluated in vitro by exposure of nematodes to bacterial suspensions or their cell-free supernatants (CFS). The effect of bacteria on nematode infestation of lettuce was also studied. results showed that most of the tested strains and CFS reduced egg hatching and juvenile survival in vitro. The bacterial suspension of Bacillus sp. B9T produced the lowest hatching of eggs. Juvenile mortality was higher when M. javanica was exposed to Bacillus sp. than to Pseudomonas spp. suspensions. Except for CFS of B9T, all filtrates inhibited hatching at levels similar to or higher than the biocontrol strain P. protegens CHA0. The CFS of CHA0 showed the highest level of juvenile mortality followed by Bacillus sp. strains and P. fluorescens TAE4. None of the inoculated rhizobacteria reverted the negative effect of infestation on the aerial dry weight of lettuce plants. However, inoculation impacted on reproduction of M. javanica by reducing the development of galls and egg masses on roots and diminishing the number of individuals both on roots and in the substrate, as well as the reproduction factor. These results show that most of the analyzed native strains can control the nematode M. javanica. Among them, P. fluorescens TAE4 and Bacillus sp. B9T showed the most promising performances for the biocontrol of this pathogen and have a potential use in the formulation of commercial products.
Topics: Animals; Argentina; Bacillus; Humans; Lactuca; Solanum lycopersicum; Pest Control, Biological; Tylenchoidea
PubMed: 33947589
DOI: 10.1016/j.ram.2021.02.010 -
Frontiers in Fungal Biology 2022The present study is a comparative study between Reactive Oxygen Species (ROS) signaling and antioxidative enzymatic signaling and deals with induced systemic resistance...
The present study is a comparative study between Reactive Oxygen Species (ROS) signaling and antioxidative enzymatic signaling and deals with induced systemic resistance (ISR) in enhancing the disease resistance in typical tomato plant ( L.) infected by the collar rot fungus, (Teleomorph: by priming with , and their microbial consortia by a single strain of , and as well as by developed microbial consortium with both bacteria. Leaf samples were collected after different durations of pathogen inoculation, i.e., 1, 2, 3, and 4 days, and the systemic level of oxidative stress parameters, such as hydrogen peroxide (HO), photosynthetic apparatus, superoxide radicals, and enzymatic antioxidants, were studied. Plant mortality under various treatments in two different seasons was calculated. The highest HO was scavenged by the microbial consortium-treated plants (B1P1) and the lowest in pathogen-challenged plants (PC) compared to the untreated control. Cellular damage and reduction in the chlorophyll pigments were the highest at 48 h, and the photosynthetic efficiency (Fv/Fm) was evaluated from 24 to 96 h; the lowest values were observed for pathogen-challenged plants and the highest for B1P1. Enzymatic antioxidants showed the maximum value for B1P1 and the minimum for PC compared to the unchallenged control. Furthermore, an analysis of variance and principal component analysis (PCA) were conducted to examine the effect of the evaluation time (ET) and inoculation conditions (ICs) alone and in combination (ET × IC) on the physiological and biochemical parameters; accordingly, the score and the loading plots were constructed. Tomato root sections inoculated with different treatments were observed through scanning electron microscopy (SEM) to validate the potentiality of primed biocontrol agents in controlling the invasion of the pathogen. Further studies on the potential of this isolate to enhance the plant growth at the field level would strengthen the possibility of using the isolate as an alternative for organic fertilizers and pesticides.
PubMed: 37746200
DOI: 10.3389/ffunb.2022.851002 -
Microorganisms Jan 2022The present study evaluates the antimicrobial susceptibility of persister cells of and after their regrowth in suspension and as biofilms. Two conventional...
The present study evaluates the antimicrobial susceptibility of persister cells of and after their regrowth in suspension and as biofilms. Two conventional (benzalkonium chloride-BAC and peracetic acid-PAA) and two emerging biocides (glycolic acid-GA and glyoxal-GO) were selected for this study. Persister cells resulted from biofilms subjected to a critical treatment using the selected biocides. All biocide treatments developed persister cells, except PAA that effectively reduced the levels of vegetative cells and endospores. persister cells comprise viable and viable but non-culturable cells. Afterwards, persister cells were regrown in suspension and in biofilms and were subjected to a second biocide treatment. In general, planktonic cultures of regrown persister cells in suspension lost their antimicrobial tolerance, for both bacteria. Regrown biofilms of persister cells had antimicrobial susceptibility close to those regrown biofilms of biocide-untreated cells, except for regrown biofilms of persister after BAC treatment, which demonstrated increased antimicrobial tolerance. The most active biocide against persister cells was PAA, which did not promote changes in susceptibility after their regrowth. In conclusion, persister cells are ubiquitous within biofilms and survive after critical biocide treatment. The descendant planktonic and biofilms populations showed similar properties as the original ones.
PubMed: 35056610
DOI: 10.3390/microorganisms10010160 -
Frontiers in Microbiology 20232P24 was isolated from soil of natural decay associated with wheat take-all and it can effectively control soil-borne diseases caused by a variety of plant pathogens....
INTRODUCTION
2P24 was isolated from soil of natural decay associated with wheat take-all and it can effectively control soil-borne diseases caused by a variety of plant pathogens. 2,4-diacetylphloroglucinol (2,4-DAPG), is produced by 2P24 and plays an important role in the prevention and control of plant diseases. To understand the resistant mechanism, in this study, we conducted experiments to explore the regulation role of in the synthesis of the antibiotic 2,4-DAPG and regulation of QS system.
METHODS
A random mini-Tn5 mutagenesis procedure was used to screen regulators for transcription in stain PM901, which containing a phlA∷lacZ transcriptional fusion reporter plasmid. We identified 12 insertion mutants could significantly change gene expression. By analyzing the amino acid sequences of the interrupted gene, we obtained a mutant strain Aa4-29 destroyed the gene, which encodes the omiga subunit. We constructed the plasmid of mutant (pBBR-△rpoZ) transformed into competent cells of 2P24 by electro-transformation assay. The strains of 2P24/pBBR, 2P24-△rpoZ/pBBR, 2P24-△rpoZ/pBBR-rpoZ were used to evaluate the regulation role of in 2,4-DAPG production and quorum sensing system.
RESULTS
According to β-galactosidase activity, we found that positively regulated the expression of (a synthesis gene of 2,4-DAPG) and (a synthesis gene of PcoI/PcoR QS signal system) at the transcriptional level. The production of 2,4-DAPG antibiotic and signal molecule AHL was influenced by . Further, was involved in regulating expression. also has a certain regulatory effect on transcription, but no effect on the transcription of , and . According to the biocontrol assay, 2P24 strains with showed obvious antagonism ability against the in cotton, while the mutant strain of lost the biocontrol effect. had a significant effect on the swimming and biofilm formation in 2P24.
CONCLUSION
Our data showed that was an important regulator of QS system, 2,4-DAPG in 2P24. This may imply that has evolved different regulatory features to adapt to different environmental threats.
PubMed: 37250031
DOI: 10.3389/fmicb.2023.1160913 -
MBio Feb 2021Plants form commensal associations with soil microorganisms, creating a root microbiome that provides benefits, including protection against pathogens. While bacteria...
Plants form commensal associations with soil microorganisms, creating a root microbiome that provides benefits, including protection against pathogens. While bacteria can inhibit pathogens through the production of antimicrobial compounds , it is largely unknown how microbiota contribute to pathogen protection . We developed a gnotobiotic model consisting of Arabidopsis thaliana and the opportunistic pathogen Pseudomonas sp. N2C3, to identify mechanisms that determine the outcome of plant-pathogen-microbiome interactions in the rhizosphere. We screened 25 phylogenetically diverse Pseudomonas strains for their ability to protect against N2C3 and found that commensal strains closely related to N2C3, including Pseudomonas sp. WCS365, were more likely to protect against pathogenesis. We used comparative genomics to identify genes unique to the protective strains and found no genes that correlate with protection, suggesting that variable regulation of components of the core Pseudomonas genome may contribute to pathogen protection. We found that commensal colonization level was highly predictive of protection, so we tested deletions in genes required for rhizosphere colonization. We identified a response regulator , and two ColR-dependent genes with predicted roles in membrane modifications ( and ), that are required for Pseudomonas-mediated protection from N2C3. We found that WCS365 also protects against the agricultural pathogen Pseudomonas fuscovaginae SE-1, the causal agent of bacterial sheath brown rot of rice, in a ColR-dependent manner. This work establishes a gnotobiotic model to uncover mechanisms by which members of the microbiome can protect hosts from pathogens and informs our understanding of the use of beneficial strains for microbiome engineering in dysbiotic soil systems. Microbiota can protect diverse hosts from pathogens, and microbiome dysbiosis can result in increased vulnerability to opportunistic pathogens. Here, we developed a rhizosphere commensal-pathogen model to identify bacterial strains and mechanisms that can protect plants from an opportunistic Pseudomonas pathogen. Our finding that protective strains are closely related to the pathogen suggests that the presence of specific microbial taxa may help protect plants from disease. We found that commensal colonization level was highly correlated with protection, suggesting that competition with pathogens may play a role in protection. As we found that commensal Pseudomonas were also able to protect against an agricultural pathogen, this system may be broadly relevant for identifying strains and mechanisms to control agriculturally important pathogens. This work also suggests that beneficial plant-associated microbes may be useful for engineering soils where microbial complexity is low, such as hydroponic, or disturbed agricultural soils.
Topics: Arabidopsis; Pseudomonas fluorescens; Pseudomonas; Soil; Plant Roots; Transcription Factors
PubMed: 35100865
DOI: 10.1128/mbio.02892-21 -
Proceedings. Biological Sciences Jan 2020Disturbances can play a major role in biological invasions: by destroying biomass, they alter habitat and resource abundances. Previous field studies suggest that...
Disturbances can play a major role in biological invasions: by destroying biomass, they alter habitat and resource abundances. Previous field studies suggest that disturbance-mediated invader success is a consequence of resource influxes, but the importance of other potential covarying causes, notably the opening up of habitats, have yet to be directly tested. Using experimental populations of the bacterium , we determined the relative importance of disturbance-mediated habitat opening and resource influxes, plus any interaction between them, for invader success of two ecologically distinct morphotypes. Resource addition increased invasibility, while habitat opening had little impact and did not interact with resource addition. Both invaders behaved similarly, despite occupying different ecological niches in the microcosms. Treatment also affected the composition of the resident population, which further affected invader success. Our results provide experimental support for the observation that resource input is a key mechanism through which disturbance increases invasibility.
Topics: Biomass; Ecology; Ecosystem; Introduced Species; Pseudomonas fluorescens
PubMed: 31992171
DOI: 10.1098/rspb.2019.2415