This study unveils the detoxification potential of insecticide-tolerant plant beneficial bacteria (PBB), i.e., Ciceribacter azotifigens SF1 and Serratia marcescens SRB1, in spinach treated with ...fipronil (FIP), profenofos (PF) and chlorantraniliprole (CLP) insecticides. Increasing insecticide doses (25–400 μg kg−1 soil) significantly curtailed germination attributes and growth of spinach cultivated at both bench-scale and in greenhouse experiments. Profenofos at 400 μg kg−1 exhibited maximum inhibitory effects and reduced germination by 55%; root and shoot length by 78% and 81%, respectively; dry matter accumulation in roots and shoots by 79% and 62%, respectively; leaf number by 87% and leaf area by 56%. Insecticide application caused morphological distortion in root tips/surfaces, increased levels of oxidative stress, and cell death in spinach. Application of insecticide-tolerant SF1 and SRB1 strains relieved insecticide pressure resulting in overall improvement in growth and physiology of spinach grown under insecticide stress. Ciceribacter azotifigens improved germination rate (10%); root biomass (53%); shoot biomass (25%); leaf area (10%); Chl-a (45%), Chl-b (36%) and carotenoid (48%) contents of spinach at 25 μg CLP kg−1 soil. PBB inoculation reinvigorated the stressed spinach and modulated the synthesis of phytochemicals, proline, malondialdehyde (MDA), superoxide anions (O2•–), and hydrogen peroxide (H2O2). Scanning electron microscopy (SEM) revealed recovery in root tip morphology and stomatal openings on abaxial leaf surfaces of PBB-inoculated spinach grown with insecticides. Ciceribacter azotifigens inoculation significantly increased intrinsic water use efficiency, transpiration rate, vapor pressure deficit, intracellular CO2 concentration, photosynthetic rate, and stomatal conductance in spinach exposed to 25 μg FIP kg−1. Also, C. azotifigens and S. marcescens modulated the antioxidant defense systems of insecticide-treated spinach. Bacterial strains were strongly colonized to root surfaces of insecticide-stressed spinach seedlings as revealed under SEM. The identification of insecticide-tolerant PBBs such as C. azotifigens and S. marcescens hold the potential for alleviating abiotic stress to spinach, thereby fostering enhanced and safe production within polluted agroecosystems.
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•Insecticides showed differential toxicity to Spinacia oleracea (L.) seedlings.•Insecticide-tolerant PGPR strains-mediated phytotoxicity alleviation was reported.•PGPR improved leaf gas-exchange attributes and stomatal behavior under stress.•PGPR-mediated reduction in insecticide-induced oxidative stress and ROS generation in spinach.•Successful colonization and establishment of strains in stressed spinach rhizosphere.
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•Many bacterial processes, including virulence factor expression, biofilm formation, and viable but non-culturable (VBNC) cell resuscitation, are mediated by quorum sensing, and ...biofilm formation complicates the treatment of various infections.•This review discussed the relationship between quorum sensing inhibitors (QSI) with biofilms and VBNC.
Quorum sensing exists widely in all kinds of microorganisms and is a communication channel for microorganisms. Many bacterial processes, including virulence factor expression, biofilm formation, and viable but non-culturable (VBNC) cell resuscitation, are mediated by quorum sensing, and biofilm formation complicates the treatment of various infections. Foodborne pathogens can enter VBNC state in extreme environments, and pathogens in VBNC state can evade traditional detection and resuscitate under appropriate conditions, causing potential harm to human health. The disruption of quorum sensing may decisively help control biofilm formation and VBNC cell resuscitation. This review describes the quorum sensing systems of various bacteria and major fungi, and summarizes the role of bacterial quorum sensing system in biofilm formation and VBNC resuscitation. In addition, the relationship between quorum sensing inhibitors (QSI) with biofilms and VBNC is also discussed.
Wheat is one of the most important strategic products in providing food security for the growing world population. The purpose of this research is to isolate and identify plant growth-promoting ...bacteria from the wheat rhizosphere and their inhibitory effect on the growth of the pathogenic fungus Fusarium sp. isolated from wheat. The initial screening of 100 bacterial strains isolated from wheat roots was done based on their ability to dissolve phosphate. The effective factors in plant growth and inhibition of fungal pathogens, such as the ability to produce IAA, siderophores, protease, biofilm, bacterial swarming motility, tolerance to salt, seed germination, and seed vigor tests, were investigated. In the initial screening, four bacterial isolates with the highest amount of phosphate dissolution were identified based on morphological and biochemical characteristics as well as the sequence of 16S rRNA region belonging to Curtobacterium sp., Arthrobacter sp., Acinetobacter calcoaceticus, and Cellulosimicrobium sp.; Curtobacterium sp. had the highest amount of IAA (6.14μg/ml), siderophore (2.25cm), protease (1.4cm), and the highest tolerance to salinity (20%) and phosphate dissolution (375.3mg/ml). In the swarming motility test, the highest values were related to Arthrobacter sp. and Curtobacterium sp. at 2.7 and 2.2cm, respectively. The highest amount of biofilm formation was associated with Acinetobacter calcoaceticus and Curtobacterium sp. with an average absorption coefficient of 0.153 and 0.139, respectively. The highest and lowest average values of percentage inhibition of pathogenic fungus colony growth were evaluated in Curtobacterium sp. isolate with a value of 57.3%, and Cellulosimicrobium sp. isolate with 33%, respectively.
Bioaugmentation is an effective technology for treating wastewater containing recalcitrant organic pollutants. However, it is restricted by several technical problems, including the difficult ...colonization and survival of the inoculated bacteria, and the time-consuming start-up process. Considering the important roles of quorum sensing (QS) in regulating microbial behaviors, this study investigated the effects of N-acyl-homoserine lactones (AHLs)-based manipulation on the start-up of biofilm reactors bioaugmented with a pyridine-degrading strain Paracoccus sp. BW001. The results showed that, in the presence of two specific exogenous AHLs (C6-HSL and 3OC6-HSL), the biofilm formation process on carriers was significantly accelerated, producing thick and structured biofilms. The protein and polysaccharide contents of the extracellular polymeric substances (EPS) and soluble microbial products (SMP) in sludge were also elevated, possibly due to the increased abundance of several EPS-producing bacterial genera. Specifically, the stability and complexity of protein structures were improved. Besides the reactor running time, the AHL-manipulation was proved to be the main factor that drove the shift of bacterial community structures in the reactors. The addition of exogenous AHLs significantly increased the succession rate of bacterial communities and decreased the bacterial alpha diversity. Most importantly, the final proportions of the inoculated strain BW001 were elevated by nearly 100% in both sludge and biofilm communities via the AHL-manipulation. These findings strongly elucidated that AHL-based QS was deeply involved in biofilm formation, sludge characteristics, and microbial community construction in bioaugmented reactors, providing a promising start-up strategy for bioaugmentation technology.
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•Biofilm formation process on carriers was accelerated by AHL-manipulation.•The exogenous AHLs improved the complexity of protein structures in EPS.•The exogenous AHLs notably decreased the bacterial alpha diversity via selection.•Higher microbial temporal turnover slope was found in the AHL-adding reactor.•AHL-manipulation facilitated the colonization of the inoculated strain in reactors.
Although Tween-20 was used as an important catalyst to increase chalcopyrite bioleaching rate by acidophiles, the effect of Tween-20 on initial adhesion and biofilm development of acidophiles on ...chalcopyrite has not been explored until now. Herein, the role of Tween-20 in early attachment behaviors and biofilm development by Acidianus manzaensis strain YN-25 were investigated by adhesion experiments, adhesion force measurement, visualization of biofilm assays and a series of analyses including extended Derjaguin Landau Verwey Overbeek (DLVO) theory, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The bacterial adhesion experiments showed that 2 mg/L of Tween-20 increased the adhesion percentage (by 8%) of A. manzaensis YN-25. Tween-20 could promote the early adhesion of A. manzaensis YN-25 by changing the Lewis acid-base interaction and electrostatic force to increase total interaction energy and adhesion force. Besides, the functional groups on the surface of cells (carboxyl, hydroxyl and amino functional groups) contributed to the adhesion of A. manzaensis YN-25 on chalcopyrite. Furthermore, the promotion of biofilm formation by Tween-20 was mainly attributed to the reduction of S0 passivation layer formation and complexing more Fe3+ on chalcopyrite surface, contributing to the erosion of chalcopyrite and creating more corrosion pits. Live/dead staining showed low live/dead ratio (ranged from 0.35 to 1.32) during the biofilm development process. This report offers a better understanding of the effects of Tween-20 on attachment and biofilm development of acidophilic microorganisms and would lay a theoretical foundation for the better application of catalyst in bioleaching.
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•Tween-20 promoted the adhesion of A. manzaensis on the chalcopyrite surface.•Tween-20 increased the interaction force between A. manzaensis and chalcopyrite.•GAB and GEL played a major role in initial adhesion in the presence of Tween-20.•Tween-20 promoted biofilm formation on chalcopyrite.•Mechanisms included S0 passivation layer reduction and promotion dissolution.
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Pseudomonas aeruginosa can utilize various virulence factors necessary for host infection and persistence. These virulence factors include pyocyanin, proteases, exotoxins, ...2-heptyl-4-hydroxyquinoline N-oxide (HQNO), phospholipases, and siderophores that enable the bacteria to cause severe infections in immunocompromised individuals. P. aeruginosa falls into the category of nosocomial pathogens that are typically resistant to available antibiotics and therapeutic approaches. P. aeruginosa bio-film formation is a major concern in hospitals because it can cause chronic infection and increase the risk of mortality. Therefore, the development of new strategies to disrupt biofilm formation and improve antibiotic efficacy for the treatment of P. aeruginosa infections is crucial. Anti-biofilm and anti-quorum sensing (QS) activity can be viewed as an anti-virulence approach to control the infectious nature of P. aeruginosa. Inhibition of QS and biofilm formation can be achieved through pharmacological approaches such as phytochemicals and essential oils, which have shown promising results in laboratory studies. A regulatory protein called LasR plays a key role in QS signaling to coordinate gene expression. Designing an antagonist molecule that mimics the natural autoinducer might be the best approach for LasR inhibition. Here we reviewed the mechanism behind antibiotic resistance and alternative approaches to combat the pathogenicity of P. aeruginosa.
Vibrio parahaemolyticus, a common foodborne pathogen, can form biofilms for survival in various environments and for bacterial transmission. Lux systems in Vibrio species are the typical ...two-component signal transduction systems, which have been demonstrated to contribute to various phenotypes; however, the functions of each homolog of the Lux system in V. parahaemolyticus in the regulation of biofilm formation remain largely unknown. In this study, we first showed that LuxQ, LuxU, and LuxO are essential for controlling biofilm formation by V. parahaemolyticus, through gene knockout studies. We also found that they acted in the same signaling pathway and their deletion mutants exhibited a similar level of biofilm formation. Furthermore, site-directed mutagenesis revealed that the conserved residues for phosphorylation in LuxQ (D784), LuxU (H56) and LuxO (D47) were critical for their regulatory functions on biofilm formation. Phos-tag™ sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed the phosphorylation of LuxU and LuxQ in vivo. Finally, qPCR analysis displayed that the three mutants had a significant decrease in the transcription level of cps loci and cpsQ compared with the wild type strain, which is consistent with the observed phenotype of biofilm formation. Therefore, we propose that LuxQ and its downstream factors LuxU and LuxO function in the same signaling cascade to control biofilm formation by regulating the expression of cpsQ and cps loci. The results of this study provide new data regarding the role of the LuxQ-LuxU-LuxO pathway in biofilm formation by V. parahaemolyticus and help further understand the complex regulatory functions of Lux pathways.
species are fungal pathogens known for their ability to cause superficial and systemic infections in the human host. These pathogens are able to persist inside the host due to the development of ...pathogenicity and multidrug resistance traits, often leading to the failure of therapeutic strategies. One specific feature of
species pathogenicity is their ability to form biofilms, which protects them from external factors such as host immune system defenses and antifungal drugs. This review focuses on the current threats and challenges when dealing with biofilms formed by
, and
, highlighting the differences between the four species. Biofilm characteristics depend on the ability of each species to produce extracellular polymeric substances (EPS) and display dimorphic growth, but also on the biofilm substratum, carbon source availability and other factors. Additionally, the transcriptional control over processes like adhesion, biofilm formation, filamentation, and EPS production displays great complexity and diversity within pathogenic yeasts of the
genus. These differences not only have implications in the persistence of colonization and infections but also on antifungal resistance typically found in
biofilm cells, potentiated by EPS, that functions as a barrier to drug diffusion, and by the overexpression of drug resistance transporters. The ability to interact with different species in
biofilms is also a key factor to consider when dealing with this problem. Despite many challenges, the most promising strategies that are currently available or under development to limit biofilm formation or to eradicate mature biofilms are discussed.
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