Pseudomonas Fluorescens Strain Research Articles

In-vitro & In-vivo Studies on Antimicrobial and Plant Growth Promoting Efficacy of Fluorescent Pseudomonads

Aims: Excessive use of chemical fungicides cause environmental pollution and its residual effects are deleterious for human and animal consumption. So, application of biological control agents in IDM is an ecofriendly complement to manage the diseases as well as to protect the environment. PGPRs are free living microorganisms which have antimicrobial properties as well as exert beneficial effects to plant growth. Study Design: This present study has been designed to identify potential indigenous fluorescent Pseudomonads strains from different crop ecosystems under Eastern Gangetic plains of West Bengal. Study of Plant growth promoting properties and antimicrobial properties were done under both in-vitro and in vivo condition. Place and Duration of Study: Uttar Banga Krishi Viswavidyalaya, Pundibari, Cooch Behar, West Bengal, Duration 03years Methodology: Under this experiment 22 bacterial isolates were isolated and purified from different rhizosphere. Isolates were identified based on different biochemical test like catalase, oxidase activity, citrate utilization. The major plant growth promoting properties like P, K and Zn solubilisation efficiency were tested. In-vitro antimicrobial properties were also tested like HCN production, Volatile and non volatile compounds production etc. Based on in-vitro performance, best performing isolate was selected for in-vivo in Lentil against Stemphylium botryosum, a major disease causing fungi of lentil. IDM practice was done in three stages like Seed treatment, Prophylactic spray and Therapeutic spray and three lentil variety WBL 77(Maitree), Pusa Ageti and MN12 were used. Results: Most of the isolates showed positive result in biochemical tests and performed well i.r.o. PGP properties and antimicrobial properties. In field trial UBPF5 gave a promising result. PF5 isolate was identified through 16S rRNA based molecular method and sample showed 99.25% similarity with Pseudomonas gessardii based on nucleotide homology and phylogenetic analysis. In comparison to different combination of treatments cuprous chloride as seed treatment, Pseudomonas sp. as prophylactic spray and for therapeutic purpose Boscalid + Pyroclostrobin were found mostly efficient in respect of disease incidence as well as plant growth and yield. Prophylactic spray with Pseudomonas sp. in combination with biological seed treatment and therapeutic application of fungicide has resulted in 26-38% reduction in disease incidence and 28-32% increment in yield. Conclusion: So, use of PGPR in combination with chemical fungicides is an eco-friendly tool to manage plant diseases in a sustainable manner.

<i>Spongia officinalis</i> -Associated <i>Pseudomonas fluorescens</i> as a Reservoir of Bioactive Compounds: A Novel Source of Natural Anticancer Compounds

Marine sponges are an important source of chemical variety and a repository of biodiversity. In this study, the microbial communities found in the marine sponge Spongia officinalis that was taken from the Kanyakumari coast in India were explored. We identified, characterized, and evaluated the bioactive potential of the sponge-associated bacteria. A total of 12 bacterial isolates were obtained, primarily consisting of gram-positive rods and some gram-negative rods and cocci. These bacterial isolates showed a variety of bioactive substances when their secondary metabolites were extracted, including phenols, flavonoids, alkaloids, saponins, terpenoids, and steroids. These chemical compounds are well-known for their numerous biological activity and health benefits. The antioxidant and anticancer effects of these metabolites were also investigated. Isolate 6 showed significant antioxidant activity, suggesting it may be able to treat cancer. With an IC50 value of 55.32 g/ml, this isolate also displayed impressive anticancer activity against HeLa cells. The screened isolate was identified as Pseudomonas fluorescens strain ATCC 13525 using 16S rRNA sequencing. This discovery emphasizes the importance of bacteria associated with marine sponges as a source of bioactive compounds with medicinal potential. The conclusion of this research highlights the diverse microbial communities found in marine sponges and their potential for use in biotechnology and medication development. Pseudomonas fluorescens was found to be a prolific generator of bioactive byproducts, including strong antioxidants and anticancer agents, which emphasizes the significance of additional marine resource exploitation for pharmacologically relevant chemicals.

Microalgae–bacteria interaction: a catalyst to improve maize (Zea mays L.) growth and soil fertility

AbstractBiofertilisers harbouring living organisms hold allure due to their prospective favourable influence on plant growth, coupled with a diminished environmental footprint and cost-effectiveness in contrast to conventional mineral fertilisers. The purpose of the present study was to evaluate the capacity of a specific microalga (MACC-612, Nostoc linckia) biomass and plant growth-promoting bacteria (PGPB) separately and together to improve crop growth and promote soil health. The research used a factorial design within a completely randomised block framework, featuring four replications for three consecutive years across different fields. The experiment utilised three levels of microalga (control, 0.3 g/L of N. linckia, MACC-612, and 1 g/L of N. linckia, MACC-612) and three levels of bacterial strains (control, Azospirillum lipoferum and Pseudomonas fluorescens). The result demonstrated that the use of N. linckia and PGPB separately or jointly as soil treatment resulted in a substantial improvement in chlorophyll, plant biomass, soil humus, and nitrogen, depending on the environmental conditions of the years. The combined use of N. linckia and PGPB results in an improvement in dry leaf weight by 35.6–107.3% at 50 days after sowing (DAS) and 29.6–49.8% at 65 DAS, compared to the control group. Furthermore, the studies show that the synergistic application of N. linckia at 0.3 g/L, in conjunction with A. lipoferum, significantly improved total nitrogen and (NO3− + NO2−)-nitrogen, registering increases of 20.7–40% and 27.1–59.2%, respectively, during the study period. The most effective synergistic combination was identified through the application of 0.3 g/L of N. linckia along with A. lipoferum. Hence, application of biofertilisers through synergistic combinations of two or more microorganisms, such as microalgae and bacteria, holds promise in improving crop chlorophyll, growth, and soil nitrogen.

Integrated remediation and detoxification of triclocarban-contaminated water using waste-derived biochar-immobilized cells by long-term column experiments

Triclocarban (TCC), an antibacterial agent commonly used in personal care products, is one of the top ten contaminants of emerging concern in various environmental media, including soil and contaminated water in vadose zone. This study aimed to investigate TCC-contaminated water remediation using biochar-immobilized bacterial cells. Pseudomonas fluorescens strain MC46 (MC46), an efficient TCC-degrading isolate, was chosen, whereas agro-industrial carbonized waste as biochar was directly used as a sustainable cell immobilization carrier. According to the long-term TCC removal performance results (160 d), the biochar-immobilized cells consistently exhibited high TCC removal efficiencies (84–97%), whereas the free MC46 removed TCC for 76–94%. At 100 days, the detachment of the MC46 cells from the immobilized cell column was observed. The micro-Fourier-transform infrared spectroscopy results indicated that extracellular polymeric substance (EPS) was produced, but polysaccharide and protein fractions were washed out of the column. The lipid fraction of EPS adhered to the biochar, promoting TCC sorption for long-term treatment. The shortening of MC46 cells improved the tolerance of TCC toxicity. The TCC-contaminated water was successfully detoxified by the biochar-immobilized MC46 cells. Overall, the waste-derived biochar-immobilized cell system proposed in this study for the removal of emerging contaminants, including TCC, is efficient, economical, and aligned with the sustainable development concept of value-added utilization of waste.

Comparative analysis of commercial cleaning and disinfection formulations and protocols for effective eradication of biofilms formed by a Pseudomonas fluorescens strain isolated from a poultry meat plant

Pseudomonas spp. is the main genus of spoilage bacteria for meat stored under aerobic chilling conditions. Given their ability to adapt to various environmental conditions and to form biofilms, they are common among residential microbiota in the food industry. Biofilms are complex, structured microbial communities encased in a self-produced exopolysaccharide matrix. Resident biofilm bacteria show increased resistance against disinfectants and dynamic or hostile environments, and are therefore a persistent source of food contamination. Hence, there is a need to design and implement control strategies that are effective against biofilms in the food industry. In this study, we tested a series of commercial cleaning and disinfection agents applied by immersion or aerosolization against robust biofilms of a Pseudomonas fluorescens strain isolated from a poultry meat plant by comparing the sessile cell counts before and after the procedure. The single application of a) an alkaline or an enzymatic detergent, b) a disinfectant based on peracetic acid and hydrogen peroxide, or c) a detergent-disinfectant based on tertiary alkylamines or sodium hypochlorite, failed to completely eradicate the biofilm. However, two-step cleaning and disinfection procedures involving the application of a detergent (either alkaline or enzymatic at 50 °C) followed by the application of the disinfectant based on peracetic acid and hydrogen peroxide at the manufacturer's recommended concentrations did result in the complete eradication (p ≤ 0.05) of the robust biofilm. In addition, cleaning and disinfection procedures applied by aerosolization showed a notable efficacy (p ≤ 0.05) against surface-dried cells and sessile cells of P. fluorescens. Therefore, this approach could be regarded as a potentially viable alternative to commonly applied immersion techniques.

A Comprehensive Perception of Biological Control Potential of Endophytes and Quality Refinement of Lagenaria siceraria.

Agriculture and livestock management practices known as organic farming rely more on internal processes than external inputs. Natural environments depend heavily on diversity, and organic farming incorporates both the stated purpose of fostering diversity as well as the use of diversity as a management tool. A more complete understanding of agriculture in terms of agro-ecology has begun to be questioned by the traditional reductionist approach to the study of agriculture. Therefore it is necessary to be aware more about the significance of microbes in processes including soil growth, plant nourishment, and the eradication of plant disease, pest, and weeds. In this study, fluorescent Pseudomonas strain (EFP56) and Trichoderma harzianum were studied for antifungal and antibacterial activity against four common root rot fungi and four common laboratory bacteria in vitro experiments. Furthermore, soil-borne disease surveillance and nutritional quality of Lagenaria siceraria, fluorescent Pseudomonas strain (EFP56) and Trichoderma harzianum were combined with neem cake and cotton cake to check their efficacy. Through the application of organic soil amendments in combination with biocontrol agents improved the quality of vegetables and their nutritional value by raising their polyphenol, carbohydrate, and protein content as well as enhancing antioxidant scavenging status. The experiments were conducted in pots and in fields to confirm their efficacy rate. The final outcomes also revealed greater induction of defense system, disease lessening and enriched fruit quality. Consortium of neem cake and cotton cake with bio-stimulants can regulate biotic as well as abiotic stress.

Are the Nutritional Properties of Organic Tomatoes Altered by Single and Combined Microbial Soil Inoculants?: A Multiperspective Approach

Biologically active compounds are key-important ingredients of tomato fruits, especially those produced by organic agricultural practices. Being biologically effective soil treatments, microbial inoculants can improve soil quality through a variety of mechanisms. Their activity can influence soil properties and plant development, thereby determining the quantity and quality of the crop. However, little research was done on how these inoculants affect the nutritional quality of the tomato fruit and on the antioxidant status of the fruits. This study investigated lycopene content and total antioxidant capacity of organically grown tomato fruits (Solanum lycopersicum L. var. ‘Mobil’) using various types of single and combined bioeffector products in two growing seasons. Single inoculation contained Trichoderma harzianum, plant growth promoting Pseudomonas sp., and phosphorus-mobilizing Bacillus amyloliquefaciens strains. The combined treatment consisted of biotic Trichoderma harzianum, Pseudomonas fluorescens, and Bacillus subtilis strains with abiotic micronutrients of zinc and manganese. Sum of ranking differences method, as a multicriteria optimization method, was used to rank the treatments and identify the ones deviating the least from the reference treatment. The results showed that all microbial soil inoculants positively affected tomato lycopene content. The combined treatment showed significantly higher lycopene content than the Control in both years. We found that weather and climate conditions also greatly influence the total antioxidant capacity. Based on our results, we recommend the use of combined bioeffective treatments to improve the food quality value of tomato fruits.

Characterization and Field Evaluation of Potential Fluorescent Pseudomonas Isolates on Growth and Yield Attributing Characters in Chickpea

The present investigation was conducted at the research and instructional farm, College of Agriculture, Indira Gandhi Krishi Vishwavidyalaya, Raipur, Chhattisgarh, India during rabi (October–December 2019) to evaluate the influence of fluorescent Pseudomonas isolates on chickpeas through characterization and field evaluation. Eighty-eight rhizosphere soil samples were derived from different locations in Bastar and Bilaspur districts of Chhattisgarh, India. Potential isolates were required for fundamental research and practical application of plant growth-promoting rhizobacterial strains on different crops. Among eighty-eight isolates, ten fluorescent Pseudomonas (visible under UV light at 360 nm) emitting strong fluorescence were selected for the course of the investigation and characterized for the production of siderophores, phosphate solubilization, indole acetic acid, 1-aminocyclopropane-1-carboxylic acid deaminase, and analysis of antagonistic potential. Of the 10 Pseudomonas isolates, 9704 was identified as the highest phosphate solubilizer, BSP-23 was identified as the highest indole acetic acid producer, and BSP-19 was the highest siderophore producer. Fluorescent Pseudomonas isolates BS-1, BS-4, 9809, BSP-14, and BSP-19 were identified to possess 1-aminocyclopropane-1-carboxylic acid deaminase-producing ability following qualitative analysis. Our present investigation indicates that beneficial effects of fluorescent Pseudomonas could be achieved through simple and cost-effective seed treatment. Three fluorescent Pseudomonas strains, 9704, BS-14, and 9829, consistently increased seed germination and improved plant growth and yield (BS-37.9% and 9704-35.7%) attributes in chickpeas. Besides, confrontation assays performed against R. bataticola expressed varying levels of inhibition. The phylogenetic affinities of 16S rRNA gene sequencing resolved the species identities of selected isolates.

Rhizobacterial community and growth-promotion trait characteristics of Zea mays L. inoculated with Pseudomonas fluorescens UM270 in three different soils.

There is an increasing demand for bioinoculants based on plant growth-promoting rhizobacteria (PGPR) for use in agricultural ecosystems. However, there are still concerns and limited data on their reproducibility in different soil types and their effects on endemic rhizosphere communities. Therefore, this study explored the effects of inoculating the PGPR, Pseudomonas fluorescens strain UM270, on maize growth (Zea mays L.) and its associated rhizosphere bacteriome by sequencing the 16S ribosomal genes under greenhouse conditions. The results showed that inoculation with PGPR P. fluorescens UM270 improved shoot and root dry weights, chlorophyll concentration, and total biomass in the three soil types evaluated (clay, sandy-loam, and loam) compared to those of the controls. Bacterial community analysis of the three soil types revealed that maize plants inoculated with the UM270 strain showed a significant increase in Proteobacteria and Acidobacteria populations, whereas Actinobacteria and Bacteroidetes decreased. Shannon, Pielou, and Faith alpha-biodiversity indices did not reveal significant differences between treatments. Beta diversity revealed a bacterial community differential structure in each soil type, with some variation among treatments. Finally, some bacterial groups were found to co-occur and co-exclude with respect to UM270 inoculation. Considered together, these results show that PGPR P. fluorescens UM270 increases maize plant growth and has an important effect on the resident rhizobacterial communities of each soil type, making it a potential agricultural biofertilizer.

Synthesis, Characterisation, and In Vitro Evaluation of Biocompatibility, Antibacterial and Antitumor Activity of Imidazolium Ionic Liquids.

In recent decades, ionic liquids (ILs) have garnered research interest for their noteworthy properties, such as thermal stability, low or no flammability, and negligible vapour pressure. Moreover, their tunability offers limitless opportunities to design ILs with properties suitable for applications in many industrial fields. This study aims to synthetise two series of methylimidazolium ILs bearing long alkyl chain in their cations (C9, C10, C12, C14, C16, C18, C20) and with tetrafluoroborate (BF4) and the 1,3-dimethyl-5-sulfoisophthalate (DMSIP) as counter ions. The ILs were characterised using 1H-NMR and MALDI-TOF, and their thermal behaviour was investigated through DSC and TGA. Additionally, the antimicrobial, anticancer, and cytotoxic activities of the ILs were analysed. Moreover, the most promising ILs were incorporated at different concentrations (0.5, 1, 5 wt%) into polyvinyl chloride (PVC) by solvent casting to obtain antimicrobial blend films. The thermal properties and stability of the resulting PVC/IL films, along with their hydrophobicity/hydrophilicity, IL surface distribution, and release, were studied using DSC and TGA, contact angle (CA), SEM, and UV-vis spectrometry, respectively. Furthermore, the antimicrobial and cytotoxic properties of blends were analysed. The in vitro results demonstrated that the antimicrobial and antitumor activities of pure ILs against t Listeria monocytogenes, Escherichia coli, Pseudomonas fluorescens strains, and the breast cancer cell line (MCF7), respectively, were mainly dependent on their structure. These activities were higher in the series containing the BF4 anion and increased with the increase in the methylimidazolium cation alkyl chain length. However, the elongation of the alkyl chain beyond C16 induced a decrease in antimicrobial activity, indicating a cut-off effect. A similar trend was also observed in terms of in vitro biocompatibility. The loading of both the series of ILs into the PVC matrix did not affect the thermal stability of PVC blend films. However, their Tonset decreased with increased IL concentration and alkyl chain length. Similarly, both the series of PVC/IL films became more hydrophilic with increasing IL concentration and alkyl chain. The loading of ILs at 5% concentration led to considerable IL accumulation on the blend film surfaces (as observed in SEM images) and, subsequently, their higher release. The biocompatibility assessment with healthy human dermal fibroblast (HDF) cells and the investigation of antitumoral properties unveiled promising pharmacological characteristics. These findings provide strong support for the potential utilisation of ILs in biomedical applications, especially in the context of cancer therapy and as antibacterial agents to address the challenge of antibiotic resistance. Furthermore, the unique properties of the PVC/IL films make them versatile materials for advancing healthcare technologies, from drug delivery to tissue engineering and antimicrobial coatings to diagnostic devices.

Preparation of Plant Growth Enhancing Bioformulation from Agricultural Wastes by Solid State Fermentation

Preparation of organic waste based bioformulation through solid state fermentation technology for application in the field offers an ecofriendly and viable alternative to sustainable food production. The present study deals with the potential of seven agrowastes as substrate carriers for the growth of indigenous strains of Pseudomonas fluorescens (Pf) and Bacillus subtilis (Bs) that stimulate plant growth. The cosubstrate (CS) with equal proportion of the seven agrowastes and both the bioinoculants (CSPfBs) proved as the best substrate carrier with highest population load of the bioinoculants at 45 days after storage (DAS). Thereafter the population declined steadily in all the bioformulations from 60 DAS to 90 DAS. However, CSPfBs gave the highest population load at 90 DAS. As individual substrate for both Pf and Bs, vermicompost performed best with a population load of 9.95 of Pf and 9.98 of Bs at 90 DAS. The bioformulations CSPfBs, VBs and VPf when applied in soil, gave the best yield in brinjal plants (Solanum melongena L. cv. Pusa Kranti) at 30 days after transplanting. Similar trends were also observed in the other yield parameters. The study indicates the scope of the prepared bioinoculant as a low cost eco friendly option for promotion of growth and yield of crops.

Nontarget effects of pre‐emergent herbicides and a bioherbicide on soil resources, processes, and communities

Community‐type conversions, such as replacement of perennials by exotic annual grasses in semiarid desert communities, are occurring due to plant invasions that often create positive plant–soil feedbacks, which favor invaders and make restoration of native perennials difficult. Exotic annual grass control measures, such as pre‐emergent herbicides, can also alter soil ecosystems directly or indirectly (i.e. via the plant community), yet there are few studies on the topic in natural, non‐cropped landscapes. We asked how spray treatments applied to soil post‐fire with the intention of inhibiting invasive annual grasses (such as Bromus tectorum L.) and releasing existing native perennial grasses affected soil resources, a microbial process, and invertebrates in three climatically varied sagebrush steppe sites. Spray treatments included chemical herbicides (imazapic and rimsulfuron) that strongly affected plant communities and a bioherbicide (Pseudomonas fluorescens strain D7) that did not. Chemical herbicides increased soil mineral nitrogen in proportion to their negative effects on plant cover for 2 years after treatments in all sites and increased soil water and net N mineralization (measured at one site) but did not affect total carbon, nitrogen, or organic matter. Invertebrate responses to herbicides varied by site, and invertebrates increased with chemical herbicides at the highest, wettest site. We show that herbicide treatments can exacerbate pulses of mineral nutrients, which previous studies have shown can weaken ecosystem resistance to invasion. Thus, restoration strategies that increase the likelihood that desired plants can capture mineralized nutrients after herbicide application will likely be more successful.

Mitigating postharvest quantitative and qualitative losses in mango fruits through the application of biocontrol agents: An in-vivo and in-vitro assessment

Mango is a commercial fruit crop of India that suffers huge postharvest losses every year. The application of biocontrol agents (BCAs) bears a vast potential for managing the same, which is yet to be exploited to its fullest extent. Hence, studies were conducted for BCAs application of Debaryomyces hansenii, Bacillus subtilis and Pseudomonas fluorescens strains on mango fruit under in-vitro, in-vivo conditions to know the efficacy of these BCAs on the postharvest pathogen, shelf life and quality retention of mango fruit. The ‘poisoned food technique’ was attempted for in-vitro studies. For the in-vivo studies, fruit of the commercial cultivar ‘Amrapali’ were un-inoculated and pre-inoculated with major postharvest pathogens (anthracnose: Colletotrichum gloeosporioides and stem-end rot: Botryodiplodia theobromae) were treated with BCA, followed by ambient storage at (24 ± 4 °C, 75 ± 5 % RH). From the results, it has been observed that under in vitro studies, BCA Debaryomyces hansenii (Strain: KP006) and Bacillus subtilis (Strain: BJ0011) at the treatment level 108 CFU mL−1 while, the Pseudomonas fluorescens at 109 CFU mL−1 (Strain: BE0001) were significantly effective for pathogen inhibition. However, under the in vivo studies, the BCA Debaryomyces hansenii (Strain: KP006) at 108 CFU mL−1 treatment level was found to significantly reduce the pathogen's decay incidence while positively influencing the shelf life and biochemical (quality) attributes. This treatment increased the storage life of mango fruit by more than three days over control fruit. Therefore, BCA Debaryomyces hansenii (Strain: KP006) at 108 CFU mL−1 can be used to control the postharvest pathological loss of mango fruit without affecting its internal quality.

Survival of a microbial inoculant in soil after recurrent inoculations

Microbial inoculants are attracting growing interest in agriculture, but their efficacy remains unreliable in relation to their poor survival, partly due to the competition with the soil resident community. We hypothesised that recurrent inoculation could gradually alleviate this competition and improve the survival of the inoculant while increasing its impact on the resident bacterial community. We tested the effectiveness of such strategy with four inoculation sequences of Pseudomonas fluorescens strain B177 in soil microcosms with increasing number and frequency of inoculation, compared to a non-inoculated control. Each sequence was carried out at two inoculation densities (106 and 108 cfu.g soil−1). The four-inoculation sequence induced a higher abundance of P. fluorescens, 2 weeks after the last inoculation. No impact of inoculation sequences was observed on the resident community diversity and composition. Differential abundance analysis identified only 28 out of 576 dominants OTUs affected by the high-density inoculum, whatever the inoculation sequence. Recurrent inoculations induced a strong accumulation of nitrate, not explained by the abundance of nitrifying or nitrate-reducing microorganisms. In summary, inoculant density rather than inoculation pattern matters for inoculation effect on the resident bacterial communities, while recurrent inoculation allowed to slightly enhance the survival of the inoculant and strongly increased soil nitrate content.

Safety evaluation of the food enzyme phosphoinositide phospholipase C from the genetically modified Pseudomonas fluorescens strain PIC.

The food enzyme phosphoinositide phospholipase C (1-phosphatidyl-1D-myo-inositol-4,5-bisphosphate inositoltrisphosphohydrolase EC 3.1.4.11.) is produced with the genetically modified Pseudomonas fluorescens strain PIC by DSM Food specialties B.V. The genetic modifications do not give rise to safety concerns. The food enzyme is free from viable cells of the production organism and its DNA. It is intended to be used in the processing of fats and oils for the production of refined edible fats and oils by degumming. Since residual amounts of the total organic solids are removed by the washing and purification steps applied during degumming, dietary exposure estimation and toxicity testing were considered unnecessary. A search for the similarity of the amino acid sequence of the food enzyme to known allergens was made and no matches were found. The Panel considered that the risk of allergic reactions by dietary exposure cannot be excluded, but the likelihood for this to occur is low. Based on the data provided, the Panel concluded that this food enzyme does not give rise to safety concerns under the intended conditions of use.

Mass multiplication of native rhizospheric bacteria on cheaply available organic substrates and their plant growth promotion potentiality on cowpea

The intensive agricultural system results into considerable environmental damage and its inevitable effects on various environmental and ecological factors. Known for their role in the natural disease-suppressiveness of particular soil, Fluorescent pseudomonads are a genus of root-associated bacteria that may colonise the roots of agricultural plants and create antifungal metabolites, making them a viable alternative to the use of chemical fungicides. The successful application of Fluorescent pseudomonads as bioinoculants depends to a great extent on their capability to establish roots and to contend with indigenous microbiome in the rhizosphere. Because of various limitations, variations in the bio control agents are bound to occur in different agro-climatic regions, so it is advisable to choose native bio control agents. In the present investigation, a comprehensive effort was undertaken to check the growth of Pseudomonas aeruginosa (GP-8), which was found to be much lesser in aqueous extracts of cow dung, vermicompost and groundnut cake as compared to the growth of GP-8 (Pseudomonas aeruginosa) in nutrient broth media. The enrichment of Nitrogen and other supplementary nutrients may be required for the development of low cost indigenous media from cheaply available substrates for commercial mass production of Pseudomonas aeruginosa (GP-8) and also a field level screening trial was undertaken with efficient native Fluorescent pseudomonads solely or in consortia for improvement of plant health and management of soil borne pathogens as well as to develop a culture media with cheap and readily available substrate sources for mass production of Fluorescent pseudomonads strains. In the present study, it was found that shoot length and root length of native Fluorescent pseudomonads inoculated cowpea plants were significantly increased as compared with those of the control plants both at 30 and 60 days after sowing.

Highly sensitive resistance spectroscopy technique for online monitoring of biofilm growth on metallic surfaces

Online techniques for monitoring biofilm formation and evolution are limited, especially as regards its application in flowing water systems. This is chiefly due to the absence of efficient non-destructive and non-invasive sensing methods. In this study, a sensitive electrical resistance spectroscopy technique is developed to monitor non-invasively and in real time the growth of biofilms over metallic surfaces inside water flow systems. To this aim, Pseudomonas fluorescens strain is used for biofilm development lasting 72 h in a laboratory-scale test channel of orthogonal cross section. Biofilm development corresponds to a progressively increasing coverage of the metallic surface area up to full coverage and a progressively increasing thickness. Biofilm development is registered by continuous recording of electrical impedance signals (time series). Proper configuration and tuning of the electronics promote the resistive contribution to the signal whereas careful grounding diminishes electrical interferences and yields superb sensing sensitivity. An increase of relative electrical resistance of around 15% is noticed in 72 h flow experiments which is attributed to both an increase of metallic surface area coverage and an increase of biofilm thickness. An independent estimation of these quantities using imaging tools and microscopy analysis, indicates that full coverage of the metallic surface occurs after only 48 h of the flow experiment, whereas biofilm thickness increases gradually along the entire 72 h of the experiment. Cross-examination of electrical signals with biofilm characteristics (metallic surface coverage and biofilm thickness) reveals that, qualitatively speaking, electrical signals are rather more sensitive to metallic surface coverage than biofilm thickness.

Dual-Temperature Microbiological Control of Cellular Products: A Potential Impact for Bacterial Screening of Platelet Concentrates?

An experimental study by the Paul-Ehrlich Institute (PEI) demonstrated that temperatures between 35 and 37 °C are too high for the growth of some bacterial strains (e.g., Pseudomonas fluorescens), leading to false negative results. Thus, the question of whether it is necessary to adapt incubation temperatures for the microbiological control of blood products, especially platelet concentrates (PCs), to enhance safety and regulatory compliance has arisen. In order to further elucidate this issue, the growth capability of different bacterial strains of interest in PCs and the detection efficacy of cultivation of these at different incubation temperatures must be taken into account. Therefore, we inoculated PCs with 46 different strains (3-6 PCs from different donors per strain) from different origins (PC isolates, reference strains) and stored PCs at 20-22 °C under constant agitation. On day three of storage, the inoculated PCs were sampled; aerobic and anaerobic culture bottles (BacT/Alert AST/NST) were each inoculated with 5 mL of sample, and culture bottles were incubated at 25 and 35 °C using the automated BacT/Alert Dual-temperature system. Bacterial proliferation was enumerated using a colony-forming assay. All strains of Enterobacteriacae (n = 5), Staphy-lococcus spp. (n = 11), Streptococcus spp. (n = 5), and Bacillus spp. (n = 4) and most Pseudomonas aeruginosa strains (4 of 5) tested showed the capability to grow in most inoculated PCs, revealing a faster time to detection (TTD) at an incubation temperature of 35 °C. The tested Pseudomonas putida (n = 3) strains showed a noticeably reduced capability to grow in PCs. Nonetheless, those with a notable growth capability revealed a faster TTD at an incubation temperature of 35 °C. Only one of the four Pseudomonas fluorescens strains tested (strain ATCC 13525) was able to grow in PCs, showing a faster TTD at an incubation temperature of 25 °C but also detection at 35 °C. The commonly detected bacteria involved in the bacterial contamination of PCs showed a superior TTD at 35 °C incubation. Only one P. fluorescens strain showed superior growth at 25 °C; however, the microbiological control at 35 °C did not fail to identify this contamination. In conclusion, the use of PC screening using a dual-temperature setting for microbiological control is presently not justified according to the observed kinetics.

Evaluation of Siderophore Production by Different Promising Microbial Isolates

Indian alkaline soils are deficient in iron due to high pH, high calcium carbonate, highly permeable coarse textured soils, and soils low in organic carbon content. This study is carried out to increase the iron use efficiency of soil by using promising microbial isolates. Production of siderophore by promising microbial isolates is a greatest invention which help in increasing uptake of iron. A short-term laboratory experiment was carried “To evaluate the siderophore productions by different promising microbial isolates using chrome azurol S assay technique”. Ten microbial isolates were inoculated on plate as well as in broth medium. Plates were observed for orange halo formation around the bacterial growth. The size of orange halo around the colony of each microbial isolates was measured. The broth cultures inoculated with inoculum, incubated at 28 ± 20C for 24-72 hr with constant shaking at 120 rpm. After the incubation, the culture broths were centrifuged at 10,000 rpm for 10 min. The cell free supernatants were subjected to quantitative estimation of siderophores by CAS-shuttle, absorbance was measured at 630 nm against a reference consisting of 0.5 ml of uninoculated broth and 0.5 ml of CAS reagent. Obtained results indicated that in both plate and broth assays medium inoculated with strain Pseudomonas fluorescens show significantly higher orange halo formation around the growth and maximum siderophore content in aliquot. Inoculation of this plant growth promoting microbial isolates will be the great achievement in replacing chemical fertilizers in agriculture.

The presence of the plant pathogen Fusarium graminearum as a soil inoculum enhances the rhizosphere survival of bacterial biocontrol strains aimed at the pathogen

AbstractThe serious wheat pathogen Fusarium graminearum causes both root rot and head blight. Some classical biocontrol tests were first used to explore the biocontrol ability of 39 Pseudomonas fluorescens strains. The five most antifungal strains B4, P13, UTPf127, UTPf125 and UTPf105 were selected to screen known antifungal antibiotic genes and greenhouse experiments. The ability of bacteria to colonize wheat rhizosphere and their effect on plant growth in the presence and absence of soil F. graminearum inoculum was studied under greenhouse conditions. Overall, biocontrol bacteria populations were significantly higher in both wheat endo‐and ectorhizosphere of pathogen‐inoculated soil than in healthy soil. The population of all strains differently decreased with time. On day 28, endorhizosphere populations of strain B4 could be detected in inoculated but not healthy soil, while UTPf127 populations remained high in endorhizospheres at all tested times. Isolate B4 and UTPf105 showed the most substantial plant growth in pathogen‐inoculated soil compared to pathogen‐inoculated soil without added bacteria. UTPf127‐treated plants grew better in control soil than when the pathogen was present. In contrast, UTPf125 and P13 showed little effect on plant growth. These results point to complex interactions between pathogen and biocontrol bacteria and suggest that a fungal pathogen in the soil can affect the survival of potential bacterial biological control agents. Additionally, they highlight the importance of screening and evaluating potential biocontrol bacteria against soilborne fungal pathogens by in vivo tests rather than relying on plate screenings.