Pseudomonas Putida Research Articles

Treatment of Cigarette Butts: Biodegradation of Cellulose Acetate by Rot Fungi and Bacteria

This study demonstrated the biodegradation of two different brands of cigarette butts (CBs), which are primarily composed of cellulose acetate, by four distinct microorganisms. These included the white rot fungus Pleurotus ostreatus, the brown rot fungus Lentinus lepideus, and the bacteria Bacillus cereus and Pseudomonas putida. After 31 days of treatment, weight loss measurements revealed a mass loss of 24–34%, where B. cereus exhibited the greatest efficacy in terms of mass loss for both brands of CBs. Fourier-Transform Infrared Spectroscopy (FTIR), confocal microscopy, and scanning electron microscopy (SEM) confirmed changes in the surface of the CBs, attributable to structural wear and material breakdown, indicating effective biodegradation by the evaluated microorganisms. Furthermore, the analyses confirmed changes in the surface of the CBs, attributable to structural wear and material breakdown, indicating effective biodegradation by the evaluated microorganisms.

Study on the Effect of Conditioners on the Degradation of Tetracycline Antibiotics in Deer Manure Composting

The unscientific disposal of agricultural solid waste introduces more antibiotics and other pollutants into the environment. Composting, as an environmentally friendly solid waste disposal method, can be used as a green way to degrade antibiotics, and conditioners can regulate the physicochemical indicators of the composting process. This article investigates the removal mechanism of tetracycline antibiotics (TCs) during the composting process by adding different regulators (biochar, zeolite, and biochar + zeolite). The results showed that the conditioning agent could significantly improve the removal efficiency and removal rate of TCs in compost. Among them, the addition of the zeolite group had the highest degradation rate of TCs, which were 91.39% (Tetracycline), 97.18% (Chlortetracycline), and 95.68% (Oxytetracycline). The combination of biochar and zeolite conditioning agents effectively minimized the migration of TCs into the soil. According to the findings of the artificial neural network model, it was determined that TCs exhibited the highest sensitivity to biochar + zeolite modulators at 31.28%. Conditioners influenced the removal of TCs in compost by impacting their physicochemical properties and microbial community structure. We isolated and domesticated a suitable microbial preparation that promotes the degradation of TCs, including Acinetobacter pittii, Stenotrophomonas maltophilia, Lactobacillus reuteri, Pseudomonas putida, and Trichosporon dohaense.

Deletion of ACC Deaminase in Symbionts Converts the Host Plant From Water Waster to Water Saver

ABSTRACTIncreasing drought events coupled with dwindling water reserves threaten global food production and security. This issue is exacerbated by the use of crops that overconsume water, undermining yield. We show here that microorganisms naturally associated with plant roots can undermine efficient water use, whereas modified bacteria can enhance it. We demonstrate that microbe‐encoded genes shape drought tolerance, likely by modulating plant hormonal balance. Specifically, we built a minimal holobiont out of Arabidopsis thaliana and either the bacterium Pseudomonas putida UW4 or its isogenic AcdS− mutant, lacking the enzyme ACC deaminase. This enzyme breaks down the precursor of ethylene, a key regulator in plant response to drought. This single mutation profoundly affected plant physiology and shifted the plant from a ‘water‐spender’ (with more growth under well‐watered conditions) to a ‘water‐spender’ phenotype. Under drought, plants associated with wild‐type bacteria consumed soil water faster, leading to a shorter period of growth followed by death. In contrast, plants associated with the AcdS− mutant managed to maintain growth by reducing water consumption via stomatal closure, thus conserving soil water. This allowed plants to survive severe water deficiency. We conclude that plant‐associated bacteria can modulate plant water use strategies, opening possibilities to engineer water‐savvy crop‐production systems.

Metal Resistance of Microorganisms as a Crucial Factor for Their Homeostasis and Sustainable Environment

Heavy metals are prevalent environmental components, but when their concentrations exceed critical thresholds, they pose environmental hazards, disrupting the sustainability of ecosystems. Microorganisms are among the first to encounter the toxic effects of metals. Therefore, it is crucial to understand both the levels and mechanisms of their resistance to maintain their homeostasis under the pressure of extreme factors as well as contribute to increasing the sustainability of ecosystems. The aim of the study was to examine two soil bacterial strains, Brevundimonas vesicularis USM1 and Pseudomonas putida USM4, to assess their resistance levels to toxic metals and to identify the mechanisms behind this resistance. For this purpose, microbiological, statistical, and bioinformatics methods were used. The comparative analysis of the two strains revealed that P. putida USM4 exhibited greater resistance to Cr(VI), Co(II), Cu(II), Ni(II), and Fe(III) compared to B. vesicularis USM1. This was confirmed by the metal concentrations at which the strains could survive, their growth dynamics, and the genetically based resistance mechanisms. These findings enhance our understanding of microbial metal resistance and contribute to the advancement of microbial-based environmental biotechnologies.

Culture-Dependent Characterization of Hydrocarbon Utilizing Bacteria and Fungi from an Artisanal Crude Oil Refining Site

Crude oil refining is a global insert responsible for the production of a wide array of petroleum based products crucial for various sectors including energy, transportation, and manufacturing. However, the artisanal form of crude oil refining, often characterized by its small scale and limited technological infrastructure, has emerged as a major environmental concern in several regions around the world. Illegal refining of crude oil has led to oil spillages which in turn lead to a disruption of the microbial population of the soil. Hence, the aim of this study was to isolate and characterize the heterotrophic and hydrocarbon utilizing bacteria and fungi from an artisanal crude oil refining site. A total of thirty six (36) soil samples were collected from three (3) artisanal crude oil refining sites at iwofe, ogbogoro and ibaa community all in Rivers State, Nigeria. The samples were collected using soil auger and subjected to standard microbiological procedures such as culturing, isolation and identification. The results revealed significantly elevated levels of heterotrophic and hydrocarbon utilizing bacteria and fungi in the soil samples, with notable variations (p≤0.05) across the different artisanal crude oil refining sites. Total Heterotrophic Bacteria (THB) counts ranged from 3.75x105CFU/g in Iwofe to 2.70x105CFU/g in Ibaa, Total heterotrophic Fungal (THF) counts ranged from 2.80x104CFU/g recorded in Ogbogoro to 1.45x104CFU/g recorded in Iwofe, Hydrocarbon Utilizing Bacteria (HUB) counts ranged from 2.25x103CFU/g in Ibaa to 1.30x103CFU/g in Iwofe and Hydrocarbon Utilizing Fungi (HUF) counts ranged from 2.50x102CFU/g recorded in Ogbogoro to 1.40x102CFU/g recorded in Ibaa community with significant differences (p≤0.05). Bacteria isolated and characterized from the soil include Enterobacter, Pseudomonas putida, Serratia and Bacillus amyloliquefaciens while fungi include Fusarium, Aspergillus, Penicillium and Mucor. The microorganisms identified in this study have been reported to play key roles in the utilization of crude oil. Pseudomonas and Bacillus were the most dominant bacterial isolates and their dominance could imply that the soil could support the growth of crops. Thus, while they utilize the hydrocarbons, they also serve as plant-growth promoting microorganisms. Although some of the microorganisms in the present study have been reported to promote the growth of plant, the dumping of crude oil products legal or illegal should be minimized to avoid the extinction of plant-promoting microorganisms.

Mercury-tolerant metalophiles: A bio tool for remediation of mercury (Hg) affected Environs

Due to their low solubility, carcinogenic and mutagenic effects, heavy metals are of critical concern to humans and the environment. Mercury (Hg) is one of the rarest and least concentrated elements in the world, but it is ranked third in terms of toxicity. The present investigation evaluates the response and tolerance limit of bacteria isolated from the saffron soil of the Kashmir Valley to various mercury concentrations (50 ppm to 400 ppm). The minimum inhibitory concentration (MIC) was calculated after 24hours by measuring the optical density. Isolated bacteria have been characterized using two efficient methods, i.e. 16S rRNA gene sequence and MALDI-TOF MS. A total of 72 isolates were investigated for the mercury tolerance and among them, only 8 isolates (Staphylococcus equorum, Leclercia adecarboxylata, Staphylococcus warneri, Klebsiella pneumoniae, Serratia plymuthica, Bacillus megaterium, Pseudomonas putida and Bacillus safensis) were found tolerant to mercury with varying MIC. In comparison, Pseudomonas putida has been found to have the maximum resistance (400 ppm) for mercury and S. plymuthica and L. adecarboxylate had the lowest resistance level (200 ppm). The sequestration potential results revealed that P. putida executed the highest sequestration potential (73%) while K. pneumoniae showed the lowest sequestration potential (51.63%). Thus mercury tolerance capacity of these species may be utilised for detoxification and removal of mercury from polluted sites, providing an eco-friendly technique for bioremediation of mercury-affected environments.

Enhanced biosynthesis of poly(3-hydroxybutyrate) in engineered strains of Pseudomonas putida via increased malonyl-CoA availability.

Malonyl-coenzyme A (CoA) is a key precursor for the biosynthesis of multiple value-added compounds by microbial cell factories, including polyketides, carboxylic acids, biofuels, and polyhydroxyalkanoates. Owing to its role as a metabolic hub, malonyl-CoA availability is limited by competition in several essential metabolic pathways. To address this limitation, we modified a genome-reduced Pseudomonas putida strain to increase acetyl-CoA carboxylation while limiting malonyl-CoA utilization. Genes involved in sugar catabolism and its regulation, the tricarboxylic acid (TCA) cycle, and fatty acid biosynthesis were knocked-out in specific combinations towards increasing the malonyl-CoA pool. An enzyme-coupled biosensor, based on the rppA gene, was employed to monitor malonyl-CoA levels invivo. RppA is a type III polyketide synthase that converts malonyl-CoA into flaviolin, a red-colored polyketide. We isolated strains displaying enhanced malonyl-CoA availability via a colorimetric screening method based on the RppA-dependent red pigmentation; direct flaviolin quantification identified four engineered strains had a significant increase in malonyl-CoA levels. We further modified these strains by adding a non-canonical pathway that uses malonyl-CoA as precursor for poly(3-hydroxybutyrate) biosynthesis. These manipulations led to increased polymer accumulation in the fully engineered strains, validating our general strategy to boost the output of malonyl-CoA-dependent pathways in P. putida.

Isolation and Characterization of Ureolytic Calcifying Bacteria from Methane Hydrate-Bearing Marine Sediments for Bio-cementation Application

In bio-calcification, microbes precipitate calcium carbonate (CaCO3), forming versatile solid substances that promotes eco-friendly materials and reduce carbon emissions. Marine bacteria can generate bio-cements to strengthen dikes and combat coastal erosion. However, the role of marine bacteria in generating bio-cements for enhancing coastal structures and combating erosion is not fully understood. This study investigates the potential of CaCO₃ precipitating bacteria isolated from methane hydrate-bearing marine sediments. Five calcifying marine bacteria were isolated using Christensen's urea agar from marine sediments collected from Gawadar coastal, Pakistan. Bacterial strains induced CaCO3 precipitation producing urease enzymes. Strains were identified as Pseudomonas putida, Bacillus altitudinis, Vibrio sp., Bacillus sp., and Vibrio plantisponsor. Energy-dispersive X-ray spectroscopy, scanning electron microscopy, and X-ray diffraction were applied for the identification and differentiation of calcite and vaterite precipitates. The growth of isolates and precipitation potential were observed optimum at 5% NaCl and pH 9.5-11. Bacillus altitudinis (ST4SD3) and Bacillus sp. (ST4SD1) produced more soluble Ca2+ (8532.53 mg/l and 7581.98 mg/l) as compare to other isolates at higher pH 10 and pH 11, favorable for CaCO3 precipitation. It is concluded that marine ureolytic bacteria possess significant potential for bio-cementation, which can stabilize methane hydrate-bearing sediments, improve soil properties, protect coastal regions from erosion, and crucial in the methane cycle, a greenhouse gas. We recommend further exploration of such bacteria's applications in marine construction and sediment stabilization to enhance the robustness and longevity of coastal infrastructures. Furthermore, such bacteria could also be beneficial in extracting gas from unconsolidated methane hydrates containing sediments.

Water-soluble chlorogenic acid-chitosan and polydatin-chitosan conjugates: antibacterial activity and inhibition of lipid and protein oxidation.

Chitosan (CS), an abundant alkaline polysaccharide, is valued for its biocompatibility, non-toxicity, and antibacterial properties. However, its limited solubility and modest antioxidant activity constrain its utility. Grafting polyphenols onto chitosan through the use of grafting reactions can enhance both the solubility and bioactivity of chitosan. Among the techniques employed, the free radical grafting method is favored for its simplicity, environmental sustainability, and its effectiveness in preserving biological activity. In this study, chlorogenic acid (CGA) and polydatin (PLD) were conjugated successfully to chitosan by a Vc/H2O2 redox system. Analytical techniques such as ultraviolet-visible (UV-visible) spectroscopy, fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and proton nuclear magnetic resonance (1H NMR) were employed to confirm the formation of covalent bonding between the polyphenol molecules and the chitosan backbone. The novel conjugates displayed superior antioxidant properties in comparison with pristine chitosan, as evidenced by their enhanced 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical, 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical, and hydroxyl radical scavenging capacities, and Fe2+ reducing power. Both CGA-CS and PLA-CS exhibited excellent lipid and protein oxidation inhibition capabilities. Furthermore, the conjugates were shown to have significant antibacterial effects against four common pathogenic bacteria: Pseudomonas fluorescens, Pseudomonas aeruginosa, Pseudomonas putida, and Staphylococcus aureus (P < 0.05). The newly synthesized water-soluble polyphenol-chitosan conjugates demonstrated remarkable biological activity, particularly CGA-CS. This study offers new insights and a strong theoretical foundation for developing natural food preservation materials with potential applications in the food industry. © 2024 Society of Chemical Industry.

CFD-guided scaling of Pseudomonas putida fermentation

This study evaluated the scale-up of Pseudomonas putida fed-batch fermentation from a 2 L benchtop-scale stirred bioreactor to a 200 L pilot-scale tank by using a validated computational fluid dynamic (CFD) model. One of the major concerns in this fermentation process is the potential reduction in mixing quality with increasing scale, leading to lower yield or product quality. For a low-risk scale-up, a multiphase Euler-Euler CFD model was developed that simulated the hydrodynamics of the fed-batch system at various filling volumes, representing different stages of the fermentation process. The model was validated using experimental data of mixing time and mass transfer coefficient. The hydrodynamic model was then coupled with a Monod kinetic model of P. putida ‘s fermentation. Response surface methodology was used to generate a performance map of the pilot bioreactor at various aeration, agitation, and bioreactor filling volumes. The study considered different established scale-up approaches, such as constant tip speed and aeration rate across scales, constant kLa, as well as constant power to unit of liquid volume (P/V). The performance of the bioreactor was assessed, and the optimum operating ranges of the input parameters were obtained at different stages of the fermentation. Using performance map the possibility of substrate and oxygen gradient formation, and the gradient severity inside the pilot bioreactor at different working volumes were evaluated.

Identification and characterization of LuxR solo homolog PplR in pathogenic Pseudomonas plecoglossicida NB2011

Pseudomonas plecoglossicida is a causative agent of visceral granulomas in large yellow croaker (Larimichthys crocea). Quorum sensing (QS) is widely involved in imparting virulence to pathogenic bacteria; however, it has not been studied in P. plecoglossicida. In this study, we annotated a LuxR family transcriptional regulator in P. plecoglossicida NB2011 and designated as PplR. We aligned the protein sequence by BlastP and Clustal X2, monitored the N-acyl-homoserine lactone (AHL) signal production through cross-feeding bioassay and HC-MS/MS; investigated exogenous AHL signal binding by recombinant expression and thin layer chromatography; constructed a deletion mutant of the target gene by method of double homologous recombination; sequenced the transcript RNA and analyzed the data; additionally, characterized phenotypes of wild type and mutant strain. The LuxR homolog PplR was found to share high similarity with PpoR—the LuxR solo of Pseudomonas putida—without a cognate LuxI. The wild-type strain did not produce any AHL signals and the recombinant LuxR protein was found to bind C6-L-homoserine lactone (C6-HSL), C8-HSL, 3-oxo-C10-HSL, and 3-oxo-C12-HSL. RNA-seq analysis indicated 84 differentially expressed genes—5 upregulated and 79 downregulated—mainly enriched in gene ontology terms, such as flagella-dependent motility, integral component of membrane, DNA binding and transcription, and metal ion binding, suggesting that PplR is a master transcription regulator. The mutant strain showed attenuated biofilm-forming ability and stress resistance, and the data support a role for PplR in the regulation of these traits in P. plecoglossicida NB2011 independent of the presence of AHL signals. This is the first study to provide QS-related information on P. plecoglossicida.

Plants-extracts mediated CuS nanoparticles: An effective antibacterial agent

Antibacterial activity of plant-mediated synthesized CuS nanoparticles against gram-positive Bacillus subtilis and gram negative Pseudomonas putida is studied in this presented work. A facile hydrothermal approach was followed to synthesize spherical shaped CuS nanoparticles using flowers extract of Tagetes patula (S1), leaves extract of Azadirachta indica (S2), and bark extract of Terminalia arjuna (S3). Crystal phase identification, average crystallites size, surface morphology, absorbance spectra and energy band gap analyses of samples were further determined using XRD, SEM, and UV-DRS spectroscopy respectively. Furthermore, under irradiation of visible light, antibacterial activity of marigold flowers mediated (S1), neem leaves mediated (S2), and arjuna bark mediated (S3) CuS samples were studied. XRD data confirmed the marigold mediated CuS sample has relatively smaller crystallites size of 10.67 nm. The estimated band gap energies for respective S1, S2, and S3 samples are 174 eV, 175 eV, and 177 eV. The antibacterial analysis of S1 sample displays its excellent antibacterial activity with the formation of relatively large inhibition zones of 29 mm and 30 mm diameters, against Bacillus subtilis and Pseudomonas putida respectively. The demonstrated antibacterial activity of biocompatible CuS nanoparticles suggests their potential use in biomedical applications.

Engineering of tnaC-Based Tryptophan Biosensors for Dynamic Control of Violacein Production.

Tryptophan not only serves as a fundamental building block for protein synthesis but also acts as a metabolic precursor for a diverse array of high-value chemicals. Although a few tryptophan-responsive biosensors are currently available, there is a growing interest in developing high-performance biosensors. In this study, we create a miniature toolkit of tryptophan biosensors based upon the leader regulatory region of the tnaCAB operon, which is responsible for tryptophan catabolism in Escherichia coli. Four variants are generated by engineering the tnaC leader sequence, which encodes a leader peptide composed of 24 amino acid residues. Subsequently, the performance of both the natural tnaC sequence and its engineered variants is assessed in a reporter strain based on the MazEF toxin-antitoxin system. The results demonstrate that two engineered variants exhibit increased sensitivity to low levels of tryptophan. Moreover, the engineered biosensors are further optimized by replacing the native promoter of tnaC with a phage-derived constitutive promoter. Intriguingly, the engineered biosensors can be reconstructed for extended application in Pseudomonas putida, a robust microbial chassis for metabolic engineering. In summary, our study expands the toolkit of tryptophan biosensors that can be broadly used for the bioproduction of many other high-value tryptophan-derived products.

Rapid, Sensitive, and Specific Microbial Whole-Cell Biosensor for the Detection of Histamine: A Potential Food Toxin.

Histamine is a biogenic amine; its level indicates food quality, as elevated levels cause food poisoning. Therefore, monitoring food at each step during processing until it reaches the consumer is crucial, but current techniques are complicated and time-consuming. Here, we designed a Pseudomonas putida whole-cell biosensor using a histamine-responsive genetic element expressing a fluorescent protein in the presence of the cognate target. We improved the performance of the proposed biosensor by optimizing the chassis, genetic regulatory element, and reporter gene. A sensitive and rapid biosensor variant was obtained with a limit of detection (LOD) of 0.39 ppm, manifesting a linear response (R2 = 0.98) from 0.28 to 18 ppm in 90 min. The biosensor showed minimal cross-reactivity with other biogenic amines and amino acids prevalent in food, making it highly specific. The biosensor effectively quantified histamine in spiked fish, prawn, and wine samples with a satisfactory recovery. Additionally, a colorimetric sensor variant PAlacZ was developed enabling histamine quantification in seafood via a smartphone application, with an LODgray of 0.23 ppm, exhibiting a linear response from 0 to 2.24 ppm. Overall, this study reports an efficient, specific, and highly sensitive biosensor with strong potential for the on-site detection of histamine, ensuring food safety.

Bioremediation of hydrocarbon pollutants by Pseudomonas putida under optimal conditions

Background: The extreme toxicity of petroleum products to human and environmental health, particularly when linked to large-scale unintentional spills, has made them one of the most serious and current environmental pollution issue. Petroleum products are a complex mixture of hydrocarbons.Methods: Oil-contaminated soil samples were gathered and utilized to isolate hydrocarbon-degrading bacterial isolates. The bacterial isolates possessing bioremediation capabilities were identified using phenotypic determination and biochemical properties. The Optimal conditions including incubation period, temperature, different pH values and different carbon sources were studied for bioremediation of crude oil by bacterial isolates.Result: In Wasit province of Iraq, Pseudomonas putida, P. fluorescens, and P. aeruginosa isolated from soil samples tainted with petroleum hydrocarbons. Pseudomonas putida have more ability for bioremediation of crude oil (68%) compared to P. aeruginosa and P. fluorescens (47%, 58%) respectively. The results of optical density (600nm), biomass and (E24%) index for Pseudomonas putida were (1.080, 1.98 and 60%) respectively. The Optimal conditions (incubation period, temperature, different pH values and different carbon sources) were studied for bioremediation of crude oil by Pseudomonas putida by using liquid BHM supplemented with 1% crude oil. The result of this study showed that the incubation period of 9 days was the optimum for bioremediation of hydrocarbons which was 88.33%. The optimum temperature and pH were 35 °C and 7 respectively. The carbon source (glucose and fructose) was optimal for hydrocarbon bioremediation.Conclusion: This bacterial isolate Pseudomonas putida can be use in petroleum hydrocarbon bioremediation process.Keywords: Pseudomonas putida; Bioremediation; Optical density

Rhizobacterial syntrophy between a helper and a beneficiary promotes tomato plant health.

None declared.Conflicts of interestMicrobial interactions impact the functioning of microbial communities. However, microbial interactions within host-associated communities remains poorly understood. Here, we report that the beneficiary rhizobacterium Niallia sp. RD1 requires the helper Pseudomonas putida H3 for bacterial growth and beneficial interactions with the plant host. In the absence of the helper H3 strain, the Niallia sp. RD1 strain exhibited weak respiration and elongated cell morphology without forming bacterial colonies. A transposon mutant of H3 in a gene encoding succinate-semialdehyde dehydrogenase displayed much attenuated support of RD1 colony formation. Through subsequent addition of succinate to the media, we found that succinate serves as a public good that supports RD1 growth. Comparative genome analysis highlighted that RD1 lacked the gene for sufficient succinate, suggesting its evolution as a beneficiary of succinate biosynthesis. The syntrophic interaction between RD1 and H3 efficiently protected tomato plants from bacterial wilt and promoted the tomato growth. The addition of succinate to the medium restored complex II-dependent respiration in RD1 and facilitated the cultivation of various bacterial isolates from the rhizosphere. Taken together, we delineate energy auxotrophic beneficiaries ubiquitous in the microbial community, and these beneficiaries could benefit host plants with the aid of helpers in the rhizosphere.

Evaluation of the Robustness Under Alkanol Stress and Adaptability of Members of the New Genus Halopseudomonas

Many species of the genus Pseudomonas are known to be highly tolerant to solvents and other environmental stressors. Based on phylogenomic and comparative genomic analyses, several Pseudomonas species were recently transferred to a new genus named Halopseudomonas. Because of their unique enzymatic machinery, these strains are being discussed as novel biocatalysts in biotechnology. In order to test their growth parameters and stress tolerance, five Halopseudomonas strains were assessed regarding their tolerance toward different n-alkanols (1-butanol, 1-hexanol, 1-octanol, 1-decanol), as well as to salt stress and elevated temperatures. The toxicity of the solvents was investigated by their effects on bacterial growth rates and presented as EC50 concentrations. Hereby, all Halopseudomonas strains showed EC50 values up to two-fold lower than those previously detected for Pseudomonas putida. In addition, the activity of the cis-trans isomerase of unsaturated fatty acids (Cti), which is an urgent stress response mechanism known to be present in all Pseudomonas species, was monitored in the five Halopseudomonas strains. Although several of the tested species were known to contain the cti gene, no significant phenotypic activity could be detected in the presence of the assayed stressors. A bioinformatic analysis of eight cti-carrying Halopseudomonas strains examining promotor binding sites, binding motifs and signal peptides showed that most of the cti genes have a lipoprotein signal peptide and promotor regions and binding motifs that do not coincide with those of Pseudomonas. These insights represent putative reasons for the absence of the expected Cti activity in Halopseudomonas, which in turn has always been observed in cti-carrying Pseudomonas. The lack of Cti activity under membrane stress conditions when the cti gene is present has never been documented, and this could represent potential negative implications on the utility of the genus Halopseudomonas for some biotechnological applications.

Impact of Plant Growth-Promoting Microorganism (PGPM) Consortium on Biochemical Properties and Yields of Tomato Under Drought Stress.

Drought is the most important abiotic stress that restricts the genetically predetermined yield potential of the crops. In the present study, four tomato varieties: Kashi Vishesh, Kashi Aman, Kashi Abhiman, and Kashi Amrit, were used to study the effect of PGPMs (plant growth-promoting microorganisms). PGPM strains, Bacillus megaterium BHUPSB14, Pseudomonas fluorescens BHUPSB06, Pseudomonas aeruginosa BHUPSB01, Pseudomonas putida BHUPSB0, Paenibacillus polymixa BHUPSB17, and Trichoderma horzianum, were used as the consortium. The control group was irrigated up to 80% of field capacity, while 7-, 14-, and 21-day water-deficit-exposed (DWD) plants' pot soil moisture was maintained to 40, 25, and 15% of the field capacity, both with and without the PGPM inoculation condition. The physiological parameters, such as electrolyte leakage, relative water content, photosynthetic efficiency, and chlorophyll color index, were significantly improved by PGPM application under progressive drought stress, compared to the control. PGPM application enhanced the proline accumulation and reduced the formation of hydrogen peroxide and lipid peroxidation under drought stress. The plant growth attributes were significantly increased by PGPM application. The Kashi Amrit variety showed the highest fruit yield among the four varieties under all the treatments. The PGPM consortium application also improved the soil physico-biological properties and nutrient availability in the soil. The PGPM consortium used in this study can potentially mitigate drought stress on tomato in drought-prone regions and act as a biofertilizer. The present study will open a new avenue of drought stress management in tomato.

The puzzle of two tandem acyl-CoA ligases of Pseudomonas putida F1.

Pseudomonas bacteria demonstrate a great deal of metabolic diversity and consequently colonize a wide range of ecological niches. A characteristic of these bacteria is a pair of genes in tandem annotated as acyl-CoA ligases involved in fatty acid degradation. The Pseudomonas putida F1 genome is annotated as having at least nine genes encoding acyl-CoA ligases which are scattered around the chromosome excepting the tandem pair. Since similar tandem pairs are found in other pseudomonads, we have constructed and characterized deletion mutants of the tandem ligases. We report that the encoded proteins are authentic acyl-CoA ligases involved in fatty acid degradation.

Draft genome sequencing of multidrug-resistant Pseudomonas putida strains, isolated from dairy cows with clinical mastitis and their farm environment.

We sequenced the genomes of three multidrug-resistant Pseudomonas putida strains namely 11CM-M1, 11CM-F1, and 11CM-S1, isolated from milk, feces, and farm soil samples collected from dairy cows with clinical mastitis. The assembled draft genomes of these P. putida strains were approximately 5.6 Mbp, with a GC content of 62.4%.