Potential Bacterial Strains Research Articles

Making waves: Enhancing pollutant biodegradation via rational engineering of microbial consortia

Biodegradation holds promise as an effective and sustainable process for the removal of synthetic chemical pollutants. Nevertheless, rational engineering of biodegradation for pollutant remediation remains an unfulfilled goal, while chemical pollution of waters and soils continues to advance. Efforts to (i) identify functional bacteria from aquatic and soil microbiomes, (ii) assemble them into biodegrading consortia, and (iii) identify maintenance and performance determinants, are challenged by large number of pollutants and the complexity in the enzymology and ecology of pollutant biodegradation. To overcome these challenges, approaches that leverage knowledge from environmental bio-chem-informatics and metabolic engineering are crucial. Here, we propose a novel high-throughput bio-chem-informatics pipeline, to link chemicals and their predicted biotransformation pathways with potential enzymes and bacterial strains. Our framework systematically selects the most promising candidates for the degradation of chemicals with unknown biotransformation pathways and associated enzymes from the vast array of aquatic and soil bacteria. We substantiated our perspective by validating the pipeline for two chemicals with known or predicted pathways and show that our predicted strains are consistent with strains known to biotransform those chemicals. Such pipelines can be integrated with metabolic network analysis built upon genome-scale models and ecological principles to rationally design fit-for-purpose bacterial communities for augmenting deficient biotransformation functions and study operational and design parameters that influence their structure and function. We believe that research in this direction can pave the way for achieving our long-term goal of enhancing pollutant biodegradation.

Microbial and physico-chemical dynamics associated with chicken feather compost preparation vis-à-vis its impact on the growth performance of tomato crop

The study aimed to assess the effectiveness of five potent keratinolytic bacterial strains, including Bacillus halotolerans L2EN1, B. cereus N27, B. cereus N14, B. megaterium N35, and B. halotolerans DPE11, in the preparation of chicken feather compost (CFC) using chicken feathers (CF) and cow dung (CD) as substrates. The experiment that involved two setups (Set-I, with a keratinolytic bacterial consortium, and Set-II, without consortium) and five treatment combinations (T1 - CF only; T2 - 3CF:1CD; T3 - 1CF:1CD; T4 - 1CF:3CD; T5 - CD only) was conducted in both plastic pots and composting pits for six months. Microbiological and physico-chemical analyses of CFC conducted monthly revealed that treatment T4 in Set-I demonstrated the most favorable microbiological (bacteria: 9.40 Log CFU/g; fungi: 4.20 Log CFU/g; actinomycetes: 3.49 Log CFU/g; enteric: 7.62 Log CFU/g; spore-formers: 4.96 Log CFU/g; diazotrophs: 6.38 Log CFU/g; proteolytic bacteria: 7.98 Log CFU/g) and physico-chemical (pH: 7.53; temperature: 34.79 °C; EC: 0.87 mmhos/cm; moisture: 45.10%; non-volatiles: 21.25%; volatiles: 78.75%; organic carbon: 45.68%; N: 7.02%; P: 0.68%; K: 2.06%; C:N ratio: 15.70) characteristics. Subsequent efficacy testing of varying proportions (%) of T4 (T1 – 5.0, T2 – 10.0, T3 – 15.0, T4 – 20.0) on tomatoes, demonstrated significantly superior growth performance than the control (without CFC). Hence, application of CFC @ 10% may be recommended as an excellent organic fertilizer for tomatoes. In conclusion, co-composting CF (1 part) with CD (3 parts) employing keratinolytic bacteria offers an eco-friendly approach for repurposing CF waste into a nitrogen-rich organic fertilizer.

Augmentation in bioleaching potential of indigenous Bacillus sp. ISO1 for metals recovery from waste computer-printed circuit boards.

The bio-cyanidation process of various cyanogenic microorganisms is found to be a sustainable and effective method for metals recovery from primary and secondary sources. This process has surpassed the limitations of the chemical cyanide treatment process; thus, prioritized as a promising approach for e-waste "urban mining" strategies. The main focus of the study was to enhance the bioleaching capacity of indigenous Bacillus sp. ISO1 and to implement optimized parameters in large-scale bioleaching operations. The assessment of various amino acids unveiled that like other cyanogenic microorganisms Bacillus sp. ISO1 also preferred glycine as a prime precursor for cyanide synthesis, as maximum metal solubilization was achieved with glycine amino acid. Other amino acids influenced the bacterial growth but not significantly affected the biocyanidation process. The evaluation and optimization of methionine as a lixiviant stimulator demonstrated that the addition of 1 mg/L methionine effectively enhance the production of glycine-utilizing cyanide lixiviant, that led to a significant solubilization of Cu (86%), Au (75%), and Ag (63%) metals. Furthermore, the kinetics of metal solubilization and operating conditions were explored at increased volume (i.e., 3 L working volume) of bioleaching medium to assess the industrial scale potential of this potent bacterial strain with optimized parameters such as temperature, pH, pulp density, and inoculum size. The significant recovery of Cu (˃ 60%) and other metals at this substantial volume suggested the implementation of a bioleaching process with this potent bacterial strain at industrial scale operations.

Impact of biosurfactant produced by Bacillus spp. on biodegradation efficiency of crude oil and anthracene

Biosurfactants are surface active molecules generated by various microorganisms, including bacteria, actinobacteria, algae, and fungi. In this study, bacterial strains are isolated from soil contaminated with used motor oil and examined for potential biosurfactant production. A minimum salt medium (MSM), with crude oil as the only carbon source, is used to isolate potential biosurfactant-producing bacterial strains. About 23 strains are isolated, and all are subjected to the primary screening methods for biosurfactant production. Based on the emulsification index, oil displacement, and drop collapse screening methods, two isolates with potential biosurfactant-producing ability are selected for further studies. The synthesis of biosurfactants, crude oil and anthracene biodegradation is carried out with strains DTS1 and DTS2. Both strains show significant outcomes in crude oil degradation. In addition, both strains can utilize anthracene as the sole carbon source. During the degradation course, changes in the growth conditions are continuously monitored by measuring turbidity and pH. In this degradation study, the biosurfactant production aptitude of the isolated strains plays an essential role in increasing the bioavailability of hydrophobic hydrocarbons. These strains are identified down to the molecular level by employing 16S rRNA gene sequencing, and the acquired sequences are submitted to get the accession numbers. These prospective strains can be utilized to remediate hydrocarbon-contaminated environments.

Elicitation of E-waste (acrylonitrile-butadiene styrene) enriched soil bioremediation and detoxification using Priestia aryabhattai MGP1

Given the rise in both usage and disposal of dangerous electronics, there is a catastrophic rise in assemblage of electronic waste (e-waste). E-waste including various plastic resins are among the most frequently discarded materials in electronic gadgets. In current digital era, managing e-waste has become universal concern. From the viewpoint of persisting lacuna of e-waste managing methods, the current study is designed to fabricate an eco-friendly e-waste treatment with native soil bacteria employing an enrichment culture method. In the presence of e-waste, indigenous soil microbes were stimulated to degrade e-waste. Microbial cultures were isolated using enrichment medium containing acrylonitrile-butadiene styrene (ABS) as the primary carbon source. Priestia aryabhattai MGP1 was found to be the most dominant e-polymer degrading bacterial isolate, as it was reported to degrade ABS plastic in disposed-off television casings. Furthermore, to increase degradation potential of MGP1, Response Surface Methodology (RSM) was adopted which resulted in optimized conditions (pH 7, shaking-speed 120 rpm, and temperature 30 °C), for maximum degradation (18.88%) after 2 months. The structural changes induced by microbial treatment were demonstrated by comparing the findings of Field emission scanning electron microscopy (FESEM) images and Fourier Transform Infrared (FTIR) spectra confirming the disappearance of ≡ C─H peaks along with C–H, C=C and C ≡N bond destabilization following degradation. Energy-dispersive X-ray (EDX) analyzers of the native and decomposed e-polymer samples revealed a considerable loss in elemental weight % of oxygen by 8.4% and silica by 0.5%. Magnesium, aluminium and chlorine which were previously present in the untreated sample, were also removed after treatment by the bacterial action. When seeds of Vigna radiata were screened using treated soil in the presence of both e-waste and the chosen potent bacterial strain, it was also discovered that there was reduced toxicity in terms of improved germination and growth metrics as a phytotoxicity criterion.

Probiotic Lactobacillus strains isolated from date waste and wastewater for the kidney stone, intestinal oxalate-degradation and antioxidant activity

Lactic acid bacteria (LAB) are probiotic organisms and are promising alternatives to manage kidney stone problems. Oxalate digesting LAB was screened from date wastes and date wastewater. LAB was isolated using De Man, Rogosa and Sharpe agar (MRS agar) medium and was subjected to oxalate degradation assay in a calcium oxalate plate. The strain was further subjected to assay for its capacity to tolerate acidic pH value and bile salt. Then, anti-urolithiatic activity assay was carried out by in vitro analysis. Based on preliminary characteristics, among 62 oxalate degrading strains, twenty-four strains exhibited a greater than 10 mm zone. The potent bacterial strains were identified as Lactobacillus cassei, L. acidophilus, L. gasseri and L. fermentum. Isolates from date wastes showed better antagonistic properties towards bacterial pathogens. At 50 µg Calcium oxalate concentration, 75.6 ± 0.865 degradation was achieved by L acidophilus. LAB isolated from date waste showed promising anti-urolithiasis activity. Hence, date waste may serve as a potential source for LAB probiotics to treat hyperoxaluria.

Biodegradation of Waste Lubricant Oil by a Novel Isolated Biosurfactant Producer- Achromobacter xylosoxidans PSA5

Waste lubricant oil (WLO) is a critical environmental issue because of its recycle and disposal challenges. A potent biosurfactant-producing bacterial strain was isolated by the enrichment culture technique using WLO as the sole carbon source from the oil-contaminated soils. The strain was identified as Achromobacter xylosoxidans (NCBI GenBank accession number: MW673656) based on the morphological, biochemical, and 16S rRNA gene sequencing. The preliminary characterization of the produced biosurfactant by biochemical methods revealed its glycolipid nature. The strain possessed extensive biodegradative potential and degraded various components present in WLO. The gas chromatography-mass spectrometry (GC-MS) analysis showed that the strain could degrade hydrocarbons (C7-C22) and diethyl phthalate, a priority pollutant, with a relative degradation of 43.87% within 7 days of incubation. The biodegradation of WLO by the strain confers its use in the bioremediation of oil-polluted environments, and the simultaneous biosurfactant production is undoubtedly a step toward greener technology.

Novel BTEX-degrading strains from subsurface soil: Isolation, identification and growth evaluation

Monoaromatic hydrocarbons such as benzene, toluene, ethylbenzene, and o, m, and p-xylenes (BTEX) are high-risk pollutants because of their mutagenic and carcinogenic nature. These pollutants are found with elevated levels in groundwater and soil in Canada at several contaminated sites. The intrinsic microbes present in the subsurface have the potential to degrade pollutants by their metabolic pathways and convert them to non-toxic products. However, the low subsurface temperature (5–10 °C) limits their growth and degradation ability. This study examined the feasibility of subsurface heat augmentation using geothermal heating for BTEX bioremediation. Novel potent BTEX-degrading bacterial strains were isolated from soil at 3.0, 42.6, and 73.2 m depths collected from a geothermal borehole during installation and screened using an enrichment technique. The selected strains were identified with Sanger sequencing and phylogenetic tree analysis, revealing that all the strains except Bacillus subtilis are novel with respective to BTEX degradation. The isolates, Microbacterium esteraromaticum and Bacillus infantis showed the highest degradation with 67.98 and 65.2% for benzene, 72.8 and 71.02% for toluene, 77.52 and 76.44% for ethylbenzene, and 74.58 and 74.04% for xylenes respectively. Further, temperature influence at 15 ± 1 °C, 28 ± 1 °C and 40 ± 1 °C was observed, which showed increased growth by two-fold and on average 35–49% more biodegradation at higher temperatures. Results showed that temperature is a positive stimulant for bioremediation, hence geothermal heating could also be a stimulant for in-situ bioremediation.

An experimental study for the identification of some bacterial strains for uranium bioremediation by gamma spectrometry

In this work, it was aimed to determine the potential bacterial strains that can be bioremediated of the radioactive uranium. The experimental analysis was made in gamma spectrometry. Uranyl acetate (CH3COO)2UO2.2H2O was used as the radioactive material. The radioactive solutions containing bacterial strains (P. chlororaphis (3N17-10); B. licheniformis (1N17-3); L. casei (NM-25); L. plantarum (NM-10); L. brevis (NM-26); L. lactis (NM-41); L. curvatus (NM-1); L. pentosus (NM-38); L. coryniformis (NM-22) and B. subtilis (N-28)) were prepared. A high purity germanium detector with a resolution of 490 eV at 122 keV was used to measure the photon intensities emitted from the radioactive solutions. The removal percentage and adsorbed amount of the investigated samples were determined. The results showed that P. chlororaphis have got an excellent sorption capacity for uranium removal.

Isolation and characterization of phosphate-solubilizing bacterium Pantoea rhizosphaerae sp. nov. from Acer truncatum rhizosphere soil and its effect on Acer truncatum growth.

The Acer truncatum Bunge, widely distributed in North China, shows excellent tolerance to low-P soils. However, little information is available on potential phosphate-solubilizing bacterial (PSB) strains from the A. truncatum rhizosphere. The objectives of this work were to isolate and characterize PSB from A. truncatum rhizosphere soil and to evaluate the effect of inoculation with the selected strain on A. truncatum seedlings. The strains were characterized on the basis of phenotypic characteristics, carbon source utilization pattern, fatty acid methyl esters analysis, 16S rRNA gene and the whole-genome sequence. A Gram-negative and rod-shaped bacterium, designated MQR6T, showed a high capacity to solubilize phosphate and produce indole-3-acetic acid (IAA) and siderophores. The strain can solubilize tricalcium phosphate (TCP) and rock phosphate (RP), and the solubilization of TCP was about 60% more effective than RP. Phylogenetic analyses based on the 16S rRNA gene and whole-genome sequences revealed that strain MQR6T formed a distinct phyletic lineage as a new species within the genus Pantoea. The digital DNA-DNA hybridization value between strain MQR6T and the closely related strains was 19.5-23.3%. The major cellular fatty acids were summed feature 3 (C16:1ω7c and/or C16:1ω6c), summed feature 8 (C18:1ω6c and/or C18:1ω7c), C14:0, C16:0, and C17:0 cyclo. Several genes related to IAA production, phosphonate transport, phosphate solubilization and siderophore biogenesis were found in the MQR6T genome. Furthermore, inoculation with the strain MQR6T significantly improved plant height, trunk diameter, dry weight and P accumulation in roots and shoot of A. truncatum seedlings compared to non-inoculated control. These plant parameters were improved even further in the treatment with both inoculation and P fertilization. Our results suggested that MQR6T represented a new species we named Pantoea rhizosphaerae, as a plant growth-promoting rhizobacterium that can solubilize inorganic P and improve growth of A. truncatum seedlings, emerging as a potential strategy to improve A. truncatum cultivation.

Zinc-solubilizing Bacillus spp. in conjunction with chemical fertilizers enhance growth, yield, nutrient content, and zinc biofortification in wheat crop.

Micronutrient deficiency is a serious health issue in resource-poor human populations worldwide, which is responsible for the death of millions of women and underage children in most developing countries. Zinc (Zn) malnutrition in middle- and lower-class families is rampant when daily calorie intake of staple cereals contains extremely low concentrations of micronutrients, especially Zn and Fe. Looking at the importance of the problem, the present investigation aimed to enhance the growth, yield, nutrient status, and biofortification of wheat crop by inoculation of native zinc-solubilizing Bacillus spp. in conjunction with soil-applied fertilizers (NPK) and zinc phosphate in saline soil. In this study, 175 bacterial isolates were recovered from the rhizosphere of wheat grown in the eastern parts of the Indo-Gangetic Plain of India. These isolates were further screened for Zn solubilization potential using sparingly insoluble zinc carbonate (ZnCO3), zinc oxide (ZnO), and zinc phosphate {Zn3(PO4)2} as a source of Zn under in vitro conditions. Of 175 bacterial isolates, 42 were found to solubilize either one or two or all the three insoluble Zn compounds, and subsequently, these isolates were identified based on 16S rRNA gene sequences. Based on zone halo diameter, solubilization efficiency, and amount of solubilized zinc, six potential bacterial strains, i.e., Bacillus altitudinis AJW-3, B. subtilis ABW-30, B. megaterium CHW-22, B. licheniformis MJW-38, Brevibacillus borstelensis CHW-2, and B. xiamenensis BLW-7, were further shortlisted for pot- and field-level evaluation in wheat crop. The results of the present investigation clearly indicated that these inoculants not only increase plant growth but also enhance the yield and yield attributes. Furthermore, bacterial inoculation also enhanced available nutrients and microbial activity in the wheat rhizosphere under pot experiments. It was observed that the application of B. megaterium CHW-22 significantly increased the Zn content in wheat straw and grains along with other nutrients (N, P, K, Fe, Cu, and Mn) followed by B. licheniformis MJW-38 as compared to other inoculants. By and large, similar observations were recorded under field conditions. Interestingly, when comparing the nutrient use efficiency (NUE) of wheat, bacterial inoculants showed their potential in enhancing the NUE in a greater way, which was further confirmed by correlation and principal component analyses. This study apparently provides evidence of Zn biofortification in wheat upon bacterial inoculation in conjunction with chemical fertilizers and zinc phosphate in degraded soil under both nethouse and field conditions.

Biochemical and Multi-Omics Approaches To Obtain Molecular Insights into the Catabolism of the Plasticizer Benzyl Butyl Phthalate in Rhodococcus sp. Strain PAE-6.

Phthalate diesters are extensively used as plasticizers in manufacturing plastic materials; however, because of their estrogenic properties, these chemicals have emerged as a global threat to human health. The present study investigated the course of degradation of a widely used plasticizer, benzyl butyl phthalate (BBP), by the bacterium PAE-6, belonging to the genus Rhodococcus. The metabolism of BBP, possessing structurally dissimilar side chains, was evaluated biochemically using a combination of respirometric, chromatographic, enzymatic, and mass-spectrometric analyses, depicting pathways of degradation. Consequently, the biochemical observations were corroborated by identifying possible catabolic genes from whole-genome analysis, and the involvement of inducible specific esterases and other degradative enzymes was validated by transcriptomic, reverse transcription-quantitative PCR (RT-qPCR) and proteomic analyses. Nonetheless, phthalic acid (PA), an intermediate of BBP, could not be efficiently metabolized by strain PAE-6, although the genome contains a PA-degrading gene cluster. This deficiency of complete degradation of BBP by strain PAE-6 was effectively managed by using a coculture of strains PAE-6 and PAE-2. The latter was identified as a Paenarthrobacter strain which can efficiently utilize PA. Based on sequence analysis of the PA-degrading gene cluster in strain PAE-6, it appeared that the alpha subunit of the multicomponent phthalate 3,4-dioxygenase harbors a number of altered residues in the multiple sequence alignment of homologous subunits, which may play a role(s) in poor turnover of PA. IMPORTANCE Benzyl butyl phthalate (BBP), an estrogenic, high-molecular-weight phthalic acid diester, is an extensively used plasticizer throughout the world. Due to its structural rigidity and hydrophobic nature, BBP gets adsorbed on sediments and largely escapes the biotic and abiotic degradative processes of the ecosystem. In the present study, a potent BBP-degrading bacterial strain belonging to the genus Rhodococcus was isolated that can also assimilate a number of other phthalate diesters of environmental concern. Various biochemical and multi-omics analyses revealed that the strain harbors all the required catabolic machinery for the degradation of the plasticizer and elucidated the inducible regulation of the associated catabolic genes and gene clusters.

Exploring bioactive compounds from a symbiotic bacterial strain of Spongiobacter sp.

Marine sponges are a host of different symbiotic groups of bacteria playing crucial roles in the protection and survival of marine sponges. Marine symbiotic bacteria from sponges are promising sources of bioactive chemicals and are increasingly being investigated. Therefore, the present study was undertaken to analyze total compounds from active symbiotic bacterial strain from sponge, Pione vastifical. Potential bacterial strain EA276 previously isolated from P. vastifical and was identified as Spongiobacter sp. Among 57 isolates, only 42% exhibited antagonistic activity. Four major classes of bacteria were reported previously where γ-Proteobacteria, was the dominant class. From these active antagonistic bacterial isolates, a potential bacterial strain Spongiobacter sp. EA276 was selected, and total metabolites were identified using GC and LC-MS analyses. Using LC-MS analysis bioactive compounds Dichlorphenamide, Amifloxacin and Carbenicillin are identified in both positive and negative mode. Plant growth hormones, Indole-3-acetic acid and Methyl jasmonate were identified using GC-MS analysis from culture extract of strain Spongiobacter sp. EA276. Our results highlighted the significance of marine flora inhabiting sponges from the Red Sea as potential source of bioactive compounds and plant growth hormones of biological and agricultural significance.

Screening of potential bacterial isolates against Phytophthora capsici and its plant growth-promoting effect on pepper plants

Phytophthora blight, is the most devastating disease of pepper production. To increase agricultural yield and control diseases, many countries in the world use synthetic agrochemicals. However, it has negative effects on human health and the environment, but there are few reports on its biological control. Out of sixty bacterial strains, four that showed biocontrol and plant growth promotion, namely Enterobacter hormaechei, Rhizobium sp., Pseudomonas fluorescens, and undetermined (AAULE51), which were isolated and identified using biochemical tests and 16S RNA sequences. All bacterial strains that showed greater than 55.5% growth inhibition of Phytophthora capsici in dual culture were selected for greenhouse and field studies. Also, the antimicrobial activity of the cell-free filtrate of the strains were assessed. AAULE51 was found to be the best inhibitor against P. capsici, ranging from 90.34 to 100% at a concentration of 20%–75%. The effects of bacterial strains on seed germination, vigor index, seedling height, and fresh weight of pepper plants were measured in vitro and showed 70−90.6%, 1069.6−2650%, 37−48 mm, and 64−70 mg, respectively. In greenhouse and field studies the biocontrol efficacy of antagonistic bacteria against P.capsici ranged from 0.6% to 94.2%, and 11%–84.6% respectively. The maximum reduction in disease severity was shown when treated with AAULE41+ AAULE51 (61.1%–94.2%). Therefore, these results suggest that selected potential bacterial strains are good candidates for agricultural biofertilizers and biopesticides.

A new paradigm in the bioremoval of lead, nickel, and cadmium using a cocktail of biosystems: a metagenomic approach.

Lead (Pb), nickel (Ni), and cadmium (Cd) are known for its harmful effects on the environment. Microbial community related to soil plays a pivotal role in configuring several properties of the ecosystem. Thus, remediation of such heavy metals using multiple biosystems had shown excellent bioremoval potential. The current study demonstrates the integrated approach of Chrysopogon zizanioides in combination with earthworm Eisenia fetida augmented with VITMSJ3 potent strain for the uptake of metals like Pb, Ni, and Cd from the contaminated soil. For the uptake of heavy metals, Pb, Ni, and Cd with the concentrations of 50, 100, and 150mgkg-1 were supplemented in pots with plants and earthworms. C. zizanioides was used for bioremoval due to their massive fibrous root system which can absorb heavy metals. A substantial increase of 70-80% Pb, Ni, and Cd was found for VITMSJ3 augmented setup. A total of 12 earthworms were introduced in each setup and were tested for the toxicity and damages in the various internal structures. Reduction in malondialdehyde (MDA) content was observed in the earthworms with VITMSJ3 strain proving less toxicity and damages. Metagenomic analysis of the soil associated bacterial diversity was assessed by amplifying the V3V4 region of the 16S rRNA gene and the annotations were studied. Firmicutes were found to be the predominant genus with 56.65% abundance in the bioaugmented soil R (60) proving the detoxification of metals in the bioaugmented soil. Our study proved that a synergistic effect of plant and earthworm in association with potent bacterial strain had higher uptake of Pb, Ni, and Cd. Metagenomic analysis revealed the changes in microbial abundance in the soil before and after treatment.

Suppression of Fusarium Wilt in Watermelon by Bacillus amyloliquefaciens DHA55 through Extracellular Production of Antifungal Lipopeptides

Fusarium wilt caused by Fusarium oxysporum f. sp. niveum is one of the most devastating fungal diseases affecting watermelon (Citrullus lanatus L.). The present study aimed to identify potent antagonistic bacterial strains with substantial antifungal activity against F. oxysporum f. sp. niveum and to explore their potential for biocontrol of Fusarium wilt in watermelon. Out of 77 isolates from watermelon rhizosphere, six bacterial strains-namely, DHA4, DHA6, DHA10, DHA12, DHA41, and DHA55-exhibited significant antifungal activity against F. oxysporum f. sp. niveum, as well as other phytopathogenic fungi, including Didymella bryoniae, Sclerotinia sclerotiorum, Fusarium graminearum, and Rhizoctonia solani. These Gram-positive, rod-shaped, antagonistic bacterial strains were able to produce exo-enzymes (e.g., catalase, protease, and cellulase), siderophore, and indole-3-acetic acid and had the ability to solubilize phosphate. In greenhouse experiments, these antagonistic bacterial strains not only promoted plant growth but also suppressed Fusarium wilt in watermelon. Among these strains, DHA55 was the most effective, achieving the highest disease suppression of 74.9%. Strain DHA55 was identified as Bacillus amyloliquefaciens based on physiological, biochemical, and molecular characterization. B. amyloliquefaciens DHA55 produced various antifungal lipopeptides, including iturin, surfactin, and fengycin, that showed significant antifungal activities against F. oxysporum f. sp. niveum. Microscopic observations revealed that B. amyloliquefaciens DHA55 exhibited an inhibitory effect against F. oxysporum f. sp. niveum on the root surface of watermelon plants. These results demonstrate that B. amyloliquefaciens DHA55 can effectively promote plant growth and suppress the development of watermelon Fusarium wilt, providing a promising agent for the biocontrol of Fusarium wilt in watermelon.

Effect of Various Carbon and Nitrogen Sources on Decolorization of Textile Dyes by Pseudomonas taiwanensis Strain TNZ3

The co-substrate is a crucial component in the bio-decolorization process that helps bacteria to grow and carry out their fundamental functions. Different types of textile dyes with diverse chemical structures are frequently employed in the textile industry, and the most of them are resistant to biodegradation because of their xenobiotic nature. Due to the low carbon content of textile dyes, particularly of azo dyes, co-metabolic conditions are required for decolorization process. Hence, the current study was aimed to determine which striking carbon and nitrogen sources are preferred for generating co-metabolic conditions to decolorize the following dyes: Disperse Yellow-3, Malachite Green, Basic Red-18, and Reactive Blue-4. Different carbon and nitrogen sources were used to isolate, screen, and evaluate different bacterial strains for dye degradation. A potential bacterial strain Pseudomonas taiwanensis strain TNZ3 was identified based on 16s rDNA sequence and selected for further study. It was found that the presence of yeast, peptone, NH4Cl, sucrose, glucose, fructose, maltose, galactose, lactose, and starch in dye contaminated media effectively enhanced azo dye degradation rate by Pseudomonas taiwanensis strain TNZ3. In the medium inoculated with Pseudomonas taiwanensis strain TNZ3, sucrose and yeast with peptone extracts induced the greatest decolorization among diverse carbon and nitrogen sources. In all dyes, the maximum decolorization occurs at 1.5% yeast extract supplementation. The results made it abundantly clear that various carbon and nitrogen sources used as co-substrates played effective role on dye decolorization process.

Mitigation of water scarcity with sustained growth of Rice by plant growth promoting bacteria.

Climate change augments the risk to food security by inducing drought stress and a drastic decline in global rice production. Plant growth-promoting bacteria (PGPB) have been known to improve plant growth under drought stress. Here in the present study, we isolated, identified, and well-characterized eight drought-tolerant bacteria from the rice rhizosphere that are tolerant to 20% PEG-8000. These strains exhibited multiple plant growth-promoting traits, i.e., 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase activity, exopolysaccharide production, phosphate (P)-solubilizing activity (51-356 µg ml-1), indole-3 acetic acid (IAA) production (14.3-46.2 µg ml-1), and production of organic acids (72-178 µg ml-1). Inoculation of bacterial consortium (Bacillus subtilis NM-2, Brucella haematophilum NM-4, and Bacillus cereus NM-6) significantly improved seedling growth and vigor index (1009.2-1100) as compared to non-inoculated stressed plants (630-957). Through rhizoscanning, efficiency of the consortium was validated by improved root parameters such as root length (17%), diameter, and surface area (18%) of all tested genotypes as compared with respective non-inoculated stressed treatments. Furthermore, the response of consortium inoculation on three rice genotypes was positively correlated with improved plant growth and drought stress ameliorating traits by the accumulation of osmoprotectant, i.e., proline (85.8%-122%), relative water content (51%), membrane stability index (64%), and production of antioxidant enzymes to reduce oxidative damage by reactive oxygen species. A decrease in temperature and improved chlorophyll content of inoculated plants were found using infrared thermal imaging and soil plant analyzer development (SPAD), respectively. The key supporting role of inoculation toward stress responses was validated using robust techniques like infrared thermal imaging and an infrared gas analyzer. Furthermore, principal component analysis depicts the contribution of inoculation on stress responses and yield of tested rice genotypes under water stress. The integration of drought-tolerant rice genotype (NIBGE-DT02) and potential bacterial strains, i.e., NM-2, NM-4, and NM-6, can serve as an effective bioinoculant to cope with water scarcity under current alarming issues related to food security in fluctuating climate.

Tracking of thermal microbial shock proteins and genomic variation of Bacillus cereus due to some abiotic stresses.

Bacillus cereus is considered the most potent bacterial strain in terms of the increment in induced proteins during thermal treatment at 52 °C for 90 min. Protein production in food-born microorganism (Bacillus cereus) recovered from contaminated food was investigated in response to heat shock treatment. Bacterial tolerance towards pH, salinity, and temperature at various levels was also investigated. Heat-shock proteins (HSPs) produced when exposed to 52 °C for up to 60 minutes led to significant differences (30%) above the untreated control (37 °C), and the maximum difference was recorded at 52°C at 90 minutes. ISSR detected a higher number of bands/primer than RAPD (13.7 vs. 12.7, respectively), and more polymorphic bands (10.7 vs. 8.4 bands/primer, respectively). The untreated bacterial strain did not grow at pH levels lower than 3, whereas the thermally treated strain grew significantly at pH two. A consistent increase in HSPs was observed, with a gradual increase in salinity of less than 16%. Surprisingly, the gradual increase in temperature did not induce tolerance against higher temperatures. However, a significant growth rate was noticed in response to heat-shocked treatments. The untreated Bacillus cereus demonstrated antibiotic resistance to gentamycin and clindamycin (1.54 and 1.65 cm, respectively), much lower than the corresponding inhibition areas with preheat-treated test pathogen which were recorded (2.37 and 2.49 cm, respectively).

Use of potential bacterial strains to remove Hexavalent Chromium from an aqueous medium and the Periyar River sediments

Chromium is one of the most abundant metals in the earth's crust mined as chromites. Industries that widely use compounds containing chromium as Cr(III) in the tanning process generally release effluents with high chromium levels into natural water resources, frequently without appropriate effluent treatment. Though physical and chemical methods of chromium removal are adopted, the processes are expensive, use a lot of energy and generate secondary toxic waste. The removal of chromium by biological resources on the other hand is more environmentally friendly, less expensive, and lacks the release of secondary pollutants. The present study is aimed towards the assessment of the Cr(VI) reduction capability of two bacterial strains, Alcaligenes sp. (S11) and Listeria sp. (S18) used as a consortium. These bacterial strains were isolated from the Periyar river of Kerala, India. Batch mode studies were carried out by live bacterial cells and an integrated study was carried out to test the bacterial strains on chromium-contaminated water and sediments through bioreactor and column study respectively under optimized conditions. The phytotoxicity of the treated water was studied on black gram. In the bioreactor study, the maximum Cr(VI) reduction capacity of bacterial consortium (S11 and S18) was found to be 97%. The successive experiment for the toxicity of treated water on the black gram indicated that there was no toxicity in the growth parameters of the plant.