Potential Bacterial Strains Research Articles

Environmental factors and potential probiotic lineages shape the active prokaryotic communities associated with healthy Penaeus stylirostris larvae and their rearing water.

Microbial dysbiosis is hypothesized to cause larval mass mortalities in New-Caledonian shrimp hatcheries. In order to confirm this hypothesis and allow further microbial comparisons, we studied the active prokaryotic communities of healthy Penaeus stylirostris larvae and their surrounding environment during the first 10 days of larval rearing. Using daily nutrient concentration quantitative analyses and spectrophotometric organic matter analyses, we highlighted a global eutrophication of the rearing environment. We also evidenced drastic bacterial community modifications in the water and the larvae samples using Illumina HiSeq sequencing of the V4 region of the 16S rRNA gene. We confirmed that Alteromonadales, Rhodobacterales, Flavobacteriales, Oceanospirillales and Vibrionales members formed the core bacteriota of shrimp larvae. We also identified, in the water and the larvae samples, several potential probiotic bacterial strains which could lead to rethink probiotic use in aquaculture (AEGEAN 169 marine group, OM27 clade, Ruegeria, Leisingera, Pseudoalteromonas and Roseobacter). Finally, investigating the existing correlations between the environmental factors and the major bacterial taxa of the water and the larvae samples, we suggested that deterministic and stochastic processes were involved in the assembly of prokaryotic communities during the larval rearing of P. stylirostris. Overall, our results showed that drastic changes mostly occurred during the zoea stages suggesting that this larval phase is crucial during shrimp larval development.

Isolation, identification, and characterization of Bacillus subtilis SMP-2 from panitenga and exploring its potential for biosurfactant production

A traditional Assamese fermented food, Panitenga, was explored for potential probiotic isolation. A potent bacterial strain exhibiting biosurfactant production ability was isolated, characterized, and identified as Bacillus subtilis SMP-2. Environmental parameters were optimized for maximum cell growth and biosurfactant production that was found to be pH 6, 30°C, 130 rpm, with glycerol as the carbon (C) source, yeast extract as the nitrogen (N) source, and a C/N ratio of 3:1. At these optimized conditions, the strain yielded 8.13 ± 0.9 g/L of lipopeptide biosurfactant. This biosurfactant remarkably reduced the surface tension of water from 72 mN/m to 37 ± 0.36 mN/m, possessed a low critical micelle concentration (CMC) of 125 mg/L, and exhibited antimicrobial properties. It persisted to be stable across a wide range of physical conditions, including variations in pH, temperature, and salinity. The significantly high production yield and noteworthy properties of the biosurfactant from Bacillus subtilis SMP-2 make it a promising candidate for applications in microbial-enhanced oil recovery (MEOR), bioremediation of oil spills, production of cosmetics and pharmaceuticals, contributing to economic growth and sustainable development.

Physicochemical Investigations of Textile Wastewater and Process Parameter Optimization for Bio-decolorization of Congo Red Dye by Pseudomonas aeruginosa MT-2 Strain

Pollution caused by dyes is a major environmental threat, posing adverse impacts on humans, animals, and plants. Therefore, the remediation of such pollutants is essential to protect the environment. This study aimed to conduct physicochemical and bacteriological analyses of textile wastewater to isolate and identify potential native bacterial strains for the decolorization of Congo red dye. Physical and nutritional process parameters were optimized to achieve maximum decolorization. The biological and chemical oxygen demands of the analyzed textile waste water were found to be above the recommended limits. In this study, 19 Congo red -decolorizing bacteria were isolated, with one bacterial culture capable of growing at a higher dye concentration of 300 mg/L. This bacterium was characterized biochemically and genetically (using 16S rRNA sequencing) and identified as the Pseudomonas aeruginosa MT-2 strain. A maximum decolorization of 94.0% was achieved at an initial dye concentration of 150 mg/L, 35°C, and pH 8.0 under static conditions. The bacterial culture also showed resistance to heavy metals such as arsenic, lead, and chromium. The biodegradation of Congo red dye was confirmed through UV-vis spectral analysis and Fourier transform infrared spectrophotometry. The findings of this study demonstrate the high remediation potential of the MT-2 strain, making it suitable for possible use in dye biodecolorization at contaminated sites.

Bio-prospecting fluoride tolerant bacteria for their optimistic contribution in instigating resilience against fluoride stress in Oryza sativa L.

In recent years, the effects of fluoride (F) pollution in numerous ecosystems such as groundwater, soil, etc. Have become a major issue worldwide. This increase in F pollution is a direct consequence of the unbridled use of fertilizers in agricultural and several other human activities that require immediate and appropriate action. Therefore, this manuscript reveals important findings on the efficacy of bacteria isolated from agricultural fields in central Chhattisgarh in manifesting resistance to F and in reversing the F-induced oxidative damage in susceptible Oryza sativa L, (Var. MTU1010). Chronic exposure of Oryza sativa L. to sodium fluoride (NaF) (50 mg L−1) severely impeded growth and various physiological parameters such as germination percentage, biomass and root and shoot length and stimulated the formation of reactive oxygen species (ROS), which enhanced electrolyte leakage and formation of cytotoxic products like malondialdehyde. To this end, potential bacterial strains, namely MT2A, MT3A, MT4A, and Du3A were isolated, screened for various plant growth promoting (PGP) traits and used to explore their efficiency to mitigate F toxicity in Oryza sativa L. in vivo. The seedlings inoculated with the bacterial strains showed significant development as evidenced by an increase in root and shoot length, biomass and chlorophyll content. Additionally, inoculation of these strains in combination with F stress significantly decreased oxidative stress by increasing the expression of protective genes encoding antioxidant enzymes and boosted agronomic traits remarkably. Overall, the manuscript demonstrates the pivotal role played by the isolated bacteria in abating ill effects of F in the Oryza sativa L. seedlings and proves their potential as protective bioagents against F stress.

Microbial Degradation of Polyester Microfibers Using Indigenously Isolated Bacterial Strain Exiguobacterium Sp.

ABSTRACTSynthetic microfibers are emerging environmental microplastic pollutants released from different industrial and domestic sources. The present investigation describes the isolation of potential bacterial strains from microplastic‐contaminated sites of Bhubaneswar city of Odisha, India. Four morphologically distinct bacterial strains were isolated using 2% polyethylene glycol (PEG) supplemented nutrient agar (NA) medium and were screened for their polymer tolerance ability by growing them on 2%–8% PEG. A single microorganism capable of growing on 8% PEG was selected for biodegradation experiment. Through 16S rRNA sequencing, the selected bacterial strain was identified as Exiguobacterium sp. with gene bank accession number ON318396. The microbial strain's microfiber biodegradation ability was assessed in a laboratory setting over a period of 28 ± 2 days, utilizing optimized conditions with an initial pH of 7, 2 mL inoculum volume, an incubation temperature of 30°C ± 2°C, and 150 rpm, using 2 g of polyester microfiber. In optimum conditions, the weight loss of the treated sample with the selected microbial strain was 19.2%. The polyester degradation was confirmed through scanning electron microscopic images viewing the degradation of the polyester microfiber surfaces. Variation in functional groups confirmed through Fourier transform infrared spectrophotometry. Detection of carbonyl (C═O) group stretching band at 1711 cm−1 through ATR‐FTIR analysis in the treated sample confirmed the polymer biodegradation. The potential isolate can efficiently degrade polyester and, in the future, can be employed as a promising solution for the sustainable treatment of synthetic microfiber pollution.

Phenazines are involved in the antagonism of a novel subspecies of Pseudomonas chlororaphis strain S1Bt23 against Pythium ultimum

Long-term use of chemical fungicides to control plant diseases caused by fungi and oomycetes has led to pathogen resistance and negative impacts on public health and environment. There is a global search for eco-friendly methods and antagonistic bacteria are emerging as alternatives. We isolated a potent antagonistic bacterial strain (S1Bt23) from woodland soil in Québec, Canada. Taxonomic characterization by 16S rRNA, multi-locus sequence analysis, pairwise whole-genome comparisons, phylogenomics and phenotypic data identified strain S1Bt23 as a novel subspecies within Pseudomonas chlororaphis. In dual culture studies, strain S1Bt23 exhibited potent mycelial growth inhibition (60.2–66.7%) against Pythium ultimum. Furthermore, strain S1Bt23 was able to significantly bioprotect potato tuber slices from the development of necrosis inducible by P. ultimum. Annotations of the whole genome sequence of S1Bt23 revealed the presence of an arsenal of secondary metabolites including the complete phenazine biosynthetic cluster (phzABCDEFG). Thin-layer (TLC) and high-performance liquid (HPLC) chromatographic analyses of S1Bt23 extracts confirmed the production of phenazines, potent antifungal compounds. CRISPR/Cas9-mediated deletion of phzB (S1Bt23ΔphzB) or phzF (S1Bt23ΔphzF) gene abrogated phenazine production based on TLC and HPLC analyses. Also, S1Bt23ΔphzB and S1Bt23ΔphzF mutants lost antagonistic activity and bioprotection ability of potato tubers against P. ultimum. This demonstrated that phenazines are involved in the antagonistic activity of S1Bt23 against P. ultimum. Finally, based on genotypic and phenotypic data, we taxonomically conclude that S1Bt23 represents a novel subspecies for which the name Pseudomonas chlororaphis subsp. phenazini is proposed.

Termite gut microbiome being a rich source of potential lignocellulolytic bacterial strains

A study was carried out to identify prospective cellulose degrading bacteria isolated from termite gut collected from various agriculture sites. Eight of the bacterial isolates displayed a very distinct zone of clearing on CMC (Carboxylmethyl cellulose) agar media after staining with 1% Congo red, indicating that they may have cellulose degrading ability. On a CMC agar plate, CRDB6 had the largest colony diameter (3.08 cm) as well as clear zone diameter (0.96 cm), however CRDB 1 has maximum cellulolytic activity (1.45 cm) followed by CRDB5 and CRDB6 (1.33 cm and 1.28 cm) respectively. CRDB3, CRDB4 and CRDB9 showed Gram negative reaction among crop residue degrading bacterial isolates, while the remainder showed Gram positive reaction. The morphological characteristics of the bacteria isolates, such as colony shape, elevation, margin, colour and opacity, differed. Isolates CRDB6 produced highest β-glucosidase activity (12.66 m L-1) followed by CRDB1 (12.20 mg m L-1) and CRDB5 (10.21 m L-1) in Luria broth culture. Indole acetic acid production (with tryptophan) was greater in CRDB1 (389.33 mg/ml), CRDB6 (356.9 m L-1) and CRDB3 (315.96 m L-1) while as P-solubilization potential was peaked in CRDB6 (2.41 m L-1) followed by CRDB4 (1.76 m L-1) and CRDB3. Overall, isolate CRDB6 exhibited the highest cellulolytic activity as compared to rest of the bacterial isolates. These results will help in preparing bacterial consortia for the management of crop residues.

Genomic insight of phosphate solubilization and plant growth promotion of two taxonomically distinct winter crops by Enterobacter sp. DRP3.

Study of rhizospheric microbiome-mediated plant growth promotional attributes currently highlighted as a key tool for the development of suitable bio-inoculants for sustainable agriculture purposes. In this context, we have conducted a detailed study regarding the characterization of phosphate solubilizing potential by plant growth-promoting bacteria that have been isolated from the rhizosphere of a pteridophyte Dicranopteris sp., growing on the lateritic belt of West Bengal. We have isolated three potent bacterial strains, namely DRP1, DRP2, and DRP3 from the rhizoids-region of Dicranopteris sp. Among the isolated strains, DRP3 is found to have the highest phosphate solubilizing potentiality and is able to produce 655.89 and 627.58µg ml-1 soluble phosphate by solubilizing tricalcium phosphate (TCP) and Jordan rock phosphate, respectively. This strain is also able to solubilize Purulia rock phosphate moderately (133.51µg ml-1). Whole-genome sequencing and further analysis of the studied strain revealed the presence of pyrroloquinoline quinone (PQQ)-dependent glucose dehydrogenase gdh gene along with several others that were well known for their role in phosphate solubilization. Further downstream, quantitative reverse transcriptase PCR-based expression study revealed 1.59-fold upregulation of PQQ-dependent gdh gene during the solubilization of TCP. Root colonization potential of the studied strain on two taxonomically distinct winter crops viz. Cicer arietinum and Triticum aestivum has been checked by using scanning electron microscopy. Other biochemical analyses for plant growth promotion traits including indole acetic acid production (132.02µg ml-1), potassium solubilization (3mg l-1), biofilm formation, and exopolymeric substances productions (1.88-2.03µg ml-1) also has been performed. This study highlighted the active involvement of PQQ-dependent gdh gene during phosphate solubilization from any Enterobacter group. Moreover, our study explored different roadmaps for sustainable farming methods and the preservation of food security without endangering soil health in the future.

Introduction of Cellulolytic Bacterium Bacillus velezensis Z2.6 and Its Cellulase Production Optimization.

Enzyme-production microorganisms typically occupy a dominant position in composting, where cellulolytic microorganisms actively engage in the breakdown of lignocellulose. Exploring strains with high yields of cellulose-degrading enzymes holds substantial significance for the industrial production of related enzymes and the advancement of clean bioenergy. This study was inclined to screen cellulolytic bacteria, conduct genome analysis, mine cellulase-related genes, and optimize cellulase production. The potential carboxymethylcellulose-hydrolyzing bacterial strain Z2.6 was isolated from the maturation phase of pig manure-based compost with algae residuals as the feedstock and identified as Bacillus velezensis. In the draft genome of strain Z2.6, 31 related cellulolytic genes were annotated by the CAZy database, and further validation by cloning documented the existence of an endo-1,4-β-D-glucanase (EC 3.2.1.4) belonging to the GH5 family and a β-glucosidase (EC 3.2.1.21) belonging to the GH1 family, which are predominant types of cellulases. Through the exploration of ten factors in fermentation medium with Plackett-Burman and Box-Behnken design methodologies, maximum cellulase activity was predicted to reach 2.98 U/mL theoretically. The optimal conditions achieving this response were determined as 1.09% CMC-Na, 2.30% salinity, and 1.23% tryptone. Validation under these specified conditions yielded a cellulose activity of 3.02 U/mL, demonstrating a 3.43-fold degree of optimization. In conclusion, this comprehensive study underscored the significant capabilities of strain Z2.6 in lignocellulolytic saccharification and its potentialities for future in-depth exploration in biomass conversion.

Microbial consortium with multifunctional attributes for the plant growth of eggplant (Solanum melongena L.).

In the past few decades, the pressure of higher food production to satisfy the demand of ever rising population has inevitably increased the use synthetic agrochemicals which have deterioration effects. Biostimulants containing beneficial microbes (single inoculants and microbial consortium) were found as an ideal substitute of synthetic chemical fertilizers. In recent years, microbial consortium is known as a better bioinoculant in comparison to single inoculant bioformulation because of multifarious plant growth-promoting advantages. Looking at the advantageous effect of consortium, in present investigation, different bacteria were isolated from rhizospheric soil and plant samples collected from the Himalayan mountains on the green slopes of the Shivaliks, Himachal Pradesh. The isolated bacteria were screened for nitrogen (N) fixation, phosphorus (P)solubilization and potassium (K) solubilization plant growth promotingattributes, and efficient strains were identified through 16S rRNA gene sequencingand BLASTn analysis. The bacteria showing a positive effect in NPK uptake were developed as bacterial consortium for the growth promotion of eggplant crop. A total of 188 rhizospheric and endophytic bacteria were sorted out, among which 13 were exhibiting nitrogenase activity, whereas 43 and 31 were exhibiting P and K solubilization traits, respectively. The selected three efficient and potential bacterial strains were identified using 16S rRNA gene sequencing as Enterobacter ludwigii EU-BEN-22 (N-fixer; 35.68 ± 00.9 nmol C2H4 per mg protein per h), Micrococcus indicus EU-BRP-6 (P-solubilizer; 201 ± 0.004 mg/L), and Pseudomonas gessardii EU-BRK-55 (K-solubilizer; 51.3 ± 1.7 mg/mL), and they were used to develop a bacterial consortium. The bacterial consortium evaluation on eggplant resulted in the improvement of growth (root/shoot length and biomass) and physiological parameters (chlorophyll, carotenoids, total soluble sugar, and phenolic content) of the plants with respect to single culture inoculation, chemical fertilizer, and untreated control. A bacterial consortium having potential to promote plant growth could be used as bioinoculant for horticulture crops growing in hilly regions.

Synthesis, Characterization and Application of Biogenic Silver Nanoparticles as Antibacterial and Antifungal Agents

In order to provide a straightforward, affordable, and environmentally friendly process for the synthesis of metallic nanoparticles, scientists are turning to natural ways like employing plant extract in response to rising antimicrobial resistance and the desire for novel biocidal agents. In this study, we evaluated the efficacy of phyto-fabricated silver nanoparticles and antimicrobial agents against selected indoor bacterial and fungal strains isolated from the lecture and office rooms of Chukwuemeka Odimegwu Ojukwu University, Uli Nigeria. The indoor microorganisms were isolated, identified, and quantified using standard methods. To prepare and generate the aqueous extract employed in the biological synthesis of the silver nanoparticle, fresh soursop seeds were room dried, crushed, heated to boiling, and double filtered. The phyto-fabricated nanoparticles were centrifuged, dried and used for physicochemical characterization and antimicrobial assay. The synthesized silver nanoparticles were characterized using UV-Vis spectrophotometry, Fourier transformed Infra-Red Spectroscopy and scanning electron microscopy analyses. The antimicrobial assay was carried out using agar well diffusion method. The results revealed that Aeromonas, Pseudomonas, Staphylococcus, Vibrio, Rhizopus, Aspergillus, Penicillium and Microsporum were identified as the predominant potential indoor bacterial and fungal pathogenic strains. The characterized biogenic nanoparticles revealed the optical, spectral and morphological features unique to silver nanoparticles. Also, the antibacterial screening revealed that the highest zone of inhibition was observed against Vibrio sp. (27.50 ± 7.5 mm) at a concentration of 30 μg/mL while standard antifungal drug (ketoconazole) had the highest zone of inhibition of 21.0 ± 1.0 mm at 3.25 μg/mL against Microsporum gypseum while standard antifungal drug (ketoconazole) and Ag-NPs had the lowest zone of inhibition of 11.0 ± 1.0 mm at 15.0 μg/mL and 7.5 μg/mL against Rhizopus sp. and Aspergillus flavus, respectively. The negative control (DMSO) had no zone of inhibition on any of the potential indoor bacterial and fungal pathogenic strains. Statistically, there was significant (P < 0.05) inhibition of bacterial and fungal pathogenic strains among the means of treatment doses of A. muricata AgNPs, ciprofloxacin and ketoconazole standard antibiotics. The excellent antimicrobial inhibition of the tested indoor bacterial and fungal strains by the A. muricata fabricated silver nanoparticles even at MIC of 3.25 μg/mL could be exploited as biostatic and biocidal agents where there is contamination or public health risk of pathogenic indoor bacteria and fungi.

Bacillus spp. isolated from intestine of Oreochromis mossambicus: Identifying a potential probiotic for tilapia culture

Aquaculture industries are currently facing a wide array of challenges including emergence of antimicrobial resistance among pathogens, increased susceptibility to diseases, lack of healthy fingerlings and overall decrease in productivity. Probiotics are safer alternatives to antimicrobials and serves as a solution all these concerns. Oreochromis mossambicus is a commercially significant fish species of the cichlid family due to its richness in micro and macronutrients, adaptability and feed efficacy. Management of pathogenic infections and availability of healthy fingerlings are two major challenges faced by the tilapia farmers at present. The current research was conducted to identify a potent bacterial strain from the intestine of O. mossambicus with active probiotic properties. A potent Bacillus strain that surpassed the safety assessments and exhibited antagonistic activity against the potential aquaculture pathogens, Staphylococcus aureus, Pseudomonas aeruginosa and Streptococcus pyogenes were selected for determination of specific probiotic properties. The strain was found tolerant to 0.3% bile, acidity up to pH 2 and 5% NaCl concentrations, substantiating its potential to survive the hostile gut environment of the host fish. Additionally, the strain exhibited auto aggregation and cell surface hydrophobicity, which are essential probiotic properties. It showed 63±3.32%. hydrophobicity and 56.65±1.65% auto aggregation in spectrophotometric studies. Moreover, it also demonstrated proteolytic activity that could benefit the host in the digestion processes. As the strain exhibited desirable probiotic traits, it was subjected to molecular characterization and identified as Bacillus tropicus ACS1. Further research is warranted to elucidate its complete potential in promoting the health, immunity and productivity of aquaculture industries.

Bioremediation of Kraft Lignin in Wastewater: Optimization of Temperature and Isolation of Valuable Compounds

Conventional methods for the treatment of complex lignin found in the pulp and paper mill effluent is a strenuous and expensive process. Microbial degradation is a promising technique to degrade lignin efficiently due to its adaptability and rapid growth of microbes in diverse environments. This study is focused on the isolation of potential ligninolytic bacterial strains from agricultural soil and decomposed wood sources for successful degradation of lignin present in the wastewater. Initially, 15 ligninolytic strains were identified and three dominant species, Staphylococcus lentus (SB5), Bacillus megaterium (RWB15) and Pseudomonas geniculata (RWP9) were isolated as per their growth tolerance pattern with different lignin concentrations. The lignin degradation study was carried out at different temperatures (25-45℃) with 1000 mg/l of feed lignin concentrations. The optimum degradation temperature of all the strains fell within the range 30-35℃. The maximum lignin degradation of SB5, RWB15 and RWP9 was identified as 89, 77 and 90% at the end of the 6th, 3rd and 7th day of biodegradation, respectively. There was a steep reduction of COD by all three microbes before attaining the stationary phase and thereafter COD reduction was sluggish due to the death phase. Besides, the microbes used in this study showed the transformation of lignin into valuable low-molecular by-products, vanillin, vanillic acid and adipic acid with their concentration being quantified as 28, 101 and 130 mg/l, respectively. This study shows the successful degradation of waste lignin and the recovery of valuable byproducts from waste streams.

Isolation, characterization, identification, genomics and analyses of bioaccumulation and biosorption potential of two arsenic-resistant bacteria obtained from natural environments

Arsenic (As) is a significant contaminant whose unrestrained entrance into different ecosystems has created global concern. At the cellular level, As forms unsteady intermediates with genetic materials and perturbs different metabolic processes and proper folding of proteins. This study was the first in this region to explore, isolate, screen systematically, and intensively characterize potent As-tolerant bacterial strains from natural environments near Raiganj town of Uttar Dinajpur, West Bengal. In this study, two potent Gram-negative bacterial strains with high tolerance to the poisonous form of As, i.e., As(III) and As(V), were obtained. Both the isolates were identified using biochemical tests and 16S rRNA gene sequencing. These bacteria oxidized toxic As(III) into less poisonous As(V) and depicted tolerance towards other heavy metals. Comparative metabolic profiling of the isolates in control and As-exposed conditions through Fourier-transform infrared spectroscopy showed metabolic adjustments to cope with As toxicity. The metal removal efficiency of the isolates at different pH showed that one of the isolates, KG1D, could remove As efficiently irrespective of changes in the media pH. In contrast, the efficiency of metal removal by PF14 was largely pH-dependent. The cell mass of both the isolates was also found to favourably adsorb As(III). Whole genome sequence analysis of the isolates depicted the presence of the arsRBC genes of the arsenic operon conferring resistance to As. Owing to their As(III) oxidizing potential, high As bioaccumulation, and tolerance to other heavy metals, these bacteria could be used to bioremediate and reclaim As-contaminated sites.

In-vitro Inhibitory Activities of Potential Probiotic Isolated from Pangasius nasutus against Aeromonas hydrophila and Streptococcus agalactiae

In aquaculture, using probiotics is crucial for strengthening the immune system and encouraging the growth and survival of many aquatic organisms, including the Pangasius species. This approach is particularly significant given the impact of bacterial diseases on Pangasius survival. This study aimed to assess the effectiveness of probiotics isolated from Pangasius nasutus as alternatives to antibiotics for combating infections caused by Aeromonas hydrophila and Streptococcus agalactiae. Potential bacteria were isolated from the intestine and stomach of healthy P. nasutus. Seventy probiotic strains were successfully isolated and further screened using A. hydrophilaand S. agalactiae as pathogens in an in vitro disc diffusion assay. Preliminary screenings indicated that five probiotic strains inhibited the growth of A. hydrophila. Stomach-derived strain S1 and intestine-derived strain L1 suppressed A. hydrophila growth with inhibition zones of 10.5±1 mm and 8.5±1 mm, respectively. Likewise, strains L2, L8, and L12 from the intestine showed inhibitory zones of 6.0±1 mm, 6.5±1 mm, and 6.0±1 mm, respectively. Of these, only L12 inhibited the growth of S. agalactiae with a clear zone of 5.0±1 mm. In the elimination of pathogenic strains, potential strains S1 and L1 did not grow on the Aeromonas isolation medium. Co-culture assays demonstrated that both potential strains significantly inhibited Aeromonas hydrophila growth at concentrations of 106 and 108 CFU mL-1 over 48- and 96-hour periods, respectively. The potential bacterial strains were identified using 16s rRNA gene sequencing and were classified as follows: S1 - Lactococcus lactis, L1 - Weissella confusa, L2 - Cosenzaea myxofaciens, L8 - Lactococcus garvieae, and L12 - Plesiomonas shigelloides. Strain S1 L. lactis and strain L1 W. confusa are suggested for further evaluation and acquired additional research to fully elucidate their mechanisms and potential as probiotics.

Exploration of bacterial strains with bioremediation potential for mercury and cyanide from mine tailings in "San Carlos de las Minas, Ecuador"

<abstract> <p>Ecuador is a developing country that relies on mining as a significant source of economic income every year; however, there needs to be more studies on the soil pollution caused by mining over time. Biological remediation as an alternative to the use of physical and chemical methods offers a more cost-effective and environmentally friendly means to counteract the negative impacts that the presence of heavy metals in mining tailings soils can cause. This study focused on soil sampling from the mining tailings of the San Carlos de las Minas sector, in the Zamora Chinchipe province in Ecuador, to find potential bacterial strains that can degrade two specific contaminants, mercury (Hg) and cyanide (CN<sup>-</sup>). For this purpose, 68 soil subsamples were collected. pH, electrical conductivity, moisture, and the concentration of the contaminants were analyzed and measured. The initial concentration of CN<sup>-</sup> was 0.14 mg/kg, and of Hg was 88.76 mg/kg. From the soil samples, eight bacterial strains were isolated, characterized at macroscopic and microscopic levels, and identified at the molecular level. The bacteria were then subjected to degradability tests for CN<sup>-</sup> and Hg, obtaining interesting results. The degradation capacity of CN<sup>-</sup> stood out for the strains <italic>Micrococcus aloeverae</italic> and <italic>Pseudomonas alcaliphila</italic>, and for the degradation of Hg, the strains <italic>Hydrogenophaga laconesensis</italic> and <italic>Micrococcus aloeverae</italic> were highlighted, achieving degradation percentages of up to 98.80%. These results emphasize the discovery of these bacterial species with potential use in cyanide and mercury remediation processes.</p> </abstract>

Biogenic synthesis of silver nanoparticle by Cytobacillus firmus isolated from the river sediment with potential antimicrobial properties against Edwardsiella tarda.

The aquatic environment, independent of their host, is more favorable to pathogenic bacteria than the terrestrial environment. Consequently, pathogenic bacteria can reach very high densities around aquatic animals and can cause high mortality. The conventional approach, such as antibiotics, has minimal effectiveness. Additionally, due to the emergence of (multiple) resistance, their use is under intense scientific and public scrutiny. Hence, there is a need for the development of alternative control techniques, with an emphasis on prevention, which is likely to be more cost-effective. In this study, a potential bacterial strain Cytobacillus firmus was isolated from polluted river sediment and characterized using a comprehensive range of techniques including biochemical, 16S rRNA sequencing and antibiogram assay. The pathogenicity of the bacteria was tested in vivo on Labeo rohita fingerlings found as non-pathogenic. Further, the bacteria were found to synthesize silver nanoparticles (AgNPs) using AgNO3 as a substrate. The obtained AgNPs were characterized by various methods, including UV-vis spectroscopy, FTIR (Fourier-transform infrared spectroscopy), and Transmission Emission Microscopy (TEM). The study found that the AgNPs were 20 nm in size on average. The antimicrobial activity of synthesized AgNPs was examined against the model freshwater pathogenic bacteria, Edwardsiella tarda and both the MIC (Minimum Inhibitory Concentration) and MBC (Minimum Bactericidal Concentration) were 0.156 μM, while biofilm inhibition activity was also observed at 0.156 μM. The AgNPs showed no haemolytic activity at 0.313 μM. Our findings suggest that C. firmus mediated bacteriogenic AgNPs modulate the activity of common pathogenic bacteria E. tarda. The thoroughness of our research process gives us confidence in the potential of applying AgNPs in aquaculture as a considerable strategy to control the E. tarda infection.

Polyhydroxyalkanoate production from food packaging waste paper

This study evaluated the production of marine biodegradable plastics, specifically polyhydroxyalkanoates (PHAs), using waste paper from food containers as a novel material source. The results showed that adding dilute sulfuric acid as a pretreatment may have a negative impact on enzyme hydrolysis efficiency. Without pretreatment, the highest glucose concentration was observed in the 50-min heating group. In the experimental group with 1% dilute sulfuric acid as a pretreatment, the highest average glucose concentration was observed in the 25-min treatment group. In flask scale experiments, the C/N ratio was controlled at 10, 20, and 30. The results showed that when the C/N ratio was 10, the PHA/CDM ratios were 16.3 and 23.6 at 48 and 72 h, respectively. After 96 h of cultivation using hydrolysis liquid from the waste paper container as the sole carbon source in a 5-L scale experiment, the PHA/CDM ratio was 28.7 and the PHA concentration was 0.95 g/L. The potential bacterial strain in this study was confirmed to be a Bacillus genus bacterium after strain identification. The signal peaks indicated that the PHA obtained from the Bacillus sp. production process was PHB.

Identification and acclimatization of the most potential 4‐chlorophenol degrading bacterial strain isolated from hazardous soil and observing its performance in various process parameters

Abstract4‐Chlorophenol is present as an essential compound of various organic compounds found in different kinds of hazardous waste. It can be easily eliminated from the industrial effluents by different physical and chemical treatment methods although best technique is bioremediation. To separate a potent bacterial strain from the soil that can dispose of 4‐chlorophenol from contaminated water, soil sample was collected from a hospital zone. Isolated bacterial colonies were segregated by the technique of soil enrichment with 500 mg/L 4‐chlorophenol and after that the enriched soil sample was serially diluted and transferred to petri plates with agar media. Twenty‐seven colonies were isolated and the most potent strain was selected in 50 mL liquid medium that was enriched previously with 500 mg/L of 4‐chlorophenol. C19 was found to be the most potent strain and it had the ability to reduce almost 99.97% of 4‐chlorophenol within 24 h, 37°C temperatures as well as in shaking condition (140–150 rpm) and pH 6.8–7.2. After the isolation, the strain was acclimatized in mineral salt medium (MSM) from lower concentration to higher concentration of 4‐chlorophenol to increase its removal capacity as well as to prepare the inoculums. Then parameter optimization study was performed where optimum temperature and pH was found to be 25°C and 6.5°C, respectively, 400 mL media volume and 8% inoculums were found to be most effective and finally 24 h time period was optimized. All these five optimum parameters were applied together to remove higher conc. of 4‐chlorophenol where almost 99.3% removals were obtained when the conc. was 600 mg/L. Moreover, more than 90% removals were obtained in case of 700, 800, and 900 mg/L concentration. Morphological, biochemical, nucleotide homology, and phylogenetic investigation of the strain was made which revealed that it was a rod shaped (Bacillus type), gram +ve, spore forming and motile bacterial strain and therefore, the selected strain was found to exhibit most extreme similarities (91.73%) with Bacillus cereus strain MK789657.

Bio-mediated detoxification of heavy metal contaminated soil and phytotoxicity reduction using novel strain of Brevundimonas vancanneytii SMA3

Heavy metals pose a serious environmental threat on a global scale due to their toxicity towards livings. Therefore, removing harmful metals from the environment has become more challenging in recent years. The objective of this study is to isolate, examine, and characterize naturally existing bacteria that possess the ability to mitigate and detoxify heavy metals such as cadmium, mercury, and lead. The selected bacteria SMA3 actively demonstrated metal tolerance during screening and was then employed for biosorption study using a lab-scale technique. The bacterium belonged to Brevundimonas sp., according to 16 S rRNA analysis. To enhance the removal efficiency of SMA3, response surface methodology (RSM) was employed, resulting in the identification of optimized conditions (pH 7, temperature 30 °C and shaking speed 120 rpm) for achieving maximum removal percentage (69.5 % of Cd, 58.6 % of Hg, and 85.1 % of Pb) within 72 h. The structural changes induced by microbial treatment were demonstrated by comparing the findings of FESEM images and FTIR spectra confirming the disappearance of C ^ C, C]O peaks along with C]O, C–O–C, C–H, and O–H bond destabilization following bioaccumulation. Moreover, in terms of phytotoxicity evaluation, it was observed that the treated soil, containing both heavy metals and the selected potent bacterial strain, exhibited reduced toxicity, resulting in improved germination and growth parameters for the seeds of Solanum lycopersicum (tomato plant). Overall, the selected bacterial strain demonstrated its potential for effectively removing multiple metals from the metal contaminated environment.