Promising Bacterial Isolate Research Articles

Delineating acetaminophen biodegradation kinetics and metabolomics using bacterial community.

Acetaminophen [N-(4-hydroxyphenyl) acetamide, APAP]is an extensively and frequently consumed over-the-counter analgesic and antiphlogistic medication. It is being regarded as an emerging pollutant due to its continuous increment in the environment instigating inimical impacts on humans and the ecosystem. Considering its wide prevalence in the environment, there is an immense need of appropriate methods for the removal of APAP. The present study indulged screening and isolation of APAP degrading bacterial strains from pharmaceuticals-contaminated sites, followed by their molecular characterization via 16SrRNA sequencing. The phylogenetic analyses assigned the isolates to the genera Pseudomonas, Bacillus, Paracoccus, Agrobacterium, Brucella, Escherichia, and Enterobacter based on genetic relatedness. The efficacy of these strains in batch cultures tested through High-performance Liquid Chromatography (HPLC) revealed Paracoccus sp. and Enterobacter sp. as the most promising bacterial isolates degrading up to 88.96 and 85.92%, respectively of 300mg L-1 of APAP within 8days of incubation. Michaelis-Menten kinetics model parameters also elucidated the high degradation potential of these isolates. The major metabolites identified through FTIR and GC-MS analyses were 4-aminophenol, hydroquinone, and 3-hydroxy-2,4-hexadienedioic. Therefore, the outcomes of this comprehensive investigation will be of paramount significance in formulating strategies for the bioremediation of acetaminophen-contaminated sites through a natural augmentation process via native bacterial strains.

Polyethylene terephthalate (PET)-degrading bacteria in the pelagic deep-sea sediments of the Pacific Ocean

Polyethylene terephthalate (PET) plastic pollution is widely found in deep-sea sediments. Despite being an international environmental issue, it remains unclear whether PET can be degraded through bioremediation in the deep sea. Pelagic sediments obtained from 19 sites across a wide geographic range in the Pacific Ocean were used to screen for bacteria with PET degrading potential. Bacterial consortia that could grow on PET as the sole carbon and energy source were found in 10 of the 19 sites. These bacterial consortia showed PET removal rate of 1.8%–16.2% within two months, which was further confirmed by the decrease of carbonyl and aliphatic hydrocarbon groups using attenuated total reflectance–Fourier-transform infrared analysis (ATR-FTIR). Analysis of microbial diversity revealed that Alcanivorax and Pseudomonas were predominant in all 10 PET degrading consortia. Meanwhile, Thalassospira, Nitratireductor, Nocardioides, Muricauda, and Owenweeksia were also found to possess PET degradation potential. Metabolomic analysis showed that Alcanivorax sp. A02-7 and Pseudomonas sp. A09-2 could turn PET into mono-(2-hydroxyethyl) terephthalate (MHET) even in situ stimulation (40 MPa, 10 °C) conditions. These findings widen the currently knowledge of deep-sea PET biodegrading process with bacteria isolates and degrading mechanisms, and indicating that the marine environment is a source of biotechnologically promising bacterial isolates and enzymes.

Evaluation of biocontrol efficacy of rhizosphere dwelling bacteria for management of Fusarium wilt and Botrytis gray mold of chickpea

BackgroundChickpea (Cicer arietinum L.) production is affected by many biotic factors, among them Fusarium wilt caused by Fusarium oxysporum f. sp. ciceri and Botrytis gray mold caused by Botrytis cinerea led to severe losses. As fungicide application is not advisable, biological management is the best alternative for plant protection. The rhizosphere-dwelling antagonistic bacteria are one of the important successful alternative strategy to manage these diseases of chickpea. Rhizosphere dwelling bacteria serve as biocontrol agents by different mechanisms like producing antibiotics, different enzymes, siderophores against pathogens and thereby reducing the growth of pathogens.ResultsThe present study aimed to isolate rhizospheric bacteria from the soils of different chickpea fields to evaluate biocontrol efficacy of the isolated bacteria to manage Fusarium wilt and Botrytis gray mold in chickpea. A total of 67 bacteria were isolated from chickpea rhizosphere from Bundelkhand region of India. Study revealed the isolated bacteria could reduce the Fusarium oxysporum f. sp. ciceris and Botrytis cinerea infection in chickpea between 17.29 and 75.29%. After screening of all the bacteria for their biocontrol efficacy, 13 most promising bacterial isolates were considered for further study out of which, three bacterial isolates (15d, 9c and 14a) have shown the maximum in vitro antagonistic effects against Fusarium oxysporum f. sp. ciceri and Botrytis cinerea comparable to in vivo effects. However, Isolate (15d) showed highest 87.5% and 82.69% reduction in disease against Fusarium wilt and Botrytis gray mold respectively, under pot condition. Three most potential isolates were characterized at molecular level using 16S rRNA gene and found to be Priestia megaterium (9c and 14a) and Serratia marcescens (15d).ConclusionThis study identified two native biocontrol agents Priestia megaterium and Serratia marcescens from the rhizospheric soils of Bundelkhand region of India for control of Fusarium wilt, Botrytis gray mold. In future, efforts should be made to further validate the biocontrol agents in conjugation with nanomaterials for enhancing the synergistic effects in managing the fungal diseases in chickpea. This study will definitely enhance our understanding of these bioagents, and to increase their performance by developing effective formulations, application methods, and integrated strategies.

Plant growth-promoting properties of endophytic bacteria isolated from some xerophytic plants distributed in arid regions (Uzbekistan)

Recent advancements in the development of endophytic microorganisms-based stimulants have shown promising potential in various fields. Research on the identification of these endophytic microorganisms has been well reported, however, there are limited studies of these endophytes isolated from plants in arid regions. Thus, isolation and identification of promising microbial endophytes from xerophytic plants is essential in technology development for sustainable agriculture in arid regions. This study aims to identify the endophytic bacteria isolated from Kochia prostrata (L.) Schrad. and Ceratoides eversmanniana (Stschegl. ex I.G.Borshch.) Botsch. & Ikonn. in vertical zones of arid regions of Uzbekistan, and examine their potential plant growth-promoting properties. Using Luria-Bertani (LB) medium, 70 distinct bacterial colony were isolated from the different segments of K. prostrata and C. eversmanniana. These isotypes were screened using NaCl-supplemented LB medium in which nine promising bacterial isolates showed tolerance to 15% NaCl. The nine promising halophytes were subjected to molecular identification using specific primers. The isolates from K. prostrata are identified as Bacillus amyloliquefaciens, Bacillus pumilus, Priestia aryabhattai, Pseudomonas putida, and Priestia endophytica. On the other hand, Priestia megaterium, Pseudomonas putida, Bacillus subtilis and Brevibacillus parabrevis were isolated from C. eversmanniana. The identified isolates also showed significant plant growth-promoting properties (N2-fixation, IAA production, phosphates solubilization, ACC deaminase production, siderophores production) and shows ability to inhibit pathogenic fungal growth. Based on the result, the identified bacterial endophytes can be processed as growth-stimulants and biological control of fungal pathogens in crops in arid regions.

A Novel Robust Screening Assay Identifies Pseudomonas Strains as Reliable Antagonists of the Root-Knot Nematode Meloidogyne incognita.

Forty-four bacterial strains isolated from greenhouse soil and beetroots were tested for their antagonistic activity against the plant-parasitic root-knot nematode (RKN) Meloidogyne incognita, which causes significant yield losses in a number of important crops worldwide. Through a novel combination of in vitro and on planta screening assays, Pseudomonas spp. 105 and 108 were identified as the most promising bacterial isolates. Both strains were evaluated for their potential to control different RKN population densities and as root protectants against nematode infestation. Regardless of the application method, both strains significantly reduced root galling caused by M. incognita. These two strains were subjected to whole genome sequencing and de novo genome assembly as a basis for phylogenetic and future functional characterization. Phylogenetic analysis revealed that both Pseudomonas strains cluster within the Pseudomonas fluorescens clade among previously characterized RKN antagonists and Pseudomonas-based biocontrol agents of plant diseases.

Deciphering the Potential of Sulphur-Oxidizing Bacteria for Sulphate Production Correlating with pH Change.

Sulphur, available in the form of sulphate, is one of the essential nutrients that is required by plants. Bacteria capable of oxidizing reduced forms of sulphur to sulphate play an important role in sulphur nutrition for plants. The present study was conducted to isolate, screen, and characterize sulphur-oxidizing bacteria from different soil samples collected from mustard rhizosphere and fly ash mixed soil. A total of 33 sulphur-oxidizing bacterial isolates (HMSOB1-33) were retrieved from soil and further screened for sulphur-oxidizing ability. Maximum solubilization index (3.76), pH reduction (3.93), and sulphate production (173.61µg/ml) were observed for the isolate HMSOB2 which on the basis of 16S rDNA sequencing was identified as Pantoea dispersa with sequence similarity 98.22%. Four other selected bacterial isolates were identified as Bacillus megaterium, Bacillus tropicus, Bacillus velezensis, and Bacillus cereus. Sulphate solubilization index (SSI) correlated positively (r = 0.91) with sulphate production; however, pH showed negative correlation (r = - 0.82) with SSI as well as sulphate production after 120h of incubation. These promising bacterial isolates could be further explored as bioinoculant after assessing plant growth traits.

Isolation, screening and characterization of gelatinase and protease producing microorganisms from organic kitchen waste

The present study was aimed at isolation, screening and identification of gelatinase and protease producing bacteria from the kitchen waste. The study was also focused on the potential of isolates to produce enzyme protease and gelatinase. The total of 157 bacterial isolates were obtained from the organic kitchen waste collected from various nearby sources. The primary screening was done to screen the potential of these isolates for their enzymatic potentials on selective media. The 57 promising bacterial isolates were found to have enzymatic potentials for both gelatinase and protease. The screened isolates were subjected to secondary screening, amongst which five isolates showed maximum production of both gelatinase and protease. These five isolates viz. KW91, KW104, KW121, KW128, KW98 were the most promising isolates showing high degree of milk and gelatin hydrolysis which may be potent in faster degradation of domestic kitchen waste.

Plant Growth-Promoting Activity of Bacteria Isolated from Asian Rice (Oryza sativa L.) Depends on Rice Genotype.

ABSTRACTAsian rice is one of the most important crops because it is a staple food for almost half of the world’s population. To have production of rice keep pace with a growing world population, it is anticipated that the use of fertilizers will also need to increase, which may cause environmental damage through runoff impacts. An alternative strategy to increase crop yield is the use of plant growth-promoting bacteria. Thousands of microbial species can exist in association with plant roots and shoots, and some are critical to the plant’s survival. We isolated 140 bacteria from two distantly related rice accessions and investigated whether their impact on the growth of four different rice accessions. The bacterial isolates were screened for their ability to solubilize phosphate, a known plant growth-promoting characteristic, and 25 isolates were selected for further analysis. These 25 phosphate-solubilizing isolates were also able to produce other potentially growth-promoting factors. Five of the most promising bacterial isolates were chosen for whole-genome sequencing. Four of these bacteria, isolates related to Pseudomonas mosselii, a Microvirga sp., Paenibacillus rigui, and Paenibacillus graminis, improved root and shoot growth in a rice genotype-dependent manner. This indicates that while bacteria have several known plant growth-promoting functions, their effects on growth parameters are rice genotype dependent and suggest a close relationship between plants and their microbial partners.IMPORTANCE In this study, endophytic bacterial isolates from roots and shoots of two distantly related rice accessions were characterized phenotypically and genotypically. From the isolated bacterial species, five of the most promising plant growth-promoting bacteria were selected to test their abilities to enhance growth of the four rice accessions. Interestingly, plant growth enhancement was both bacterial isolate specific and plant genotype specific. However, the positive interactions between plant and bacteria could not easily be predicted because rice growth-promoting bacteria isolated from their host plants did not necessarily stimulate growth of their own host.

Biochemical and Biological Evaluation of an L-Asparaginase from Isolated Escherichia coli MF-107 as an Anti-Tumor Enzyme on MCF7 Cell Line

Background: One of the most widely used anticancer agents is microbial L-ASNase. Herein, we assessed the biochemical and biological properties of an isolated L-ASNase from a Gram-negative bacteria strain, Escherichia coli MF-107. Methods:Using garden asparagus, we obtained several bacterial isolates. These strains were further screened for L-ASNase activity. A promising bacterial isolate was selected for L-ASNase production and subsequent purification. The molecular weight of purified L-ASNase was determined. The MTT assay was applied to assess the cytotoxic effect of the purified enzyme. Also, for caspase activity determination and the apoptotic effect of purified enzyme on in cells, we conducted a real-time PCR method. Results:The molecular weight of the enzyme was approximately 37 kDa. In the pH range of 7.5 to 8, the enzyme had considerable stability. At 35 °C, the purified L-ASNase optimum activity was recorded. The cytotoxic effect of the enzyme on treated cells was dose-dependent with an IC50 value of 5.7 IU/ml. The Bax gene expression considerably raised by 5.75-fold (p < 0.001) upon L-ASNase treatment. On the other hand, the anti-apoptotic Bcl-2 gene expression showed a 2.63-fold increase compared to the control (p < 0.05). It was detected that the mRNA levels of caspase-3 and p53 were considerably upregulated (5.93 and 1.85-fold, respectively). We did not find any alternation in the caspase-8 activity of the treated cells compared to untreated cells. Conclusion:In this research, the proliferation of the breast cancer cells remarkably inhibited via the cytotoxic effect of isolated L-ASNase from microbial sources.

Living in a bottle: Bacteria from sediment-associated Mediterranean waste and potential growth on polyethylene terephthalate.

Ocean pollution is a worldwide environmental challenge that could be partially tackled through microbial applications. To shed light on the diversity and applications of the bacterial communities that inhabit the sediments trapped in artificial containers, we analyzed residues (polyethylene terephthalate [PET] bottles and aluminum cans) collected from the Mediterranean Sea by scanning electron microscopy and next generation sequencing. Moreover, we set a collection of culturable bacteria from the plastisphere that were screened for their ability to use PET as a carbon source. Our results reveal that Proteobacteria are the predominant phylum in all the samples and that Rhodobacteraceae, Woeseia, Actinomarinales, or Vibrio are also abundant in these residues. Moreover, we identified marine isolates with enhanced growth in the presence of PET: Aquimarina intermedia, Citricoccus spp., and Micrococcus spp. Our results suggest that the marine environment is a source of biotechnologically promising bacterial isolates that may use PET or PET additives as carbon sources.

Bacteria from tropical semiarid temporary ponds promote maize growth under hydric stress

World climate change has triggered soil water stress and imposed limitations on agricultural production. Plant growth-promoting bacteria (PGPBs) have been an efficient strategy to improve the biological supply and growth of plants under distinct abiotic stress conditions. We hypothesized that the soils from a temporary pond may harbor PGPBs with potential strains which increase maize tolerance to water deficit. We studied rhizosphere and bulk soil of Mimosa bimucronata in a temporary pond from semiarid Northeast Brazil to access strains with characteristics to promote plant growth and mitigate abiotic stress for maize crop. We isolated 355 bacterial isolates, from which 96 were selected based on the morphophysiological characterization to assess IAA production (42 % produced over 50 μg mL-1 of IAA), calcium phosphate solubilization (with one isolate achieving medium IS), biofilm and exopolysaccharides production (66 % and 98 % of isolates, respectively). Based on these mechanisms, the 30 most promising bacterial isolates were selected to assess biological nitrogen fixation (74 % of the isolates showed nitrogenase activity greater than 20 C2H4.h-1.mg-1), ACC deaminase activity (80 % of isolates) and growth in medium with reduced water activity (8 % of isolates grew in medium with water activity (Aw) of 0.844). We sequenced the 16S rRNA gene from the seven most promising isolates in in vitro and in vivo assays, which were identified as Staphylococcus edaphicus, Bacillus wiedmannii, Micrococcus yunnanensis, Streptomyces alboflavus, Streptomyces alboflavus, Bacillus wiedmanni and Bacillus cereus. In vivo, eleven isolates and three bacterial consortia did not differ from the control with nutrient solution, for total leaf area and root dry mass of maize. S. alboflavus (BS43) had the best in vivo results, not differing from the control with nutrient solution. We highlight the unpublished potential of Staphylococcus edaphicus and Streptomyces alboflavus in promoting the growth of plants under water stress. In addition, it is the first report of bacteria isolated from a temporary pond in the Brazilian semiarid which promoting plant growth attributes and development.

Manipulation of insect gut microbiota towards the improvement of Bactrocera oleae artificial rearing

AbstractBactrocera oleae (Rossi) (Diptera: Tephritidae) is the main pest of olive trees (Olea europaea L.), causing major damages in olive crops. Improvement of mass rearing is a prerequisite for the successful development of large‐scale sterile insect technique (SIT) applications. This can be achieved through the enrichment of artificial diets with gut bacteria isolates. We assessed the efficiency of three gut bacteria previously isolated from Ceratitis capitata (Wiedemann), and four isolated from B. oleae, as larval diet additives in both live and inactivated/dead forms. Our results showed that dead Enterobacter sp. AA26 increased pupal weight, whereas both live and dead cells increased pupal and adult production and reduced immature developmental time, indicating that its bacterial cells serve as a direct nutrient source. Live Providencia sp. AA31 improved pupal and adult production, enhanced male survival under stress conditions, and delayed immature development. Dead Providencia sp. AA31, however, did not affect production rates, indicating that live bacteria can colonize the insect gut and biosynthesize nutrients essential for larval development. Live and dead Bacillus sp. 139 increased pupal weight, accelerated immature development, and increased adult survival under stress. Moreover, live Bacillus sp. 139 improved adult production, indicating that Bacillus cells are a direct source of nutrients. Dead Serratia sp. 49 increased pupal and adult production and decreased male survival under stress conditions whereas live cells decreased insect production, indicating that the live strain is entomopathogenic, but its dead cells can be utilized as nutrient source. Klebsiella oxytoca, Enterobacter sp. 23, and Providencia sp. 22 decreased pupal and subsequent adult production and were harmful for B. oleae. Our findings indicate that dead Enterobacter sp. AA26 is the most promising bacterial isolate for the improvement of B. oleae mass rearing in support of future SIT or related population suppression programs.

Isolation and characterization of local Azotobacter isolate) producing bio-plastics and consuming waste vegetable oils

Polyhyroxyalkanotes (PHAs) are a family of polyhydroxyesters synthesized by numerous bacteria as an intracellular carbon and energy storage compound under nutrient-limiting conditions with excess carbon. An extensive screening program was previously done to isolate a promising bacterial isolate capable of polyhydroxyalkanoate (PHA) production. Polyhydroxalkanoates are biodegradable thermo polyesters like poly-β-hydroxybutyrate (PHB), which can be produced intracellularly as carbon and energy reserves. In this present study, out of 35 isolates, as many as 12 isolates were found to accumulate PHA which isolated from the oil and plastic contaminated soils, collected from different contaminated sites in Baghdad. However only one bacterial colony is selected among others based on maximum PHA yield (4.8g/L) after 48 hrs of incubation at 30°C with 54 % of PHA. Bacteria from this colony was characterized by morphological, biochemical and identified as Azotobater. The maximum PHA yield was recorded under the dry weight basis with 3% of corn oil wastes as the sole carbon source. However, Sudan black stained cells showed the presence of large quantities of granules in the cell cytoplasm when viewed under microscope. The polymer was extracted for the purpose of studying its physical and chemical properties.

Bioprospecting of Halotolerant Bacterial Isolates for Potassium Recovery from K‐Feldspar

AbstractPotassium‐solubilizing bacteria were isolated from solar salt pans of an experimental salt farm and Sambhar Lake, mining areas of Naseerabad, and wastewater from a marble cutting machinery. Seven promising bacterial isolates from Makrana, three from Sambhar Lake, and three from Naseerabad were found to have comparatively better potassium‐solubilizing capacity. Out of these, three potential bacterial isolates were identified as Acinetobacter soli (MTCC 5918), Enterobacter xiangfangensis (MTCC 5917), and Acinetobacter baumannii (MTCC 5916). A. soli was found to have maximum potassium‐releasing capacity in the supernatant which may be further applied as a biofertilizer.

Screening, Optimization and Extraction of Polyhydroxyalkanoates (PHAs) from Bacillus thuringienesis

Aims: This study illustrated obtaining bacterial isolates capable to produce polyhydroxyalkanoates (PHA) under stressed conditions and also using cheap wastes for production process. Study Design: Two­step throughput screening of 50 bacterial isolates by lipophylic stain (Sudan black B) and flouroscence stain (Nile red) will be carried on, then the best condition for PHA production followed by identification of most potent isolate by molecular charterization will be investigated. Place and Duration of Study: The study were performed in physiological lab in botany & microbiology department in faculty of science, Al­azhar university and NRC from October 2012 until April 2014. Methodology: Bacterial isolates will be investigated using two different indicator stains, Sudan Black and Nile Red, for PHA productivity then the highly producing isolate will be identified. Factors controlling PHA production and stressed condition will be studied Original Research Article Desouky et al.; JABB, Article no. JABB.2014.004 41 alternatively depends on increasing of PHA production which will be assayed quantitatively by converting PHA to crotonic acid. Biopolymer will be extracted using successive solvents. Result: Five soil samples were collected from different localities contaminated with industrial wastes and 50 isolates of bacteria were purified then screened for PHA production by using Sudan black B as a primary screening and confirmed by fluorescent Nile red staining. Eleven promising bacterial isolates were selected based on their PHA yields. Out of eleven natural promising isolates, BS11 was found to be the most efficient PHA producer and identified as Bacillus thuringiensis (KJ206079). The effect of different conditions on PHA produced by B. thuringiensis including carbon sources, nitrogen sources, incubation temperatures, pH and incubation periods were studied. The highest amount of PHA was obtained from this isolate using medium containing 30 g/l molasses, 0.8 g/L ammonium sulphate at pH 7.5 and incubation temp at 35oC and after 72 hours. In conclusion, after the optimization of PHA synthesizing conditions, B. thuringiensis accumulate up to 69 % of its dry weight and can be employed for industrial production. Conclusion: The experiment indicate the efficiency of two­throughput screening systems targeting PHA producing isolates. Also optmiziation of PHA producing factors for the most potent producing strain, Bacillus thuringiensis (KJ206079), was increased from 2.5 g/L to 4.1 g/L and represent about 69% cell dry weight.

Improved Properties of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Produced byComamonassp. EB172 Utilizing Volatile Fatty Acids by Regulating the Nitrogen Source

This study presents the effect of carbon to nitrogen ratio (C/N) (mol/mol) on the cell growth and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) accumulation by Comamonas sp. EB172 in 2 L fermenters using volatile fatty acids (VFA) as the carbon source. This VFA was supplemented with ammonium sulphate and yeast extract in the feeding solution to achieve C/N (mol/mol) 5, 15, 25, and 34.4, respectively. By extrapolating the C/N and the source of nitrogen, the properties of the polymers can be regulated. The number average molecular weight (M n) of P(3HB-co-3HV) copolymer reached the highest at 838 × 103 Da with polydispersity index (PDI) value of 1.8, when the culture broth was supplemented with yeast extract (C/N 34.4). Tensile strength and Young's modulus of the copolymer containing 6–8 mol% 3HV were in the ranges of 13–14.4 MPa and 0.26–0.34 GPa, respectively, comparable to those of polyethylene (PE). Thus, Comamonas sp. EB172 has shown promising bacterial isolates producing polyhydroxyalkanoates from renewable carbon materials.

Microbial degradation of Textile Dye (Remazol Black B) by Bacillus spp. ETL-2012

In the present study, an attempt was made to examine the potential of isolated bacterium for decolorization of Remazol (azo dye) in batch reactors. Bacteria from soil, & dye waste were subjected to acclimatization with azo dye, in the basal nutrient media. The most promising bacterial isolate was used for further dye degradation studies. Biochemical characteristics revealed the isolated organism as Bacillus spp. The optimum pH and temperature for the decolorization was 6.0 and 37oC, respectively. This decolorization potential increased the applicability of this microorganism for the dye removal. The results suggest that the Bacillus spp. ETL-2012 can be used as a useful tool to treat waste water containing reactive dyes.

Biodegradation of C.I. Reactive Red 195 by Enterococcus faecalis strain YZ66

Synthetic dyes are extensively used in textile dyeing, paper, printing, colour photography, pharmaceutics, cosmetics and other industries. Among these, azodyes represents the largest and most versatile class of synthetic dyes. As high as 50% of the dyes are released into the environment during manufacture and usage. Traditional methods of treatment are found to be expensive and have operational problems. Biological decolourization has been investigated as a method to transform, degrade or mineralize azo dyes. In the present studies bacteria from soil from dye waste area, dye waste, sewage and dung were subjected to acclimatization with C.I. Reactive Red 195 an azo dye, in the basal nutrient media. The most promising bacterial isolate was used for further dye degradation studies. The 16s rRNA gene sequencing and biochemical characteristics revealed the isolated organism as Enterococcus faecalis strain YZ66. The strain showed 99.5% decolourization of the selected dye (Reactive Red 195-50 mg/l) within one and half hour in static anoxic condition. The optimum pH and temperature for the decolourization was 5.0 and 40°C respectively. The biodegradation was monitored by UV-Vis, FTIR, TLC and HPLC. The final products were characterized by Gas chromatography and Mass Spectrophotometry. Toxicity study demonstrated no toxicity of the biodegradation product. The results suggest that the isolated organism E. faecalis strain YZ 66 can be used as a useful tool to treat waste water containing reactive dyes.

Microbial surfactant-enhanced mineral oil recovery under laboratory conditions

Microbial enhanced oil recovery (MEOR) is potentially useful to recover incremental oil from a reservoir being beyond primary and secondary recovery operations. Effort has been made to isolate and characterize natural biosurfactant produced by bacterial isolates collected from various oil fields of ONGC in Assam. Production of biosurfactant has been considered to be an effective major index for the purpose of enhanced oil recovery. On the basis of the index, four promising bacterial isolates: Pseudomonas aeruginosa (MTCC7815), P. aeruginosa (MTCC7814), P. aeruginosa (MTCC7812) and P. aeruginosa (MTCC8165) were selected for subsequent testing. Biosurfactant produced by the promising bacterial isolates have been found to be effective in the recovery of crude oil from saturated column under laboratory conditions. Two bacterial strains: P. aeruginosa (MTCC7815) and P. aeruginosa (MTCC7812) have been found to be the highest producer of biosurfactant. Tensiometer studies revealed that biosurfactants produced by these bacterial strains could reduce the surface tension ( σ) of the growth medium from 68 to 30 mN m −1 after 96 h of growth. The bacterial biosurfactants were found to be functionally stable at varying pH (2.5–11) conditions and temperature of 100 °C. The treatment of biosurfactant containing, cell free culture broth in crude oil saturated sand pack column could release about 15% more crude oil at 90 °C than at room temperature and 10% more than at 70 °C under laboratory condition.

Biological control of Dutch elm disease by Pseudomonas species

SUMMARYAntagonism of a selected group of bacteria against Ophiostoma (=Ceratocystis) ulmi, the Dutch elm disease pathogen, was determined on agar media. Four promising bacterial isolates, all fluorescent Pseudomonads, were used for field experiments and for further tests on in vitro antagonism against several fungi. It was shown that only slight differences existed in antagonism against different O. ulmi isolates. Also Ceratocystis fagacearum and C. fimbriata were inhibited similarly to O. ulmi.In field experiments bacteria were applied to elm trees by low pressure injection or by injection with a specially developed ‘gouge‐pistol’. Elms treated only with bacteria remained healthy throughout two growing seasons. Elms inoculated with O. ulmi developed severe Dutch elm disease symptoms. Trees, inoculated first with O. ulmi and treated subsequently with bacteria also developed severe Dutch elm disease symptoms. Trees treated with bacteria first and inoculated subsequently with O. ulmi showed significantly fewer symptoms, especially those where treatments were carried out with the gouge‐pistol.