Characterization of new diesel-degrading bacteria isolated from freshwater sediments / Caracterización de nuevas bacterias degradadoras de diesel aisladas de sedimentos de agua dulce

As the result of diesel’s extensive production and use as fuel for transportation, pollution with such complex mixtures of hydrocarbons is a major concern worldwide. The present study’s focus was to investigate the presence of diesel-degrading bacteria in different Danube Delta freshwater sediments. Ten bacterial strains capable to grow in a minimal medium with diesel as the sole carbon source were isolated and characterized in this study. Based on the phenotypic and molecular characteristics, the ten strains belong to four genera and seven species, such as Pseudomonas (P. aeruginosa, P. nitroreducens, P. resinovorans, P. multiresinivorans), Acinetobacter (A. tandoii), Bacillus (B. marisflavi), and Stenotrophomonas (S. maltophilia). All these bacteria were excellent biosurfactant producers, and they were able to tolerate saturated hydrocarbons, like n-heptane, n-decane, n-pentadecane, and n-hexadecane. The ten strains possess at least one alkane hydroxylase gene in their genome, and they were also able to tolerate and degrade diesel. Higher biodegradation rates of diesel were acquired for the strains from the genera Pseudomonas, Acinetobacter, and Stenotrophomonas, compared with that obtained for the Bacillus strain. Due to their remarkable potential to degrade diesel and produce biosurfactants, the ten isolated bacteria are attractive candidates for bioremediation of diesel-polluted environments.(AU)

Characterization of new diesel-degrading bacteria isolated from freshwater sediments.

As the result of diesel's extensive production and use as fuel for transportation, pollution with such complex mixtures of hydrocarbons is a major concern worldwide. The present study's focus was to investigate the presence of diesel-degrading bacteria in different Danube Delta freshwater sediments. Ten bacterial strains capable to grow in a minimal medium with diesel as the sole carbon source were isolated and characterized in this study. Based on the phenotypic and molecular characteristics, the ten strains belong to four genera and seven species, such as Pseudomonas (P. aeruginosa, P. nitroreducens, P. resinovorans, P. multiresinivorans), Acinetobacter (A. tandoii), Bacillus (B. marisflavi), and Stenotrophomonas (S. maltophilia). All these bacteria were excellent biosurfactant producers, and they were able to tolerate saturated hydrocarbons, like n-heptane, n-decane, n-pentadecane, and n-hexadecane. The ten strains possess at least one alkane hydroxylase gene in their genome, and they were also able to tolerate and degrade diesel. Higher biodegradation rates of diesel were acquired for the strains from the genera Pseudomonas, Acinetobacter, and Stenotrophomonas, compared with that obtained for the Bacillus strain. Due to their remarkable potential to degrade diesel and produce biosurfactants, the ten isolated bacteria are attractive candidates for bioremediation of diesel-polluted environments.

Role of Indigenous Bacteria in Corrosion of Two Types of Carbon Steel.

This study aimed to investigate the presence of both aerobic and anaerobic bacteria in a water sample collected from a nuclear power plant and establish if the indigenous bacteria or the products of their metabolic activities could initiate the corrosion of two different types of carbon steel (i.e., A570, 1045). The aerobic (heterotrophic, iron-oxidizing) and anaerobic (sulfate-reducing) bacteria were detected in low numbers in the water sample. Three bacterial strains were isolated by the enrichment procedure from this sample. Based on phenotypic and genotypic characteristics, the isolated bacteria were identified as Stenotrophomonas maltophilia IBBCn1 (MT893712), Stenotrophomonas maltophilia IBBCn2 (MT893713), and Bacillus thuringiensis IBBCn3 (MT893714). The bacteria existing in the water sample were able to initiate the corrosion of carbon steel A570 and 1045. The sulfate-reducing bacteria were detected in higher numbers than the heterotrophic bacteria and iron-oxidizing bacteria at the end of the biocorrosion experiments. The carbon steel coupons revealed macroscopic and microscopic changes in the surface characteristics, and these changes could be due to biofilm formation on their surfaces and the accumulation of the corrosion products. The corrosion rate varied from one type of carbon steel to another, depending on the incubation conditions and the chemical composition of the coupons.

Biosurfactant production by a Bacillus megaterium strain.

The aim of the present study was to investigate the ability of Bacillus megaterium IBBPo17 (GenBank KX499518) cells to produce biosurfactant when the growth was done in the presence of long-chain n-alkane n-hexadecane on medium supplemented with yeast extract, proteose peptone, starch, or cellulose. B. megaterium IBBPo17 revealed a higher growth in the presence of n-hexadecane when the medium was supplemented with yeast extract, proteose peptone, or starch, compared with cellulose. Biosurfactant production was higher when B. megaterium IBBPo17 was grown in the presence of n-hexadecane on yeast extract, proteose peptone, or starch supplemented medium, compared with biosurfactant produced on cellulose supplemented medium. A direct correlation between cell growth and biosurfactant production was observed. When the growth of B. megaterium IBBPo17 cells was higher, the decrease in pH values of the medium was higher too, and more amount of CO2 was released. Changes in cell morphology, aggregation of the cells in clusters, and biofilm formation were observed when B. megaterium IBBPo17 was grown in the presence of n-hexadecane on medium supplemented with yeast extract, proteose peptone, starch, or cellulose. Due to its physiological abilities, this Gram-positive bacterium could be a promising candidate for the bioremediation of petroleum hydrocarbon polluted environments.

Response Mechanisms in Serratia marcescens IBBPo15 During Organic Solvents Exposure.

Serratia marcescens strain IBBPo15 (KT315653) which possesses serratiopeptidase (ser) gene (KT894207) exhibited good solvent tolerance. During the exposure of S. marcescens IBBPo15 cells to 5 % organic solvents, n-decane was less toxic for this bacterium, compared with n-hexane, cyclohexane, ethylbenzene, toluene, and styrene. The exposure of the S. marcescens IBBPo15 cells to n-hexane, cyclohexane, ethylbenzene, toluene, and styrene induced the formation of large clusters, while in control and n-decane-exposed cells, only organization into small clusters was observed. The data obtained suggested that S. marcescens IBBPo15 cells produced some secondary metabolites (i.e., surfactant serrawettin, red pigment prodigiosin) which are well known as valuable molecules due to their large applications. The exposure of the bacterial cells to organic solvents induced secondary metabolites profile modifications. However, S. marcescens IBBPo15 possesses only alkB1, todM, rhlAB, pswP, mpr, and ser genes, the unspecific amplification of other fragments being acquired also when the primers for alkM1, xylM, ndoM, and C23DO genes were used. Modifications of DNA patterns were not depicted in S. marcescens IBBPo15 cells exposed to organic solvents.

Highly Solvent Tolerance in Serratia marcescens IBBPo15

ABSTRACT The aim of this study was to investigate the solvent tolerance mechanisms in Serratia marcescens strain IBBPo15 (KT315653). Serratia marcescens IBBPo15 exhibited remarkable solvent-tolerance, being able to survive in the presence of high concentrations (above 40%) of toxic organic solvents, such as cyclohexane, n-hexane, n-decane, toluene, styrene, and ethylbenzene. S. marcescens IBBPo15 produced extracellular protease and the enzyme production decreased in cells exposed to 5% cyclohexane, n-hexane, toluene, styrene, and ethylbenzene, as compared with the control and n-decane exposed cells. S. marcescens IBBPo15 cells produced carotenoid pigments and alteration of pigments profile (i.e., phytoene, lycopene) were observed in cells exposed to 5% cyclohexane, n-hexane, n-decane, toluene, styrene, and ethylbenzene. The exposure of S. marcescens IBBPo15 cells to 5% cyclohexane, n-hexane, n-decane, toluene, styrene, ethylbenzene induced also changes in the intracellular (e.g., 50 kDa protein) and extracellular (e.g., 39, 41, 43, 53, 110 kDa proteins) proteins profile. Significant RAPD, ARDRA, rep-PCR and PCR pattern modifications were not observed in DNA extracted from S. marcescens IBBPo15 cells exposed to 5% cyclohexane, n-hexane, n-decane, toluene, styrene, and ethylbenzene. Though only HAE1 and acrAB genes were detected in the genome of S. marcescens IBBPo15 cells, the unspecific amplification of other fragments being observed also when the primers for ompF and recA genes were used.

Response of Rhodococcus erythropolis strain IBBPo1 to toxic organic solvents.

Recently, there has been a lot of interest in the utilization of rhodococci in the bioremediation of petroleum contaminated environments. This study investigates the response of Rhodococcus erythropolis IBBPo1 cells to 1% organic solvents (alkanes, aromatics). A combination of microbiology, biochemical, and molecular approaches were used to examine cell adaptation mechanisms likely to be pursued by this strain after 1% organic solvent exposure. R. erythropolis IBBPo1 was found to utilize 1% alkanes (cyclohexane, n-hexane, n-decane) and aromatics (toluene, styrene, ethylbenzene) as the sole carbon source. Modifications in cell viability, cell morphology, membrane permeability, lipid profile, carotenoid pigments profile and 16S rRNA gene were revealed in R. erythropolis IBBPo1 cells grown 1 and 24 h on minimal medium in the presence of 1% alkanes (cyclohexane, n-hexane, n-decane) and aromatics (toluene, styrene, ethylbenzene). Due to its environmental origin and its metabolic potential, R. erythropolis IBBPo1 is an excellent candidate for the bioremediation of soils contaminated with crude oils and other toxic compounds. Moreover, the carotenoid pigments produced by this nonpathogenic Gram-positive bacterium have a variety of other potential applications.

Response of Rhodococcus erythropolis strain IBBPo1 to toxic organic solvents

Abstract Recently, there has been a lot of interest in the utilization of rhodococci in the bioremediation of petroleum contaminated environments. This study investigates the response of Rhodococcus erythropolis IBBPo1 cells to 1% organic solvents (alkanes, aromatics). A combination of microbiology, biochemical, and molecular approaches were used to examine cell adaptation mechanisms likely to be pursued by this strain after 1% organic solvent exposure. R. erythropolis IBBPo1 was found to utilize 1% alkanes (cyclohexane, n-hexane, n-decane) and aromatics (toluene, styrene, ethylbenzene) as the sole carbon source. Modifications in cell viability, cell morphology, membrane permeability, lipid profile, carotenoid pigments profile and 16S rRNA gene were revealed in R. erythropolis IBBPo1 cells grown 1 and 24 h on minimal medium in the presence of 1% alkanes (cyclohexane, n-hexane, n-decane) and aromatics (toluene, styrene, ethylbenzene). Due to its environmental origin and its metabolic potential, R. erythropolis IBBPo1 is an excellent candidate for the bioremediation of soils contaminated with crude oils and other toxic compounds. Moreover, the carotenoid pigments produced by this nonpathogenic Gram-positive bacterium have a variety of other potential applications.

Physiological cellular responses and adaptations of Rhodococcus erythropolis IBBPo1 to toxic organic solvents.

A new Gram-positive bacterium, Rhodococcus erythropolis IBBPo1 (KF059972.1) was isolated from a crude oil-contaminated soil sample by enrichment culture method. R. erythropolis IBBPo1 was able to tolerate a wide range of toxic compounds, such as antibiotics (800-1000µg/mL), synthetic surfactants (50-200µg/mL), and organic solvents (40%-100%). R. erythropolis IBBPo1 showed good tolerance to both alkanes (cyclohexane, n-hexane, n-decane) and aromatics (toluene, styrene, ethylbenzene) with logPOW (logarithm of the partition coefficient of the solvent in octanol-water mixture) values between 2.64 and 5.98. However, alkanes were less toxic for R. erythropolis IBBPo1 cells, compared with aromatics. The high organic solvent tolerance of R. erythropolis IBBPo1 could be due to the presence in their large genome of some catabolic (alkB, alkB1, todC1, todM, xylM), transporter (HAE1) and trehalose-6-phosphate synthase (otsA1, KF059973.1) genes. Numerous and complex physiological cellular responses and adaptations involved in organic solvent tolerance were revealed in R. erythropolis IBBPo1 cells exposed 1 and 24hr to 1% organic solvents. R. erythropolis IBBPo1 cells adapt to 1% organic solvents by changing surface hydrophobicity, morphology and their metabolic fingerprinting. Considerable modifications in otsA1 gene sequence were also observed in cells exposed to organic solvents (except ethylbenzene).

Characterization of some bacteriocins produced by lactic acid bacteria isolated from fermented foods.

Lactic acid bacteria (LAB) isolated from different sources (dairy products, fruits, fresh and fermented vegetables, fermented cereals) were screened for antimicrobial activity against other bacteria, including potential pathogens and food spoiling bacteria. Six strains have been shown to produce bacteriocins: Lactococcus lactis 19.3, Lactobacillus plantarum 26.1, Enterococcus durans 41.2, isolated from dairy products and Lactobacillus amylolyticus P40 and P50, and Lactobacillus oris P49, isolated from bors. Among the six bacteriocins, there were both heat stable, low molecular mass polypeptides, with a broad inhibitory spectrum, probably belonging to class II bacteriocins, and heat labile, high molecular mass proteins, with a very narrow inhibitory spectrum, most probably belonging to class III bacteriocins. A synergistic effect of some bacteriocins mixtures was observed. We can conclude that fermented foods are still important sources of new functional LAB. Among the six characterized bacteriocins, there might be some novel compounds with interesting features. Moreover, the bacteriocin-producing strains isolated in our study may find applications as protective cultures.

Multidrug resistance in hydrocarbon-tolerant Gram-positive and Gram-negative bacteria.

New Gram-positive and Gram-negative bacteria were isolated from Poeni oily sludge, using enrichment procedures. The six Gram-positive strains belong to Bacillus, Lysinibacillus and Rhodococcus genera. The eight Gram-negative strains belong to Shewanella, Aeromonas, Pseudomonas and Klebsiella genera. Isolated bacterial strains were tolerant to saturated (i.e., n-hexane, n-heptane, n-decane, n-pentadecane, n-hexadecane, cyclohexane), monoaromatic (i.e., benzene, toluene, styrene, xylene isomers, ethylbenzene, propylbenzene) and polyaromatic (i.e., naphthalene, 2-methylnaphthalene, fluorene) hydrocarbons, and also resistant to different antimicrobial agents (i.e., ampicillin, kanamycin, rhodamine 6G, crystal violet, malachite green, sodium dodecyl sulfate). The presence of hydrophilic antibiotics like ampicillin or kanamycin in liquid LB-Mg medium has no effects on Gram-positive and Gram-negative bacteria resistance to toxic compounds. The results indicated that Gram-negative bacteria are less sensitive to toxic compounds than Gram-positive bacteria, except one bacteria belonging to Lysinibacillus genus. There were observed cellular and molecular modifications induced by ampicillin or kanamycin to isolated bacterial strains. Gram-negative bacteria possessed between two and four catabolic genes (alkB, alkM, alkB/alkB1, todC1, xylM, PAH dioxygenase, catechol 2,3-dioxygenase), compared with Gram-positive bacteria (except one bacteria belonging to Bacillus genus) which possessed one catabolic gene (alkB/alkB1). Transporter genes (HAE1, acrAB) were detected only in Gram-negative bacteria.