Alkane utilization by Rhodococcus strain NTU-1 alone and in its natural association with Bacillus fusiformis L-1 and Ochrobactrum sp

Linear (n-hexadecane) and branched (pristane) alkanes were degraded by a mixed culture isolated from an oil-contaminated field. The degradation was accompanied by formation of biofloccules. The culture was composed of Rhodococcus strain NTU-1, Bacillus fusiformis L-1, and Ochrobactrum sp. Rhodococcus strain NTU-1 carried out the degradation of the alkane via a hydroxylase. Bacillus fusiformis L-1 and Ochrobactrum sp. did not degrade the alkanes but aided the flocculation by forming more rigid bacterial aggregates that enhanced the trapping of alkanes. In batch cultures, transformation and removal of the linear and branched alkanes was achieved within 66 h with more than 95% efficiency.     

Phenol and <Emphasis Type="Italic">n</Emphasis>-alkanes (C<Subscript>12</Subscript> and C<Subscript>16</Subscript>) utilization: influence on yeast cell surface hydrophobicity

This study was focused on the role of two types of diametrically different carbon sources, n-alkanes represented by a mixture of dodecane–hexadecane, and phenol on modification of the cell surface hydrophobicity. Capabilities of using either solely hydrocarbons or hydrocarbons in the mixture with phenol as well as phenol itself by yeast species Candida maltosa, Yarrowia lipolytica and Pichia guilliermondii were investigated. Studies were complemented by cell biomass formation measurements. The corresponding cell surface hydrophobicity was assessed by microbial adhesion to the hydrocarbon test (MATH). Degradation of phenol was examined using GC-SPE technique, whereas hydrocarbons were extracted prior to gravimetric determination. Results obtained indicated that the hydrophobic or hydrophilic nature of the carbon source had significant influence on the cell surface hydrophobicity. Although the results differed for some individual yeast strains, the generalization can be made that there is the correlation between the best hydrocarbon and phenol degradation and corresponding cell wall properties of the yeast examined.     

Cell Surface Hydrophobicity as a Pellicle Formation Factor in Film Strain of Saccharomyces

The film strain of Saccharomyces grows through non-film and film stages. The differences in cell surface hydrophobicity were examined at both stages. The degree of hydrophobic was quantitatively determined by comparing distribution ratios of cells between buffered aqueous and organic solvent phases. The cell surface in the film stage was more hydrophobic than that in the non-film stage, whereas the inherent non-film strain of Saccharomyces always showed low hydrophobicity. These results indicate that the change from non-film to film stage was due to a change in cells from hydrophilic to hydrophobic. The effects of growth conditions on hydrophobicity were further examined with the film strain Saccharomyces bayanus. Ethanol as sole carbon source more efficiently increased hydrophobicity than glucose. The increase in hydrophobicity seemed to depend upon respiration accompanying assimilation of ethanol. It was also found that the addition of a limited amount of biotin, as well as higher pH in medium lowered hydrophobicity. Variation in degree of pellicle formation was positively related to that of cell surface hydrophobicity.     

Effect of electrode surface properties on enhanced electron transfer activity in microbial fuel cells

The influence of electrode surface chemistry over biofilm growth was evaluated for photo‐bioelectrocatalytic fuel cell. A consortium of photosynthetic bacteria was grown onto different electrodes designed with polyethylenimine (PEI) and multiwall carbon nanotubes as hydrophilic and hydrophobic modifier, respectively. The designed electrodes were loaded with 0.08, 0.17, and 0.33 μg/cm² of PEI to change the hydrophilicity. However, 0.56, 0.72, and 0.83 mg/cm² of multiwall carbon nanotubes were used to alter the hydrophobicity of the electrodes. The surface chemistry of electrode and bio‐interaction was evaluated as a function of contact angle and biofilm formation. The results were compared with those obtained with a carbon paper electrode. The contact angle on the untreated electrode (carbon paper) was 118°, whereas for hydrophobic and hydrophilic electrodes, the maximum and minimum contact angles were 170° and 0°, respectively. Interestingly, the maximum biofilm growth (0.2275 g, wet basis) was observed on highly hydrophobic surface; however, the maximum electrochemical performance (246 mV) was shown by the most hydrophilic electrode surface. PEI‐based electrode with good biofilm formation showed comparatively higher electrogenic activity.     

Effects of pantolactone and butyrolaectone on the pleiotropic phenotypes of lon mutants and on thermal induction of the SOS phenomena in a tif mutant of Escherichia coli K12

Hydrophobic and charge-charge interactions of Salmonella typhimirium and Serratia marcescens were determined and related to their content of fimbriae and lipopolysaccharide (LPS). The cell surface structures were characterized with hydrophobic interaction chromatography (HIC), electrostatic interaction chromatography (ESIC) and particle electrophoresis measurements. The degree of interaction at the air-water interface was tested using a monolayered lipid film applied to an aqueous surface. The cell surface hydrophobicity of S. typhimurium in the presence of fimbriae was less in smooth than in rought bacteria. Examination of a series of rough mutants of S. typhimurium indicates that reduction of the O-side chain and core oligosaccharides was correlated with increased cell hydrophobicity. The enrichment factors at the air-water interface were significantly higher for fimbriated than for non-fimbriated S. typhimurium cells. Fimbriated S. marcescens cells were less hydrophobic and adhered to a lesser degree at the air-water surface than non-fimbriated counterparts. Electrophoretic measurements and adsorption to ion exchangers gives different information about the surface charge of bacteria. The latter technique gives the interaction between localized charged surfaces.Abbreviations HIC hydrophobic interaction chromatography - ESIC electrostatic interaction chromatography - LPS lipopolysaccharide - PBS phosphate buffered saline solution     

Purification and characterization of a novel halostable cellulase from Salinivibrio sp. strain NTU-05

A halostable cellulase with a molecular mass of 29 kDa was purified from culture supernatants of the halophilic bacterium Salinivibrio sp. NTU-05 by way of the Fast Protein Liquid Chromatography method and the biochemical properties of the halostable cellulase was studied. The enzyme was active over a range of 0–25% sodium chloride examined in culture broth. The optimum cellulase activity was observed at 5% sodium chloride. Results from the salinity stability test indicated 24% of enzyme activity was retained at 25% sodium chloride for 4 h. The enzyme was also shown to be slightly thermostable with 40% residual activity under 60 °C for 4 h. The enzyme has a K_m of 3.03 mg/ml and a V_max of 142.86 mol/min/mg when tested using carboxymethyl-cellulose (CMC). The enzyme activity increased in the presence of K⁺, Mg²⁺, Na⁺ ions and decreased when Hg²⁺ ions were present. The deduced internal amino acid sequence of the Salinivibrio sp. NTU-05 cellulase showed similarity to the sequence of the glycoside hydrolase family protein. These are some of the novel characteristics that make this enzyme have potential applications in cellulose biodegradation.     

Modulation of cell surface hydrophobicity in the benthic cyanobacterium Phormidium J-1

A shift from cell-surface hydrophobicity to hydrophilicity was experimentally induced in the benthic hydrophobic cyanobacterium Phormidium sp. strain J-1, by mechanical shearing, chloramphenicol, and proteolytic treatment after preincubation with sodium dodecyl sulfate (SDS). Treatment with SDS alone, while releasing large amounts of protein and carbohydrates from the cell wall, did not affect cell surface hydrophobicity.Ultrastructural analysis showed the cells, to be enveloped by a double-layered minicapsule. Treatments affecting cellsurface hydrophobicity also caused changes in capsular components. A model, describing cell-surface structure, composition and properties in Phormidium J-1, was constructed by correlating ultrastructural data with surface properties.Abbreviations SDS Sodium dodecyl sulfate - DCMU 3(3,4-dichlorophenyl)-1,1-dimethylurea This paper is contributed in honor of Prof. G. Drews on the occasion of his sixtieth birthday     

Hydrophobic features of EPS extracted from anaerobic granular sludge: an investigation based on DAX-8 resin fractionation and size exclusion chromatography

The hydrophobic fractionation of extracellular polymeric substances (EPS) extracted from anaerobic granular sludge was performed on the DAX-8 resin (two elution pH conditions, i.e., pH 2 and pH 5 were tested). The impact of seven different EPS extraction methods on EPS hydrophobicity features was assessed. The results showed that the extraction methods and bulk solution pH influenced dramatically the biochemical composition of the EPS, and in turn, the hydrophobicity determined. Besides, EPS extracting reagents i.e., formaldehyde, ethanol, sodium dodecyl sulfate (SDS), and Tween 20 not only introduced extra carbon content in the total organic carbon (TOC) measurement but also interacted with the DAX-8 resin. By comparing the apparent molecular weight (aMW) distribution of untreated and pH-adjusted EPS samples, more complete EPS aMW information was preserved at pH 5. Thus, elution at pH 5 was preferred in this study for the qualitative analysis of EPS hydrophobic features. The hydrophobic fraction of EPS retained by the resin at pH 5 was ascribed to a wide aMW range, ranging from >440 to 0.3 kDa. Within this range, EPS molecules ranging from 175 to 31 kDa were mostly retained by the DAX-8 resin, which indicates that these EPS molecules are highly hydrophobic.

     

藤椒精油对腐败解淀粉芽孢杆菌DY1a生物被膜的抑制作用

【背景】芽孢杆菌是豆制品的重要腐败菌,在气液界面形成生物膜,对产品生产带来持续污染。【目的】探讨藤椒精油(Zanthoxylum armatum DC.essential oil,ZA-EO)对腐败解淀粉芽孢杆菌DY1a菌体及生物被膜的抑制作用与机制。【方法】采用气相色谱-质谱(gas chromatography-mass spectrometer,GC-MS)分析藤椒精油主要成分与相对含量,通过二倍稀释法测定藤椒精油对菌株的最低抑菌浓度(minimum inhibitory concentration,MIC)和最低杀菌浓度(minimum bactericidal concentration,MBC),并分析精油对腐败菌胞外蛋白酶活性、腐败菌生物被膜形成抑制及成熟生物被膜的清除作用,采用扫描电镜结合三维光学显微镜分析生物被膜形貌结构变化,测定生物被膜胞外聚合物(extracellular polymeric substance,EPS)多糖与蛋白质含量变化;并通过细菌运动能力、细胞黏附及自聚集能力、细胞表面疏水性和Zeta电位来初步探讨藤椒精油对生物被膜的抑制机理。【结果】藤椒精...     

Role of hydrophobicity in bacterial adherence to carbon nanostructures and biofilm formation

The role of cell and surface hydrophobicity in the adherence of the waterborne bacterium Mycobacterium smegmatis to nanostructures and biofilm formation was investigated. Carbon nanostructures (CNs) were synthesized using a flame reactor and deposited on stainless steel grids and foils, and on silicon wafers that had different initial surface hydrophobicities. Surface hydrophobicity was measured as the contact angle of water droplets. The surfaces were incubated in suspensions of isogenic hydrophobic and hydrophilic strains of M. smegmatis and temporal measurements of the numbers of adherent cells were made. The hydrophobic, rough mutant of M. smegmatis adhered more readily and formed denser biofilms on all surfaces compared to its hydrophilic, smooth parent. Biofilm formation led to alterations in the hydrophobicity of the substratum surfaces, demonstrating that bacterial cells attached to CNs are capable of modifying the surface characteristics.     

Unfolding Studies of <Emphasis Type="Italic">Escherichia coli</Emphasis> Maltodextrin Glucosidase Monitored by Fluorescence Spectroscopy

Equilibrium unfolding of a 69-kDa monomeric Escherichia coli maltodextrin glucosidase (MalZ) was studied using intrinsic and extrinsic fluorescence spectroscopy. The unfolding transition of MalZ followed a three-state process, involving the formation of a stable intermediate state having more exposed hydrophobic surface. It was found that the protein structure can be easily perturbed by low concentration of guanidium hydrochloride (GdnHCl) and, at a GdnHCl concentration of 2 M, MalZ was denatured completely. The active site of the protein also has been proved to be sensitive to a low concentration of GdnHCl since MalZ deactivated at 0.5 M GdnHCl completely. The surface hydrophobicity and ANS-binding site of the protein have been determined to be 150.7 and 0.24, respectively. Perhaps the formation of the stable unfolding intermediate, having higher surface hydrophobicity, may be one of the reasons for aggregation of MalZ and its recognition by chaperonin GroEL during the assisted folding pathway.     

Cell surface hydrophobicity ofStaphylococcus aureus measured by the salt aggregation test (SAT)

Well-defined laboratory strains as well as 72 clinical strains ofStaphylococcus aureus isolated from bovine mastitis were investigated for surface hydrophobicity by the salt aggregation test (SAT).Staphylococcus aureus strain Cowan 1, rich in protein A and fibronectin-binding surface proteins, was found to show high surface hydrophobicity, whereas strain Wood 46, deficient in these surface proteins, showed low surface hydrophobicity. SAT showed a significant difference in surface hydrophobicity (P<0.001) between protein A-positive and A-negative strains measured by ²-test analysis. Comparison of SAT values with results obtained from hydrophobic interaction chromatography (HIC) showed a good correlation (P<0.025). A high-level protein-A-producing mutant (SA 113prA-3) showed increased surface hydrophobicity as compared with the parent strain (SA 113), whereas ten protein-A-negative mutants showed low surface hydrophobicity in SAT. Of the 72 clinical isolates tested by SAT, 47 (65%) showed autoaggregating properties, i.e., the strains aggregated even in isotonic buffers. Tween 80 (1% vol/vol) and ethylene glycol (50% vol/vol) prevented autoaggregation of some hydrophobic strains aggregating in phosphate-buffered saline. However, 2M of a chaotropic agent (NaSCN) was more efficient in preventing autoaggregation of the strains tested. Heating of cell suspensions to 80°C or 100°C as well as trypsin andStreptomyces griseus protease treatment generally caused a decrease in the cell surface hydrophobicity. This indicates that protein A, fibronectin-binding proteins, and probably other as yet unidentified proteins contribute to the high surface hydrophobicity of most strains isolated from bovine mastitis.     

Role of Cell Hydrophobicity on Colony Formation in Microcystis (Cyanobacteria)

Colony formation is highly import ant for the competitive advantage of the cyanobacterium Microcystis over other phytoplankton species. The laboratory‐grown colonial Microcystis strains isolated from Lake Taihu (China) maintained colonial forms under the low light condition (10 μE m^–2 s^–1). The cell surface hydrophobicities of the Microcystis colonies were measured by cyanobacterial adherence to xylene in comparison with unicellular Microcystis strains. The cells of the tested colonial strains were all hydrophobic, while the cells of the tested unicellular strains were all hydrophilic. Incubation under the higher light condition (75 μE m^–2 s^–1) leaded to the significant decrease in the cell hydrophobicities of the colonial Microcystis and the transition from colonial forms to unicellular forms. These findings indicated that the cell hydrophobicity of Microcystis may play a role in cell‐cell adherence and colony formation. Phosphate‐limitation, nitrate‐limitation and pH did not affect cell hydrophobicities of colonial Microcystis. Treatment with proteolytic enzymes had no effect on the cell hydrophobicity, indicating that cell surface proteins did not contribute to high cell hydrophobicity. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Phase partition of gaseous hexane and surface hydrophobicity of Fusarium solani when grown in liquid and solid media with hexanol and hexane

The filamentous fungus, Fusarium solani, was grown in liquid and solid culture with glucose, glycerol, 1-hexanol and n-hexane. The partition coefficient with gaseous hexane (HPC) in the biomass was lower when grown in liquid medium with 1-hexanol (0.4) than with glycerol (0.8) or glucose (1) The HPC for surface growth were 0.2 for 1-hexanol, 0.5 for glycerol, 0.6 for glucose, and 0.2 for F. solani biomass obtained from a biofilter fed with gaseous n-hexane. These values show a 200-fold increase in n-hexane solubility when compared to water (HPC = 42). Lower HPC values can be partially explained by increased lipid accumulation with 1-hexanol, 10.5% (w/w) than with glycerol (8.5% w/w) or glucose (7.1% w/w). The diameter of the hyphae diminished from 3 μm to 2 μm when F. solani was grown on solid media with gaseous n-hexane thereby doubling the surface area for gaseous substrate exchange. The surface hydrophobicity of the mycelia increased consistently with more hydrophobic substrates and the contact angle of a drop of water on the mycelial mat was 113° when grown on n-hexane as compared to 75° with glucose. The fungus thus adapts to hydrophobic conditions and these changes may explain the higher uptake of gaseous hydrophobic substances by fungi in biofilters.     

Diel vertical migration thresholds of Karenia brevis (Dinophyceae)

Light and nutrient availability change throughout dinoflagellate diel vertical migration (DVM) and/or with sub-population location in the water column along the west Florida shelf. Typically, the vertical depth of the shelf is greater than the distance a sub-population can vertically migrate during a diel cycle, limiting the ability of a sub-population to photosynthetically fix carbon toward the surface and access nutrients sub-surface. This project investigated changes of Karenia brevis (C.C. Davis) G. Hansen et Moestrup intracellular carbon, nitrogen, internal nitrate (iNO₃), free amino acid (FAA), and total lipid concentrations in high-light, nitrate-replete (960 μmol quanta m⁻² s⁻¹, 80 μM NO₃), and high-light, nitrate-reduced (960 μmol quanta m⁻² s⁻¹, <5 μM NO₃) mesocosms. The nitrate-reduced mesocosm had a slowed cell division rate when compared to the nitrate-replete mesocosm. Minimum intracellular carbon, nitrogen, iNO₃, FAA, and total lipid concentrations during the largest surface sub-population aggregations led to the conclusion that daughter cells resulting from cell division received unequal shares of the parental resources and that this inequality influenced migration behavior. Nutrient reduced daughter cells were more strongly influenced by light and phototaxis for carbon production than their replete same cell division sister cells during vertical migration thus rapidly increasing the fulfillment of constituents through photosynthesis. Vertical migration was consistent with an optimization scheme based on threshold limits through utilization or formation of photosynthate. We propose a simplified conceptual model describing how K. brevis is transported along the benthos of the west Florida shelf from off-shore to on-shore. Dynamic carbon thresholds are also suggested for future DVM modeling efforts on K. brevis populations transported between nitrogen replete and nitrogen reduced environmental conditions.     

Biosurfactants,an help in the biodegradation of hexadecane? The case of <Emphasis Type="Italic">Rhodococcus</Emphasis> and <Emphasis Type="Italic">Pseudomonas</Emphasis> strains

The roles of the extracellular biosurfactants produced by two bacterial strains, Pseudomonas aeruginosa GL1 and Rhodococcus equi Ou2, in hexadecane uptake and biodegradation were compared. For this purpose, cell hydrophobicity and production of glycolipidic biosurfactants were evaluated during bacterial growth on hexadecane, as well the effects of these biosurfactants on culture supernatants properties i.e., surface and interfacial tensions, and emulsification and pseudosolubilization capacities. The results showed that the role of biosurfactants was different in these two strains and was directly related to the hydrophobicity of the bacterial cells concerned. Extracellular biosurfactants produced by strain R. equi Ou2 had only a minor role in hexadecane degradation. Direct interfacial accession appeared to be the main mechanism for hexadecane uptake by the hydrophobic cells of strain R. equi Ou2. On the contrary, the biosurfactants produced by P. aeruginosa GL1 were required for growth on hexadecane, and their pseudosolubilization capacity rather than their emulsification capacity was involved in substrate degradation, allowing uptake from hexadecane micelles by the hydrophilic cells of this bacterium. The roles of biosurfactants thus differ widely among bacteria degrading hydrophobic compounds. J.-P. Vandecasteele—in retirement     

Oily sludge degradation by bacteria from Ankleshwar, India

Three bacterial strains, Bacillus sp. SV9, Acinetobacter sp. SV4 and Pseudomonas sp., SV17 from contaminated soil in Ankleshwar, India were tested for their ability to degrade the complex mixture of petroleum hydrocarbons (such as alkanes, aromatics, resins and asphaltenes), sediments, heavy metals and water known as oily sludge. Gravimetric analysis showed that Bacillus sp. SV9 degraded approx. 59% of the oily sludge in 5 days at 30 °C whereas Acinetobacter sp. SV4 and Pseudomonas sp. SV17 degraded 37% and 35%. Capillary gas chromatographic analysis revealed that after 5 days the Bacillus strain was able to degrade oily sludge components of chain length C₁₂–C₃₀ and aromatics more effectively than the other two strains. Maximum drop in surface tension (from 70 to 28.4 mN/m) was accompanied by maximum biosurfactant production (6.7 g l⁻¹) in Bacillus sp. SV9 after 72 h, these results collectively indicating that this bacterial strain has considerable potential for bioremediation of oily sludge.     

Growth-associated biosynthesis of astaxanthin in heterotrophic Chlorella zofingiensis (Chlorophyta)

The green microalga Chlorella zofingiensis can produce the ketocarotenoid astaxanthin under heterotrophic culture conditions. Here we report the growth-associated biosynthesis of astaxanthin in this biotechnologically important alga. With glucose as sole carbon and energy source, C. zofinginesis grew fast in the dark with rapid exhaustion of nitrogen and carbon sources from media, leading to a high specific growth rate (0.034 h⁻¹). Cultures started at a cell concentration of about 3.4 × 10⁹ cells l⁻¹ reached, after 6 days, standing biomass values of 1.6 × 10¹¹ cells or 8.5 g dry weight l⁻¹. Surprisingly, the biosynthesis of astaxanthin was found to start at early exponential phase, independent of cessation of cell division. A general trend was observed that the culture conditions benefiting cell growth also benefited astaxanthin accumulation, indicating that astaxanthin was a growth-associated product in this alga. The maximum cell dry biomass and astaxanthin yield were 11.75 g l⁻¹ and 11.14 mg l⁻¹ (about 1 mg g⁻¹), simultaneously obtained in the fed-batch culture with a combined glucose–nitrate mixture addition, which were the highest ever reported in dark-heterotrophic algal cultures. The possible reasons why dark-heterotrophic C. zofingiensis could produce astaxanthin during the course of cell growth were discussed.     

Influence of cell surface properties on adhesion ability of bifidobacteria

Adhesion ability of bifidobacteria to the intestinal mucosa is considered to be the prerequisite for colonization of bifidobacteria and can protect against gastrointestinal pathogens infection. The aim of this study was to investigate bifidobacterial surface traits related to adhesion ability in vitro and characterize the cell surface substances that may be involved in the adhesion process of bifidobacteria. Twelve strains of Bifidobacterium spp. were studied for the correlation among their adhesion ability, autoaggregation ability and surface hydrophobicity. The strain that exhibited good adhesion ability also showed high degree of hydrophobicity and strong autoaggregation ability. Pepsin treatment had negative effect on the surface traits and adhesion ability of B. bifidum KLDS2.0603 (P < 0.01), it revealed that hydrophobicity, autoaggregation and adhesion process maybe mediated by proteinaceous components on the surface of cell. Moreover, the adhesion and autoaggregation ability decreased after extraction of B. bifidum KLDS2.0603 with 5 mol l⁻¹ LiCl, and an unreported 50-kDa surface protein which can bind to Caco-2 cell was observed by western blotting. Our results indicated that surface hydrophobicity and autoaggregation ability can be used together for preliminary screening the strains with high adhesion ability, and the present of the surface proteinaceous components would contribute to understand the interactions between bifidobacteria and human intestinal mucosa.     

Effect of Environmental Conditions on Hydrophobicity of Marine Bacteria Adapted to Textile Effluent Treatment

Summary Bioflocculation of bacteria isolated from the marine biomass acclimatized to textile wastewater has been achieved. Pseudomonas was the main genus found in the marine biomass. This bacterium showed an important hydrophobicity but slightly weaker than that of pilot plant genera adapted to the conventional sewage. This hydrophobicity provided the bacteria with hydrophobic characters, especially those of the polymeric extracellular substances (ECS) released in the sewage. Whereas some factors such as the divalent cations, calcium and magnesium had an effect on this bacterial hydrophobicity, glucose concentration did not have any impact. Furthermore, the physiological state of the cells hatched in the sewage had an impact on the hydrophobicity. Indeed, during the logarithmic growth phase, cell hydrophobicity increase enhanced floc formation, thus improving wastewater treatment.