Changes In Cell Surface Properties Research Articles

Changes in cell surface properties of Pseudomonas fluorescens by adaptation to NaCl induced hypertonic stress.

Determination of the effect of water stress on the surface properties of bacteria is crucial to study bacterial induced soil water repellency. Changes in the environmental conditions may affect several properties of bacteria such as the cell hydrophobicity and morphology. Here, we study the influence of adaptation to hypertonic stress on cell wettability, shape, adhesion, and surface chemical composition of Pseudomonas fluorescens. From this we aim to discover possible relations between the changes in wettability of bacterial films studied by contact angle and single cells studied by atomic and chemical force microscopy (AFM, CFM), which is still lacking. We show that by stress the adhesion forces of the cell surfaces towards hydrophobic functionalized probes increase while they decrease towards hydrophilic functionalized tips. This is consistent with the contact angle results. Further, cell size shrunk and protein content increased upon stress. The results suggest two possible mechanisms: Cell shrinkage is accompanied by the release of outer membrane vesicles by which the protein to lipid ratio increases. The higher protein content increases the rigidity and the number of hydrophobic nano-domains per surface area.

Removal of cyanobacteria using novel pre-pressurized coagulation: The effect of cellular properties and algogenic organic matter characteristics

• Pre-pressurized coagulation reduces coagulant dosage for M. flos-aquae removal. • Changes in cell properties/AOM characteristics after pre-pressurization is studied. • Pre-pressurization ruptures mucilaginous sheath and raises coagulation efficiency. • Exposure to more electronegative functional groups promotes the cell-CPAM binding. Pressurization pretreatment is reported as a novel pretreatment method for the coagulation removal of Microcystis sp . from eutrophicated water, as less coagulant is required than without pressurization. However, how cellular properties and algogenic organic matter (AOM) characteristics change with pressurization pretreatment and thus reduce the coagulant dose are still not understood. Using Microcystis flos-aquae in Lake Taihu, this study analyzed the changes in cellular morphology, size distribution, and charge density, as well as the changes in concentration and composition of cell-based protonated functional groups. Coagulation experiments using different combinations of cells and AOM with/without pressurization pretreatment showed that the changes in cell surface properties played a bigger role in coagulation enhancement than AOM. The enhancement of the coagulation efficiency of M. flos-aquae with pressurization pretreatment is related to the rupture of the mucilaginous sheath and subsequent exposure of cells with more active functional groups, the content of phosphodiester, carboxyl and phosphoryl functional groups on the surface of M. flos-aquae cells increased by 55%, 29% and 203%, respectively. Thus increasing the binding sites between M. flos-aquae cells and cationic polyacrylamide (CPAM). As a result, with pressurization pretreatment, the dose of CPAM was reduced from 5 mg L −1 to 0.8 mg L −1 for the same removal efficiency of 90%. These results may help us understand the mechanism by which pressurization treatment impacts M. flos-aquae coagulation and thus provide a new perspective for the low-cost and sustainable removal of cyanobacterial blooms.

Uptake mechanism of di-n-butyl phthalate by Novosphingobium species DNB-S3

Phthalate esters (PAEs) in the environment are mainly reported to be removed through the biochemical degradation by microorganisms. However, the adsorption of DBP is the initial process of using it as a carbon source. In this process, little is known about changes in cell surface properties at the subcellular level of degrading bacteria. In our work, Novosphingobium species DNB-S3 was found to be an efficient DBP-degrading bacterium with 95% DBP removal in 72 h at an initial concentration of 500 mg L−1. In soil simulation experiment, the initial concentration of DBP decreased from 25 mg kg−1 to 1.9 mg kg−1 after the inoculation of DNB-S3. In addition, DNB-S3 also showed degradation capability on other PAEs. DNB-S3 was cultured under four treatment conditions with different carbon sources, namely MSM-DBP, MSM-GLU, MSM-DBP + GLU, and LB. The cell surface hydrophobicity, functional groups on cell surface and morphological changes of DNB-S3 were further investigated. Morphological studies showed that the presence of DBP induced the disappearance of microcapsule on DNB-S3. Infrared spectroscopy and Raman spectra of DNB-S3 surface showed that the lipid-containing groups on the outer membrane were externally exposed from cellular structure, resulting in an increase of cell surface hydrophobicity (CSH). Eventually, the high CSH indicates that DNB-S3 has an efficient ability of DBP uptake. Our research adds an interesting dimension to the degradation study of bacterially mediated organic pollutants and the uptake mechanisms of hydrocarbons.

Genetic diversity of Legionella pcs and pmtA genes and the effect of utilization of choline by Legionella spp. on induction of proinflammatory cytokines.

Legionella species synthesize phosphatidylcholine (PC) in two independent pathways: the three-step methylation of phosphatidylethanolamine PMT pathway and the one-step PCS pathway, in which the Pcs enzyme catalyzes the reaction between choline and CDP-diacylglycerol to form PC. Legionella pcs genes encode highly hydrophobic proteins with phosphatidylcholine synthase activity, which contain up to eight transmembrane helices with N- and C-termini located inside the bacterial cell. The comparative analysis of nucleotide sequences of pcs showed that these genes share high sequence identity among members of the Legionellaceae family. Legionella pmtA genes involved in the PMT pathway encoded small cytosolic proteins with putative phosphatidylethanolamine N-methyltransferase activity. The pmtA genes identified in Legionella species had lower sequence identity to each other than the pcs genes. The phylogenetic tree constructed based on the pcs and pmtA gene sequences showed phylogenetic relatedness between Legionella spp. and other bacteria. The utilization of extracellular choline by the four Legionella species leads to changes not only in the lipid components but also in proteins, and the interactions between these components lead to changes in cell surface properties, which result in a decline in induction of proinflammatory cytokines (TNF-α and IL-6).

Investigation of the effect of different environmental conditions on biofilm structure of Salmonella enterica serotype Virchow via FTIR spectroscopy

This study aims to describe the content of polymeric matrix components under different incubation temperatures and pH levels. Optimal biofilm production of 15 S. Virchow isolates occurred following the incubation in LB-NaCl for 72h, at pH 6.6 and 20°C. The expression of csgA, csgD, adrA and bcsA genes at 20°C, 25°C and 30°C in S. Virchow DMC18 was analyzed, and it was discovered that the maximum production of cellulose and curli fimbriae occurred at 20°C. The physical characteristics of pellicle structure of S. Virchow DMC18 was determined as rigid at 20°C, while becoming fragile at higher temperatures. FTIR analyses confirmed the obtained molecular findings. The intensities of the 16 different peaks originating from carbohydrate, protein, and nucleic acid in the spectra of biofilm samples significantly diminished (p < 0.05) with the increasing temperature. The highest intensities of lipids and carbohydrates were observed at 20°C indicating the changes in cell surface properties.

Restoration of polar-flagellum motility and biofilm-forming capacity in the mmsB1 mutant of the alphaproteobacterium Azospirillum brasilense Sp245 points to a new role for a homologue of 3-hydroxyisobutyrate dehydrogenase.

The bacterium Azospirillum brasilense can swim and swarm owing to the rotation of a constitutive polar flagellum (Fla) and inducible lateral flagella, respectively. They also form biofilms on various interfaces. Experimental data on flagellar assembly and social behaviours in these bacteria are scarce. Here, for the first time, the chromosomal coding sequence mmsB1 for a homologue of 3-hydroxyisobutyrate dehydrogenase (protein accession Nos. ADT80774 and E7CWE2) was shown to play a role in the assembly of motile Fla and in biofilm biomass accumulation. In the previously obtained mutant SK039 of A. brasilense Sp245, an Omegon-Km insertion in mmsB1 was concurrent with changes in cell-surface properties and with suppression of Fla assembly (partial) and Fla-dependent motility (complete). Here, the immotile leaky Fla- mutant SK039 was complemented with the expression vector pRK415-borne mmsB1 gene of Sp245. In the complemented mutant, the elevated relative cell hydrophobicity and changed relative membrane fluidity of SK039 returned to the wild-type levels; also, biofilm biomass accumulation increased and even reached Sp245's levels under nutritionally rich conditions. In strain SK039 (pRK415-mmsB1), the percentage of cells with Fla became significantly higher than that in mutant SK039, and the Fla-driven swimming velocity was equal to that in strain Sp245.

Streptomycin favors biofilm formation by altering cell surface properties.

Studies have shown that external stress induces biofilm formation, but the underlying details are not clearly understood. This study investigates the changes in cell surface properties leading to increase in biofilm formation by Staphylococcus aureus and Pseudomonas aeruginosa in the presence of streptomycin. Bacterial attachment in the presence and absence of streptomycin was quantified by fluorescence spectroscopy. In addition, cell surface charge and contact angle were measured and the free energy barrier for attachment was modeled using extended Derjaguin-Landau-Verwey-Overbeek (xDLVO) theory. Peptides from bacterial cell surface were shaved by protease treatment and identified with ultra-performance liquid chromatography (UPLC)-QTOF and a homology search program SPIDER. Biofilm formation increased significantly in the presence of streptomycin (10mg/L) in the culture. Bacterial cell surface charge reduced, and hydrophobicity increased leading to a net decrease in the free energy barrier for attachment. Extracellular matrix-binding protein was positively regulated in S. aureus under stress, indicating stronger interaction between bacterial cells and solid surface. In addition, several other proteins including biofilm regulatory proteins, multidrug efflux pumps, transporters, signaling proteins, and virulence factors were differentially expressed on bacterial cell surface, which is indicative of a strong stress response by bacteria to streptomycin treatment.

Changes in cell surface properties and biofilm formation efficiency in Azospirillum brasilense Sp245 mutants in the putative genes of lipid metabolism mmsB1 and fabG1

The previously obtained insertion mutants ofAzospirillum brasilense Sp245 in the genes mmsBl and fabG1 (strains SK039 and Sp245.1610, respectively) were characterized by impaired flagellation and motility. The putative products of expression of these genes are 3-hydroxyisobutyrate dehydrogenase and 3-oxoacyl-[acyl-carrier protein] reductase, respectively. In the present work, A. brasilense- Sp245 strains SK039 and Sp245.1610 were found to have differences in the content of 3-hydroxyhexadecanoic, hexadecanoic, 3-hydroxytetradecanoic, hexadecenoic, octadecenoic, and nonadecanoic acids in their lipopolysaccharide prepa- rations, as well as in cell hydrophobicity and hemagglutination activity and dynamics of cell aggregation, in biomass amount, and in the relative content of lipopolysaccharide antigens in mature biofilms formed on hydrophilic or hydrophobic surfaces.

Mitigation of Fe0 nanoparticles toxicity to Trichosporon cutaneum by humic substances

Zero-valent iron nanoparticles (nZVI) are a relatively new option for the treatment of contaminated soil and groundwater. However, because of their apparent toxicity, nZVI in high concentrations are known to interfere with many autochthonous microorganisms and, thus, impact their participation in the remediation process. The effect of two commercially available nZVI products, Nanofer 25 (non-stabilized) and Nanofer 25S (stabilized), was examined. Considerable toxicity to the soil yeast Trichosporon cutaneum was observed. Two chemically different humic substances (HSs) were studied as a possible protection agent that mitigates nZVI toxicity: oxidized oxyhumolite X6 and humic acid X3A. The effect of addition of HSs was studied in different phases of the experiment to establish the effect on cells and nZVI. SEM and TEM images revealed an ability of both types of nZVI and HSs to adsorb on surface of the cells. Changes in cell surface properties were also observed by zeta potential measurements. Our results indicate that HSs can act as an electrosteric barrier, which hinders mutual interaction between nZVI and treated cell. Thus, the application of HS seems to be a promising solution to mitigating the toxic action of nZVI.

Rahnella sp. strain EK12: Cell surface properties and diesel oil biodegradation after long-term contact with natural surfactants and diesel oil

The changes in cell surface properties of Rahnella sp. strain EK12 and modifications in genetic material after long-term contact with saponins and rhamnolipids, were investigated. Rhamnolipids caused a decrease of hydrophobicity in liquid cultures compared with saponins. On the other hand, in cultures with rhamnolipids, the addition of diesel oil results in a rapid rise of cell surface hydrophobicity. The similar effect was not so significant in the presence of saponins. For the bacteria grown in the presence of saponins or rhamnolipids, but without diesel oil, the ratio of unsaturated to saturated fatty acids decreased, in comparison to the control culture. The differences observed in hydrophobicity, zeta potential and fatty acids profiles, indicated various mechanisms of an interaction between a surfactant and a bacterial cells. The results have also shown an impact of the long-term contact on changes in genetic material of Rahnella sp. strain EK12 cells. Moreover, the presence of saponins led to significant increase of diesel oil biodegradation.

Change in cell surface properties of Lactobacillus casei under heat shock treatment.

We undertake this study in the aim to give new insight about the change in cellular physiological state under heat shock treatment and probiotic strain screening procedure. Different cell properties have been studied like adhesive ability to biotic and abiotic surfaces, the cell surface hydrophobicity and the fatty acids profiles. Compared to the normal cells, the heated cells increased their adhesive ability to biotic surface. However, the adhesion to abiotic surface was decreased. The cell surface hydrophobicity of the heated strains showed a significant decrease (P < 0.05). Our data revealed that high temperature change the fatty acids profiles of the treated cells, especially the proportions of unsaturated and saturated fatty acid. In fact, the ratio of saturated to unsaturated fatty acids of the heated Lactobacillus casei cells was significantly higher than that of the control cells (P < 0.05). The present finding could firstly add new insight about the response of probiotic to stressful conditions, such us the important role of cell membrane, considered as the first main structure to be damaged by physicochemical stress, in stress resistance because of their composition that can change in adaptation to harsh conditions. Secondly, there is no relationship between changes in membrane composition and fluidity induced by heat shock treatment and adhesion to biotic and abiotic surface.

Impact of Alkyl Polyglucosides Surfactant Lutensol GD 70 on Modification of Bacterial Cell Surface Properties.

Alkyl polyglucosides, due to their low toxicity and environmental compatibility, could be used in biodegradation of hydrophobic compounds. In this study, the influence of Lutensol GD 70 on the cell hydrophobicity and zeta potential was measured. The particle size distribution and surfactant biodegradation were also investigated. Microbacterium sp. strain E19, Pseudomonas stutzeri strain 9, and the same strain cultivated in stress conditions were used in studies. Adding surfactant to the diesel oil system resulted in an increase of the cell surface hydrophobicity and the formation of cell aggregates (a high polydispersity index). The correlation between cell hydrophobicity and zeta potential in examined samples was not found. The results showed a significant influence of Lutensol GD 70 on the changes in cell surface properties. Moreover, a high biodegradation of a surfactant (over 50 %) by tested strains was observed. The biodegradation of Lutensol GD 70 depends on the length of both polar and nonpolar chains. A long-term contact with diesel oil of stressed strain modifies not only cell surface properties but also its ability to a surfactant biodegradation.

A new insight into the role of intracellular nickel levels for the stress response, surface properties and twitching motility by Haemophilus influenzae.

Nickel acts as a co-factor for a small number of enzymes in bacteria. Urease is one of the two nickel-dependent enzymes that have been identified in Haemophilus influenzae; glyoxalase I is the other. However, nickel has been suggested to have roles in H. influenzae that can not attributed to the function of these enzymes. We have previously shown that in the H. influenzae strain Rd KW20 the inability to acquire nickel led to alterations to the cell-type; an increased biofilm formation and changes in cell surface properties. Here we report the differences in the genome wide gene expression between Rd KW20 and a strain incapable of importing nickel (nikQ); revealing a link between intracellular nickel levels and genes involved in metabolic pathways, stress responses and genes associated with surface factors such as type IV pili. We have then taken a strain previously shown to use type IV pili both in biofilm formation and for twitching motility (86-028NP) and have shown its homologous genes (NTHI1417-1422; annotated as cobalt transporter, cbiKLMOQ) did import nickel and mutations in this locus had pleiotropic effects correlating to stress response and motility. Compared to wild type cells, the nickel depleted cells were more electronegativity charged, they aggregated and formed a biofilm. Correct intracellular nickel levels were also important for resistance to oxidative stress; the nickel depleted cells were more sensitive to oxidative stress. The nickel depleted cells were also non-motile, but the addition specifically of nickel returned these cells to a wild type motility state. We have also analysed the role of nickel uptake in a naturally, urease negative strain (the blood isolate R2866) and depleting intracellular nickel (a nikQ mutant) in this strain effected a similar range of cell functions. These data reveal a role for the capacity to acquire nickel from the environment and for the correct intracellular nickel levels as part of H. influenzae stress response and in signalling for a switch to a sessile bacterial lifestyle.

Adaptation of coimmobilized Rhodococcus cells to oil hydrocarbons in a column bioreactor

The possible adaptation of the association of Rhodococcus ruber and Rhodococcus opacus strains immobilized on modified sawdust to oil hydrocarbons in a column bioreactor was investigated. In the bioreactor, the bacterial population showed higher hydrocarbon and antibiotic resistance accompanied by the changes in cell surface properties (hydrophobicity, electrokinetic potential) and in the content of cellular lipids and biosurfactants. The possibility of using adapted Rhodococcus strains for the purification of oil-polluted water in the bioreactor was demonstrated.

Growth in the presence of sucrose may decrease attachment of some oral bacteria to abiotic surfaces

Synthesis of cell-bound glucan from dietary sucrose by oral pathogenic bacteria may influence bacterial cell surface properties and colonization of surfaces. This study investigated the effects of the addition of 2 % sucrose to culture medium on cell surface properties (hydrophobicity, charge, and auto-aggregation) and colonization activities (attachment and biofilm formation) on three abiotic surfaces (hydroxyapatite, glass, and stainless steel) of two Streptococcus mutans strains, one Streptococcus salivarius strain, one Streptococcus mitis strain, and one Actinomyces naeslundii strain. The results showed that the additional sucrose reduced the hydrophobicity of three strains (44-62 %) and increased that of one strain (31 %). Cellular aggregation of one strain was decreased (13 %) and that of another increased (21 %). No change in the surface charge of strains was apparent. Additional sucrose also inhibited the attachment of three strains (0.6-1.3 log CFU cm−2) and enhanced that of one strain (0.5-1.3 log CFU cm−2) to glass and stainless steel. The attachment of two strains to hydroxyapatite was reduced (0.9-1.3 log CFU cm−2). Biofilm formation by four strains was enhanced on all surfaces (0.4-1 log CFU cm−2). No relationship between changes in cell surface properties and changes in colonization activities was apparent. Sucrose does not always enhance oral bacterial colonization of abiotic surfaces.

Physicochemical surface properties of Cupriavidus metallidurans CH34 and Pseudomonas putida mt2 under cadmium stress

Cupriavidus metallidurans CH34 and Pseudomonas putida mt2 were used as cadmium (Cd) resistant and sensitive bacteria, respectively to study the effect of Cd on physicochemical surface properties which include the study of surface charge and hydrophobicity which are subjected to vary under stress conditions. In this research work, effective concentration 50 (EC50 ) was calculated to exclude the doubt that dead cells were also responding and used as reference point to study the changes in cell surface properties in the presence of Cd. EC50 of C. metallidurans CH34 was found to be 2.5 and 0.25 mM for P. putida mt2. The zeta potential analysis showed that CH34 cells were slightly less unstable than mt2 cells as CH34 cells exhibited -8.5 mV more negative potential than mt2 cells in the presence of Cd in growth medium. Cd made P. putida mt2 surface to behave as intermediate hydrophilic (θw = 25.32°) while C. metallidurans CH34 as hydrophobic (θw = 57.26°) at their respective EC50 . Although belonging to the same gram-negative group, both bacteria behaved differently in terms of changes in membrane fluidity. Expression of trans fatty acids was observed in mt2 strain (0.45%) but not in CH34 strain (0%). Similarly, cyclopropane fatty acids were observed more in mt2 strain (0.06-0.14%) but less in CH34 strain (0.01-0.02%). Degree of saturation of fatty acids decreased in P. putida mt2 (36.8-33.75%) while increased in C. metallidurans CH34 (35.6-39.3%). Homeoviscous adaptation is a survival strategy in harsh environments which includes expression of trans fatty acids and cyclo fatty acids in addition to altered degree of saturation. Different bacteria show different approaches to homeoviscous adaptation.

Ecotoxicological impact of sunlight assisted photoreduction of hexavalent chromium present in wastewater with zinc oxide nanoparticles on common Anabaena flos-aquae

Hexavalent chromium is more toxic and carcinogenic compared to its trivalent counterpart. Hexavalent chromium can be photocatalytically reduced to trivalent one using zinc oxide semiconductor and solar or UV radiation as light source. But an important ecological aspect is whether the net toxicity decreases after the photocatalytic process. In the present work, we have selected Anabaena flos-aquae as the model organism and examined whether the net toxicity to which it has been exposed in water decreases after photocatalytic reduction of hexavalent chromium using ZnO semiconductor as photocatalyst. We have studied the cumulative toxicities of both chromium (before and after treatment) and ZnO (both nano and micro) separately and as a suspension of ZnO in chromium. Quantitative cell surface roughness analysis was conducted using AFM to confirm the changes in cell surface properties.

Differences and dynamic changes in the cell surface properties of three Pseudomonas aeruginosa strains isolated from petroleum-polluted soil as a response to various carbon sources and the external addition of rhamnolipids

Three Pseudomonas aeruginosa strains isolated from petroleum-polluted soil were the subject of studies concerning changes in cell surface properties. Fundamentally different reactions could be observed for each of the studied strains after a cultivation on various carbon sources. The experiments carried out during the logarithmic growth phase showed, that the changes in the cell surface hydrophobocity values were dynamic and substrate dependant. An external addition of rhamnolipids to the tested systems resulted in further shifts in the CSH values. All of the strains displayed miscellaneous phenotypic properties during MATH, sedimentation profile, Zeta potential and surface tension measurements. The obtained results lead to a conclusion, that the presence of rhamnolipids seems to be the key factor to this phenomenon, as all of the studied strains exhibited the ability to produce this biosurfactant in a different degree.

Alkyl hydroperoxide reductase has a role in oxidative stress resistance and in modulating changes in cell-surface properties in Azospirillum brasilense Sp245

An ahpC mutant derivative of Azospirillum brasilense Sp245 (strain SK586) that encodes an alkyl hydroperoxide reductase was found to be more sensitive to oxidative stress caused by organic hydroperoxides compared with the wild-type. In addition, the ahpC mutant strain had multiple defects in a large array of cellular functions that were consistent with alteration of cell-surface properties, such as cell morphology in stationary phase, Calcofluor White-, Congo Red- and lectin-binding abilities, as well as cell-to-cell aggregation and flocculation. All phenotypes of the ahpC mutant were complemented by in trans expression of AhpC, and overexpression of AhpC in the wild-type strain was found to affect the same set of phenotypes, suggesting that the pleiotropic effects were caused by the ahpC mutation. SK586 was also found to be fully motile, but it lost motility at a higher rate than the wild-type during growth, such that most SK586 cells were non-motile in stationary phase. Despite these defects, the mutant did not differ from the wild-type in short-term colonization of sterile wheat roots when inoculated alone, and in competition with the wild-type strain; this implied that AhpC activity may not endow the cells with a competitive advantage in colonization under these conditions. Although the exact function of AhpC in affecting these phenotypes remains to be determined, changes in cell morphology, surface properties, cell-to-cell aggregation and flocculation are common adaptive responses to various stresses in bacteria, and the data obtained here suggest that AhpC contributes to modulating such stress responses in A. brasilense.

1,2,3,4,6-penta-O-galloyl-beta- d-glucose attenuates renal cell migration, hyaluronan expression, and crystal adhesion

Calcium oxalate monohydrate (COM) crystals bind avidly to the surface of proliferating and migrating renal endothelial cells, and oxalate-induced peroxidative injury can promote crystal attachment to renal epithelial cells. 1,2,3,4,6-penta-O-galloyl-beta- d-glucose (PGG), isolated from a traditional herbal remedy, inhibits vascular endothelial growth factor (VEGF) stimulated proliferation and migration of human umbilical vein endothelial cells (HUVECs) and has antioxidant activity. This study was performed to determine if PGG altered calcium oxalate monohydrate (COM) crystal adhesion to cells, perhaps via a change in cell surface properties. PGG significantly decreased COM crystal adhesion to cultured MDCK I cells at a low concentration (< 10 μM) which was not cytotoxic. PGG exerted anti-adhesion effects whether cells or crystals were pre-coated. PGG also inhibited cell migration after scrape-wounding, decreased subsequent adhesion of crystals to proliferating and migrating cells, and decreased expression of the crystal binding molecule hyaluronan. These findings suggest that PGG represents a potential urolithiasis prevention compound. Anti-crystal adhesion effects appear multifaceted involving crystal coating by PGG, as well as decreased cell migration and the associated surface expression of hyaluronan. The latter represents a novel mechanism of nephrolithiasis prevention.