Advances in bacterial adsorption and transport of aromatic compounds / 生物工程学报

Aromatic compounds are a class of organic compounds with benzene ring(s). Aromatic compounds are hardly decomposed due to its stable structure and can be accumulated in the food cycle, posing a great threat to the ecological environment and human health. Bacteria have a strong catabolic ability to degrade various refractory organic contaminants (e.g., polycyclic aromatic hydrocarbons, PAHs). The adsorption and transportation are prerequisites for the catabolism of aromatic compounds by bacteria. While remarkable progress has been made in understanding the metabolism of aromatic compounds in bacterial degraders, the systems responsible for the uptake and transport of aromatic compounds are poorly understood. Here we summarize the effect of cell-surface hydrophobicity, biofilm formation, and bacterial chemotaxis on the bacterial adsorption of aromatic compounds. Besides, the effects of outer membrane transport systems (such as FadL family, TonB-dependent receptors, and OmpW family), and inner membrane transport systems (such as major facilitator superfamily (MFS) transporter and ATP-binding cassette (ABC) transporter) involved in the membrane transport of these compounds are summarized. Moreover, the mechanism of transmembrane transport is also discussed. This review may serve as a reference for the prevention and remediation of aromatic pollutants.

Influence of Cell Surface Hydrophobicity on Adhesion and Biofilm Formation in Candida albicans and Several Bacterial Species

The purpose of this study is to investigate the correlation of cell surface hydrophobicity (CSH) and biofilm formation or adhesion in Candida albicans (C. albicans) and several pathogenic bacteria. All of C. albicans (n=82) and 7 bacterial species (Escherichia coli, n=25; Klebsiella pneumoniae, n=33; Morganella morganii, n=21; Proteus mirabilis, n=33; Proteus vulgaris, n=12; Pseudomonas aeruginosa, n=31; Staphylococcus aureus, n=31) were isolated clinically. CSH was quantified with microbial adhesion to hydrocarbons. Biofilm formation was determined by tetrazolium salt reduction assay. Adhesion assay was performed by counting colonies after culture the microbes adhered to HeLa cells. Although high CSH-expressing bacterial species showed greater adherence to HeLa cells and larger amounts of biofilm formation on polystyrene, the significant relationships within same species were not shown. In C. albicans, however, strong positive correlations were observed between CSH and biofilm formation (r =0.708; p < 0.05) or cell adhesion (r =0.509; p < 0.05). These results suggest that hydrophobic force of bacteria may play a minor role in adhesion and biofilm formation, but CSH of C. albicans may be an important factor for adherence on surface and biofilm forming process.

The effects of lemon essential oil,limonene and tea polyphenols on cell surface hydrophobicity and adher-ence of Streptococcus mutans / 实用口腔医学杂志

Objective:To explore the effects of the natural plant ingredients lemon essential oil(LEO),limonene(LIM)and tea poly-phenols(TP)on the cell surface hydrophobicity and adherence of Streptococcus mutans(S.mutans).Methods:S.mutans were treated by sub-minimal inhibitory concentration(MIC)levels of LEO,LIMand TP respectively.Adsorption to hexadecane was used to measure the hydrophobic interaction of S.mutans.A classical 96-cell microtitre plate production assay using crystal violet staining was employed to visualize the adherence of S.mutans to hard tissue surface.Results:LEO,LIMand TP at sub-MIC levels could inhibit the cell sur-face hydrophobicity and adherence of S.mutans in a dose-dependent manner(P <0.05).At 1 /2 MIC and 1 /20 MIC,the inhibitary effect of LEO was stronger than that of LIMand TP(P <0.05).Conclusion:LEO may possess anticariogenic potential.

Effect of ethyl acetate extract from Huanglian Jiedu Decoction on virulence factors of Candida albicans / 中草药

Objective: To observe the effects of ethyl acetate extract from Huanglian Jiedu Decoction (EAHJD) on the virulence factors of Candida albicans. Methods: Egg-yolk medium, milk-plate medium, and olive oil emulsification were used respectively to test the activities of phospholipase (PL), aspartic protease (Sap), and lipase (Lip) of C. albicans. The water-hydrocarbon two-phase assay was applied to measure the cell surface hydrophobicity (CSH) of C. albicans. qRT-PCR was adopted to observe the expression of virulence factors related genes. Results: EAHJD had no effect on the activity of PL. EAHJD (1 250 μg/mL) could significantly inhibit the activity of PL and Lip better than that by 312 μg/mL EAHJD. EAHJD could reduce CSH of C. albicans in a dose-independent manner and CSH1 was down-regulated by 7.69, 3.57, and 2.95 folds by 1 250, 312, and 78 μg/mL EAHJD, respectively. The expression of secretory enzyme related genes displayed different changing folds: PLC1, Sap2, Sap3, Sap9, Lip3, Lip4, and Lip6 were down-regulated; PLB1, PLC2, Sap1, Sap10, and Lip5 had no distinct change treated by EAHJD. Conclusion: EAHJD could inhibit the activities of virulence factors of C. albicans.

Inhibitory effects of Tribulus terrestris L. steroid saponin TTS-12 on formation of Candida albicans biofilm / 第二军医大学学报

Objective: To investigate the influence of TTS-12, a steroid saponin from Tribulus terrestris L., on the formation of Candida albicans biofilm, and to discuss the possible mechanism. Methods: The inhibition of C. albicans biofilm formation by TTS -12 was observed by confocal scanning laser microscopy; XTT method was used to investigate the influence of different concentrations of TTS-12 on C. albicans biofilm formation. The water-hydrocarbon two-phase assay was used to measure the cell surface hydrophobicity of C. albicans treated with different concentrations of TTS-12. The expression of CSH1 mRNA was measured by real-time RT-PCR. Results: Compared with control group, TTS-12 treatment resulted in loose C. albicans biofilm, and it dose-dependently inhibited C. albicans biofilm formation. The cell surface hydrophobicity in the TTS-12-treated groups was lower than that in the control group; consistent with this, TTS-12-treated cells also expressed significantly lower levels of CSH1 mRNA than cells in control group (P<0. 01). Conclusion: TTS-12 may inhibit the formation of C. albicans biofilm through inhibiting CSHI gene expression.

Effect of Drugs and Chemical Agents on Cell Surface Hydrophobicity and Adhesion of Cryptococcus neoformans / 中华皮肤科杂志

Objective To explore the pathogenic relationship between cell surface hydrophobicity (CSH) and adhesion of Cryptococcus neoformans (C.neoformans) to host cells. Method Some drugs and chemical agents were used to pre treat the yeast to observe the impact of iatrogenic factors on CSH, adhesion to host cells and capsule of the yeasts which were treated pretreated with low concentration of drugs and chemical agents for short duration in vitro. Results The results showed that both amphotericin B (AmB) and fluconazole (FCZ) decreased the adhesion of the yeasts, and caused vasiation of CSH. Ampicillin (AMP) had little influence on CSH and adhesion of the yeasts to host cells, but it caused characteristic ultrastructural changes of outer wall of yeasts and acapsulated changes which were reversible as AmB did. FCZ produced a different ultrazstructural change of the yeast′s wall and capsulated change. The chemical agents, such as PHA, ConA, fucose, mercaptoethanol and trypsin decreased CSH and adhesion level of the yeast while lectin increased adhesion level. Conclusion The above data suggest that there is no significant relationship among CSH, adhesion to host cells and the capsule of C.neoformans which are three independent biologic features of the cell wall surface of yeasts.