Cell surface hydrophobicity of Staphylococcus species and adhesion onto biomaterials

Water Stress-Driven Changes in Bacterial Cell Surface Properties

Increased drought intensity and frequency exposes soil bacteria to prolonged water stress. While numerous studies reported on behavioral and physiological mechanisms of bacterial adaptation to water stress, changes in bacterial cell surface properties during adaptation are not well researched. We studied adaptive changes in cell surface hydrophobicity (CSH) after exposure to osmotic (NaCl) and matric stress (polyethylene glycol 8000 [PEG 8000]) for six typical soil bacteria (Bacillus subtilis, Arthrobacter chlorophenolicus, Pseudomonas fluorescens, Novosphingobium aromaticivorans, Rhodococcus erythropolis, and Mycobacterium pallens) covering a wide range of cell surface properties. Additional physicochemical parameters (surface chemical composition, surface charge, cell size and stiffness) of B. subtilis and P. fluorescens were analyzed to understand their possible contribution to CSH development. Changes in CSH caused by osmotic and matric stress depend on strain and stress type. CSH of B. subtilis and P. fluorescens increased with stress intensity, R. erythropolis and M. pallens exhibited a generally high but constant contact angle, while the response of A. chlorophenolicus and N. aromaticivorans depended on growth conditions and stress type. Osmotically driven changes in CSH of B. subtilis and P. fluorescens are accompanied by increasing surface N/C ratio, suggesting an increase in protein concentration within the cell wall. Cell envelope proteins thus presumably control bacterial CSH in two ways: (i) by increases in the relative density of surface proteins due to efflux of cytoplasmic water and subsequent cell shrinkage, and (ii) by destabilization of cell wall proteins, resulting in conformational changes which render the surface more hydrophobic. IMPORTANCE Changes in precipitation frequency, intensity, and temporal distribution are projected to result in increased frequency and intensity of droughts and heavy rainfall events. Prolonged droughts can promote the development of soil water repellency (SWR); this impacts the infiltration and distribution of water in the soil profile, exposing soil microorganisms to water stress. Exposure to water stress has recently been reported to result in increased cell surface hydrophobicity. However, the mechanism of this development is poorly understood. This study investigates the changes in the physicochemical properties of bacterial cell surfaces under water stress as a possible mechanism of increased surface hydrophobicity. Our results improve understanding of the microbial response to water stress in terms of surface properties, the variations in stress response depending on cell wall composition, and its contribution to the development of SWR.

Contribution of the hydrophobic effect to microbial infection

The hydrophobic effect has been known for decades. Numerous researchers have invoked the hydrophobic effect to explain how pathogens adhere to tissues. In some cases, inhibition of adhesion can be brought about by low concentrations of aromatic compounds, such as p-nitrophenol or tryptophan. Because the hydrophobic effect has been considered to be nonspecific, the molecular biology of adhesive hydrophobins has not been studied in as much detail as lectin adhesins. The literature provides compelling evidence that a large number of bacterial and fungal pathogens depend on hydrophobic interactions for successful colonization of a host. Several laboratories are now developing effective antiadhesins, based on inhibition of hydrophobic interactions between the host and the pathogen.

Review: Microbial colonization of prosthetic devices

The threat of bacterial colonization and biofilm formation poses the most important limitation on the use and development of prosthetic devices in human medicine. Data from the literature suggest that microbial adherence effected by the glycocalyx is a fundamental factor in sepsis involving biomaterials and that it may explain the resistance of such infections to host defense mechanisms and to antibiotherapy. A full appreciation of the existence and the consequences of the biofilm mode of bacterial growth is required so that we can both prevent and eliminate these protected microbial reservoirs.

Semi-log model for interpreting the results of swabbing surfaces naturally contaminated

Two mathematical models for depicting microbial depletions during six consecutive swabbings of refrigerated tank wall and teat skin were tested. Although a second degree polynomial equation gave a better adjustment of the data, a first degree equation was preferred to calculate the total numbers of micro-organisms possibly retrieved from surfaces by swabbing. This model was used for estimating the level of milk contamination by teat skin.

Cell surface hydrophobicity of Bifidobacterium bifidum subsp. pennsylvanicum

The possible role of lipoteichoic acid with respect to cell surface properties of Bifidobacterium bifidum subsp. pennsylvanicum was studied. Standard suspensions of bacteria were mixed with octane or xylene. B. bifidum subsp. pennsylvanicum was shown to possess a strongly hydrophobic cell surface. Hydrophobicity of the bacteria could be reduced by treatment with trypsin, pepsin (at pH 4.5), HCl and penicillin. The latter treatment resulted in an increased excretion of lipoteichoic acid. Albumin was capable of inhibiting the adherence to octane when it was present in the assay buffer. The data suggest that both protein and lipoteichoic acid may be involved in cell surface hydrophobicity. A great divergence in cell surface properties was observed within the genus Bifidobacterium.

Effects of antimetabolites on the adhesion of an estuarine Vibrio sp. to polystyrene

The effect of various metabolic inhibitors and antibiotics on the adhesion of an estuarine bacterium, Vibrio proteolytica, to polystyrene was investigated. Cells were either exposed to the substratum and the antimetabolite simultaneously or grown in the presence of a 25% MIC and presented the substratum in the absence of the antimetabolite. Based on the response elicited, these inhibitors could be divided into three classes: (i) those that had little or no effect on adhesion (fluorodeoxyuridine and nalidixic acid); (ii) those that only inhibited adhesion after growth at the 25% MIC (ampicillin, oxacillin, and streptomycin); and (iii) those that inhibited attachment when administered simultaneously with the substratum (azide, dinitrophenol, chloramphenicol, puromycin, azauridine, rifampin, p-chloromercuribenzoate, and cephalothin). Cells killed by heating, Formalin, or mercuric chloride treatment were also less adhesive than viable cells. Collectively, these results indicate that (i) physiologically active cells are more adhesive than dead or physiologically impaired cells, (ii) impairment of cell wall synthesis by beta-lactam antibiotics renders cells less adhesive, and (iii) energy production and protein synthesis (including transcription) are both involved in some aspect of the adhesion process, whereas DNA synthesis is not.