Bacterial cell surface amphiphiles

Staphylococcal LTA antagonizes the B cell-mitogenic potential of LPS

Lipoteichoic acid (LTA) of Gram-positive bacteria is regarded as the counterpart biomolecule of lipopolysaccharide (LPS) of Gram-negative bacteria because of their structural and immunological similarities. Although LPS induces a strong polyclonal expansion of B cells, little is known about the effect of LTA on B cell proliferation. In the present study, we prepared LTAs from Gram-positive bacteria and examined their effect on splenic B cell proliferation. Unlike LPS, LTA did not induce B cell proliferation. Instead, Staphylococcus aureus LTA (Sa.LTA) appeared to inhibit LPS-induced B cell proliferation in vitro, ex vivo, and in vivo models. Such effect was observed neither in splenocytes from Toll-like receptor 2 (TLR2)-deficient mice nor in the purified splenic B cells. Furthermore, decreased ERK phosphorylation appeared to be responsible for this phenomenon. Collectively, our results support that Sa.LTA inhibited LPS-induced B cell proliferation through the decrease of ERK phosphorylation via TLR2 signaling pathway.

Structure/function relationships of lipoteichoic acids

The role of lipoteichoic acids (LTAs) from Gram-positive bacteria as immunostimulatory molecules was controversial for many years, as inadequate preparation methods as well as heterogeneous and endotoxin-contaminated commercial preparations led to conflicting results. An improved purification methodology for LTA now yields potent bioactive and chemically defined material, which is currently being characterized in various models. A synthetic analogue of Staphylococcus aureus LTA has proven the structure/function relationship. The key role of D-alanine esters for the immune response of LTA was confirmed by synthetic derivatives. The glycolipid anchor of LTA plays a central role analogous to the lipid A of LPS. Methodological aspects and criteria for quality assessment of LTA preparations are discussed.

A comparative study of biological activities of lipoteichoic acid and lipopolysaccharide

Lipoteichoic acids (LTAs) of Gram-positive bacteria and lipopolysaccharide (LPS) are structurally similar and share several biological activities. In this study, the capacity of LTAs for inducing the cell surface expression of adhesion molecules ICAM-1, VCAM-1, and ELAM-1 by HUVEC were investigated and compared to that of LPS. In the presence of serum, LTA from Staphylococcus aureus, Streptococcus sanguis, Streptococcus pyogenes and Streptococcus mutans dose-dependently stimulated adhesion molecule expression above control levels although they were 100-1000 times less potent than LPS. LTA from Streptococcus faecalis and Bacillus subtilis had no effects. Similar to LPS, the activity of the LTAs was dose-dependently inhibited by polymyxin B, whereas unlike LPS, LTA activity decreased in the presence of triethylamine. The LTAs also exhibited reactivity in the Limulus amebocyte lysate (LAL) assay correlating with their ability to induce ICAM-1 expression. However, their LAL reactivity was approximately 3-6 orders of magnitude less than that of LPS. Furthermore, LTA-stimulated ICAM-1 expression was serum-dependent and inhibited by anti-CD14 antibody, 63D3. Thus, LTA shares several properties with LPS including inhibition by polymyxin B, reactivity in the LAL assay, and stimulation of endothelial cells via a CD14-dependent mechanism. These results suggests a possible role for LTAs in the inflammatory response due to infections with Gram-positive bacteria.

Undecaprenyl pyrophosphate involvement in susceptibility of Bacillus subtilis to rare earth elements

The rare earth element scandium has weak antibacterial potency. We identified a mutation responsible for a scandium-resistant phenotype in Bacillus subtilis. This mutation was found within the uppS gene, which encodes undecaprenyl pyrophosphate synthase, and designated uppS86 (for the Thr-to-Ile amino acid substitution at residue 86 of undecaprenyl pyrophosphate synthase). The uppS86 mutation also gave rise to increased resistance to bacitracin, which prevents cell wall synthesis by inhibiting the dephosphorylation of undecaprenyl pyrophosphate, in addition to enhanced amylase production. Conversely, overexpression of the wild-type uppS gene resulted in increased susceptibilities to both scandium and bacitracin. Moreover, the mutant lacking undecaprenyl pyrophosphate phosphatase (BcrC) showed increased susceptibility to all rare earth elements tested. These results suggest that the accumulation of undecaprenyl pyrophosphate renders cells more susceptible to rare earth elements. The availability of undecaprenyl pyrophosphate may be an important determinant for susceptibility to rare earth elements, such as scandium.

Surface Characterization of Three Marine Bacterial Strains by Fourier Transform IR, X-ray Photoelectron Spectroscopy, and Time-of-Flight Secondary-Ion Mass Spectrometry, Correlation with Adhesion on Stainless Steel Surfaces

Adhesion of bacterial strains on solid substrates is likely related to the properties of the outer shell of the micro-organisms. Aiming at a better understanding and control of the biofilm formation in seawater, the surface chemical composition of three marine bacterial strains was investigated by combining Fourier transform IR spectroscopy, X-ray photoelectron spectroscopy (XPS), and time-of-flight secondary-ion mass spectrometry (ToF-SIMS). The D41 strain surface showed evidence of proteins, as deduced from the NH2 and NCO XPS and ToF-SIMS fingerprints; this strain was found to adhere to stainless steel, glass, or Teflon surfaces in a much higher quantity (2 orders of magnitude) than the two other ones, DA and D01. The latter are either enriched in COOH or sulfates, and this makes them more hydrophilic and less adherent to all substrates. Correlations with physicochemical properties and adhesion seem to demonstrate the role of the external layer composition, in particular the role of proteins more than that of hydrophobicity, on their adhesion abilities.

Role of lipopolysaccharides in the adhesion, retention, and transport of Escherichia coli JM109

The role of lipopolysaccharides (LPS) in bacterial adhesion was investigated via atomic force microscopy (AFM). Adhesion between a silicon nitride tip and Escherichia coli JM109 was measured in water and 0.01 M phosphate-buffered saline (PBS) on untreated cells and on a sample of E. coli treated with 100 mM ethylenediaminetetraacetic acid (EDTA), which removes approximately 80% of the LPS molecules. LPS removal decreased the adhesion affinity between the bacterial cells and the AFM tip from -2.1 +/- 1.8 to -0.40 +/- 0.36 nN in water and from -0.74 +/- 0.44 to -0.46 +/- 0.23 nN in 0.01 M PBS (statistically different, Mann-Whitney rank sum test, P < 0.01). The distributions of adhesion affinities between E. coli LPS macromolecules and the AFM tip could be described by gamma distribution functions. Direct measurements of the adhesive force between E. coil and a surface were compared with adhesion in batch and column experiments, and agreement was observed between the influences of LPS on adhesion in each system. Bacterial batch retention to glass or in packed beds to quartz sand decreased after LPS removal. When interaction forces were measured during the approach of the AFM tip to a bacterium, steric repulsive forces were seen for both treated and untreated cells, but the repulsion was greater when the LPS was intact A model for steric repulsion predicted a reduction of the equilibrium length of the surface polymers from 242 to 64 nm in water and from 175 to 81 nm in buffer, after removal of a portion of the LPS. DLVO calculations based on conventional and soft-particle DLVO theories predicted higher energy barriers to adhesion for all surfaces after LPS removal, consistent with experimental findings. Adhesion forces between the AFM tip and bacterial polymers were correlated with bacterial attachment and retention, while measurements of interaction forces during the approach of the AFM tip to the bacterium did not correlate with subsequent adhesion behavior to glass or quartz sand.

Effect of lipoteichoic acid on the uptake of Streptococcus pyogenes by HEp-2 cells

Lipoteichoic acid (LTA) is thought to play a role in the interactions between Streptococcus pyogenes and host cells. We have examined the effect of exogenous LTA on the adherence and entry of S. pyogenes JRS4 strain into HEp-2 epithelial cells. LTA markedly inhibited bacterial entry in a concentration-dependent manner, up to 250 microg ml(-1). In contrast, LTA had only a slight inhibitory effect on adherence. LTA also inhibited the entry but not adherence of Salmonella typhimurium strain into HEp-2 cells. Binding experiments showed a dose-dependent binding of LTA to cells up to 10 microg ml(-1). Confocal laser microscopy imaging and analysis revealed that LTA was internalized by the epithelial cells and colocalized with F-actin. These results might imply that, following binding, exogenous LTA enters HEp-2 cells and exerts a cytotoxic effect that interferes with bacterial internalization. A possible target for LTA activity might be the actin cytoskeleton, which is known to be essential for bacterial uptake.

Lipoteichoic acid acts as an antagonist and an agonist of lipopolysaccharide on human gingival fibroblasts and monocytes in a CD14-dependent manner

CD14 has been implicated as a receptor of lipoteichoic acid (LTA) and other bacterial components as well as lipopolysaccharide (LPS). Since the structures of LTAs from various gram-positive bacteria are heterogeneous, we analyzed the effects of LTAs on the secretion of interleukin-8 (IL-8) by high- and low-CD14-expressing (CD14(high) and CD14(low)) human gingival fibroblasts (HGF). While Bacillus subtilis LTA had an IL-8-inducing effect on CD14(high) HGF which was considerably weaker than that of LPS, Streptococcus sanguis and Streptococcus mutans LTAs had practically no effect on the cells. B. subtilis LTA had only a weak effect on CD14(low) HGF, as did LPS. S. sanguis and S. mutans LTAs at a 1,000-fold excess each completely inhibited the IL-8-inducing activities of both LPS and a synthetic lipid A on CD14(high) HGF. The effect of LPS was also inhibited by the presence of an LPS antagonist, synthetic lipid A precursor IVA (LA-14-PP), with a 100-fold higher potency than S. sanguis and S. mutans LTAs and by anti-CD14 monoclonal antibody (MAb). S. sanguis and S. mutans LTAs, LA-14-PP, and anti-CD14 MAb had no significant effect on phorbol myristate acetate-stimulated IL-8 secretion by HGF. These LTAs also inhibited the IL-8-inducing activity of B. subtilis LTA on CD14(high) HGF, as did LA-14-PP and anti-CD14 MAb. The antagonistic and agonistic functions of LTAs were also observed with human monocytes. Binding of fluorolabeled LPS to human monocytes was inhibited by S. sanguis LTA, although the inhibition was 100 times weaker than that of LPS itself, and anti-CD14 MAb inhibited fluorolabeled LPS and S. sanguis LTA binding. Binding of LTAs to CD14 was also observed with nondenaturing polyacrylamide gel electrophoresis. These results indicate that LTAs act as antagonists or agonists via a CD14-dependent mechanism, probably due to the heterogeneous structure of LTAs, and that an antagonistic LTA might be a useful agent for suppressing the periodontal disease caused by gram-negative bacteria.

A lipoteichoic acid fraction of Enterococcus hirae activates cultured human monocytic cells via a CD14-independent pathway to promote cytokine production, and the activity is inhibited by serum components

To elucidate the cellular activation mechanisms of lipoteichoic acid (LTA) compared with those of lipopolysaccharide (LPS), a quantitatively major LTA fraction, QM-1M, was prepared from hot phenol-water extracts of Enterococcus hirae (ATCC 9790) by hydrophobic octyl-Sepharose chromatography and by ion-exchange membrane (QMA-Mem Sep 1010) chromatography as a 60% 1-propanol- and 1 M NaCl-eluted fraction. Unlike the reference Escherichia coli LPS, QM-1M did not demonstrate any ability to induce cytokines in a human whole blood culture system in this study, whereas QM-1M induced a few cytokines such as interleukin (IL)-8 and tumor necrosis factor-alpha in human monocytic THP-1 cell and human peripheral mononuclear cell (PBMC) cultures in the absence of serum. Fetal calf and human sera decreased the above cytokine induction by QM-1M in THP-1 and PBMC cultures, whereas sera increased activities of the reference LPS. IL-8 induction in the absence of serum in response to QM-1M was demonstrated to proceed through a CD14-independent pathway unlike the reference LPS.

Acidity and calcium interaction affecting cell envelope stability inRhizobium

Calcium improves the ability of many rhizobia to survive and persist in acid soils, but the mechanism responsible for this phenomenon has not been studied in detail. Here, we present data examining the combined effects of pH and calcium on the cell envelope of Rhizobium strains that differ in pH tolerance. The effect of pH and calcium on solute uptake was demonstrated by a change in the resistance to selected antimicrobial agents. When grown at pH 5.0, all strains exhibited fatty acid methyl ester profiles that were significantly different from those obtained using cells grown at pH 7.0. These differences included changes in the C16:C18 ratio and the percentage of 19:0 cyclopropane in the membrane. Both pH and calcium level had marked effects on Rhizobium etli UMR1632 lipopolysaccharide-banding patterns, but there was little evidence of a change in lipopolysaccharides with pH and calcium in Rhizobium tropici UMR1899. Both pH and calcium influenced expression of outer membrane proteins in all strains.Key words: Rhizobium, acidity, calcium, lipopolysaccharide, cell envelope, outer membrane protein.

A subpopulation of human urothelial cells is stimulated to proliferate by treatment in vitro with lipoteichoic acid, a cell wall component of Streptococcus faecalis

Urinary tract infection with gram-positive bacteria is common. Avenues for ingress of bacteria into the bladder include luminal and suburothelial infection. Terminally differentiated superficial urothelial cells lining the lumen of the bladder are often shed in response to infection. In contrast, infection-induced altered function of progenitors of urothelial cells residing in the basal layer of the urothelium is likely to have long lasting effects on the structure and function of the urothelium. The main objective of the present studies was to investigate in vitro the possibility that exposure to lipoteichoic acid, a cell wall component of the gram-positive Streptococcus faecalis (LT-2), stimulates basal urothelial cells to proliferate. To simulate conditions that restrict proliferation and inhibit terminal differentiation of urothelial cells in the basal layer, secondary cultures of urothelial cells (UT) were grown on collagen or fibronectin coated substrate in medium containing low levels of Ca2+ (0.2 mM) and growth factors (0.005% bovine pituitary extract [BPE]). Under these conditions, UT cultures displayed a highly reproducible colony size distribution, possibly due to the fact that colonies were progeny of basal cells with various proliferative potentials, retained in vitro. In cultures grown under growth-restricting conditions the majority of progenitors appeared to be quiescent, just like stem cells in the basal layer of the urothelium. Thus, the population of large colonies (more than six cells/colony), was small when a steady state of growth was achieved, 3-7 days after seeding. Growth factors (0.005-0.5% BPE) caused a dose-dependent increase in this population of large colonies. Moreover, treatment of UT grown under growth-restricting conditions (0.005% BPE) with LT-2 increased steady-state levels of the population of large colonies to levels obtained in cultures growing under optimal conditions with respect to growth factors. These results indicated that the subpopulation of progenitors, quiescent under normal conditions, could be stimulated to proliferate. Two lines of evidence were consistent with the possibility that treatment with LT-2 stimulated proliferation of the subpopulation of progenitors and that large colonies were the progeny of this subpopulation of single cells: (1) treatment with LT-2 increased the percentage of single cells that incorporated bromodeoxyuridine (i.e., proliferated) in a time-dependent manner. (2) An increase in the percentage of large colonies was found following LT-2-triggered proliferation of single cells. We propose that, under normal conditions, cells produced in response to LT-2-triggered proliferation of stem cells are removed from the system due to an increased rate of differentiation followed by apoptosis. Recurrent infection and inflammation may not allow these processes to proceed effectively, resulting in chronic injury to the bladder. Moreover, under conditions in which stem cells accumulate mutations that incapacitate their progeny to undergo apoptosis, LT-triggered proliferation could be a contributing factor to tumorigenesis.

Nitric oxide mediates the action of lipoteichoic acid on the function of human urothelial cells

Gram-positive bacteria are recognized pathogens in urinary tract infections. Lipoteichoic acids, major components of the cell wall of gram-positive bacteria, are important virulence attributes, but their mechanism of action is not well understood. We have postulated that infection-induced altered function of progenitors of urothelial cells (UT) residing in the basal layer is likely to have long-lasting effects on the architecture and function of the urothelium. Our earlier in vitro studies in UT of basal type, grown under growth restricting conditions, have shown that 1) treatment with lipoteichoic acid from Streptococcus faecalis (LT-2) stimulates a subpopulation of progenitors of urothelial cells to proliferate, and 2) resulting large colonies differentiated at an increased rate under conditions simulating those in the basal layer of the urothelium. The hypothesis underlying the present studies was that nitric oxide (NO) mediated LT-2 action on these functions of UT. Immunocytochemical studies using an antibody against inducible nitric oxide synthase (iNOS) confirmed expression of iNOS in LT-2-treated UT. Our hypothesis was tested by treating UT grown under growth restricting conditions (0.005% bovine pituitary extract) with LT-2 (25 micrograms/ml), in the presence or absence of inhibitors of NOS (1 mM NG-nitro-L-arginine methyl ester [L-NAME]; 1 microM dexamethasone [DEXA]) or 25 microM hemoglobin, a potent inactivator of NO. Treatment with LT-2 in the presence of these agents prevented the following effects of LT-2 alone: 1) the stimulatory effect on proliferation of single cells, as well as within the resulting large colonies; 2) the subsequent differentiation of large colonies resulting from this proliferative activity, as indicated by distribution of beta 1 subunit-containing integrins to cell-cell contacts; 3) the inhibitory effect on the subsequent ability of LT-2-treated UT to attach to extracellular matrix proteins. These studies suggest that induction of NOS by LT-2, initially aimed at restricting the replication of infectious agents, may have potential cost of damage to the host bladder by interfering with urothelial differentiation.

Long-term treatment with lipoteichoic acid from Streptococcus faecalis affects differentiation and expression and cellular distribution of beta 1 integrins in human urothelial cells

Gram-positive bacteria are recognized pathogens in urinary tract infections. Cellular mechanisms triggered by lipoteichoic acids (LTs), cell well components of gram-positive bacteria, have not been completely defined. We have postulated that infection-induced altered function of progenitors of urothelial cells residing in the basal layer is likely to have long lasting effects on the architecture and function of the urothelium. Our recent studies in vitro showed that treatment of poorly differentiated urothelial cells of basal type with LT from Streptococcus faecalis (LT-2) stimulated rapid proliferation of a subpopulation of progenitors of urothelial cells, supporting this possibility (Elgavish et al., 1996, J. Cell. Physiol., 169:42-51). The hypothesis underlying the present studies was that, following LT-triggered increase in proliferation of progenitors, the rate of differentiation of the resulting progeny was also stimulated. We proposed that this mechanism may allow rapid removal of cells from the injured area and replacement by cells that have not been exposed to infection. To simulate in vitro conditions in the basal layer that inhibit terminal differentiation, cells grew on fibronectin or collagen-coated substrate, in medium containing low Ca2+ (0.2 mM) and low levels of growth factors (0.005% bovine pituitary extract [BPE]). During the last 3 days in culture, cells grew in the same low Ca2+ (0.2 mM) medium, but without BPE, with or without LT-2. In a positive control group, cells grew during their last 3 days in culture in medium without BPE and LT-2 but in which levels levels of Ca2+ were higher (2 mM), a condition known to stimulate differentiation in other cell types. Several lines of evidence supported the possibility that long-term treatment with LT-2 stimulated progression of large colonies (i.e., the progeny resulting from LT-triggered proliferation) to a more differentiated state: (1) the rate of their differentiation, determined by criterion of intense cytokeratin 8 expression, was increased; (2) steady-state level of beta mRNA and expression of beta 1 subunit of integrins at the protein level were inhibited; (3) in contrast to large colonies in control cultures, the entire population of LT-2-treated large colonies contained beta 1 integrins distributed at cell-cell contacts. Raising extracellular Ca2+ concentration to 2 mM induced similar effects, suggesting that LT-2 may act by stimulating an increase in intracellular levels of Ca2+. However, further studies will be needed to elucidate the molecular mechanisms underlying the stimulatory effect of LT-2 on proliferation of progenitors of urothelial cells in the basal layer of the urothelium and subsequent differentiation of their progeny. We propose that these processes may have a causative role in the pathological changes that occur in the aftermath of chronic or recurrent suburothelial infection in the urinary bladder.

Effects of Actinomyces amphiphile on the fluidity of endothelial cells: a spin label study

Actinomyces amphiphile (AcA) is an amphipathic molecule produced by Actinomyces viscosus that exhibits several biological activities. The effect of AcA on the fluidity and permeability of the plasma membrane in human umbilical vein endothelial cells was analyzed by a spin label method with 5- and 16-stearic acid nitroxide labels (SAL). These labels help to visualize the fluidity at the shallow (5-SAL) and deep (16-SAL) portions of the lipid bilayer. Cells were incubated with and without AcA (control) at 37 degrees C for 6 hours, and membrane fluidity was periodically measured. Another spin label, 4-(N, N-dimethyl-N-hexadecyl) ammonium-2, 2, 6, 6-tetramethyl-piperidine-1-oxyliodine (CAT-16), was also used to assess the physical state of the cell surface. The order parameter of 5-SAL was significantly lower in the cells incubated with AcA than in control cells after the six-hour incubation. The motion parameter of 16-SAL was significantly lower in AcA-treated cells than in controls after 4 and 6 hours of incubation. These findings indicated that the AcA increased the fluidity. There were no significant differences between the AcA-treated and control cells incubated for only 2 hours. In addition, there were no differences in CAT-16 measurements between AcA-treated and control cells. The release of endoplasmic lactate dehydrogenase (LDH) into the medium tended to increase in the AcA-treated vs. the control cells. LDH release increased in both a dose- and time-dependent manner, indicating that AcA increased the permeability of plasma membranes. These findings suggest that AcA alters the biophysical properties of the plasma membranes of endothelial cells, affecting membrane function.

Physicochemical properties of PM-factor, a surface-active agent produced by Pseudomonas marginalis

An extracellular surface-active agent, PM-factor, was obtained by high-speed centrifugation from the culture broth of Pseudomonas marginalis PD-14B. PM-factor exhibited emulsifying activity on a broad spectrum of hydrocarbon liquids, including aromatics, aliphatics, crude oil, and creosote. The factor appeared as ball-shaped particles of varying diameter when examined by electron microscopy (0.16-1.4 microns). Gel filtration chromatography demonstrated a high molecular mass of the factor (> 10(6) Da). The ultraviolet absorption spectrum manifested a peak in the region 200 nm rather in the region 260-280 nm. Amino acid analysis showed a very low amount of aromatic amino acids residues in the protein moiety of PM-factor. The presence of 3-deoxy-D-mannooctulosonic acid, heptose, hexosamine, phosphorus, and 3-hydroxy fatty acid indicated that PM-factor contained lipopolysaccharide. The emulsifying activity of PM-factor was inhibited strongly by mercuric chloride and moderately by EDTA. Polymyxin B, Ca2+, and Mg2+ markedly stimulated the factors emulsifying activity. Roles of the bioemulsifier in the functioning of P. marginalis as a plant pathogen and in bioremediation are discussed.

Effects of growth factors, hormones, bacterial lipopolysaccharides, and lipotechoic acids on the clonal growth of normal ureteral epithelial cells in serum-free culture

In vitro tissue culture techniques were employed to study the effects of bacterial endotoxins on the growth of normal epithelial cells from the human ureter (NHU). Primary cultures of NHU cells were initiated from explant outgrowth cultures of human ureteral tissue and cultured on collagen gel in F-12* medium containing 1% fetal calf serum (FCS). Optimal clonal growth of secondary cultures of NHU cells seeded at relatively low seeding cell densities, directly on plastic dishes, was achieved in F-12* medium containing bovine pituitary extract (0.5% BPE) and 0.05% BSA. Results indicated that insulin in the F-12* medium could be replaced by three orders of magnitude less IGF-1. Further clonal growth experiments demonstrated that PGE1 is growth stimulatory and can replace BPE as a growth factor requirement. This finding was in agreement with the fact that BPE growth requirement could be replaced by cholera toxin or dibutyryl cAMP. These results suggested that both BPE and cholera toxin operated by activation of a cAMP-dependent mitogenic pathway. Seven gram-negative bacterial lipopolysaccharides (LPS) and three gram-positive bacterial lipotechoic acids (LT) were tested for their effects on NHU clonal growth. Three out of the five LPS derived from Escherichia coli (strains 055:B5, 0128:B12, and 0127:B8), LPS from Klebsiella pneumoniae, and LPS from Pseudomonas aeruginosa all showed significant growth inhibitory effects at minimally effective doses ranging from 5 to 25 micrograms/ml. LPS derived from E. coli strain (0111:B4) had no growth effects at the highest concentration tested (100 micrograms/ml). In contrast, LT derived from Streptococcus pyogenes, S. faecalis, Staphylococcus aureas, and Bacillus subtilis all markedly enhanced clonal growth at concentrations ranging from 1 microgram/ml less than [LT] less than 50 micrograms/ml. LT from Strep. pyogenes was inhibitory to clonal growth at 100 micrograms/ml. The growth inhibitory effects of LPS were shown to be sensitive to the presence of hydrocortisone in the growth medium, indicating that LPS effects on growth are mediated via the arachidonic acid cascade. We speculate that these results indicate a link between the susceptibility of uroepithelial tissue to the pathogenic microflora seen in urinary tract diseases and the differential sensitivity of proliferation-competent uroepithelial cells to growth inhibition by LPS produced by gram-negative bacteria. However, further studies with uropathogenic serotypes will be necessary to corroborate this possibility. The growth-stimulating activity of LTs produced by gram-positive bacteria may be due to their ability to bind to cell-associated fibronectin and to activate the fibronectin receptor as part of ligand receptor-induced mitogenic transmembrane signalling pathway.

Stimulation of monokine production by lipoteichoic acids

Lipoteichoic acids (LTAs) isolated from bacterial species, including Staphylococcus aureus, Streptococcus pyogenes A, Enterococcus faecalis, Streptococcus pneumoniae, and Listeria monocytogenes, were tested for their ability to stimulate the production of interleukin-1 beta (IL-1 beta), IL-6, and tumor necrosis factor alpha in cultured human monocytes. LTAs from S. aureus and S. pneumoniae failed to induce monokine production when applied in the concentration range of 0.05 to 5.0 micrograms/ml. However, LTAs from several enterococcal species (0.5 to 5 micrograms/ml) induced the release of all three monokines at levels similar to those observed after lipopolysaccharide stimulation. The kinetics of IL-1 beta and tumor necrosis factor alpha release elicited by LTAs closely resembled those observed following lipopolysaccharide application. Cytokine production occurred in the presence of both fetal calf serum and autologous human serum. Hence, it was not dependent on complement activation and could not be suppressed by naturally occurring human antibodies. Deacylation caused the total loss of monocyte stimulatory capacity. Deacylated LTAs were unable to prevent monocyte activation by intact LTAs, so primary binding of these molecules probably does not involve a simple interaction of a membrane receptor with the hydrophilic portion of the molecule. The results identify some species of LTAs as inducers of monokine production in human monocytes.

Relationship of the chemical structure and immunobiological activities of lipoteichoic acid from Streptococcus faecalis (Enterococcus hirae) ATCC 9790

Two molecular species of lipoteichoic acid (LTA 1 and LTA 2) were isolated from whole cells of Streptococcus faecalis (Enterococcus hirae) ATCC 9790 by hydrophobic chromatography on Octyl Sepharose CL-4B. Chemical analysis revealed that LTA 1 and LTA 2 contained two and four acyl lipid anchors respectively. LTA 1 was less active than LTA 2 in inducing cytokines, except interleukin-1 (IL-1), but their in vivo antitumour effects were similar. LTA 2 was a potent inducer of tumour necrosis factor (TNF) and interferon (IFN) production and had excellent antitumour activity against Meth A fibrosarcoma established in mice. Deacylation of LTA 2 by alkaline hydrolysis abolished these biological activities. The phosphatidylglycolipid fraction derived from LTA 2 after acid hydrolysis could also induce TNF, IFN, and IL-1 production, as well as having antitumour activity against Meth A fibrosarcoma. Therefore, the lipid anchor portion of S. faecalis LTA may play an important role in the manifestation of these various biological activities.

Purification and characterization of Streptococcus adjacens (nutritionally variant Streptococcus serotype II) group antigen

Nutritionally variant streptococci (NVS) possess amphiphiles which are serologically distinct from lipoteichoic acid and which serve as group-specific antigens for NVS. The objective of this study was to purify and characterize the NVS serotype II (Streptococcus adjacens) amphiphile. Amphiphile was isolated from stationary-phase culture supernatants of NVS strain 81 (NVS serotype II). Phenol-water extracts of culture supernatants were subjected to hydrophobic interaction chromatography and gel filtration chromatography. A homogeneous preparation of amphiphile (22 mg; 8.5 x 10(6) hemagglutination units) was recovered, and its approximate molecular size (23,000 to 24,000 Da) and chemical composition were determined. Purified S. adjacens amphiphile contained phosphorus, ribitol, galactose, galactosamine, alanine, and fatty acids in molar ratios of 1.00:0.88:1.39:1.10:0.08:0.24. Since ribitol, galactose, and galactosamine were the primary carbohydrate components, the amphiphile may exist as a polyribitol phosphate with galactose and galactosamine substituents. Preliminary structural analysis demonstrated the presence of phosphodiester bonds within the amphiphile structure. Finally, the amphiphile serves as the S. adjacens group antigen.

Bacterial polymers: physicochemical aspects of their interactions at interfaces

How do bacteria stick to a surface? There is still not enough information about to answer this question especially at the molecular level. This question only gives rise to more questions. What is the structure of the true adhesive bacterial polymer? Is only one bacterial polymer or several polymers involved in the adhesion process? What is the role of proteins associated with the bacterial polysaccharides? What type of polymer is produced for the adhesion to hydrophobic surfaces? Is the polymer produced as a response to the surface? This review is an attempt to summarize the physicochemical aspects of bacterial polymers and their interaction with surfaces. It was tried to give an overview of the literature published in this field. The article is divided into the following sections: first, the forces involved in bacterial adhesion are discussed. Third, different fluid conditions are investigated. Fourth, the nature of different bacterial polymers which are important for the interaction with a surface is elaborated. Fifth, the current knowledge about biological polymers at interfaces is shown. And sixth, the role of polymers in the adhesion of bacteria available to date is highlighted.

Stimulation of oxidative burst in human monocytes by lipoteichoic acids

Lipoteichoic acid isolated from Streptococcus faecalis or Streptococcus pyogenes caused direct activation of the respiratory burst in human peripheral blood monocytes. This activity appears to be related to the ability of lipoteichoic acid to bind to the monocyte membrane and trigger the polarization of receptors (capping).

The ability to sensitize host cells for destruction by autologous complement is a general property of lipoteichoic acid

Previous studies have demonstrated that lipoteichoic acid (LTA) from Streptococcus pneumoniae binds to erythrocytes and renders them susceptible to lysis by autologous complement. The present study was performed to determine whether LTA from two other gram-positive bacterial species had the ability to render mammalian cells susceptible to lysis by autologous complement. Human erythrocytes were sensitized with LTA from S. pneumoniae, Streptococcus pyogenes, or Lactobacillus fermentum. Under incubation in normal autologous serum, lysis was observed with each of the LTA-sensitized erythrocyte preparations. When erythrocytes from a C2-deficient patient were sensitized with the LTA preparations and then incubated in autologous, C2-deficient serum, the erythrocytes sensitized with S. pyogenes or L. fermentum LTA demonstrated relatively little lysis, whereas the erythrocytes sensitized with S. pneumoniae LTA yielded near-total lysis. After reconstitution of the C2-deficient serum with purified human C2, lysis was observed with all three LTA preparations. When erythrocytes from an agammaglobulinemic patient were sensitized with either the S. pyogenes or the L. fermentum LTA, they were not lysed in the presence of autologous agammaglobulinemic serum, whereas the erythrocytes sensitized with S. pneumoniae LTA were completely lysed. Serum obtained from the agammaglobulinemic patient after reconstitution with intravenous pooled gamma globulin was able to lyse autologous erythrocytes sensitized with each of the three LTA preparations. These results demonstrate that the ability to render host cells susceptible to lysis by autologous complement is a general property of LTA. Whether activation of the autologous complement occurs by the classical or alternative pathways and whether it is antibody dependent depends on the nature of the bacterial LTA.

Structural studies on lipoteichoic acids from four Listeria strains

The lipoteichoic acids were isolated from phenol extracts of four Listeria strains representing serotypes 4a, 4b, 6a, and 6 to compare the differences in structure of amphiphilic polysaccharides from various serotypes of Listeria spp. The lipoteichoic acids from the four strains examined had the same structure in both hydrophilic chains and lipid portions. On the basis of the results of nuclear magnetic resonance spectroscopy and Smith degradation, the hydrophilic chains were shown to be 1,3-linked poly(glycerol phosphate) in which some of the glycerol residues had alpha-galactosyl substituents. The lipid portions were released by treatment with 46% hydrogen fluoride or 98% acetic acid. They were determined to be 3(1)-(2'-O-alpha-D-galactopyranosyl-alpha-D-glucopyranosyl)-1(3), 2-diacylglycerol and 3(1)-[6'-phosphatidyl-2'-O-(alpha-D-galactopyranosyl)-alpha- D-glucopyranosyl]-1(3),2-diacylglycerol. The degrees of glycosyl substitution and proportions of the two lipids varied to some extent among these four strains.

Critical micelle concentrations of lipoteichoic acids

Purified lipoteichoic acids (LTAs) from several gram-positive organisms have been shown, by methods involving spectral changes of an added merocyanine dye probe, to have critical micelle concentrations in the range of 1 to 10 micrograms/ml, suggesting that acylated LTAs in their monomer forms may represent the major configuration of extracellular LTAs in bacterial culture fluids. The critical micelle concentrations obtained did not differ markedly with degree of carbohydrate substitution of the polymers. The significance of these findings in relation to the biological properties of LTA is discussed.

Interaction between limulus amoebocyte lysate and soluble antigens from Pseudomonas aeruginosa and Staphylococcus aureus studied by quantitative immunoelectrophoresis

To investigate the interaction of Limulus amoebocyte lysate (LAL) with gram-negative bacteria, soluble antigens from sonicated Pseudomonas aeruginosa were studied by various crossed-immunoelectrophoresis methods before and after reaction with LAL. Of 64 possible, at least 7 antigens were affected, as indicated by precipitin pattern, after the reaction with LAL. The precipitates corresponding to lipopolysaccharide and Pseudomonas "common antigen" disappeared. This reaction was inhibited when LAL was pretreated with lipopolysaccharide or by heating. Several of the reacting antigens have been shown to cross-react with many other strains of both gram-negative and gram-positive bacteria. Soluble antigens from a protein A-deficient strain of Staphylococcus aureus were also studied. LAL reacted with at least four of these antigens, including the teichoic acid complex. It is concluded that LAL is highly reactive with lipopolysaccharide, but it can react with other antigens from gram-negative and gram-positive bacteria as well. It is suggested that LAL interacts with biologically important antigens from the bacterial membrane. It is proposed that the reactivity and specificity of LAL for various microbial antigens can be studied by immunoelectrophoretic techniques.

31P-NMR studies of the oral pathogen Streptococcus mutans: observation of lipoteichoic acid

We have used 31P-nuclear magnetic resonance spectroscopy to identify phosphorus-containing compounds in whole cells of two serotype c strains of the oral pathogen Streptococcus mutans. The major resonance, centered at 0 ppm in whole cells, was attributed to lipoteichoic acid on the basis of its chemical shift, insensitivity to pH changes, cellular localization and a comparison with spectra obtained with purified lipoteichoic acid from S. mutans. The linewidths of resonances observed for intact cells and purified lipoteichoic acid were moderately narrowed by increasing the ionic strength, and substantially broadened in the presence of the lectin concanavalin A. Experiments with purified lipoteichoic acid suggest that this compound in whole cells is complexed with divalent cations such as Mg2+. Intracellular pools of other phosphorus-containing metabolites were found to be low when compared to the lipoteichoic acid concentration in both starved and glycolyzing cells.

[Cell wall proteins of Escherichia coli: a substance resembling the thermolabile enterotoxin (LT)]

In ultrasonic extracts of all 19 investigated non-enterotoxigenic E. coli strains a substance (LTLS) could be detected reacting positively in all tests which are commonly used to detect specifically E. coli thermolabile enterotoxin (LT). Culture supernatants of these strains in general did not contain LTLS in detectable amounts. LTLS can be found in the whole cell, however, the membrane fraction contains the highest quantities. Released LTLS appears mainly aggregated with components of the cell wall, especially with lipopolysaccharides. This fact in combination with the very low quantities produced by the bacteria renders very difficult purification of LTLS.

Lipoteichoic acid from Listeria monocytogenes

A lipoteichoic acid (LTA) was extracted from Listeria monocytogenes (serotype 1) by phenol-water partition and isolated by gel-filtration chromatography. The LTA exhibited amphiphilic properties by changes in gel-filtration mobility in the presence of detergent buffers and after mild base hydrolysis. In a hemagglutination assay, Listeria LTA bound antibody prepared against a known LTA from Streptococcus spp. Listeria LTA inhibited the binding of anti-LTA antibody to a Lactobacillus LTA in a hemagglutination inhibition assay. The Listeria LTA contained glucose, galactose, fatty acids, glycerol, and phosphate with molar ratios of 0.05, 0.07, 0.21, 0.94, and 1.0 to phosphate, respectively. Adjacent glycerols were linked between the C-1 and C-3 positions by phosphodiesters (structural type 1). The average chain length was 19 +/- 2 (standard deviation) glycerol-phosphate repeating units. Approximately one glycosyl side chain was present per LTA molecule. The side chain was a galactose-containing disaccharide. The lipid portion of the LTA was a galactose- and glucose-containing glycolipid which may have been a phosphoglycolipid, but the structure was not confirmed. Major fatty acids of LTA and the glycolipid were 17:anteiso, 15:anteiso, 16:iso, 16:n, and 18:n. L. monocytogenes contained cell wall products typical of gram-positive bacteria which is in contrast to the reports by others of the presence of lipopolysaccharides from L. monocytogenes.

Fatty acid composition in phenol extracts from actinomyces species

Fatty acid composition in phenol extracts of some strains of Actinomycetaceae was investigated by the combined system of gas chromatography and mass spectrometry (GC-MS). A variety of fatty acids was detected in these extracts, including branched and straight-chain acids.