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PubMed2005

Cloning, expression and phylogenetic analysis of Hemolin, from the Chinese oak silkmoth, Antheraea pernyi.

The Chinese oak silk moth Antheraea pernyi is an important silk producer. To understand microbial resistance of this moth, we cloned Hemolin, encoding a multifunctional immune protein belonging to the immunoglobulin superfamily, and examined the expression in gonads and fat body. The ApHemolin amino acid sequence was compared to other Hemolin sequences in order to predict functional sites. Several sites were conserved; among them a phosphate binding site, which according to 3D structure modelling does not appear in neuroglian, the phylogenetically closest related protein. In addition, two conserved KDG sequences in the C-C' loop of immunoglobulin domains 1 and 3, give rise to gamma-turns, which is a common motif in the C'-C'' loop of the hypervariable region L2 in vertebrate immunoglobulins. The comparisons also show variable regions of specific interest for future studies of hemolin and its interaction with microbial entities.

Amino Acid Motifs↗
PubMed2005

A novel caspase-1/toll-like receptor 4-independent pathway of cell death induced by cytosolic Shigella in infected macrophages.

Shigella-induced macrophage cell death is an important step in the induction of acute inflammatory responses that ultimately lead to bacillary dysentery. Cell death was previously reported to be dependent upon the activation of caspase-1 via interaction with IpaB secreted by intracellular Shigella, but in this study, we show that Shigella infection of macrophages can also induce cell death independent of caspase-1 or IpaB activity. Time-lapse imaging and electron microscopic analyses indicated that caspase-1-dependent and -independent cell death is morphologically indistinguishable and that both resemble necrosis. Analyses of Shigella mutants or Escherichia coli using co-infection with Listeria suggested that a component common to Gram-negative bacteria is involved in inducing caspase-1-independent cell death. Further studies revealed that translocation of bacterial lipid A into the cytosol of macrophages potentially mediates cell death. Notably, cell death induced by cytosolic bacteria was TLR4-independent. These results identify a novel cell death pathway induced by intracellular Gram-negative bacteria that may play a role in microbial-host interactions and inflammatory responses.

Animals↗
PubMed2002

Synthesis and anti-microbial activity of isothiosemicarbazones and cyclic analogues.

It is known that some derivatives of both thiourea and thiosemicarbazide exhibit potent anti-microbial activity. In order to investigate the effects on the biological properties of structural modifications of such structures, we have synthesised and studied some arylidenisothiosemicarbazones. In this paper we report on the synthesis and structure-activity relationships of some isothiosemicarbazones, where the arylidene group has been replaced with a cycloalkyl group and the sulfur atom has been either differently substituted or enclosed in a thiazole ring.

Animals↗
PubMed2024

Dissecting host-microbe interactions with modern functional genomics.

Interrogation of host-microbe interactions has long been a source of both basic discoveries and benefits to human health. Here, we review the role that functional genomics approaches have played in such efforts, with an emphasis on recent examples that have harnessed technological advances to provide mechanistic insight at increased scale and resolution. Finally, we discuss how concurrent innovations in model systems and genetic tools have afforded opportunities to interrogate additional types of host-microbe relationships, such as those in the mammalian gut. Bringing these innovations together promises many exciting discoveries ahead.

Genomics↗
PubMed1999

Phototrophs in high-iron-concentration microbial mats: physiological ecology of phototrophs in an iron-depositing hot spring.

At Chocolate Pots Hot Springs in Yellowstone National Park the source waters have a pH near neutral, contain high concentrations of reduced iron, and lack sulfide. An iron formation that is associated with cyanobacterial mats is actively deposited. The uptake of [(14)C]bicarbonate was used to assess the impact of ferrous iron on photosynthesis in this environment. Photoautotrophy in some of the mats was stimulated by ferrous iron (1.0 mM). Microelectrodes were used to determine the impact of photosynthetic activity on the oxygen content and the pH in the mat and sediment microenvironments. Photosynthesis increased the oxygen concentration to 200% of air saturation levels in the top millimeter of the mats. The oxygen concentration decreased with depth and in the dark. Light-dependent increases in pH were observed. The penetration of light in the mats and in the sediments was determined. Visible radiation was rapidly attenuated in the top 2 mm of the iron-rich mats. Near-infrared radiation penetrated deeper. Iron was totally oxidized in the top few millimeters, but reduced iron was detected at greater depths. By increasing the pH and the oxygen concentration in the surface sediments, the cyanobacteria could potentially increase the rate of iron oxidation in situ. This high-iron-content hot spring provides a suitable model for studying the interactions of microbial photosynthesis and iron deposition and the role of photosynthesis in microbial iron cycling. This model may help clarify the potential role of photosynthesis in the deposition of Precambrian banded iron formations.

Bicarbonates↗
PubMed2006

The role of HLA molecules in susceptibility to chronic rheumatic heart disease.

Only a small fraction of the streptococcal pharyngitis progress to rheumatic carditis, which implies that environmental, host and microbial factors interact to cause an aberrant immune response against the antigens of the microorganism that cross-react with cardiac tissues. Although there are numerous studies and a general consensus on the relation between human leucocyte antigen (HLA) class II antigens and rheumatic heart disease (RHD), the details and the culprit antigens are still controversial. The study was undertaken to examine 100 patients with chronic RHD and 100 controls for HLA class I and class II antigens for differences in prevalence. All samples were typed at the HLA-DRB1/3/4/5 and DQB1 loci by the sequence-specific primer (PCR-SSP) method at low resolution. For HLA class I antigens, HLA-B13 frequency was marginally increased in patients with RHD compared to controls without reaching statistical significance. For class II antigens, RHD patients had higher frequencies for HLA-DRB1*01 (RHD 24%, controls 10%), DRB1*04 (RHD 35%, controls 26%), DRB1*07 (RHD 18%, controls 11%) and HLA-DQB1*02 (RHD 32%, controls 17%) without reaching statistical significance, and significantly lower frequencies for DRB1*13 (Pc < 0.003, OR: 5.69), DRB5* (Pc < 0.003, OR: 33) and DRB3* (Pc = 0.03, OR: 2.66) compared to controls. It was concluded that host, microbial and environmental factors collude to create acute rheumatic fever (RF) and chronic rheumatic valve disease. The HLA-DRB1*13, DRB5* and DRB3* were protective against the development of rheumatic valve damage.

Aortic Valve↗
PubMed2005

Structure-activity relation of human beta-defensin 3: influence of disulfide bonds and cysteine substitution on antimicrobial activity and cytotoxicity.

Human beta-defensins form a group of cysteine-rich antimicrobial peptides which have been found in epithelial tissue and, more recently, in the male genital tract. They play a role in the defense against microbial pathogens in innate immunity and display additional chemotactic functions in the adaptive immune system. An important characteristic of antimicrobial peptides is that they also exhibit toxic potential on eukaryotic cells. Very little is known about the structure dependence of antimicrobial and cytotoxic effects. We investigated human beta-defensin 3 (hBD-3), a potent broad-spectrum antimicrobial effector peptide, regarding the influence of structural parameters on the antimicrobial and cytotoxic activity. We have established a structure-activity relation of the hBD-3 using synthetic derivatives differing in length, charge, disulfide connectivity, and overall hydrophobicity. The antimicrobial activity of the peptides was compared to the cyctotoxic effects on monocytic THP-1 cells and the hemolytic activity on human erythrocytes. We found that it is not important for antimicrobial and cytotoxic activity whether and how cysteine residues are arranged to form disulfide bonds. Substitution of half-cystinyl residues by tryptophan resulted in increased activities, while other substitutions did not change activity. Correlation of activities with the structural changes demonstrates that the activity on eukaryotic cells appears to depend strongly on the overall hydrophobicity. In contrast, the antimicrobial potency of hBD-3 peptides is determined by the distribution of positively charged amino acid residues and hydrophobic side chains. The results facilitate the understanding of beta-defensin interaction with different cell types and guide the design of antimicrobially active peptides.

Amino Acid Sequence↗
PubMed2001

In vitro model of infectious crystalline keratopathy: tissue architecture determines pattern of microbial spread.

PURPOSE: To develop an in vitro model of infectious crystalline keratopathy using human corneal buttons and to test the hypothesis that the compactness of the corneal stroma determines the pattern of microbial spread. METHODS: Twenty human corneal buttons obtained after penetrating keratoplasty for keratoconus (KC) and eight human corneal buttons obtained from eye bank (EB) donor eyes were maintained in organ culture. Fourteen buttons (10 KC and 4 EB donors) were maintained in a turgid state (swollen, edematous) and 14 in a nonturgid state (compact, normal state of deturgescence) by the omission or addition of 5% dextran to the culture medium. Eight KC and four EB nonturgid buttons and eight KC and four EB turgid buttons were inoculated with Streptococcus viridans (Lancefield group G, gram-positive) organisms. Two KC nonturgid and two KC turgid buttons were inoculated with Klebsiella oxytoca (gram-negative) organisms. Bacterial migration and spread in the tissue were observed by light and electron microscopy. RESULTS: Of the nonturgid buttons, six KC buttons and all four EB buttons inoculated with S. viridans and both KC buttons inoculated with K. oxytoca demonstrated an arborizing, crystallike pattern of bacterial spread. In the turgid buttons, five KC and all four EB buttons inoculated with S. viridans and both KC buttons inoculated with K. oxytoca demonstrated globular, amorphous colonies. This was in complete contrast to the needlelike branching appearance seen in nonturgid corneal buttons. Electron microscopy confirmed an interlamellar spread of the bacterial colonies. CONCLUSIONS: This is the first in vitro model of bacterial keratitis. It demonstrates that the pattern of spread of bacteria within corneal tissue is largely determined by the compactness of the corneal stroma. Altering tissue architecture changed the pattern of bacterial migration and spread. This model has considerable potential in further understanding host-microbe interactions and microbial spread that occurs during infection.

Adult↗
PubMed2026

Autoimmune disease-associated pathobionts: mechanisms and therapeutic potential of phage-based approaches.

The gut microbiota is a critical regulator of systemic immune homeostasis; accumulating evidence implicates specific commensal bacteria, termed "pathobionts," in autoimmune disease pathogenesis. However, the definition of pathobionts remains context-dependent, as their effects are influenced by host genetics and host-microbe interactions. In this review, we summarize representative pathobionts supported by functional evidence in selected extraintestinal autoimmune diseases and discuss how these mechanisms may inform phage-based microbiome-targeted interventions. Mechanistically, pathobionts contribute to autoimmune disease through multiple pathways, including molecular mimicry, induction of intestinal T helper 17 and T follicular helper cell responses, disruption of regulatory T cell homeostasis, intestinal barrier dysfunction, and bacterial translocation from the gut to extraintestinal sites. These processes highlight the central role of gut-associated lymphoid tissue in initiating systemic autoimmunity, and targeting disease-associated microbes represents a promising therapeutic strategy. Whole-phage therapy, which enables highly specific bacterial elimination, has shown efficacy in preclinical immune-mediated disease models, but may be affected by variable in vivo replication, bacterial receptor-mediated resistance, anti-phage immune responses, and ecological effects on the resident microbiome. Phage-derived enzymes that lyse bacterial cell walls, such as endolysins, represent a complementary therapeutic modality that specifically targets bacterial peptidoglycan through cell wall-binding and catalytic domains. Collectively, these findings support the concept that pathobiont-targeted interventions, particularly phage-based strategies, may provide microbiome-directed, immunosuppression-sparing therapeutic approaches for selected patient subsets.

Humans↗
PubMed2026

Desert-derived Ensifer sp. SA403 enhances potato salt tolerance by reshaping rhizosphere microbiome functions and host responses.

Soil salinization increasingly threatens global food security, and potato (Solanum tuberosum L.), a moderately salt-sensitive crop, is particularly vulnerable to saline soils. Plant growth-promoting rhizobacteria (PGPR) offer a promising strategy to improve crop performance, yet how PGPR interact with native microorganisms to enhance potato salt tolerance remains poorly understood. In this study, we identified a desert-derived PGPR strain, Ensifer sp. SA403, which substantially enhanced potato performance under high salinity across sterile, non-sterile and field conditions. Physiologically, inoculation with SA403 reduced shoot Na&#x207a; accumulation and increased the K&#x207a;/Na&#x207a; ratio; notably, these effects were markedly stronger in non-sterile substrates than under sterile conditions, indicating that SA403-mediated ion homeostasis relies on cooperation with the resident microbiota rather than on the strain acting alone. Metagenomic profiling indicated that SA403 strain reshaped rhizosphere communities, significantly enriching beneficial taxa such as Priestia and Bradyrhizobium, and upregulated functional pathways involved in glutathione and sulfur metabolism. Furthermore, host transcriptomic analyses showed that SA403 modulated plant responses to salt stress, with differentially expressed genes enriched in jasmonic acid signaling, ethanolamine metabolism and amino-acid biosynthesis pathways. Field trials on saline soils confirmed that SA403 significantly increased seedling emergence and tuber weight. Together, our results demonstrate that SA403 functions as a biological mediator that optimizes rhizosphere microecology and coordinates ion balance and host signaling to enhance potato salt tolerance. These findings support the potential of SA403 as a robust PGPR-based tool for sustainable potato production on saline soils.

Rhizosphere↗
PubMed2001

Adaptation of bacteria to the intestinal niche: probiotics and gut disorder.

The gastrointestinal tract is a complex ecosystem host to a diverse and highly evolved microbial community composed of hundreds of different microbial species. The interactions that occur between this complex microbial community and the human host have become the focus of scientific research due to increases in the incidence of illnesses associated with deficient or compromised microflora (e.g., gastrointestinal tract infections, inflammatory bowel disease (Crohn's disease and ulcerative colitis), irritable bowel syndrome, antibiotic-induced diarrhea, constipation, food allergies, cardiovascular disease, and certain cancers). Effective multidisciplinary research programs now complement conventional microbiology with molecular ecology techniques to provide culture-independent analysis of the gastrointestinal ecosystem. Furthermore, as we acquire an understanding of gut microflora composition and processes such as intestinal adherence, colonization, translocation, and immunomodulation, we are also elucidating mechanisms by which these can be influenced. This knowledge not only allows scientists to define the activities and interactions of "functional food"-borne beneficial bacteria in the gut, but will also provide the scientific basis for the development of innovative biotechnology-based products tailored to prevent specific diseases and promote overall human gastrointestinal health.

Bacterial Physiological Phenomena↗
PubMed1994

Function of antimicrobial proteins in insects.

We have isolated and characterized various antimicrobial proteins from the haemolymph of Sarcophaga peregrina (flesh fly) larvae. Of these the sarcotoxin I family is a group of proteins mainly active against Gram-negative bacteria whereas sapecin is active mainly against Gram-positive bacteria. In addition to its function in defence, sapecin also plays a role in insect development. Recently, we identified a hendecapeptide of the sapecin homologue sapecin B that has the same antibacterial activity as the original sapecin B. Both sarcotoxin I and sapecin are inducible proteins synthesized de novo by the fat body and/or haemocytes and secreted into the haemolymph when the insect is in the acute phase response to bacterial infection. Antifungal protein (AFP) is constitutively present in the haemolymph and is active against certain fungi but not bacteria. These various antimicrobial proteins interact with microbial membranes. Sarcotoxin I interferes with membrane functions such as ATP synthesis and amino acid transport. The fungicidal activity of AFP is enhanced synergistically by sarcotoxin I, although sarcotoxin I alone has no appreciable antifungal activity. It is clear that the flesh fly has the ability to mount a potent defence response against microbial parasites by mobilizing several antimicrobial proteins.

Amino Acid Sequence↗
PubMed1996

Adherence of oral microorganisms to human parotid salivary proteins.

Bacterial colonisation of oral surfaces by microorganisms may be dependent on their interaction with specific host receptor molecules. Primary oral colonisers are known to remove specific proteins from parotid saliva. The aim of this study was to determine whether these interactions facilitate microbial attachment to a surface and hence identify specific salivary components as putative host receptor molecules. Parotid saliva was resolved by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and then electroblotted onto nitrocellulose membranes. Suspensions of fluorescently labelled microorganisms were incubated with the blots and salivary components with adherent bacteria identified as fluorescent bands under ultraviolet (UV) transillumination. Species of streptococci known to be early colonisers of the clean tooth surface were found to adhere specifically to certain salivary proteins, especially to basic proline-rich proteins (PRPs). Polymorphic variations in these patterns could form the basis of differences in oral microflora, susceptibility to oral infections and consequent disease.

Bacterial Adhesion↗
PubMed1998

Interaction of Sulfate-Reducing Bacteria with Molybdenum Dissolved from Sputter-Deposited Molybdenum Thin Films and Pure Molybdenum Powder.

When sputter-deposited Mo thin films were exposed to sulfate-reducing bacterium Desulfovibrio desulfuricans, dissolved Mo markedly delayed the culture growth and reduced the rate of sulfate reduction. The interaction led to an orange coloration of the culture liquid. X-ray photoelectron spectroscopy of dried culture droplets revealed that Mo dissolution products existed mostly in pentavalent state, and a smaller amount of molybdate and molybdenum disulfide. In contrast, Mo dissolution in uninoculated medium was negligible. Subsequently, different concentrations of molybdate, ranging from 0.1 to 20 mM, were added to the growth medium and it was found that a low concentration of molybdate (1 mM) was able to reduce the culture growth rate and sulfate reduction by forming Mo(V)-S complexes. In order to study the dependence of the degree of interaction upon microbial activity and growth-dependent metabolic products, 1.0 g/L Mo powder was added to (a) the growth medium, (b) a 3-day-old culture, and, (c) the supernatants of 2 h to 5-day-old cultures. Ultraviolet-visible spectroscopy indicated that the Mo(V)-S complexes consisted of a Mo-S compound analogous to a binuclear dioxobridged Mo(V)-cysteine complex (314 nm) and Mo(V)-containing molybdenyl thiocyanate (468 nm). Dissolution of Mo was induced by H2S, a product of the bacterial sulfate reduction, and was further increased probably by sulfur-containing amino groups and proteins. Copyright 1998 Academic Press.

Journal Article↗
PubMed1982

Macrophage activation and effector mechanisms against microbes.

The term activation is used to designate biochemical and functional changes that are induced in macrophages by a variety of stimuli, including interaction with microbial products, synthetic substances, immunoglobulins of different classes, and factors released by lymphocytes. The changes observed comprise an increased capacity to destroy intracellular microorganisms and non-microbial target cells as well as the stimulation of biochemical pathways leading to the release of enzymes and the generation of various toxic compounds. Activation may thus be viewed as a process aimed at recalling those metabolic functions that are necessary for killing, when phagocytosis has failed to evoke them. The increased microbicidal capacity of activated macrophages is linked to the production of oxygen intermediates, as illustrated by the study of macrophage toxicity for certain intracellular protozoan parasites. Scavengers of oxygen metabolites inhibit parasite killing in macrophages; on the contrary, agents that stimulate the production or utilization of such intermediates enhance the microbicidal effect of phagocytes. Several mechanisms enable microorganisms to survive within macrophages. In some instances, intracellular survival appears to depend on the capacity of microorganisms to be endocytized without awakening the host cell oxidative machinery. In addition, the endowment of microorganisms in endogenous enzymatic scavengers of oxygen metabolites may play a role in promoting intracellular survival. These and other mechanisms, such as the property to avoid the harmful effects of lysosomal constituents by inhibiting phagosome-lysosome fusion, or by releasing agents that block the lysosomal enzymatic machinery, may explain why certain microbes are able to survive within activated macrophages.

Animals↗
PubMed1992

Lack of in vitro antiviral activity of fluoroquinolones against herpes simplex virus type 2.

The antiviral activity against herpes simplex virus type 2 (HSV-2) of five fluoroquinolones (ciprofloxacin, lomefloxacin, ofloxacin, pefloxacin, rufloxacin) was tested in vitro. Their efficacy was evaluated as reduction of the cytopathic effect (CPER) exerted by HSV-2 on Vero cells in comparison with novobiocin and acycloguanosine. Our results show a very poor antiviral effect of five quinolones (CPER50 = 200 mg/l) that was comparable with their cytotoxicity (TCIC50 less than 200 mg/l). Novobiocin shows a lower toxicity (TCIC50 = 400 mg/l) and a slight antiviral activity (CPER50 = 120 mg/l). Acycloguanosine shows a TCIC50 greater than 400 mg/l and a CPER50 of 3.125 mg/l. The therapeutic indices gave values ranging from 0.12 to 2 for quinolones, of 3.3 for novobiocin, and greater than 128 for acycloguanosine. The antiviral efficacy of acycloguanosine was not affected by concentrations of quinolones active against bacteria (1-10 mg/l) whereas it was drastically reduced by higher doses of quinolones (greater than 50 mg/l). Our data suggest that fluoroquinolones cannot be considered drugs able to inhibit HSV-2 replication in vitro.

Acyclovir↗
PubMed1992

Differential effects of bismuth and salicylate salts on the antibiotic susceptibility of Pseudomonas aeruginosa.

The influence of salicylate or bismuth salts on antibiotic action against Pseudomonas aeruginosa was assessed in broth cultures. Sodium salicylate (2.5 mM) had no significant effect on the activity of any antibiotic tested. In contrast, bismuth compounds (0.5 mM) produced a significant change in the inhibitory activity of several antibiotics against all strains. Bismuth salts reduced imipenem activity by up to 20-fold, enhanced gentamicin or amikacin activity three to five-fold, and enhanced cefpirome or cefepime activity by as much as 10-fold against antibiotic-sensitive and resistant strains. Bismuth salts had little effect on cefoperazone, ceftazidime, or mezlocillin activity. Combining bismuth salts with aminoglycosides or fourth-generation cephalosporin antibiotics may help to combat the growing problem of resistant Pseudomonas aeruginosa.

Anti-Bacterial Agents↗