Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “HEMOLYSINS”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 271 records · Page 15Linked to original sources
PubMed1980

Simplified purification and biophysicochemical characteristics of Kanagawa phenomenon-associated hemolysin of Vibrio parahaemolyticus.

Kanagawa phenomenon-associated hemolysin (K-hemolysin) was purified by Sephadex gel and ion-exchange column chromatography, after the culture supernatant had been adsorbed on and eluted from diethylaminoethyl-Sepharose CL-6B, and acid precipitated. K-hemolysin was a heat-stable and trypsin-susceptible protein with an apparent molecular weight of 44,000, the subunit of which was 22,000. The isoelectric point was 4.9. The minimum hemolytic dose was 0.1 mug/ml. The fifty percent lethal dose by intravenous injection was 1.4 mug. Electron microscopy of the small intestine of suckling mice orally challenged with the highest dose (50 mug) not only showed disappearance of epithelial cell microvilli, but also structural disturbances of the endoplasmic reticulum and mitochondrial swelling. One blueing dose representing permeability factor activity was 0.3 mug, and positive reaction in the rabbit ileal loop appeared at above 125 mug. Besides these data in experimental models, we discovered the appearance of an antibody in patients which neutralizes K-hemolysin during the course of the disease. This finding reinforces our view that K-hemolysin plays a most significant role in the pathogenesis of this enteric human disease.

Amino Acids↗
PubMed1980

Production and properties of heat-stable extracellular hemolysin from Pseudomonas aeruginosa.

Of 12 strains of Pseudomonas aeruginosa, 10 were found to produce heat-stable extracellular hemolysin in highly aerated peptone broth supplemented with glycerol, fructose, or mannitol. Glucose supported good hemolysin production only in medium that was highly buffered. The yield of both cells and hemolysin was lower with organic acids as supplement. Growth-limiting phosphate concentrations produced maximum hemolysin levels. Purified hemolysin preparations contained two hemolytic glycolipids. The kinetics of hemolysis at various levels of purified lysin and the effects of variation in lysin and erythrocyte concentration are described.

Glycerol↗
PubMed1981

Investigation of a hemolysin produced by enteropathogenic Treponema hyodysenteriae.

A hemolysin produced by Treponema hyodysenteriae, the etiological agent of swine dysentery, was investigated. A virulent isolate (B204) was inoculated into a standard culture medium consisting of Trypticase soy broth without dextrose (BBL Microbiology Systems) supplemented with 10% fetal calf serum in an atmosphere of 70:30 deoxygenated H2-CO2. Sterile cell-free filtrates were prepared at 2-h intervals and assayed for hemolytic activity by using washed sheep erythrocytes. The maximum hemolytic titer was obtained during the early log phase of growth (4 h). A loss of hemolytic activity was observed when cell-free filtrates were stored at 23 and 4 degrees C. Storage at -20 or -80 degrees C after lyophilization resulted in retention of the hemolytic titer for periods of up to 30 days. Enzymatic inactivation of the hemolysin was accomplished with pronase, but not with deoxyribonuclease, ribonuclease, lipase, or trypsin. Addition of exogenous ribonucleic acid-core to the standard culture medium resulted in a dose-dependent increase in the amount of hemolysin produced. The hemolysin could be purified by acid and ammonium sulfate precipitation followed by ion exchange and molecular sieve chromatography. The molecular weight of the hemolysin was 68,000 when determined by sodium dodecyl sulfate-polyacrylamide slab gel electrophoresis.

Hemolysin Proteins↗
PubMed1982

High-molecular-weight hemolysin of Clostridium tetani.

Clostridium tetani excretes hemolysins of two size classes, a high-molecular-weight hemolysin (HMH), which was eluted near void volume of a Sepharose 6B column, and conventional tetanolysin (molecular weight, approximately 50,000). The total hemolysin activity in the culture supernatant increased sharply with growth of bacteria and remained at a high level during autolysis. The content of HMH, however, decreased from 41% at 4 h of culture to 0.4% at the early stage of autolysis. The cell bodies also exhibited hemolytic activity, 70% of which could be solubilized and separated into HMH and the 50,000 Mr tetanolysin as extracellular hemolysins. The activity ratio of HMH to the total solubilized hemolysins was 0.45, on the average, at 6 h of culture but was 0.23 at the middle of logarithmic growth. Partially purified HMH from both sources appeared as broken pieces of cytoplasmic membranes under an electron microscope. The ratio of proteins to phospholipids in HMH was found to 3.26, a value similar to that in cell membrane. The total cell hemolytic activity decreased by 90 or 75% upon addition of chloramphenicol or anti-tetanolysin serum, respectively, into a 6-h-old culture of bacteria. It is suggested that HMH is a complex of tetanolysin with a membrane fragment and releases the conventional tetanolysin during bacterial culture.

Bacterial Toxins↗
PubMed1982

Effect of Escherichia coli alpha-hemolysin on human peripheral leukocyte viability in vitro.

To gain further evidence that Escherichia coli alpha-hemolysin has a role in pathogenesis, its effect on human peripheral leukocyte viability was studied in vitro. Viability of leukocytes exposed to low doses of alpha-hemolysin decreased nearly 10-fold within 15 min of exposure. This response was dose and time dependent and was neutralized by antiserum, heat, proteases, and lipase. To gain further evidence that alpha-hemolysin was the molecule responsible for leukotoxicity, preparations of alpha-hemolysin were passed through a hydrophobic interaction chromatographic column. Alpha-hemolysin prepared in this way retained its leukotoxic activity. Both hemolytic and leukotoxic activities copurified at the same ratio and were inactivated to the same degree by heating at 56 degrees C. Lysis of leukocytes, if it occurs in vivo, would enhance the chances of survival for an invading hemolytic E. coli.

Cell Survival↗
PubMed1971

Separation of two hemolysins from Aeromonas hydrophila by isoelectric focusing.

Two hemolytic proteins (hemolysin I and II) with isoelectric points of 5.5 and 4.3 were purified by isoelectric focusing from the culture supernatant fluid of Aeromonas hydrophila. The purified hemolysins were unstable after dialysis and upon heating at 37 C and were inactivated by proteolytic enzymes. The two hemolysins were lethal for mice in a dose of 10 mug (hemolysin I) and 3 mug (hemolysin II) and showed similar hemolytic spectra on red cells of different species. Both were also cytotoxic for HeLa cells and human fibroblasts and gave dermonecrosis in rabbits.

Aeromonas↗
PubMed1985

Detection of the thermostable direct hemolysin gene and related DNA sequences in Vibrio parahaemolyticus and other vibrio species by the DNA colony hybridization test.

A specific gene probe for the Vibrio parahaemolyticus thermostable direct hemolysin gene was constructed and used to examine the presence or absence of the thermostable direct hemolysin gene or related DNA sequences in V. parahaemolyticus and other vibrios by the DNA colony hybridization method. The gene probe consisted of a 406-base-pair, completely internal fragment covering 71% of the structural gene with PstI linkers added to the ends. Six copies of this 415-base-pair PstI fragment were cloned into plasmid pBR322, which yielded large amounts of the probe DNA. One hundred forty-one V. parahaemolyticus strains were tested with the gene probe, and the results were compared with those of phenotypic assays for the thermostable direct hemolysin. All Kanagawa phenomenon-positive strains were gene positive. However, 86% of the strains that exhibited weak Kanagawa phenomenon and 16% of Kanagawa phenomenon-negative strains also reacted with the gene probe. Immunological methods for the detection of the thermostable direct hemolysin (modified Elek test, enzyme-linked immunosorbent assay) showed better correlation with gene probe results. All gene-positive strains produced hemolysin detectable in the enzyme-linked immunosorbent assay, although occasional strains showed weak reaction. The modified Elek test was slightly less sensitive than the enzyme-linked immunosorbent assay. All gene-negative strains were also negative in these immunological assays. One hundred twenty-one strains of Vibrio spp. other than V. parahaemolyticus were tested with the gene probe; only Vibrio hollisae strains reacted with the probe under stringent conditions.

Base Sequence↗
PubMed1985

Bacterial adherence and hemolysin production from Escherichia coli induces histamine and leukotriene release from various cells.

We investigated the role of bacterial adherence and hemolysin production from Escherichia coli parent and genetically cloned strains as to their effects on histamine release from rat mast cells and leukotriene generation from human polymorphonuclear granulocytes. These mediators were involved in the induction of inflammatory disease processes and led, for example, to enhancement of vascular permeability, chemotaxis (leukotriene B4 [LTB4]), chemoaggregation, lysosomal enzyme release, and smooth muscle contraction, (LTC4, LTD4, and LTE4). Washed bacteria (E. coli K-12 MS+ Hly +/-; E. coli 536 MS+ MR +/-) as well as their culture supernatants were analyzed. Washed E. coli K-12 (Hly+), unlike Hly- strains, induced high amounts of histamine release from rat mast cells and chemotactic activity from human polymorphonuclear granulocytes. Significant leukotriene release was obtained with washed E. coli K-12 Hly+ strains and their bacterial culture supernatants. Leukotriene induction was dependent on the amount of hemolysin activity present in the supernatant. However, additional soluble factors should also be considered. The presence of hemolysin appeared to accelerate and enhance the rate of phagocytosis of bacteria by neutrophils. When E. coli 536 (MS+ MR +/- Hly +/-) strains were analyzed, the simultaneous presence of MR+ pili and hemolysin production led to an increase in histamine release as compared with MR- Hly+ strains. The genetically cloned MR+ Hly+ E. coli 536 strain induced higher amounts of leukotrienes as compared with the wild-type strain. Our data suggest a potent role for adhesins and hemolysin as virulence factors in inducing the release of inflammatory mediators.

Adhesiveness↗
PubMed1988

Iron-regulated hemolysin production and utilization of heme and hemoglobin by Vibrio cholerae.

El Tor and non-O1 strains of Vibrio cholerae were analyzed to determine whether synthesis of secreted hemolysin was influenced by the concentration of iron in the medium. Synthesis of hemolysin was found to be iron regulated in both El Tor and non-O1 isolates. Increased levels of hemolytic activity were detected in supernatants of iron-starved cells. Spontaneous hemolysin-deficient mutants of one non-O1 strain were found to occur at high frequency. These variants also failed to synthesize vibriobactin, the iron transport compound utilized by V. cholerae. Another non-O1 strain was found to synthesize both hemolysin and vibriobactin constitutively. When the cloned Escherichia coli fur gene, encoded on the plasmid pABN203, was introduced into this constitutive strain, normal iron regulation of both hemolysin and vibriobactin was reestablished. The ability of V. cholerae to utilize mammalian iron compounds was determined, and it was found that both hemin and hemoglobin could serve as sole sources of iron.

Catechols↗
PubMed1991

Superoxide generation by human neutrophils induced by low doses of Escherichia coli hemolysin.

Escherichia coli hemolysin (Hly) was isolated from bacterial culture supernatants by polyethylene glycol precipitation and centrifugation in glycerol density gradients. The toxin preparations contained less than 1 mol of lipopolysaccharide per 10 mol of protein, and they had no fatty acids. The capacity of purified hemolysin to stimulate superoxide anion production in polymorphonuclear leukocytes was monitored kinetically in a lumimeter by using the lucigenin assay and was correlated with the kinetics of transmembrane pore formation. When applied to leukocytes suspended in protein-free buffer, very low concentrations (0.02 to 0.1 HU/ml) of the toxin strongly stimulated the production of superoxide anions; shortly thereafter, irreversible membrane permeabilization occurred. When the toxin was applied at concentrations exceeding 0.2 to 0.3 HU/ml, membrane permeabilization was so rapid that the cells were unable to mount a respiratory burst. When applied in the narrow range of 0.05 to 0.1 HU/ml, E. coli hemolysin rivaled phorbol myristate acetate in its capacity to stimulate production of superoxide anions. Additionally, hemolysin applied at doses that elicited no pore formation (0.01 to 0.02 HU/ml) primed leukocytes for an augmented response to subsequent challenge by the phorbol ester. These data demonstrate that very low doses of E. coli hemolysin can evoke cellular reactions that appear independent of and precede transmembrane pore formation and cell death.

Bacterial Proteins↗
PubMed1994

Improved purification and characterization of hemolysin BL, a hemolytic dermonecrotic vascular permeability factor from Bacillus cereus.

Bacillus cereus causes diarrheal and emetic food poisoning syndromes as well as a variety of mild to severe infections. A dermonecrotic vascular permeability (VP) factor has been implicated as a virulence factor in these illnesses. Hemolysin BL was previously identified as a unique tripartite hemolysin possessing VP activity. In this study, a high-yield purification scheme, which allowed quantitative characterization of hemolysin BL activity and determination of the molecular weight, pI, and N-terminal sequence of each component, was developed. Milligram quantities of the B, L1, and L2 components were highly purified by a combination of anion-exchange and hydroxylapatite chromatographies. The combined components had VP activity at low doses and were necrotic at higher doses. The toxin exhibited an unusual dose-response zone phenomenon in turbidometric hemolysis assays. Activity increased at doses up to 200 ng/ml, then decreased at doses up to 350 ng/ml, and was constant at doses up to at least 2,500 ng/ml. This behavior may provide an explanation for the unusual discontinuous pattern typical of hemolysin BL in gel diffusion assays. At high concentrations of one or two components, the presence of low amounts of the complementary component(s) resulted in full hemolytic activity. Erythrocytes were protected from lysis by Zn2+ at micromolar concentrations but not by Ca2+ and Mg2+ at concentrations up to 25 mM. These data provide guidelines for future work on this toxin and indicate that hemolysin BL is the dermonecrotic VP factor implicated as a B. cereus virulence factor.

Amino Acid Sequence↗
PubMed1994

Effect of growth factors on Escherichia coli alpha-hemolysin-induced mediator release from human inflammatory cells: involvement of the signal transduction pathway.

Previously, we have shown that Escherichia coli alpha-hemolysin represents a potent stimulus for inflammatory mediator release (O2- release, beta-glucuronidase release, and leukotriene generation) from human polymorphonuclear granulocytes (PMN) as well as for histamine release from a human lymphocyte-monocyte-basophil cell suspension (LMB). In contrast, the E. coli alpha-hemolysin leads to a downregulation of cytokine release (interleukin 6 [IL-6], tumor necrosis factor alpha, and IL-1 beta) from human LMB. This study was undertaken (i) to analyze the priming efficacy of growth factors (granulocyte-macrophage colony-stimulating factor [GM-CSF] and granulocyte CSF [G-CSF]) on inflammatory mediator release from human PMN and LMB challenged with hemolysin-producing E. coli bacteria as well as with cell-free E. coli alpha-hemolysin and (ii) to identify major components involved in GM-CSF and G-CSF priming. GM-CSF pretreatment led to an increased chemiluminescence response from human PMN by up to 100%, leukotriene B4 generation was enhanced up to fivefold, and histamine release from human LMB increased from 45% +/- 15% to 75% +/- 5% (mean +/- standard distribution) of the total histamine content. G-CSF priming induced an increase in the chemiluminescence response by up to 50% +/- 5% from human PMN and an increase in histamine release from human LMB by 20% +/- 5%. The growth factors, GM-CSF and G-CSF, modulated neither beta-glucuronidase release from human PMN nor IL-8 release from human PMN and LMB challenged with the E. coli alpha-hemolysin. GM-CSF and G-CSF pretreatment increased the fluoride (NaF)-induced chemiluminescence response by up to 10-fold; the serine/threonine phosphatase inhibitor okadaic acid inhibited GM-CSF- and G-CSF-induced priming. NaF-induced histamine release was enhanced up to 60 and 30% by GM-CSF and G-CSF priming, respectively. GM-CSF and G-CSF pretreatment did not modulate phorbol 12-myristate 13-acetate-induced chemiluminescence response or histamine release. GM-CSF by itself induced an increase in 5-lipoxygenase-specific mRNA expression within 5 min. Our results indicate that (i) GM-CSF and G-CSF interact with inflammatory cells via distinct cellular signalling, (ii) the signal transduction pathway is dependent on the cellular mediator, and (iii) the use of growth factors may be a potent tool to influence the clinical outcome in infectious diseases.

Bacterial Proteins↗
PubMed1998

Characterization of the roles of hemolysin and other toxins in enteropathy caused by alpha-hemolytic Escherichia coli linked to human diarrhea.

Escherichia coli strains producing alpha-hemolysin have been associated with diarrhea in several studies, but it has not been clearly demonstrated that these strains are enteropathogens or that alpha-hemolysin is an enteric virulence factor. Such strains are generally regarded as avirulent commensals. We examined a collection of diarrhea-associated hemolytic E. coli (DHEC) strains for virulence factors. No strain produced classic enterotoxins, but they all produced an alpha-hemolysin that was indistinguishable from that of uropathogenic E. coli strains. DHEC strains also produced other toxins including cytotoxic necrotizing factor 1 (CNF1) and novel toxins, including a cell-detaching cytotoxin and a toxin that causes HeLa cell elongation. DHEC strains were enteropathogenic in the RITARD (reversible intestinal tie adult rabbit diarrhea) model of diarrhea, causing characteristic enteropathies, including inflammation, necrosis, and colonic cell hyperplasia in both small and large intestines. Alpha-hemolysin appeared to be a major virulence factor in this model since it conferred virulence to nonpathogenic E. coli strains. Other virulence factors also appear to be contributing to virulence. These findings support the epidemiologic link to diarrhea and suggest that further research into the role of DHEC and alpha-hemolysin in enteric disease is warranted.

Animals↗
PubMed2001

Cloning of a beta-hemolysin gene of Brachyspira (Serpulina) hyodysenteriae and its expression in Escherichia coli.

Brachyspira (Serpulina) hyodysenteriae induces a mucohemorrhagic diarrheal disease in pigs. The production of a beta-hemolysin has been considered a major virulence attribute of this organism. Previous reports have failed to correlate a specific cloned gene sequence with a purified beta-hemolytic protein sequence. Thus, questions still remain concerning the structural gene sequence of the hemolysin. To answer this question unequivocally, the beta-hemolytic toxin was purified from extracts of log-phase spirochetes, and the N-terminal amino acid sequence was determined (K-D-V-V-A-N-Q-L-N-I-S-D-K) and compared with the translated sequences of previously cloned genes, tlyA to tlyC. The lack of homology between tlyA to tlyC translated sequences and the purified beta-hemolytic toxin sequence resulted in the study that is reported here. A degenerate probe was designed based on the N-terminal amino acid sequence of the purified beta-hemolysin and used to screen a B. hyodysenteriae genomic library. Three overlapping clones were identified, and one was sequenced to reveal an open reading frame coding for a putative 8.93-kDa polypeptide containing the N-terminal sequence of the purified beta-hemolysin. To distinguish this gene from the tlyA to tlyC genes, it has been designated hlyA. A hemolysis-negative Escherichia coli strains containing hlyA was beta-hemolytic on blood agar media. Also, the hemolytic activity of the recombinant protein had identical protease and lipase sensitivities and electrophoretic mobility to those of native B. hyodysenteriae beta-hemolysin. Based on sequence analysis, the translated protein had a pI of 4.3, an alpha-helical structure, and a phosphopantetheine binding motif. Hybridization analysis of genomic DNA indicated that the hlyA gene was present in B. hyodysenteriae and B. intermedia but was not detected in B. innocens, B. pilosicoli, or B. murdochii under high-stringency conditions. The location of hlyA on the chromosomal map was distinct from the locations of tlyA, tlyB, and tlyC.

Amino Acid Sequence↗
PubMed2006

Characterization of Bacteroides fragilis hemolysins and regulation and synergistic interactions of HlyA and HlyB.

This study describes the presence of 10 hemolysin orthologs in the genome of the opportunistic human anaerobic pathogen Bacteroides fragilis, which is currently classified as a nonhemolytic bacterium. The hemolysins were designated HlyA through HlyI plus HlyIII. All cloned hemolysin genes were able to confer hemolytic activity to a nonhemolytic Escherichia coli strain on blood agar plates. Interestingly, HlyH was found to be present in the genome of the B. fragilis NCTC9343 strain but absent in strains 638R, YCH46, and Bacteroides thetaiotaomicron VPI-5482. The hemolysins HlyA, HlyB, and HlyIII were selected for further characterization. HlyA, HlyB, and HlyIII were cytolytic to erythrocytes on liquid hemolytic assay. When hlyA and hlyB were expressed together in a nonhemolytic E. coli strain, the strain showed enhanced hemolytic activity on blood agar plates. Further analysis revealed that HlyA and HlyB have synergistic hemolytic activity as detected by the liquid hemolytic assay. In addition, the two-component hemolysins HlyA and HlyB form a protein-protein complex in vivo as determined by bacterial two-hybrid system assay. The hlyB and hlyA genes are organized in an operon that is coordinately regulated by iron and oxygen. Northern blot hybridization analysis revealed that hlyBA were expressed as a bicistronic mRNA induced approximately 2.5-fold under low-iron conditions and repressed in iron-rich medium. The normal iron-regulated expression of hlyBA mRNA was lost in the furA mutant strain. In contrast, the hlyA gene was also expressed as a single mRNA in iron-rich medium, but its expression was reduced approximately threefold under low-iron conditions in a Fur-independent manner. This suggests that hlyA alone is regulated by an unidentified iron-dependent regulator. Moreover, the expression levels of hlyBA and hlyA were reduced about threefold following oxygen exposure and treatment with hydrogen peroxide. Taken together, these results suggest that iron and oxidative stress have an effect on the control of hlyBA and hlyA transcriptional levels. A hlyBA mutant was constructed, and its hemolytic activity was greatly diminished compared to those of the hlyIII mutant and parent strains. In addition, the hlyBA mutant had a significant modification in colony morphology and growth deficiency compared to the parent strain. The implications of these findings for the pathophysiology of B. fragilis in extraintestinal infections and competition in ecological systems for this organism are discussed.

Animals↗
PubMed2006

Identification and characterization of a hemolysin gene cluster in Vibrio anguillarum.

Vibrio anguillarum is a causative agent of vibriosis in fish. Hemolytic activity has been suggested as a virulence factor by contributing to hemorrhagic septicemia and diarrhea. In order to identify and characterize the hemolysin genes and examine the role of hemolytic activity in virulence, a mini-Tn10Kan mutagenesis clone bank of V. anguillarum was screened. While no hemolysin-negative strains were observed, several mutants with two- to threefold-increased hemolytic activity were found. The region containing the insertion mutation was cloned, sequenced, and found to contain the V. anguillarum hemolysin (vah1) and two other open reading frames, coding for a putative lactonizing lipase (llpA) and a putative phospholipase (plp). The mini-Tn10Kan was inserted into plp. Site-directed mutagenesis of each gene revealed that mutations in vah1 and llpA did not affect hemolytic activity, but insertions into plp caused a two- to threefold increase in hemolysis. Double mutations in plp and either vah1 or llpA resulted in wild-type hemolytic activity. Complementation of plp restored hemolytic activity to wild-type levels. Spectrophotometric determination of hemolysin specific activity revealed that activity on a per cell basis peaked during the first 2 h of growth in LB20. Real-time quantitative reverse transcriptase PCR used to quantitate transcription of the hemolysin genes plp and vah1 in V. anguillarum wild-type strains M93Sm and NB10 revealed that transcription of plp and vah1 peaked at 2 h of growth in LB20. Additionally, expression of vah1 measured in the plp mutant strain, JL01, during the first 2 h of growth was >8 times higher than that in M93Sm. Mutations in plp and llpA did not affect virulence of V. anguillarum. The mutation in vah1 attenuated V. anguillarum virulence in fish. These data show that several genes are responsible for hemolytic activity in V. anguillarum. At least three genes (plp, llpA, and vah1) are responsible for one hemolytic activity. The data also suggest that plp acts as a negative regulator of vah1 and llpA.

Animals↗
PubMed1973

Effects of staphylococcal alpha-, beta-, delta-, and gamma-hemolysins on human diploid fibroblasts and HeLa cells: evaluation of a new quantitative as say for measuring cell damage.

Human diploid embryonic lung fibroblasts and HeLa cells were cultivated in Eagle minimaĺ essential medium supplemented with 10% calf serum. Monolayer cultures were labeled with (3)H-uridine and treated with highly purified staphylococcal alpha-, beta-, delta-, or gamma-hemolysin. The release of soluble radioactive substances into the medium was used as an indicator of damage to the cell membrane after treatment with each hemolysin. The assay method described is simple, sensitive, and rapid. It allows quantitative estimation of changes in membrane permeability to be detected before a morphological damage is observed microscopically. Upon incubation for up to 30 min with highly purified staphylococcal hemolysins, only delta-hemolysin caused release of a significant amount of tritiated substances from fibroblasts. Such leakage occurred immediately after addition of delta-lysin and was independent of temperature. With minor exceptions, this was similar to the release of isotopes after treatment of the cells with the nonionic detergent Triton X-100. Treatment of fibroblasts with combinations of two or three of these toxins gave neither a synergistic nor an antagonistic effect. Evidence is presented which indicates that delta-hemolysin is the only important fibroblast damaging activity in crude preparations of extracellular proteins of four strains of S. aureus, whereas HeLa cells are susceptible also to purified alpha-toxin.

Cell Line↗
PubMed1983

Transport of hemolysin across the outer membrane of Escherichia coli requires two functions.

Among a large collection of hemolysis-negative mutants obtained by mutagenesis of the Hly plasmid pHly152 with Tn5, we have isolated two classes of mutants which are defective in the transport of hemolysin across the outer membrane. The two cistrons (hylBa and hlyBb) which are affected in these mutants are located adjacent to each other on the hly determinant but are transcribed from different promoters. Recombinant plasmids were constructed which carry the two functions as combined or separated cistrons. These were shown to complement the two types of transport mutants. Studies on the compartmentation of hemolysin in these two classes of mutants indicate that most hemolysin (greater than 70%) in hlyBa mutants is located in the periplasmic space, whereas in hlyBb mutants a larger portion of hemolysin is associated with the outer membrane fraction. The phenotypic appearance of colonies from hlyBb mutants is that of beta-hemolytic Escherichia coli strains, indicating that a substantial portion of hemolysin has already reached the outside of the outer membrane without being released into the medium. Release was achieved readily when hlyBb mutants were complemented with a recombinant plasmid carrying hlyBb.

Cell Membrane↗