The kinetics of progressive reactions in systems containing saponin,digitonin, and sodium taurocholate

The relations between lysin concentration, percentage hemolysis at the moment at which the lysin concentration is reduced by dilution, and the amount of hemolysis which follows the dilution as a result of the reaction being "progressive" point to there being an "internal" phase at the red cell surfaces, in which the lysin is less affected by the dilution than in the system as a whole. A second possibility, i.e. that the combination of lysin molecules with certain components of the cell surface has an ultimate effect on neighboring components which depend on the former for their stability cannot, however, be ruled out. In systems containing digitonin or sodium taurocholate, this internal phase, once formed, seems to be almost unaffected by the dilution of the system; i.e., these lysins are very firmly held at the cell surfaces. In systems containing saponin the lysin is less firmly attached, so that dilution of the system affects its concentration appreciably.     

The combination between hemolysins and red cells or ghosts,as studied with a radioactive lysin and with new color reactions

The quantity of a radioactive hemolysin, sodium dodecyl sulfonate-S³⁵, taken up by red cells from concentrations too small to produce hemolysis varies with the lysin concentration, and does so in a way which can be described by an adsorption isotherm. Attempts to use color reactions or surface tension measurements to determine the quantity of digitonin, saponin, and the bile salts taken up by red cells from hypolytic concentrations have failed, principally because chromogenic, and also surface-active, substances are liberated from the cells when the lysin is added. Color reactions with the anthrone reagent show that digitonin and saponin are both taken up by or fixed to red cell ghosts; the extent of the uptake, however, is uncertain, again because of the liberation of chromogenic substances. Comparison of the results of the various methods which measure the apparent amount of lysin fixed, or utilized in reactions between lysins and red cells or ghosts show discrepancies between results given by direct methods (measurement of radioactivity or of color) and indirect methods (addition of a second population after lysis of a first, and dependence of the position of the asymptote of the time-dilution curve on the number of red cells). The discrepancies are traceable to the inhibitory effects of substances liberated from the red cells or ghosts. The ease with which a lysin, once taken up by red cells, can be detached by diluting the system determines the extent to which the hemolytic reaction is "progressive," but has no observed connection with the quantity taken up in the first place. There is now ample evidence that lysis in systems containing simple hemolysins is a process involving two stages in time and two phases, and that it is usually complicated by reactions between the hemolysin and liberated inhibitory material.     

THE PROLYTIC LOSS OF K FROM HUMAN RED CELLS

The prolytic loss of K., i.e. the loss of K which takes place from red cells exposed to hypolytic concentrations of lysins, has been measured in systems containing distearyl lecithin, sodium taurocholate, sodium tetradecyl sulfate, saponin, and digitonin, by means of the flame photometer. The lysins are added in various concentrations to washed red cells from heparinized human blood, and the K in the supernatant fluids is determined after various intervals of time and at various temperatures. The prolytic loss K_p is compared in every experiment with the loss K_s into standard systems containing isotonic NaCl alone, with no lysin. The losses K_s and K_p increase with time, so that new steady states are approached logarithmically. The values of K_p which correspond to the new steady states depend on the lysin used, being greatest with taurocholate and smallest with digitonin. The temperature coefficient of the loss is positive, and the extent and course of the losses have no apparent relation to the prolytic shape changes. In systems in which the loss of K is appreciable, it can be inhibited by the addition of plasma or of either cholesterol or serum albumin. Of these two substances, even when used in quantities which have an approximately equal effect in inhibiting hemolysis, serum albumin is much the more effective. Just as the prolytic loss of K occurs without the loss of any Hb, so in concentrations of lysin sufficient to produce hemolysis the loss of K, expressed as a percentage of the total red cell K, increases much more rapidly with lysin concentration than does the loss of Hb expressed as a percentage of the total Hb. The explanation of these relations depends on whether the loss of K is treated as being all-or-none in the case of the individual cell or as being the result of the loss of part of the K from all of the cells. This point has still to be decided.     

A zone phenomenon and a progressive reaction occurring with a radioactive hemolysin,sodium erucate,I 131

Sodium erucate reacts progressively (i.e., once the reaction is started in a time which is so short that the lysin is in contact with the red cells for 30 seconds, it cannot be stopped even by being diluted 10-fold) with human red cells at pH 7. At the same time, systems containing the lysin and human red cells show a zone phenomenon, lysis occurring most readily in a certain concentration of lysin but more slowly in larger or smaller concentrations. Sodium erucate-I¹³¹ can be used to investigate both the zone phenomenon and the progressive character of the reaction. As regards the former, large concentrations of the lysin react relatively poorly with the red cell surfaces and the resistance of the red cells is relatively high. This may be due to the presence of an admixed inhibitor or to the development of an inhibitory state. The lysin is taken up and fixed by material in the red cell surface, so that the "internal phase" of lysin attached to the cell surfaces is so firmly fixed that a 10-fold dilution has no effect on it. It follows that lysis in these systems is progressive, as it is found to be.     

Volume changes in hemolytic systems containing resorcinol,taurocholate, and saponin

Simultaneous measurement of hemolysis, the volume of the intact cells, and the K lost from the intact cells of systems containing resorcinol, sodium taurocholate, and saponin shows that the volume increases may be conspicuously small while the K losses are large, and that the volume increases are un-equal for equal K losses produced by different lysins. In higher concentrations of the same lysins, the critical volume for hemolysis is a function of the nature of the lysin and of its concentration. It is impossible to say whether these observations are compatible with the current "dual mechanism" and "colloid osmotic" hypotheses of hemolysis, in which the swelling of the cell is supposed to result from the lysin having made it cation-permeable. The difficulty to be overcome is that the theory cannot be developed to describe volume changes in finite time unless we know what assumptions to make about the mobilities of K and Na, the forces driving them into and out of the cell, etc. The experimental results do not suggest, however, that any simple set of assumptions would be satisfactory. The conditions which regulate the upper limit of the swelling, i.e. the point at which a swelling phenomenon becomes a hemolytic phenomenon, are functions of the nature of the lysin and sometimes of its concentration. They require to be specified by an independent statement, over and above any statement which may be made about the rate at which swelling occurs in the system. The simplest view of the situation is that the conditions which regulate the critical volume and those which regulate the rate of swelling are both functions, as yet undefined, of the reaction which takes place between the lysin and the structural components of the red cell.     

THE MECHANISM OF THE INHIBITION OF HEMOLYSIS

The principal conclusion of this investigation is that the inhibitory effect of plasma or serum on hemolysis by saponin and lysins of the same type is similar in nature to the inhibitory effects of certain sugars and electrolytes, which again are similar to the acceleratory effects produced by indol, benzene, and other substances already studied. All these effects, both inhibitory and acceleratory, are the result of reactions between the inhibitors or accelerators and those components of the red cell membrane which are broken down by lysins. The inhibitory effect of plasma on saponin hemolysis has a number of properties in common with the inhibition produced by sugars and electrolytes and with accelerations in general. (a) The temperature coefficient is small and negative. (b) The extent of the inhibition depends on the type of red cell used in the hemolytic system. (c) The most satisfactory measure of the extent of the inhibition, the constant R, is a function of the concentration of lysin in the system, and (d) R is a linear function of the quantity of inhibitor present. It is also shown that the inhibitory effect of plasma, and serum is not entirely dependent on its protein content. The process underlying the phenomenon of lysis and its acceleration or inhibition seems to be one in which the lysin reacts with a component or components of the cell membrane in such a way as to break down its semipermeability to hemoglobin, and in which the accelerator or inhibitor also reacts with the same component in such a way as to increase or decrease the effectiveness of the lysin in producing breakdown. The membrane is considered as being an ultrastructure made up of small areas or spots of varying degrees of resistance to breakdown, the resistances being distributed according to a negatively skew type of frequency curve, and the process of lysis seems to begin with the least resistant spots breaking down first. These spots may be arranged in some regular spatial pattern, and the membrane has also to be regarded as possessing spots of varying rigidity of form. The accelerator or inhibitor changes the resistance of every reactive spot in the ultrastructure by a factor R, which suggests that acceleration and inhibition are results of some over-all effect, such as that of changing the extent to which lysin is concentrated at the surface or partitioned between the material of the membrane and the surrounding fluid. Some kind of combination between the accelerator or inhibitor and the material of the ultrastructure is presumably involved; at first the combination seems to be a loose one and partly reversible, but later some of the loose links are replaced by more permanent combinations involving the same types of bond as are broken down by the lysins themselves.     

A progressive reaction occurring with a radioactive hemolysin,sodium oleate-I 131

Sodium oleate reacts progressively with human red cells at pH 7. By progressive is meant a reaction which is not adequately described as reversible or irreversible; such reactions cannot be stopped once they are under way, and are probably associated with a more or less stable "internal" lysin phase at the cell surfaces. The uptake of the lysin and the effect of dilution on the uptake can be studied by converting sodium oleate into the radioactive form, sodium oleate-I¹³¹. The uptake is a parabolic function of the lysin initially present in the system, and the effect of a tenfold dilution of systems in which red cells have remained in contact with the lysin for 2 minutes is to reduce the lysin taken up at the cell surfaces twofold. The lysin rapidly forms a relatively stable layer at the cell interfaces, and this layer is little affected by the dilution of the system as a whole.     

THE KINETICS OF IN VIVO HEMOLYTIC SYSTEMS

This paper is concerned with a variety of questions which bear on the occurrence of hemolysis in vivo, and with the possibility of regarding the contents of the blood stream as a hemolytic system in which a steady state is maintained by the production of new red cells to replace those which are destroyed. The material which is dealt with includes the following. 1. Mixtures of Lysins, Accelerators, and Inhibitors.—The effects of individual accelerators and inhibitors in mixtures, like the effects of individual lysins, are roughly additive in simple systems, the acceleration or inhibition produced by the individual substances being most conveniently measured in terms of R-values. 2. Normal Intravascular Lysins.—These probably play only a small part in red cell destruction unless their concentration rises to unusual levels, or unless their effects are enhanced by accelerators, or by the reduction of the concentration of normal inhibitors. The three normal in vivo hemolytic processes for which there is substantial evidence involve (a) the action of the bile salts and of the soaps derived from chyle, (b) the action of the spleen, and (c) the action of hemolytic substances derived from tissues. The recent observations of Maegraith, Findlay, and Martin on the presence of widely distributed tissue lysins are confirmed except for their conclusion that these lysins are species-specific. Species-specific tissue lysins, if present, are not the only lysins derivable from tissues by simple immersion in saline, for non-species-specific lytic substances can also be obtained, and seem to be similar to the "lysolecithin" which some regard as responsible for the action of the spleen on red cell fragility and shape. 3. Plasma Inhibitors.—About 30 per cent of the total inhibitory effect of plasma for saponin hemolysis is due to the contained cholesterol, while 25 per cent at most is due to the plasma proteins, particularly globulins. The remaining 45 per cent is probably accounted for by enhancing effects among the inhibitors; e.g., the enhancing effect of lecithin on the cholesterol inhibition. The mechanism of the inhibition is still incompletely understood; probably reactions between inhibitor and lysin and reactions between inhibitor and components of the red cell surface are both involved, and it is important to observe that the inhibitory effect of plasma or of a plasma constituent may be greater in systems containing one lysin than in systems containing another. No evidence for diffusible inhibitory substances in plasma has been found, and the variations observed in the inhibitory power of human plasma seem to be related to the combined concentrations of cholesterol, protein, and probably lecithin, rather than to the cholesterol content alone. For this reason the inhibitory power tends to be low under conditions of poor nutrition. 4. The Steady State and the Kinetics of Hemolysis In Vivo.—On the assumption that the steady state is the result of a balance between a process which produces red cells and a process which destroys them, equations have been developed for the way in which cells of different resistances are affected when the rate of destruction changes. A method for analyzing experimental curves is described and illustrated. In general, this part of the paper relates the level of the red cell count in the animal to the intensity of the hemolytic processes taking place in vivo, and does not lend itself to detailed abstraction.     

COMPARATIVE KINETICS OF HEMOLYSIS INDUCED BY BACTERIAL AND OTHER HEMOLYSINS

A study has been made of the kinetics of lysis induced by various hemolytic agents. The course of bemolysis was followed by mixing lysin with washed human erythrocytes, removing samples from the mixture, and estimating colorimetrically the hemoglobin in the supernatant fluid of the centrifuged samples. Most of the curves (but not all of them, e.g. tyrocidine) obtained by plotting degree of hemolysis against time, were S-shaped. The initiation of lysis by streptolysin S'' was delayed, and in this property, streptolysin S'' was similar to Cl. septicum hemolysin. None of the other lysins studied exhibited a long latent period preceding lysis. The maximum rate of hemoglobin liberation was found, in the range of lysin concentrations studied, to be a linear function of concentration when theta toxin of Cl. welchii, pneumolysin, tetanolysin, or streptolysin S'' was the lytic agent. With comparable concentrations of saponin, sodium taurocholate, cetyl pyridinium chloride, tyrocidine, duponol C, lecithin-atrox venom mixture, or streptolysin O, the relation between rate and concentration was non-linear. The critical thermal increment associated with hemolysis was determined for systems containing pneumolysin, theta toxin, streptolysin S'', streptolysin O, tetanolysin, and saponin. The findings concerning the effect of concentration and temperature on the rate of hemolysis provide a basis for classifying hemolytic agents (Tables I and II). Hemolysis induced by Cl. septicum hemolysin was found to be preceded by two phases: a phase of alteration of the erythrocytes and a phase involving swelling. Antihemolytic serum inhibited the first but not the second phase while sucrose inhibited the second but not the first phase.     

Separation and assay of lysins and lysin-inhibitor complexes in blood and tissues

1. A process of extraction and assay, which combines the features of several existing methods, is described for the lytic materials which can be obtained from blood, plasma, serum, and tissues. At least two alcohol-soluble substances, one ether-soluble ("soap-like") and the other insoluble in ether in the cold ("lysolecithin-like"), can be obtained from preincubated blood, plasma, or serum. The hemolytic activity (or concentration) of the soap-like lysin obtained from blood is greater than that of the lysolecithin-like substance, but for plasma and serum the reverse is true, i.e. the red cells are involved in the production of the soap-like lysin, and probably supply some of it when acted upon by enzymes contained in plasma and serum. Preincubation of the blood or plasma increases the yield of lysin two- or threefold, and small quantities of both soap-like and lysolecithin-like lysins can be obtained from unpreincubated blood or plasma. 2. The soap-like lysins obtained from preincubated mouse liver are some 5 to 15 times as active as, or occur in some 5 to 15 times the concentration of, those obtained from blood or plasma. The lysolecithin-like lysins of preincubated liver are about twice as active as, or occur in about twice as great concentration of, those obtained from blood. Because of the shape of the time-dilution curve for these lysins, the relations between their activities, or concentrations, are often quite different from those which one would anticipate if one were to consider only the times required for the production of hemolysis. 3. Paper chromatography can be used to separate the soap-like and the lysolecithin-like lysins obtainable from small quantities of preincubated mouse liver homogenates or preincubated mouse blood. The presence of lysins is detected by their effect on the red cells of a suspension as it wets the paper. Various technical procedures for separating lytic components and for demonstrating that they move on the paper along with protein components are described. 4. Paper strip electrophoresis can be used to show that the supernatant fluid of a preincubated mouse liver homogenate contains at least two protein components and at least two lytic components, not very closely associated in their electrophoretic behavior. 5. Observations on the physical nature of the alcohol- and ether-soluble lysin point to its having a soap-like character. Its activity, as well as that of the lysolecithin-like lysin, is inhibited by cholesterol, by lecithin, and by various fractions of serum. Some of these effects have been studied quantitatively. The most inhibitory of the protein fractions are those which contain lipoproteins; i.e., II + III and IV + V.     

Staphylococcal virolysin,a phage-induced lysin; its differentiation from the autolysis of normal cells

Virolysin is a lysin which appears in Staphylococcus aureus K₁ cells infected with phage P₁₄; together with phage, virolysin is released from phage-infected cells at the time of lysis. Autolysin is a lysin formed by uninfected cells of the K₁ strain; autolysin is released from uninfected cells by autolysis. They show the following similarities: Both agents act within the genus Micrococcus. They lyse cells only after the cell has been subjected to a damaging or "sensitizing" treatment, such as heat, bacteriophage, acetone, or ultraviolet irradiation. The course of lysis of heated cells by both lysins has been found to proceed in a similar manner. A constant percentage of cells is lysed, independent of the concentration of lysin; the residual cells remain resistant to either lysin. Lysis proceeds logarithmically with time, and the velocity constants K are proportional to the lysin concentration. K increases with increasing temperature. Both lysins are unaffected by antiserum to the phage. They are inhibited alike by a number of chemicals, including known enzyme inhibitors. Both agents are destroyed by proteolytic enzymes and are precipitated by 40 per cent saturation with (NH₄)₂SO₄. Both lysins are very thermolabile. The two lysins differ with respect to their pH optimum, antigenic relationship and specificity for Micrococcus lysodeikticus. These results suggest that (1) both lysins have many properties associated with enzymes, (2) the lysis of heated cells, which they produce, has some of the characteristics of a chemical reaction, (3) the lysin from the phage-infected cell is clearly different from the lysin of the uninfected cell.     

THE EFFECT OF HEMOLYTIC SUBSTANCES ON WHITE CELL RESPIRATION

Substances such as saponin, the bile salts, etc., which produce lysis of red cells also produce cytolysis of white cells from rabbit peritoneal exudates, the arbitrary criterion of their cytolytic effect being their ability to depress the O₂ consumption of the leucocytes. The amount of cytolysis increases regularly as the amount of the added lysin is increased, and sufficiently large quantities of saponin, sodium taurocholate, sodium glycocholate, or sodium oleate are capable of virtually abolishing the O₂ consumption altogether. At the same time, it can be shown that a lysin such as saponin is used up in combining with the white cells in much the same way as it is used up in combining with red cells, and the reduction in oxygen consumption appears to be roughly proportional to the amount so combined. The action of these lytic substances on white cells, in fact, is very similar to their action on red cells, due allowance being made for the fact that the cytolysis of the white cell is probably not an all-or-none process like hemolysis. White cell respiration is also depressed in hypotonic solutions, the respiration being virtually linear with the tonicity.     

Homology modeling,substrate docking,and molecular simulation studies of mycobacteriophage Che12 lysin A

Mycobacteriophages produce lysins that break down the host cell wall at the end of lytic cycle to release their progenies. The ability to lyse mycobacterial cells makes the lysins significant. Mycobacteriophage Che12 is the first reported temperate phage capable of infecting and lysogenising Mycobacterium tuberculosis. Gp11 of Che12 was found to have Chitinase domain that serves as endolysin (lysin A) for Che12. Structure of gp11 was modeled and evaluated using Ramachandran plot in which 98 % of the residues are in the favored and allowed regions. Che12 lysin A was predicted to act on NAG-NAM-NAG molecules in the peptidoglycan of cell wall. The tautomers of NAG-NAM-NAG molecule were generated and docked with lysin A. The stability and binding affinity of lysin A – NAG-NAM-NAG tautomers were studied using molecular dynamics simulations.     

Vitelline-coat lysin: Comparison of lysins among three species in the genus Tegula

Vitelline-coat lysins from two species of marine mollusc of the genus Tegula, Tegula lischkei and Tegula sp., were purified and their properties compared with those of Tegula pfeifferi. Cross-reaction tests among these three species proved that the lysin action on the vitelline coat was species specific. Each of the lysins from these three species is a single, basic polypeptide with a molecular weight of 16000-17000 and an isoelectric point of pH 10.5. All of them share a common antibody recognition site(s) for the anti-T. pfeifferi lysin antibody. Their amino acid sequences were analyzed using intact lysins and peptides separated by reverse phase high-performance liquid chromatography after V8 proteinase digestion. The amino acid sequences of the N-terminus (Nos 1-66) from the three species showed 98% homology, and those of the C-terminus (Nos 91-118) showed 89% homology. It was concluded that the species specificity of the vitelline coat lysin appears to be determined by a sequence of 24 residues (Nos 67-90) in the middle region of the molecule.     

Enhancement of the direct antimicrobial activity of Lysep3 against <Emphasis Type="Italic">Escherichia coli</Emphasis> by inserting cationic peptides into its C terminus

Phage lysins are considered promising antimicrobials against resistant bacterial infections. Some lysins have been reported for the prevention and treatment of Gram-positive bacterial infection. Gram-negative bacterial phage lysins, however, can only destroy the bacterial cell wall from inside because of the obstruction of the bacterial outer membrane that prevents direct hydrolysis of the bacterial wall peptidoglycan from the outside, severely restricting the development of lysins against Gram-negative bacteria. In this study, genetic engineering techniques were used to fuse a 5 cationic amino acid polypeptide (KRKRK), a 10 cationic amino acid polypeptide (KRKRKRKRKR), a 15 cationic amino acid polypeptide (KRKRKRKRKRKRKRK), and a polypeptide including both cationic and hydrophobic amino acids (KRKRKFFVAIIP) to the C-terminus of the Escherichia coli phage lysin Lysep3 to obtain four fusion lysins (5aa, 10aa, 15aa, Mix). The bactericidal effects of those four lysins on E. coli were then compared in vitro. Our results showed that the fusion of hydrophobic and positively charged amino acids, Mix, can kill E. coli effectively; the fusion of positively charged amino acids alone at the C-terminus (5aa, 10aa, 15aa) also showed bactericidal activity against E. coli from the outside, with the bactericidal activity gradually increasing with the positive charge at the C-terminus of the lysin. Collectively, improving the positive charge at the C-terminus of E. coli bacteriophage lysin Lysep3 increases its bactericidal ability from outside E. coli, providing a new practical method for the development of anti-Gram-negative bacterial lysins.     

Effects of simple haemolysins in hypotonic systems

Summary Except for a small inhibition which is due to decreased electrolyte content, the lytic effect of simple lysins such as saponin and the bile salts are the same for cells in hypotonic systems as they are for cells in isotonic systems. Similarly the resistance to hypotonic solutions of cells which have been exposed to sub-lytic quantities of a variety of lysins is not less than that of untreated cells; in fact, it is often somewhat greater.The lytic effects of hypotonie solutions and of the simple lysins are accordingly non-additive, and the implications of this observation are discussed.     

PROLYTIC ION EXCHANGES PRODUCED IN HUMAN RED CELLS BY METHANOL,ETHANOL, GUAIACOL,AND RESORCINOL

When the washed red cells of heparinized human blood are exposed at 4°C. to methanol, ethanol, guaiacol, or resorcinol in hypolytic concentrations in isotonic NaCl, the prolytic loss of K at the end of 20 hours varies from about 25 per cent of the initial K content of the cells in the case of 3.1 M methanol to about 55 per cent of the initial K in the case of 0.04 M resorcinol. As in the case of the prolytic losses observed with other lysins, the K loss is rapid at first and then slows down so that what appears to be a new steady state is reached logarithmically. The K lost from the cells during the period of the prolytic loss is replaced by an approximately equivalent amount of Na, derived from the isotonic NaCl in which the cells are suspended. The Na which enters can be replaced by K by washing the cells in isotonic KCl, and this K can again be replaced by Na by washing the cells in isotonic NaCl. The remainder of the cell K., i.e. the K which was not lost during the period of the prolytic loss, is retained in the cell unaffected by these washing procedures. The capacity of red cells for undergoing disk-sphere transformations is scarcely affected by their having been exposed to hypolytic concentrations of methanol, ethanol, guaiacol, or resorcinol in isotonic NaCl, and their resistance to osmotic hemolysis and to lysis by saponin and digitonin is altered only in minor respects even when as much as 50 per cent of the cell K has been exchanged for Na. Some restriction to the movement of K between the cell and its environment is apparently modified irreversibly when the cell is exposed to hypolytic concentrations of lysins, and the modification is such that only a fraction of the cell K is affected, the fraction being a function of the lysin concentration, the duration of its action, and other factors. A modification of some part of the cell structure and of the properties dependent on its integrity is probably involved: K may be lost more readily from some cells than from others, from some parts of the cell more readily than from other parts, or the explanation may lie in changes in the extent to which Hb binds ions or in modifications of metabolic processes.     

Construction of a chimeric lysin Ply187N-V12C with extended lytic activity against staphylococci and streptococci

Developing chimeric lysins with a wide lytic spectrum would be important for treating some infections caused by multiple pathogenic bacteria. In the present work, a novel chimeric lysin (Ply187N-V12C) was constructed by fusing the catalytic domain (Ply187N) of the bacteriophage lysin Ply187 with the cell binding domain (146-314aa, V12C) of the lysin PlyV12. The results showed that the chimeric lysin Ply187N-V12C had not only lytic activity similar to Ply187N against staphylococcal strains but also extended its lytic activity to streptococci and enterococci, such as Streptococcus dysgalactiae, Streptococcus agalactiae, Streptococcus pyogenes, Enterococcus faecium and Enterococcus faecalis, which Ply187N could not lyse. Our work demonstrated that generating novel chimeric lysins with an extended lytic spectrum was feasible through fusing a catalytic domain with a cell-binding domain from lysins with lytic spectra across multiple genera.     

Bacteriophage lytic enzymes: novel anti-infectives

Bacteriophage lytic enzymes, or lysins, are highly evolved molecules produced by bacterial viruses (bacteriophage) to digest the bacterial cell wall for bacteriophage progeny release. Small quantities of purified recombinant lysin added to gram-positive bacteria causes immediate lysis resulting in log-fold death of the target bacterium. Lysins have now been used successfully in animal models to control pathogenic antibiotic resistant bacteria found on mucosal surfaces and in blood. The advantages over antibiotics are their specificity for the pathogen without disturbing the normal flora, the low chance of bacterial resistance to lysins and their ability to kill colonizing pathogens on mucosal surfaces, capabilities that were previously unavailable. Thus, lysins could be an effective anti-infective in an age of mounting antibiotic resistance.