Genetic analysis fo the mycobacillin biosynthetic pathway in Bacillus subtilis B3

Twelve mycobacillin-negative (My-) mutants of Bacillus subtilis B3 were isolated from an auxotrophically tagged mycobacillin producer organism. In whole-cell fermentations of some of these My- mutants a penta- and a nonapeptide accumulated; these peptides were also obtained in a cell-free system in which a new tripeptide was also detected. The amino acid composition, N- and C-terminal residues and amino acid sequence of these peptides agreed with those of equivalent segments of the mycobacillin molecule. The mycobacillin-synthesizing enzyme can be divided into three fractions that catalyse different steps in biosynthesis, and the defective enzyme fractions in the various mutant strains were identified by reconstitution experiments in vitro. The defects were further pin-pointed in mutant enzyme fractions by an ATP in equilibrium Pi exchange reaction and also by cell-free synthesis involving the use of membrane-bound enzyme. The defects so identified indicated the formation of tri-, penta- and nonapeptides as intermediates in the mycobacillin biosynthetic pathway.

Physico-chemical interaction of mycobacillin with Aspergillus niger protoplast membrane, the site of its action

Mycobacillin partially quenched the strong fluorescence when 1-anilino naphthalene 8-sulfonate (ANS) was added to protoplast or plasma membrane but is without any effect on weak fluorescence when added to cell-free extract. There are two classes of ANS binding sites on protoplast or plasma membrane of which one class is sensitive to mycobacillin, being competitively abolished by it. Mycobacillin also non-competitively inhibits the binding of pyrene, a lipid specific probe. Thus it follows from the inhibition by mycobacillin of ANS or pyrene binding to protoplast or plasma membrane that the site of action of the antibiotic is located in the plasma membrane. Interaction between mycobacillin and the plasma membrane is physico-chemical in nature.

Mutual and self-sensitivity among antibiotically active mutant derivatives from the inactive degenerate Aspergillus versicolor N5

Antibiotically active producer mutants derived from the spontaneous degenerate parent Aspergillus versicolor N5 possessed not only mutual but also self-sensitive activity. The producer mutants, like the inactive parent, were only 3.5-fold less sensitive than the most sensitive unrelated organism, Trichophyton rubrum. The germination of spores is generally more sensitive than growth of vegetative cells. The antifungal spectrum of these mutual and self-sensitive mutants was fairly wide, unlike the host range specificity of bacteriocinogenic strains acting on organisms closely related to the producers. The self and mutual growth inhibitory principle was finally identified as the antibiotics mycoversilin and versilin in the case of producer mutants (N5)17 and N5T10(7), respectively, or Vx, an antibiotic of unknown molecular species, in the case of another producer mutant N5T10(8). Thus self-sensitivity, instead of self-resistance, of these antibiotically active mutant derivatives is a unique property among filamentous fungi in having simultaneously expressed two loci of contradictory functions, one for synthesis of, and the other for sensitivity towards, the same or related antibiotics.

Structure and stability of gamma-crystallins. II. Differences in microenvironments and spatial arrangements of cysteine residues

The gamma-crystallin fractions II, III and IV from calf eye lens were treated with the thiol-specific fluorescent probe 2-(4'-maleimidylanilino)naphthalene-6-sulfonate (MIANS), in order to determine the reactivity of the seven (gamma-II) or six (gamma-III, gamma-IV) cysteine residues. Two classes of reactive cysteines were distinguished by variations in fluorescence intensity with increasing molar excess of the probe, and approximately three cysteines were nonreactive in each gamma-crystallin. From the position of the emission maximum, it is apparent that MIANS-labeled cysteines of gamma-IV are in the least hydrophobic environment. Fluorescence energy transfer was observed from tryptophan to MIANS-labeled cysteines in both gamma-II and gamma-III crystallins, with efficiencies of 86% and 89%, respectively, but not in gamma-IV crystallin. We suggest that the spatial arrangements and microenvironments of cysteine residues of gamma-crystallins are sufficiently different from each other to account for the variations in fluorescence characteristics of the MIANS-labeled proteins and the lack of energy transfer in gamma-IV crystallins.

Role of selective pressure by screening organisms in the development of producer mutant isolates of different antibiotic markers

The phenotypes of producer mutant isolates when obtained after mutagenesis of the spontaneous degenerate Aspergillus versicolor N5 by screening on Trichophyton rubrum and those on A. niger G3Br were found to be markedly different. In respect of phenotypic character anti-T. rubrum producer mutant isolates resembled the parental type more closely (which is specifically active against T. rubrum and generally against dermatophytes) than anti-A. niger mutant isolates. This clearly indicates not only the role of selective pressure of the screening organism in the development of a given producer mutant isolate but also shows the possibility of recovery of a producer type of the lost antibiotic marker.

Role of ATP and enzyme-bound nascent peptides in the control of elongation for mycobacillin synthesis

The enzyme fraction A, a constituent of the three-fraction (A, B and C) enzyme complex mycobacillin synthetase, elongated tri- and tetra-peptides, under enzyme-bound conditions, to tetra- and penta-peptides respectively in the presence of the 'next' amino acid (in the mycobacillin sequence). The enzyme fraction B synthesized hexapeptide from free pentapeptide and the next amino acid, but synthesized heptapeptide from hexapeptide only under enzyme-bound conditions in the presence of the next amino acid. Similarly, the enzyme fraction C synthesized decapeptide from free nonapeptide in the presence of the next amino acid, but undecapeptide only from enzyme-bound decapeptide in the presence of the next amino acid during the elongation process. The Km values for the initiating reactions for each of the three enzyme fractions were 6-7-fold lower than those for the succeeding reactions catalysed by each of the enzyme fractions. The specificity of the initiation and elongation is discussed in the light of these findings.

Selective action of mycobacillin on the uptake of releasable cell materials by Aspergillus niger

The uptake of normally releasable (i.e. releasable in the absence of the antibiotic) cell constituents (namely lysine, proline, ATP, Pi, Na+, K+ and Ca2+) by sensitive cells of Aspergillus niger that occurs in the absence of mycobacillin is gradually enhanced with increase in concentration of the antibiotic until the uptake attains the maximum. With still higher concentrations the uptake decreases until it becomes the same as in the control without mycobacillin. Uptake follows saturation kinetics both in the absence and in the presence of the antibiotic. Mycobacillin significantly increases Vmax. for uptake with any effect on Km, Mycobacillin has no action on the uptake of non-releasable materials.

Enhancement of adherence and growth of Chlamydia trachomatis by estrogen treatment of HeLa cells

Treatment of HeLa 229 cultures with 17-beta-estradiol or with diethylstilbestrol, a synthetic estrogen analog, prior to infection with Chlamydia trachomatis UW31 (serovar K) or LGV440 (serovar L1) led to a 50 to 60% enhancement of chlamydial inclusion formation. After infection, the presence of estrogen was required for the enhancement. The optimal concentration of estrogen required was 10(-10) M. At least 18 h of preinfection treatment plus 12 h of postinfection treatment was necessary. The adherence of purified radioactive elementary bodies of C. trachomatis to estrogen-treated HeLa cells was stimulated in an estrogen dose- and exposure-dependent manner. The requirements for both pre- and postinfection exposure to the hormone suggest that alterations in the cell membrane as well as in the metabolic capacity of the host cells is required for intracellular chlamydial development. Cycloheximide did not prevent estrogen enhancement of chlamydial adherence or subsequent intracellular development of inclusions.

Relationship between sporulation and synthesis of mycobacillin and dipicolinic acid under condition of catabolite repression in Bacillus subtilis

Sporulation was repressed in the parent strain by various carbon sources whereas glucose-resistant mutants were resistant to them but not to glycerol 2-phosphate. Both mycobacillin and dipicolinic acid synthesis were repressed in the parent by some of the compounds tested, viz. glucose, pyruvate and glycerol 2-phosphate. However, these syntheses in the glucose-resistant mutants were not repressed by glucose and pyruvate but were repressed by glycerol 2-phosphate. The possible interrelationship between sporulation, dipicolinic acid and mycobacillin synthesis is discussed in light of these findings.

Host modification of the adherence properties of Chlamydia trachomatis

The adherence of Chlamydia trachomatis LGV440(L1) to human HeLa 229 and mouse McCoy cells was stimulated by the lectin wheat germ agglutinin (WGA) and inhibited by the sugars N-acetyl-D-glucosamine, N-acetyl-D-galactosamine and chitobiose, but only when the chlamydiae had been passaged several times in HeLa cells. After passage in McCoy cells, the lectin and the sugars elicited little response. The non-LGV serovar UW-31(K), however, differed from LGV440(L1) in that, regardless of passage, the lectin and sugar effects were observed only in HeLa cells. Affinity chromatography on WGA-agarose confirmed that HeLa-grown LGV440(L1) bound to a significantly greater extent relative to McCoy-grown chlamydiae. In addition, participation of heterogeneous chlamydial ligands was suggested by the observation that the adherence of heated (60 degrees C, 5 min) UW-31(K) to HeLa cells at 37 degrees C was not inhibited at all, but at 5 degrees C, the adherence rate was greatly reduced, indicating the participation of heat-stable as well as heat-labile ligands. These data are interpreted to indicate that the passage history of C. trachomatis results in the acquisition of altered surface components that participate in the initial interaction of the bacterium with the host.

Characterization of three-fraction mycobacillin synthetase

Mycobacillin synthetase lacks aspartic acid racemase, alanine racemase and glutamic acid racemase activities. The enzyme also does not respond to ATP-[32P]Pi exchange, nor does it catalyse the antibiotic synthesis in presence of amino acids of configuration opposite to that present in the molecule. Preincubation with optical isomers of opposite configuration inhibited the ATP-[32P]Pi exchange reaction to the extent of 60-90%. None of the three fractions of mycobacillin synthetase contained a pantothenic acid arm. Two molecules of ATP are required to synthesize one peptide bond of mycobacillin. Intermediate peptides of mycobacillin are not covalently linked to the three-fraction mycobacillin synthetase.

Purification of the constituent enzyme fractions of mycobacillin synthetase

The final purification of the three-fraction enzyme complex mycobacillin synthetase was done by hydroxyapatite column chromatography and sucrose-density-gradient centrifugation; each of the fractions obtained migrates as a single component in SDS/polyacrylamide-gel electrophoresis and gel electrofocusing. The Mr of the enzyme fractions A, B and C by gel filtration is 260 000, 190 000 and 105 000, and that by SDS/polyacrylamide-gel electrophoresis is 252 000, 198 000 and 108 000 respectively. None of the enzyme fractions appears to possess subunit structure.

Selective action of mycobacillin on the cellular permeability of Aspergillus niger

Cells of Aspergillus niger normally release not all but of some specific cell constituents viz., lysine, proline, ATP, Pi, Na+, K+ and Ca2+ in the absence of mycobacillin. Mycobacillin enhances the release of these materials without causing lysis. The time and concentration of mycobacillin for optimum release depends on the nature of the materials involved.

Structure and stability of gamma-crystallins. I. Spectroscopic evaluation of secondary and tertiary structure in solution

The three major bovine gamma-crystallin fractions (gamma-II, gamma-III and gamma-IV) are known to have closely related (80-90%) amino acid sequences and three-dimensional folding of the polypeptide backbone. Their chiroptical and emission properties, as measured by circular dichroism (CD) and fluorescence, are now shown to differ distinctly. The far-ultraviolet CD spectra indicate that all three gamma-crystallins have predominantly beta-sheet conformation (45-60%) with only subtle differences in secondary structure. The fluorescence emission maxima of gamma-II, gamma-III and gamma-IV, due to the four tryptophan residues, appear at 324, 329 and 334 nm, respectively, suggesting that tryptophan residues are buried in environments of decreasing hydrophobicity. Corresponding differences in quantum yield may be due to fluorescence quenching by neighboring sulfur-containing residues. Titratable tyrosines are maximal for gamma-III, as manifested from difference absorption spectra at alkaline pH. The near-ultraviolet CD spectra differ in position, magnitude and sign of tryptophan and tyrosine transitions. In addition, a characteristic CD maximum at 235 nm, presumably due to tyrosine-tyrosine exciton interactions, differs in magnitude for each gamma-crystallin. This study shows that the environment and interactions of the aromatic residues of the individual gamma-crystallin fractions are quite different. These variations in tertiary structure may be significant, in terms of stability of gamma-crystallins towards aggregation and denaturation, for understanding lens transparency and cataract formation in general.

Effect of allopurinol on neutrophil superoxide production, chemotaxis, or degranulation

Recent studies examining the effect of allopurinol on bacterial killing by leukocytes [Tubaro et al., Biochem. Pharmac. 29, 3018 (1980); Tritsch and Neiswander, Life Sci. 32, 1359 (1983)] have been interpreted by those authors as proof that xanthine oxidase is the major superoxide producing enzyme in activated leukocytes. To test the assertion that xanthine oxidase is involved in the production of superoxide by activated human neutrophils, the xanthine oxidase content of neutrophils was measured, and the effect of allopurinol on neutrophil functions, including superoxide production, was studied. Neutrophils were found to contain a level of xanthine oxidase insufficient to account for the flux of superoxide associated with neutrophil activation. Allopurinol did not inhibit superoxide production induced by opsonized zymosan, phorbol myristic acetate, or formylmethionylleucylphenylalanine. Furthermore, neither chemotaxis nor degranulation was affected by allopurinol. Allopurinol was also found ineffective in blocking superoxide-mediated carrageenan-induced foot edema in the rat. These studies are interpreted as evidence that xanthine oxidase is not a major superoxide-generating system in activated neutrophils as has been suggested by others.

Derepression of sporulation and synthesis of mycobacillin and dipicolinic acid by guanosine 3':5'-cyclic monophosphate under conditions of glucose repression in Bacillus subtilis

Dibutyryl cyclic GMP, but not dibutyryl cyclic AMP, derepresses sporulation and synthesis of mycobacillin and dipicolinic acid under conditions of glucose repression in Bacillus subtilis strain B34. Neither of these compounds appears to affect sporulation and synthesis of mycobacillin and dipicolinic acid in this strain under normal physiological conditions. Mutants insensitive to glucose repression were indifferent to the addition of either of the nucleotides both in the presence and in the absence of glucose. A role for dibutyryl cyclic GMP in annulling the repressing effect of glucose on sporulation and on synthesis of mycobacillin and dipicolinic acid is thus indicated.

Functional characterization of constituent enzyme fractions of mycobacillin synthetase

The enzyme fraction A, a constituent enzyme of the three-fraction enzyme mycobacillin synthetase, independently and sequentially activated five amino acids starting from L-proline, producing the pentapeptide Pro(Asp1,Glu1,Tyr1)Asp. The fractions B and C were unable to function independently. However, the fraction B synthesized the nonapeptide Pro(Asp3,Glu1,Tyr2,Ser1)Leu, sequentially activating the pentapeptide and next four amino acids, whereas the fraction C synthesized mycobacillin by the sequential activation of the nonapeptide and the remaining four amino acids. The pH optima of the above enzymes are almost identical (pH 7.8), but their Km values are a little different.

Sensitized photo-oxidation of bovine alpha-crystallin: change in microenvironments of thiol groups

Methylene blue- or riboflavin-sensitized photo-oxidation of alpha-crystallin caused a major change in the environment of thiol groups of the protein which could not be significantly prevented by inhibitors specific for active species of oxygen, 1O2, .OH, O.2, and H2O2. In contrast, the sensitizer N-formylkynurenine had no such effect. Sensitizer-induced change in the microenvironments of thiol groups was attributed to a conformational alteration, probably an unfolding of the protein.

Age-related changes in protein conformation in bovine lens crystallins

In order to investigate the conformational changes associated with the aging process, circular dichroism (CD), absorption and fluorescence measurements of bovine lens crystallins isolated from the nucleus of old (cow) and young (calf) animals are reported. Results show considerable differences in spectroscopic parameters between the young and old alpha-crystallin; however, no such changes were observed for beta- and gamma-crystallins. Age-related changes include an increased absorption in near-u.v. and decreased intensity in the far-u.v. region; near-u.v. circular dichroism shows a considerable difference, whereas the dichroism in far-u.v. remains the same. The decrease in tryptophan fluorescence of old alpha-crystallin is of the same magnitude as is the increase in non-tryptophan fluorescence. The fluorescence of the sulfhydryl (SH) specific probe, 2-(4'-maleimidylanilino) naphthalene-6-sulfonate, indicates that accessible (to the probe) SH groups of cow alpha-crystallin are fewer than those of calf, and they are also in a more polar environment. This study demonstrates that, with aging, alpha-crystallin undergoes a change in the tertiary structure involving tryptophan, tyrosine and cysteine residues. This conformational change has been explained by the suggestion that a large portion of the protein unfolds during the aging process, resulting in a change in interaction properties between the aromatic amino acid residues and between the residues and the peptide backbone. The unfolding is also associated with the accessibility, reactivity and spatial arrangement of these residues, including the cysteine by which aggregation or cross-linking of the protein is likely to occur.

Translocation of mycobacillin synthetase in Bacillus subtilis

The extracellular release of mycobacillin from Bacillus subtilis first occurred in the medium at the onset of stationary phase and continued at a high rate even after 6 days. Mycobacillin synthetase activity appeared earlier than late-exponential phase in the cytosol of producer cells and was not sedimentable even at 105 000 g. The activity then quickly reached the maximum late in the stationary phase. With further increase in the age of the culture, the activity gradually disappeared from the cytosol, to reappear concomitantly in the membrane in an insoluble particulate form, even in absence of protein synthesis. The membrane-bound synthetase activity was sedimentable at 10 000 g and was fairly active even after 5 days.

Accumulation of peptides by mycobacillin-negative mutants of Bacillus subtilis B3

Thirteen mycobacillin-negative (My-) mutants of Bacillus subtilis B3 were isolated from an auxotrophically tagged mycobacillin producer organism. The wild-type producer, three feeble producers and three strictly My- mutants did not accumulate any ninhydrin-positive peptide in the culture medium while the remaining seven My- mutants did accumulate ten such peptides whose amino acid composition indicated that there might be only three different peptides. The N-terminal and C-terminal amino acid residues implicated one of these peptides as a pentapeptide intermediate in mycobacillin synthesis; this was further confirmed by its molecular weight and sequence. Studies on cell-free synthesis showed that only the enzyme system from the wild-type strain synthesized mycobacillin while the defective ones from all the My- mutants synthesized one and the same pentapeptide as found in the culture broth of some of the mutants. Further studies in which the enzymes responsible for mycobacillin synthesis by cell-free extracts were separated into three fractions, A, B and C, showed that seven of the mutants were defective in fraction B whereas the three other mutants had defects in both fractions B and C. Thus the pentapeptide Pro----Asp----Glu----Tyr----Asp appears to be implicated in mycobacillin biosynthesis.

Mycoversilin, a new antifungal antibiotic. III. Mechanism of action on a filamentous fungus Trichophyton rubrum

Mycoversilin is active against filamentous fungi, being specifically inhibitory to Trichophyton rubrum, minimum inhibitory concentration being 15 micrograms/ml. Mycoversilin inhibits sporulation to the extent of 28.5% even at the growth inhibitory concentration whereas inhibition of spore germination requires higher concentration. It has no effect on radial growth. Further it shows no action either on the release of UV absorbing materials or on the respiration of T. rubrum. However, the antibiotic inhibits in vivo synthesis of protein fairly strongly, DNA moderately and RNA slightly at the minimum inhibitory concentration. Cell-free protein synthesis is also strongly inhibited, the site of action being the inhibition of leucyl-tRNA formation by the antibiotic which has no action on leucine activation.

Standardization of parameters for the mycobacillin synthetase activity

An effective method of preparation involving sonication was developed for cell-free mycobacillin synthetase from Bacillus subtilis. The enzyme showed optimum activity at a buffer concentration of 50 mM (Tris-HCl) and pH 7.5. ATP and Mg2+ which were essential for synthesis showed an optimum requirement at a ratio of 1:1. The synthetase was markedly inhibited by ADP whereas AMP was without any effect. ATP or ATP-generating system could not be replaced by GTP, UTP or CTP. Co2+ and Mn2+ could to some extent substitute Mg2+. Mercapto reagents inhibited the antibiotic synthesis. Exogenous addition of pantothenic acid had no effect.

Mycoversilin, a new antifungal antibiotic. II. Structure elucidation

The structure of a new antifungal antibiotic, mycoversilin, produced by Aspergillus versicolor (N5)17 was determined as I by various spectroscopic and chemical methods. Mycoversilin is a unique polynuclear aromatic compound having two methyl and six hydroxyl groups and two ether linkages. The acetyl derivative prepared was found to have no antifungal property.

Mycoversilin, a new antifungal antibiotic. I. Fermentation, isolation and biological properties

A new antifungal antibiotic, mycoversilin, was isolated from the culture filtrate of Aspergillus versicolor (N5)17 by repeated column chromatography and recrystallized from ethyl acetate as homogeneous fine needles. Maximum production took place in a medium containing 4% glucose and 1% peptone at pH 3.5, temperature 28 degrees C after 8-9 days of incubation under stationary condition. Mycoversilin is a narrow spectrum antibiotic with activity against filamentous fungi, particularly Trichophyton rubrum (MIC 15 micrograms/ml).

Fractionation of the mycobacillin-synthesizing enzyme system

The mycobacillin-synthesizing enzyme system was highly purified by fractionation at 30-55% (NH4)2SO4 saturation. The enzyme concentrate on Sephadex G-200 gel chromatography was resolved into three distinct fragments. Each of the fragments on further purification by DEAE-cellulose ion-exchange chromatography behaved as a single-component system, as clearly indicated by the sharpness of the peaks in the elution diagram. None of the fragments alone nor any two of them in all possible combinations possessed mycobacillin-synthesizing activity, which was restored only when the three fragments were used together in the test system.

Influence of lectins, hexoses, and neuraminidase on the association of purified elementary bodies of Chlamydia trachomatis UW-31 with HeLa cells

Using highly purified elementary bodies of Chlamydia trachomatis UW-31 (serotype K), we found that HeLa 229 monolayer cultures bound more 32P-labeled chlamydiae after pretreatment with the lectin wheat germ agglutinin. The lectin, on the other hand, inhibited competitively when chlamydial association was assayed in the presence of polycations. The two effects of wheat germ agglutinin were abolished when N-acetylneuraminic acid (NeuNAc)- or N-acetylglucosamine (GlcNAc)-preincubated wheat germ agglutinin was used. Brief exposure of HeLa cells to neuraminidase abolished the ability to bind the elementary bodies, whether or not polycations were present. Furthermore, at 5 degrees C but not at 37 degrees C, NeuNAc, GlcNAc and N-acetylgalactosamine inhibited chlamydial association only in the absence of the polycation DEAE-dextran. The results suggest that NeuNAc residues on the plasma membrane are the principal, but not the only, receptors for this strain of C. trachomatis.

Purification of Chlamydia trachomatis lymphogranuloma venereum elementary bodies and their interaction with HeLa cells

A procedure has been developed to yield infectious elementary bodies of the lymphogranuloma venereum strains LGV 434 and 404 of Chlamydia trachomatis, labelled during intracellular growth in HeLa 229 cells. The final preparation, obtained after velocity sedimentation of a polycarbonate membrane-filtered sample through a sucrose gradient, is free of host proteins and, more importantly, of chlamydial reticulate bodies. Using such purified preparations, it was found that the association of LGV 434 elementary bodies with HeLa 229 cultures was unaffected by the pretreatment of the host cells with a variety of lectins or with neuraminidases from Clostridium perfringens and Vibrio cholerae. The association was inhibited by dextran sulphate and by mild trypsin treatment of HeLa cultures. Treatment of purified elementary bodies with trypsin, chymotrypsin, neuraminidases and a variety of carbohydrates and lectins did not produce any change in the rate of association with HeLa cultures. Heat-inactivated elementary bodies were significantly less able to associate with the host cells.

Modulation of bacterial association to HeLa cell cultures by cell density and by chlamydial infection

The effect of cell density on the rate of association of Escherichia coli and Staphylococcus aureus by monolayer cultures of HeLa 229 cells was investigated. Radioactively labeled bacteria were incubated with sparsely and densely plated cells. The rate of bacterial uptake was 10- to 20-fold higher in sparse cultures. Kinetic analysis of data with different multiplicities of input bacteria showed that the Km of the reaction was unaltered, whereas the Vmax was inversely related to cell density. Pretreatment of HeLa cultures with dibutyryl adenosine 3',5'-phosphate had little effect on the rate of bacterial association. The simultaneous presence of an obligately parasitic bacterium, Chlamydia trachomatis LGV434, enhanced the Vmax of association of E. coli and S. aureus. This effect was more pronounced in dense HeLa cell cultures. Heat-inactivated chlamydiae were unable to modify the association. Enhanced association persisted for at least 3 h after infection with chlamydiae.

Exoprotease production by sporogenous and asporogenous mycobacillin non-producer mutants of Bacillus subtilis

Mycobacillin non-producers, whether sporogenous or asporogenous, possess less exoprotease, but effective exoprotease producers are not always good mycobacillin yielders. There might exist a minimum level of exoprotease formation for elaboration of mycobacillin.

Glycolytic enzyme activities in malignant cells grown in vitro and in vivo

Cell proximity has a profound effect on the glycolytic enzyme levels observed in mammalian cells grown in vitro. Hexokinase activity generally increased with the increasing cell density of both untransformed and virus-transformed cultures. In contrast, phosphofructokinase and pyruvate kinase activities were generally elevated only in crowded cultures of transformed cells. A spontaneous experimental mouse tumor cell line (EMT6) exhibited cell crowding-dependent elevations in glycolytic enzyme levels when cultured in vitro. The glycolytic enzyme levels of experimental mouse tumors grown in vivo, on the other hand, were constant and normally less than those observed in cultured EMT6 cells.

Deoxyribonucleic acid synthesis, cell cycle progression, and division of Chlamydia-infected HeLa 229 cells

The fate of lymphogranuloma venereum strain Chlamydia-infected HeLa 229 cells was examined by determining the rate of deoxyribonucleic acid synthesis and the kinetics of entry into and progression through S phase and by time-lapse cinemicrography. At an input multiplicity of 5 or less, Chlamydia-infected cells showed no inhibition of host deoxyribonucleic acid synthesis or cell cycle progression. Cinemicrography showed division of inclusion-containing cells, with one or both daughters receiving chlamydial inclusions. Analysis of the family trees indicated that the generation times of infected HeLa 229 were not altered relative to those of the uninfected cells.