Antimicrobial activity of extracts from macroalgae Ulva lactuca against clinically important Staphylococci is impacted by lunar phase of macroalgae harvest

Staphylococcus aureus is a common human bacterial pathogen that causes skin and soft tissue infections. Methicillin-resistant Staph. aureus (MRSA) are increasingly drug-resistant, and thus there is great need for new therapeutics to treat Staph. aureus infections. Attention has focused on potential utility of natural products, such as extracts of marine macroalgae, as a source of novel antimicrobial compounds. The green macroalgae Ulva lactuca produces compounds inhibitory to human pathogens, although the effectiveness of U. lactuca extracts against clinically relevant strains of Staph. aureus is poorly understood. In addition, macroalgae produce secondary metabolites that may be influenced by exogenous factors including lunar phase, but whether lunar phase affects U. lactuca antimicrobial capacity is unknown. We sought to evaluate the antibacterial properties of U. lactuca extracts against medically important Staphylococci, and to determine the effect of lunar phase on antimicrobial activity. We report that U. lactuca methanolic extracts inhibit a range of Staphylococci, and that lunar phase of macrolagae harvest significantly impacts antimicrobial activity, suggesting that antimicrobial properties can be maximized by manipulating time of algal harvest. These findings provide useful parameters for future studies aimed at isolating and characterizing U. lactuca anti-Staphylococcal agents.

SIGNIFICANCE AND IMPACT OF THE STUDY

The growing prevalence of antibiotic-resistant human pathogens such as methicillin-resistant Staphylococcus aureus (MRSA) has intensified efforts towards discovery and development of novel therapeutics. Marine macroalgae like Ulva lactuca are increasingly recognized as potential sources of antimicrobials, but the efficacy of U. lactuca extracts against common, virulent strains of Staph. aureus is poorly understood. We demonstrate that U. lactuca methanolic extracts inhibit a variety of clinically relevant Staphylococcus strains, and that the antimicrobial activity can be maximized by optimizing time of algal harvest. These findings provide potentially useful parameters for future work of isolating and identifying novel antimicrobial agents from macroalgae.

A prospective phase III, randomized, double-blind, placebo-controlled study of brodalumab in patients with moderate-to-severe plaque psoriasis

BACKGROUND

The interleukin-17 cytokine family plays a central role in psoriasis pathogenesis.

OBJECTIVES

To evaluate the efficacy and safety of brodalumab, a human anti-interleukin-17 receptor antibody, in treating patients with moderate-to-severe plaque psoriasis.

METHODS

In this phase III, double-blind, placebo-controlled study (NCT01708590; AMAGINE-1), adult patients in the U.S.A., Canada and Europe were randomized to brodalumab (140 or 210 mg) or placebo every 2 weeks (Q2W), with an additional dose at week 1, for a 12-week induction phase. At week 12, patients receiving brodalumab who achieved static Physician's Global Assessment 0 or 1 (sPGA success) were rerandomized to the placebo or induction dose. After week 16, patients with sPGA ≥ 3 were re-treated with the induction dose. After ≥ 12 weeks of retreatment, patients with sPGA 2 for ≥ 4 weeks or sPGA ≥ 3 were rescued with brodalumab 210 mg Q2W. At week 12, patients randomized to brodalumab with sPGA ≥ 2 or placebo received brodalumab 210 mg Q2W. Coprimary end points were the percentage of patients with ≥ 75% improvement in Psoriasis Area and Severity Index score (PASI 75) and sPGA success at week 12.

RESULTS

There were 661 patients randomized: 220 placebo, 219 brodalumab 140 mg and 222 brodalumab 210 mg. At week 12, 60% (140 mg) and 83% (210 mg) vs. 3% (placebo) achieved PASI 75, and 54% (140 mg) and 76% (210 mg) vs. 1% (placebo) achieved sPGA success. The safety profile was considered acceptable.

CONCLUSIONS

Brodalumab therapy resulted in significant clinical benefit and an acceptable safety profile in patients with moderate-to-severe plaque psoriasis.

Changes in serum free testosterone, sleep patterns, and 5-alpha-reductase type I activity influence changes in sebum excretion in female subjects

BACKGROUND/PURPOSE

Sebum is thought to play an important role in acne vulgaris and sebum excretion rate (SER) is often used as a marker of efficacy in acne studies. This study explored factors that could induce intra-subject variability in SER.

METHODS

SER was measured twice, 7 days apart, on the forehead of 40 healthy subjects. At each visit, the following parameters were also evaluated: serum androgen levels, 5-alpha-reductase type I gene expression, forehead temperature, sleep habits, diet, facial washing routine, and UV exposure.

RESULTS

There was a positive correlation between the time subjects fell asleep on Day 0 and the change in SER for the left (P = 0.010; R = 0.402) and right sides (P = 0.002; R = 0.467) of the forehead. There was a significant inverse correlation between SER and 5-alpha-reductase type 1 expression and between free testosterone levels and 5-alpha-reductase type 1 expression. In sub-analyses performed on men and women, these correlations were only significant for women.

CONCLUSION

Variations in sleep patterns, free testosterone, and 5-alpha-reductase type 1 activity are associated with changes in sebum excretion in women. This could explain some of the inter-subject variability in SER measured between visits in clinical studies.

A randomized phase 2a efficacy and safety trial of the topical Janus kinase inhibitor tofacitinib in the treatment of chronic plaque psoriasis

BACKGROUND

Tofacitinib (CP-690,550) is a novel Janus kinase inhibitor in development as an oral formulation for the treatment of several inflammatory diseases including psoriasis.

OBJECTIVES

This phase 2a study aimed to assess the efficacy, systemic safety, local tolerability and systemic pharmacokinetics of topical tofacitinib in mild-to-moderate plaque psoriasis.

METHODS

Two tofacitinib ointment formulations were evaluated in this multicentre, double-blind, vehicle-controlled trial (NCT01246583). Seventy-one patients were randomized 2 : 1 : 2 : 1 to 2% tofacitinib ointment 1, vehicle 1, 2% tofacitinib ointment 2 and vehicle 2, each administered twice daily for 4 weeks to a single fixed 300 cm(2) treatment area containing a target plaque with or without one or more nontarget plaques and normal skin.

RESULTS

The primary endpoint of percentage change from baseline in the Target Plaque Severity Score at week 4 demonstrated statistically significant improvement for ointment 1 [least squares mean (LSM) -54.4%] vs. vehicle 1 (LSM -41.5%), but not ointment 2 (LSM -24.2%) vs. vehicle 2 (LSM -17.2%). Secondary endpoints (target plaque area and Itch Severity Item) improved similarly for tofacitinib ointment vs. corresponding vehicle. Adverse event (AE) occurrence was similar across treatment groups. All AEs were mild or moderate and none were serious or led to subject discontinuation. One application-site AE (erythema) was reported. Tofacitinib mean systemic exposure was minimal and was greater for ointment 1 than for ointment 2.

CONCLUSIONS

Tofacitinib ointment 1 was well tolerated and efficacious compared with vehicle for the treatment of plaque psoriasis. Further study of topical tofacitinib for psoriasis treatment is warranted.

Efficacy and safety of topical WBI-1001 in patients with mild to moderate psoriasis: results from a randomized double-blind placebo-controlled, phase II trial

BACKGROUND

There is a need for the development of novel non-steroidal topical drugs for the treatment of psoriasis.

OBJECTIVE

To assess the efficacy and safety of topical 1.0% WBI-1001 in patients with mild to moderate plaque psoriasis.

METHODS

A total of 61 patients with 1-10% body surface area (BSA) covered with plaque psoriasis and a physician's global assessment score (PGA) of 2-4 were randomized (2:1) to receive either 1% WBI-1001 in a cream formulation or placebo, applied twice daily for 12 weeks. Efficacy was evaluated using PGA, BSA and Psoriasis Area and Severity Index (PASI). The primary endpoint was the change from baseline (Day 0) in PGA at week 12.

RESULTS

The improvement in PGA at week 12 was 62.8% for patients randomized to WBI-1001 when compared with 13.0% for patients randomized to placebo (P<0.0001). At week 12, the proportion of patients who achieved a PGA of clear or almost clear and the mean improvement in BSA were 67.5% and 79.1%, respectively, for patients randomized to WBI-1001, when compared with 4.8% (P<0.0001) and an increase of 9.4% (P<0.0001), respectively, for patients randomized to placebo. More application site adverse drug reactions were observed in patients randomized to WBI-1001 than in those randomized to placebo. These adverse drug reactions were all mild or moderate in intensity.

CONCLUSION

Topical WBI-1001 induces rapid and significant improvement in patients with plaque psoriasis.

Randomized study comparing the efficacy and tolerance of a lipophillic hydroxy acid derivative of salicylic acid and 5% benzoyl peroxide in the treatment of facial acne vulgaris

BACKGROUND

New topical treatments for acne vulgaris are needed for patients who have tolerance problems with current treatments.

AIMS

To compare the efficacy and tolerance of a lipophillic derivative of salicylic acid (lipo hydroxy acid or LHA) containing formulation and 5% benzoyl peroxide in subjects with acne vulgaris.

METHODS

Eighty subjects with mild to moderate facial acne were randomized to receive either the LHA formulation twice a day or benzoyl peroxide once a day for 12 weeks. Efficacy and tolerance were evaluated at days 0, 28, 56 and 87. Results LHA formulation and benzoyl peroxide decreased the number of inflammatory lesions from baseline to week 12 by 44% and 47% and noninflammatory lesions by 19% and 23%, respectively. There was no statistically significant difference between the two treatments (P = 0.748; P = 0.445).

CONCLUSION

These results suggest that the LHA formulation could be a treatment option to consider in mild to moderate acne vulgaris patients that are intolerant to benzoyl peroxide.

A new scalp formulation of calcipotriol plus betamethasone dipropionate compared with each of its active ingredients in the same vehicle for the treatment of scalp psoriasis: a randomized, double-blind, controlled trial

BACKGROUND

There is a need for new treatments for scalp psoriasis, as many topical treatments are cosmetically unacceptable and difficult to apply, resulting in poor compliance.

OBJECTIVES

To compare the efficacy and safety of a new, once-daily, two-compound scalp formulation (Xamiol; LEO Pharma A/S, Ballerup, Denmark) containing calcipotriol 50 microg g(-1) plus betamethasone 0.5 mg g(-1) (as dipropionate), with the active ingredients as single compounds in the same vehicle.

METHODS

This 8-week, multicentre, double-blind, parallel-group study, randomized adult patients with scalp psoriasis involving > 10% of the scalp to the two-compound scalp formulation (n = 568), betamethasone dipropionate 0.5 mg g(-1) (n = 563), or calcipotriol 50 microg g(-1) (n = 286). The primary efficacy measure was the proportion of patients with 'absence of disease' or 'very mild disease' according to investigators' assessments at week 8.

RESULTS

The proportion of patients with 'absence of disease' or 'very mild disease' at week 8 was significantly higher in the two-compound group (68.4%) than the betamethasone dipropionate (61.0%, P = 0.0079) or calcipotriol (43.4%, P < 0.0001) groups. The proportion of patients rating their scalp psoriasis as 'clear' or 'almost clear' was significantly higher for the two-compound scalp formulation (69.6%) than for betamethasone dipropionate (59.9%, P = 0.0006) or calcipotriol (44.7%, P < 0.0001). The incidence of lesional/perilesional adverse events was lower in the two-compound and betamethasone dipropionate groups than the calcipotriol group.

CONCLUSIONS

The two-compound scalp formulation was well tolerated and more effective in the treatment of scalp psoriasis than either of its individual components in the same vehicle.

Etanercept in the treatment of palmoplantar pustulosis

INTRODUCTION

Palmoplantar pustulosis (PPP) is a chronic, recurrent and difficult to treat skin condition characterized by the presence of pustules, erythema, and hyperkeratosis on palms and soles.

METHODS

Fifteen subjects with PPP were randomized (2:1) to receive subcutaneous injections of either etanercept 50 mg or a placebo twice a week for 3 months. All subjects then received the etanercept 50 mg injections twice a week for an additional 3 months.

RESULTS

Etanercept was well tolerated by subjects with PPP. The decrease in median Palmoplantar Pustulosis Area and Severity Index (PPPASI) score from baseline to 24 weeks was statistically significant for subjects treated with etanercept for 24 weeks (P = 0.038, n = 10) but not for subjects in the placebo/etanercept cross-over group (P = 0.125, n = 5). Comparison of changes in PPPASI from baseline to week 12 was not statistically significant for subjects assigned to etanercept or to placebo. Some subjects treated with etanercept presented good clinical improvements in PPP severity whereas others showed an increase in PPP severity.

CONCLUSION

This study showed that etanercept was well tolerated in subjects with PPP and suggests that some PPP subjects might benefit from etanercept therapy. Larger studies are needed to assess PPP response to etanercept including the influence of smoking and the presence or absence of psoriasis outside palms and soles.

Effects of dihydrotestosterone on gene expression in mammary gland

Breast cancer is the most common cancer among women. Androgens, the male sexual hormones produced by ovary, act as protector of mammary gland. To elucidate the possible effects of dihydrotestosterone (DHT) on the transcriptome of mammary gland, serial analysis of gene expression was carried out on three groups of gonadectomized mice. After gonadectomy (GDX), DHT was injected 3 or 24h before sacrifice, whereas the control (GDX) group received vehicle solution. Approximately 42,000 tags were sequenced in each group. Genes involved in the cytoskeletal and extracellular matrix, such as troponin I skeletal fast 2 and keratin complex 1 acidic gene 14, were upregulated. In the immunity, complement component 1 q subcomponent gamma polypeptide and expressed sequence tag similar to lectin galactose binding soluble 3 were downregulated by DHT, whereas serine (or cystein) proteinase inhibitor clade A member 1a was upregulated. In the energy metabolism, the gene expression level of cytochrome c oxidase subunit I was upregulated by DHT, while NADH dehydrogenase subunit 2 was downregulated. In addition, transcripts involved in transport metabolism, such as apolipoprotein A-1, were upregulated by DHT, whereas retinol binding protein 4 plasma was downregulated. Several previously unknown sequence tags were identified, which may allow to characterize new molecules of interest. These results suggest the suppression of immune response in normal mammary gland after DHT injection. This study can assist in refining research on the role of androgens in mammary gland homeostasis and breast cancer.

Reproducibility, bioinformatic analysis and power of the SAGE method to evaluate changes in transcriptome

The serial analysis of gene expression (SAGE) method is used to study global gene expression in cells or tissues in various experimental conditions. However, its reproducibility has not yet been definitively assessed. In this study, we have evaluated the reproducibility of the SAGE method and identified the factors that affect it. The determination coefficient (R²) for the reproducibility of SAGE is 0.96. However, there are some factors that can affect the reproducibility of SAGE, such as the replication of concatemers and ditags, the number of sequenced tags and double PCR amplification of ditags. Thus, corrections for these factors must be made to ensure the reproducibility and accuracy of SAGE results. A bioinformatic analysis of SAGE data is also presented in order to eliminate these artifacts. Finally, the current study shows that increasing the number of sequenced tags improves the power of the method to detect transcripts and their regulation by experimental conditions.

Effects of dihydrotestosterone on adipose tissue measured by serial analysis of gene expression

Intra-abdominal fat accumulation is related to several diseases, especially diabetes and heart disease. Molecular mechanisms associated with this independent risk factor are not well established. Through the serial analysis of gene expression (SAGE) strategy, we have studied the transcriptomic effects of castration and dihydrotestosterone (DHT) in retroperitoneal adipose tissue of C57BL6 male mice. Approximately 50,000 SAGE tags were isolated in intact and gonadectomized mice, as well as 3 and 24 h after DHT administration. Transcripts involved in energy metabolism, such as glyceraldehyde-3-phosphate dehydrogenase, malic enzyme supernatant, fatty acid synthase, lipoprotein lipase, hormone-sensitive lipase and monoglyceride lipase, were upregulated by DHT. Transcripts involved in adipogenesis, and cell cycle and cell shape organization, such as DDX5, C/EBPalpha, cyclin I, procollagen types I, III, IV, V and VI, SPARC and matrix metalloproteinase 2, were upregulated by DHT. Cell defense, division and signaling, protein expression and many novel transcripts were regulated by castration and DHT. The present results provide global genomic evidence for a stimulation of glycolysis, fatty acids and triacylglycerol production, lipolysis and cell shape reorganization, as well as cell proliferation and differentiation, by DHT. The novel transcripts regulated by DHT may contribute to identify new mechanisms involved in the action of sex hormones and their potential role in obesity.

DPCP for the treatment of alopecia areata

Topical immunotherapy with diphencyprone (DPCP) for the treatment of severe alopecia areata has been used since 1983 and is felt to be the treatment of choice by many dermatologists. Although there have been no major side effects reported since its initial use, there remain some unknowns regarding its safety. Because DPCP has at least a 40% success rate for cosmetically acceptable regrowth in extensive alopecia areata, its availability is an important matter for patients with alopecia areata.

Management of androgenetic alopecia

Androgenetic alopecia is by far the most common cause of hair loss. It affects approximately 50% of men by the age of 50 and 20 to 53% of women by the age 50. Although it is a medically benign condition, it is a significant psychosocial issue for many patients. Various different treatment options are now available for androgenetic alopecia. The best treatment option for women with androgenetic alopecia Ludwig stage I and II is minoxidil 5% solution. If it is not effective after 1 year, antiandrogens can be tried, but there are no large studies showing their efficacy and they have considerable adverse effects. Also, for patients with alopecia that is unresponsive to treatment or with Ludwig stage III, hair transplantation can be offered if the occipital donor area is sufficient. For men, we always offer minoxidil or finasteride therapy and leave the choice of therapy to the patient. Some patients may prefer a systemic agent, whereas others may favor a topical agent. If the condition is not stabilized after 1 year or if the patient wants greater hair density, hair transplantation can be discussed. There have been tremendous advances in the treatment of hair loss in recent years and the future is very encouraging. As our knowledge of androgenetic alopecia pathophysiology increases, novel targeted treatments will potentially be developed.

Calmodulin point mutations affect Drosophila development and behavior

Calmodulin (CAM) is recognized as a major intermediary in intracellular calcium signaling, but as yet little is known of its role in developmental and behavioral processes. We have generated and studied mutations to the endogenous Cam gene of Drosophila melanogaster that change single amino acids within the protein coding region. One of these mutations produces a striking pupal lethal phenotype involving failure of head eversion. Various mutant combinations produce specific patterns of ectopic wing vein formation or melanotic scabs on the cuticle. Anaphase chromosome bridging is also seen as a maternal effect during the early embryonic nuclear divisions. In addition, specific behavioral defects such as poor climbing and flightlessness are detected among these mutants. Comparisons with other Drosophila mutant phenotypes suggests potential CAM targets that may mediate these developmental and behavioral effects, and analysis of the CAM crystal structure suggests the structural consequences of the individual mutations.

Spontaneous avoidance behavior in Drosophila null for calmodulin expression

The regulatory protein calmodulin is a major mediator of calcium-induced changes in cellular activity. To analyze the roles of calmodulin in an intact animal, we have generated a calmodulin null mutation in Drosophila melanogaster. Maternal calmodulin supports calmodulin null individuals throughout embryogenesis, but they die within 2 days of hatching as first instar larvae. We have detected two pronounced behavioral abnormalities specific to the loss of calmodulin in these larvae. Swinging of the head and anterior body, which occurs in the presence of food, is three times more frequent in the null animals. More strikingly, most locomotion in calmodulin null larvae is spontaneous backward movement. This is in marked contrast to the wild-type situation where backward locomotion is seen only as a stimulus-elicited avoidance response. Our finding of spontaneous avoidance behavior has striking similarities to the enhanced avoidance responses produced by some calmodulin mutations in Paramecium. Thus our results suggest evolutionary conservation of a role for calmodulin in membrane excitability and linked behavioral responses.

A second maternally expressed Drosophila gene encodes a putative RNA helicase of the "DEAD box" family

Recently, a family of proteins containing the conserved motif Asp-Glu-Ala-Asp, the "DEAD box" proteins, has been identified. This family is typified by the eukaryotic translation initiation factor eIF4A, and its members are believed to share the functional property of ATP-dependent RNA unwinding. One of the previously identified members of this family (vasa) is the product of a maternally expressed gene from Drosophila melanogaster that is known to play a role in the formation of the embryonic body plan. We report here the isolation of a Drosophila gene that has an mRNA expression pattern somewhat similar to that of vasa and also encodes a DEAD box protein. We have termed this gene ME31B to reflect its maternal (ovarian germ-line) expression and its location within the 31B chromosome region. Comparisons with the other members of this family reveal that although ME31B is most like the protein Tif1/Tif2, which probably represents the Saccharomyces cerevisiae version of eIF4A, it is unlikely that ME31B represents the Drosophila eIF4A protein per se. A search for mutations in the ME31B gene has established that the P element which causes the female-sterile mutation flipper lies in the 3' flank of the ME31B gene.

Receptors for the Fc portion of immunoglobulins (FcR) on murine oral mucosal T cells

The incidence and distribution of immunoglobulin receptors on oral mucosal T cells were investigated. Enrichment of either Thy-1.2, L3T4 or Lyt-2.2-positive cells was achieved by the use of a panning procedure following cell extraction by an optimized digestion method that preserved all three T-cell markers. The percentage of cells possessing Fc receptors was determined by using immunoglobulin-coated (IgM, IgG or IgA) fluorescent microspheres in a multipoint rosetting assay. We report that approximately 60% of Thy-1.2, L3T4 and Lyt-2.2 positive cells bear Fc gamma R whereas less than 5% of T cells of any subset bear Fc alpha R or Fc mu R. In frozen tissue sections, Fc gamma R+ cells were mainly scattered throughout the basal and suprabasal epithelium and were observed at a lower frequency in the minor salivary gland network. From their distribution, it is anticipated that Fc gamma R+ cells may be involved in the surveillance of the epithelium while the minor Fc alpha R+ L3T4+ T lymphocyte population may promote the expression of sIgA by resident sIgM-bearing B cells, and their differentiation into IgA plasma cells.

Tissue distribution and cytofluorometric analysis of oral mucosal T cells in the BALB/c mouse

The incidence and distribution of Thy-1.2+, Lyt-2.2+ and L3T4+ cells in the murine oral mucosa were investigated using qualitative and quantitative approaches. From immunostaining of frozen tissue sections, it appeared that the majority of oral T cells are located either in the epithelium or within the minor salivary gland network. The occurrence of Thy-1.2+, L3T4+ and Lyt-2.2+ cells at these sites points to two strategic lines of defence in the event of mucosal infections or aggression. A quantitative analysis of oral T-cell subsets was made possible by optimizing an enzymatic digestion procedure which preserves all three T-cell surface markers. Flow cytometric analysis of oral mucosal cells demonstrated that the helper phenotype is about twice as numerous as the cytotoxic/suppressor phenotype in the mucosa. Furthermore, in single cell suspensions, virtually all Thy-1+ cells were either L3T4+ or Lyt-2.2+ in the mucosa and in the spleen. From this frequency analysis and our previous studies, we conclude that T cells are a major component of the oral immune system, being 2-3 times as numerous as B cells or macrophages. Present data on the spatial distribution and characteristic ratio of T-cell subsets assess the basal activity of the local T-cell populations in healthy animals and lay the basis for comparative studies of both qualitative and quantitative variations occurring during mucosal infections or autoimmune reactions.

Beta-tubulin mutants of the unicellular green alga Chlamydomonas reinhardtii

Two beta-tubulin mutants of the unicellular green alga Chlamydomonas reinhardtii have been isolated on the basis of altered sensitivity to the growth-inhibitory effect of colchicine. The two mutations of colR4 and colR15 have been found to be tightly linked, mapping to a previously unmarked site in linkage group XII. The drug-resistance phenotypes of both mutations segregated in genetic crosses with the presence of distinct, acidic variant beta-tubulin isoforms found assembled into the microtubules of the flagella. Analysis of the in vitro translation products of total poly(A)+ RNA from the mutants provided evidence that the variant proteins are altered primary beta-tubulin gene products. Compared to wild type, strains carrying the mutations expressed an increased resistance to the inhibitory effects of colchicine in clonal growth, flagellar assembly, and germination of meiotic products, suggesting that the beta-tubulin altered in the mutants participates in multiple microtubule functions.

Biosynthesis of kitasamycin (leucomycin) by leucine analog-resistant mutants of Streptomyces kitasatoensis

The biosynthesis of kitasamycin in Streptomyces kitasatoensis B-896 was profoundly influenced by the addition of precursors to complex and defined media: l-valine and l-leucine directed biosynthesis towards the pairs A(4)/A(5) (R(2) = butyryl) and A(1)/A(3) (R(2) = isovaleryl), respectively, and total kitasamycin titers were doubled and quadrupled, respectively. S. kitasatoensis B-896 was very resistant (>20 mg/ml) to alpha-aminobutyric acid, an analog of l-valine, but very susceptible to l-leucine analogs 5', 5', 5'-trifluoroleucine and 4-azaleucine (5 to 10 mug/ml). The inhibition by 4-azaleucine could be reversed by l-leucine, but by none of the other amino acids of the pyruvate family or the amino acids of the aspartate pathway. 4-Azaleucine-resistant mutants were isolated which in the absence of any precursors overproduced l-leucine and a kitasamycin complex mainly consisting of the pair A(1)/A(3). These 4-azaleucine-resistant mutants are presumed to be regulatory mutants in which alpha-isopropylmalate synthase, the first enzyme of the l-leucine pathway, has become either derepressed or desensitized to leucine feedback inhibition. l-Leucine-regulatory mutants have economic value: in the absence of expensive precursors, they produce a kitasamycin complex in which the most potent pair A(1)/A(3) is dominant and the least active components are absent.

Antimycin A fermentation. I. Production and selection of strains

Increase in antimycin A production was achieved through a parallel strain and medium improvement program: a 125-fold augmentation (75 to 9,500 mug/ml) was obtained. The selective system included antimycin A productivity, conidiation, sensitivity to ultraviolet radiation, growth rate and yield, and absence of pigment and actinomycin D production. Among the original strains tested one natural isolate possessed high productivity and several of the above characteristics, and was selected for mutagenesis. Spontaneous and induced variability was then exploited in isolating high-producing strains. The first mutagen used was ultraviolet radiation; it was replaced by ethylenimine when it became no longer efficient in increasing variability. As new, high producers were isolated, the medium was modified to best suit their requirements for still higher productivity. The critical environmental factors were absence of phosphate and organic salts, concentration of the nitrogen source and ratio organic/inorganic nitrogen, ratio ammonium sulfate/calcium carbonate, and addition of slowly utilizable carbon sources, such as lactose and oil; optimum temperature and initial pH were 25 degrees C and 7.0. Aeration/agitation requirements of improved strains were high. Fermentation was characterized by abrupt pH changes which impaired rapid accumulation of the antibiotic. Antimycin A was produced during both the trophophase and idiophase.