Don Hahn - Academia.edu (original) (raw)
Papers by Don Hahn
Phoslactomycins H (<b>1</b>) and I (<b>2</b>), two new members of the pho... more Phoslactomycins H (<b>1</b>) and I (<b>2</b>), two new members of the phoslactomycin class of chemistry, were isolated from <i>Streptomyces</i> sp. MLA1839 on the basis of their antifungal activities. Their structures were elucidated using extensive NMR spectroscopy and mass spectrometry. Phoslactomycin H (<b>1</b>) featured a rare and unprecedented <i>N</i>,<i>N</i>-dimethylamine substitution at C-4 and existed as a hydroxy acid rather than the more common lactone. Herein, we report the structure of these compounds and their biological activities
Journal of natural products, Jan 26, 2018
Three novel cyclodepsipeptides, alveolarides A (1), B (2), and C (3), each possessing the rare 2,... more Three novel cyclodepsipeptides, alveolarides A (1), B (2), and C (3), each possessing the rare 2,3-dihydroxy-4-methyltetradecanoic acid unit and a β-phenylalanine amino acid residue, along with the known peptide scopularide were isolated and identified from the culture broth of Microascus alveolaris strain PF1466. The pure compounds were evaluated for biological activity, and alveolaride A (1) provided strong in vitro activity against the plant pathogens Pyricularia oryzae, Zymoseptoria tritici, and Ustilago maydis. Moderate activity of alveolaride A was observed under in planta conditions against Z. tritici, Puccinia triticina, and Phakopsora pachyrhizi. Structures of 1, 2, and 3 were determined by detailed analysis of NMR (1D and 2D) and mass spectrometry data. The partial absolute configuration of alveolaride A (1) was established.
Genetics, 1986
The two genes required for proline utilization by S. typhimurium form a divergent operon. Express... more The two genes required for proline utilization by S. typhimurium form a divergent operon. Expression of the put operon is induced by proline and subject to catabolite repression. Genetic evidence suggests that putA protein autogenously represses transcription of the putA and putP genes. In order to establish the molecular mechanism of put operon regulation we isolated regulatory mutations in the put control region. These mutants were selected using two phenotypes: (1) the ability to degrade a toxic proline analogue, dehydroproline, due to overexpression of putA enzyme activity, or (2) overexpression of lacZ from put::Mud operon fusions. The effect of each mutation on transcription in both directions was determined by measuring lacZ expression from putA and putP operon fusions. These regulatory mutations were cis-dominant when the putA protein was provided in trans, and they map in a region between the two genes. The phenotypes of the mutants suggest that (1) the put regulatory regio...
Journal of Bacteriology, 1991
Tn5099, a promoter probe transposon for Streptomyces spp., was constructed by inserting a promote... more Tn5099, a promoter probe transposon for Streptomyces spp., was constructed by inserting a promoterless xylE gene and a hygromycin resistance gene into IS493. Tn5099 transposed into different sites in the Streptomyces griseofuscus genome, and the xylE reporter gene was expressed in some of the transposition mutants. Strains containing Tn5099 insertions that gave regulated expression of the xylE gene were identified.
Journal of Bacteriology, 1991
FP43 is a temperate bacteriophage for Streptomyces griseofuscus that forms plaques on many Strept... more FP43 is a temperate bacteriophage for Streptomyces griseofuscus that forms plaques on many Streptomyces species. FP43 virions contain 56 kb of double-strand DNA that is circularly permuted and terminally redundant, and contains 65% G + C. A physical map of the FP43 genome was constructed, and the origin for headful packaging (pac) was localized to an 8.8-kb region of the genome (hft) that mediates high-frequency transduction by FP43 of plasmid pRHB101. The phage attachment site (attP), a replication origin (rep), a region that inhibits plaque formation (pin), and a 3-kb deletion (rpt) that caused a 100-fold reduction in plasmid transduction were mapped.
Journal of General Microbiology, 1990
Bacteriophage FP22 has a very broad host range within streptomycetes and appeared to form lysogen... more Bacteriophage FP22 has a very broad host range within streptomycetes and appeared to form lysogens of Streptomyces ambofaciens ATCC 15154. FP22 shared strong cross-immunity and antibody cross-reactivity with bacteriophage P23, but not with seven other streptomycete bacteriophages. FP22 particles had a head diameter of 71 nm and a tail length of 307 run. The FP22 genome was 131 kb, which is the largest bacteriophage genome reported for streptomycetes. The G + C content of the genome was 46 mol% and restriction mapping indicated that FP22 DNA had discrete ends. NaCl-and pyrophosphate-resistant deletion mutants were readily isolated and the extent of the deletions defined at least 23 kb of dispensable DNA in Qvo regions of the genome. The DNA was not cleaved by most restriction endonucleases (or isoschizomers) which have been identified in the streptomycetes, including the tetranucleotide cutter MboI (GATC). 2 g Fe2(S04)3. 7H20. BC agar comprised Bennett's medium plus 4 mM-Ca(N0J2. Cells were grown on AS-1 agar (Baltz, 1980) for spore formation.
ACS Symposium Series, 2013
MGG Molecular & General Genetics, 1990
Salmonella typhimurium can degrade proline for use as a carbon, nitrogen, or energy source. To de... more Salmonella typhimurium can degrade proline for use as a carbon, nitrogen, or energy source. To determine whether a futile cycle occurs which degrades the proline accumulated by proline biosynthesis, we studied the expression and enzymatic activity of the proline utilization (put) pathway under conditions which increase the concentration of the intracellular proline pools: catabolism of the dipeptide glycyl-proline, overproduction of proline due to a mutation which prevents feedback inhibition of proline biosynthesis, and accumulation of proline due to osmotic stress. The results indicate that: (i) internal proline induces the p u t genes, but only when accumulated to concentrations greater than the normal proline biosynthetic pool; and (ii) degradation of proline pools accumulated under high osmotic pressure is limited because proline oxidase is directly inhibited under these conditions.
Journal of Natural Products, 2006
Journal of Natural Products, 2007
The ansacarbamitocins are a new family of maytansinoids that are unusually substituted with a glu... more The ansacarbamitocins are a new family of maytansinoids that are unusually substituted with a glucose subunit and two carbamate functional groups and exhibit modest activity against some agricultural fungal disease organisms. Ansacarbamitocins A-F ( 1- 6) all consist of the same macrocyclic core as the ansamitocins, with variation occurring on the glucose unit, while ansacarbamitocins A1 and B1 ( 7, 8) additionally lack the epoxide group on C-4 and C-5.
Journal of Natural Products, 2013
Phoslactomycins H (1) and I (2), two new members of the phoslactomycin class of chemistry, were i... more Phoslactomycins H (1) and I (2), two new members of the phoslactomycin class of chemistry, were isolated from Streptomyces sp. MLA1839 on the basis of their antifungal activities. Their structures were elucidated using extensive NMR spectroscopy and mass spectrometry. Phoslactomycin H (1) featured a rare and unprecedented N,N-dimethylamine substitution at C-4 and existed as a hydroxy acid rather than the more common lactone. Herein, we report the structure of these compounds and their biological activities.
Journal of Industrial Microbiology & Biotechnology, 2005
Spinosyns, a novel class of insect active macrolides produced by Saccharopolyspora spinosa, are u... more Spinosyns, a novel class of insect active macrolides produced by Saccharopolyspora spinosa, are used for insect control in a number of commercial crops. Recently, a new class of spinosyns was discovered from S. pogona NRRL 30141. The butenyl-spinosyns, also called pogonins, are very similar to spinosyns, differing in the length of the side chain at C-21 and in the variety of novel minor factors. The butenyl-spinosyn biosynthetic genes (bus) were cloned on four cosmids covering a contiguous 110-kb region of the NRRL 30141 chromosome. Their function in butenyl-spinosyn biosynthesis was confirmed by a loss-of-function deletion, and subsequent complementation by cloned genes. The coding sequences of the butenyl-spinosyn biosynthetic genes and the spinosyn biosynthetic genes from S. spinosa were highly conserved. In particular, the PKS-coding genes from S. spinosa and S. pogona have 91-94% nucleic acid identity, with one notable exception. The butenyl-spinosyn gene sequence codes for one additional PKS module, which is responsible for the additional two carbons in the C-21 tail. The DNA sequence of spinosyn genes in this region suggested that the S. spinosa spnA gene could have been the result of an in-frame deletion of the S. pogona busA gene. Therefore, the butenyl-spinosyn genes represent the putative parental gene structure that was naturally engineered by deletion to create the spinosyn genes.
Journal of Industrial Microbiology, 1991
To expand the application of molecular genetics to many different streptomycete species, we have ... more To expand the application of molecular genetics to many different streptomycete species, we have been developing two potentially widely applicable methodologies: transposon mutagenesis and plasmid transduction. We constructed three transposons from the Streptomyces lividans insertion sequence IS493. Tn5096 and Tn5097 contain an apramycin resistance gene inserted in different orientations between the two open reading frames of IS493. These transposons transpose from different plasmids into many different sites in the Streptomyces griseofuscus chromosome and into its resident linear plasmids. Tn5099 contains a promoterless xylE gene and a hygromycin-resistance gene inserted in IS493 close to one end. Tn5099 transposes in S. griseofuscus giving operon fusions in some cases that drive expression of the xylE gene product, catechol deoxygenase, giving yellow colonies in the presence of catechol. We have also developed plasmid vectors that can be transduced into many streptomycete species by bacteriophage FP43. We describe the characterization of FP43 and mapping of several bacteriophage functions. The region of cloned FP43 DNA essential for plasmid transduction includes the origin for headful packaging.
Journal of Chemical Ecology, 2013
A multiyear effort to identify new natural products was built on a hypothesis that both phytotoxi... more A multiyear effort to identify new natural products was built on a hypothesis that both phytotoxins from plant pathogens and antimicrobial compounds might demonstrate herbicidal activity. The discovery of one such compound, mevalocidin, is described in the current report. Mevalocidin was discovered from static cultures of two unrelated fungal isolates designated Rosellinia DA092917 and Fusarium DA056446. The chemical structure was confirmed by independent synthesis. Mevalocidin demonstrated broad spectrum postemergence activity on grasses and broadleaves and produced a unique set of visual symptoms on treated plants suggesting a novel mode of action. Mevalocidin was rapidly absorbed in a representative grass and broadleaf plant. Translocation occurred from the treated leaf to other plant parts including roots confirming phloem as well as xylem mobility. By 24 hr after application, over 20 % had been redistributed throughout the plant. Mevalocidin is a unique phytotoxin based on its chemistry, with the uncommon attribute of demonstrating both xylem and phloem mobility in grass and broadleaf plants.
Phoslactomycins H (<b>1</b>) and I (<b>2</b>), two new members of the pho... more Phoslactomycins H (<b>1</b>) and I (<b>2</b>), two new members of the phoslactomycin class of chemistry, were isolated from <i>Streptomyces</i> sp. MLA1839 on the basis of their antifungal activities. Their structures were elucidated using extensive NMR spectroscopy and mass spectrometry. Phoslactomycin H (<b>1</b>) featured a rare and unprecedented <i>N</i>,<i>N</i>-dimethylamine substitution at C-4 and existed as a hydroxy acid rather than the more common lactone. Herein, we report the structure of these compounds and their biological activities
Journal of natural products, Jan 26, 2018
Three novel cyclodepsipeptides, alveolarides A (1), B (2), and C (3), each possessing the rare 2,... more Three novel cyclodepsipeptides, alveolarides A (1), B (2), and C (3), each possessing the rare 2,3-dihydroxy-4-methyltetradecanoic acid unit and a β-phenylalanine amino acid residue, along with the known peptide scopularide were isolated and identified from the culture broth of Microascus alveolaris strain PF1466. The pure compounds were evaluated for biological activity, and alveolaride A (1) provided strong in vitro activity against the plant pathogens Pyricularia oryzae, Zymoseptoria tritici, and Ustilago maydis. Moderate activity of alveolaride A was observed under in planta conditions against Z. tritici, Puccinia triticina, and Phakopsora pachyrhizi. Structures of 1, 2, and 3 were determined by detailed analysis of NMR (1D and 2D) and mass spectrometry data. The partial absolute configuration of alveolaride A (1) was established.
Genetics, 1986
The two genes required for proline utilization by S. typhimurium form a divergent operon. Express... more The two genes required for proline utilization by S. typhimurium form a divergent operon. Expression of the put operon is induced by proline and subject to catabolite repression. Genetic evidence suggests that putA protein autogenously represses transcription of the putA and putP genes. In order to establish the molecular mechanism of put operon regulation we isolated regulatory mutations in the put control region. These mutants were selected using two phenotypes: (1) the ability to degrade a toxic proline analogue, dehydroproline, due to overexpression of putA enzyme activity, or (2) overexpression of lacZ from put::Mud operon fusions. The effect of each mutation on transcription in both directions was determined by measuring lacZ expression from putA and putP operon fusions. These regulatory mutations were cis-dominant when the putA protein was provided in trans, and they map in a region between the two genes. The phenotypes of the mutants suggest that (1) the put regulatory regio...
Journal of Bacteriology, 1991
Tn5099, a promoter probe transposon for Streptomyces spp., was constructed by inserting a promote... more Tn5099, a promoter probe transposon for Streptomyces spp., was constructed by inserting a promoterless xylE gene and a hygromycin resistance gene into IS493. Tn5099 transposed into different sites in the Streptomyces griseofuscus genome, and the xylE reporter gene was expressed in some of the transposition mutants. Strains containing Tn5099 insertions that gave regulated expression of the xylE gene were identified.
Journal of Bacteriology, 1991
FP43 is a temperate bacteriophage for Streptomyces griseofuscus that forms plaques on many Strept... more FP43 is a temperate bacteriophage for Streptomyces griseofuscus that forms plaques on many Streptomyces species. FP43 virions contain 56 kb of double-strand DNA that is circularly permuted and terminally redundant, and contains 65% G + C. A physical map of the FP43 genome was constructed, and the origin for headful packaging (pac) was localized to an 8.8-kb region of the genome (hft) that mediates high-frequency transduction by FP43 of plasmid pRHB101. The phage attachment site (attP), a replication origin (rep), a region that inhibits plaque formation (pin), and a 3-kb deletion (rpt) that caused a 100-fold reduction in plasmid transduction were mapped.
Journal of General Microbiology, 1990
Bacteriophage FP22 has a very broad host range within streptomycetes and appeared to form lysogen... more Bacteriophage FP22 has a very broad host range within streptomycetes and appeared to form lysogens of Streptomyces ambofaciens ATCC 15154. FP22 shared strong cross-immunity and antibody cross-reactivity with bacteriophage P23, but not with seven other streptomycete bacteriophages. FP22 particles had a head diameter of 71 nm and a tail length of 307 run. The FP22 genome was 131 kb, which is the largest bacteriophage genome reported for streptomycetes. The G + C content of the genome was 46 mol% and restriction mapping indicated that FP22 DNA had discrete ends. NaCl-and pyrophosphate-resistant deletion mutants were readily isolated and the extent of the deletions defined at least 23 kb of dispensable DNA in Qvo regions of the genome. The DNA was not cleaved by most restriction endonucleases (or isoschizomers) which have been identified in the streptomycetes, including the tetranucleotide cutter MboI (GATC). 2 g Fe2(S04)3. 7H20. BC agar comprised Bennett's medium plus 4 mM-Ca(N0J2. Cells were grown on AS-1 agar (Baltz, 1980) for spore formation.
ACS Symposium Series, 2013
MGG Molecular & General Genetics, 1990
Salmonella typhimurium can degrade proline for use as a carbon, nitrogen, or energy source. To de... more Salmonella typhimurium can degrade proline for use as a carbon, nitrogen, or energy source. To determine whether a futile cycle occurs which degrades the proline accumulated by proline biosynthesis, we studied the expression and enzymatic activity of the proline utilization (put) pathway under conditions which increase the concentration of the intracellular proline pools: catabolism of the dipeptide glycyl-proline, overproduction of proline due to a mutation which prevents feedback inhibition of proline biosynthesis, and accumulation of proline due to osmotic stress. The results indicate that: (i) internal proline induces the p u t genes, but only when accumulated to concentrations greater than the normal proline biosynthetic pool; and (ii) degradation of proline pools accumulated under high osmotic pressure is limited because proline oxidase is directly inhibited under these conditions.
Journal of Natural Products, 2006
Journal of Natural Products, 2007
The ansacarbamitocins are a new family of maytansinoids that are unusually substituted with a glu... more The ansacarbamitocins are a new family of maytansinoids that are unusually substituted with a glucose subunit and two carbamate functional groups and exhibit modest activity against some agricultural fungal disease organisms. Ansacarbamitocins A-F ( 1- 6) all consist of the same macrocyclic core as the ansamitocins, with variation occurring on the glucose unit, while ansacarbamitocins A1 and B1 ( 7, 8) additionally lack the epoxide group on C-4 and C-5.
Journal of Natural Products, 2013
Phoslactomycins H (1) and I (2), two new members of the phoslactomycin class of chemistry, were i... more Phoslactomycins H (1) and I (2), two new members of the phoslactomycin class of chemistry, were isolated from Streptomyces sp. MLA1839 on the basis of their antifungal activities. Their structures were elucidated using extensive NMR spectroscopy and mass spectrometry. Phoslactomycin H (1) featured a rare and unprecedented N,N-dimethylamine substitution at C-4 and existed as a hydroxy acid rather than the more common lactone. Herein, we report the structure of these compounds and their biological activities.
Journal of Industrial Microbiology & Biotechnology, 2005
Spinosyns, a novel class of insect active macrolides produced by Saccharopolyspora spinosa, are u... more Spinosyns, a novel class of insect active macrolides produced by Saccharopolyspora spinosa, are used for insect control in a number of commercial crops. Recently, a new class of spinosyns was discovered from S. pogona NRRL 30141. The butenyl-spinosyns, also called pogonins, are very similar to spinosyns, differing in the length of the side chain at C-21 and in the variety of novel minor factors. The butenyl-spinosyn biosynthetic genes (bus) were cloned on four cosmids covering a contiguous 110-kb region of the NRRL 30141 chromosome. Their function in butenyl-spinosyn biosynthesis was confirmed by a loss-of-function deletion, and subsequent complementation by cloned genes. The coding sequences of the butenyl-spinosyn biosynthetic genes and the spinosyn biosynthetic genes from S. spinosa were highly conserved. In particular, the PKS-coding genes from S. spinosa and S. pogona have 91-94% nucleic acid identity, with one notable exception. The butenyl-spinosyn gene sequence codes for one additional PKS module, which is responsible for the additional two carbons in the C-21 tail. The DNA sequence of spinosyn genes in this region suggested that the S. spinosa spnA gene could have been the result of an in-frame deletion of the S. pogona busA gene. Therefore, the butenyl-spinosyn genes represent the putative parental gene structure that was naturally engineered by deletion to create the spinosyn genes.
Journal of Industrial Microbiology, 1991
To expand the application of molecular genetics to many different streptomycete species, we have ... more To expand the application of molecular genetics to many different streptomycete species, we have been developing two potentially widely applicable methodologies: transposon mutagenesis and plasmid transduction. We constructed three transposons from the Streptomyces lividans insertion sequence IS493. Tn5096 and Tn5097 contain an apramycin resistance gene inserted in different orientations between the two open reading frames of IS493. These transposons transpose from different plasmids into many different sites in the Streptomyces griseofuscus chromosome and into its resident linear plasmids. Tn5099 contains a promoterless xylE gene and a hygromycin-resistance gene inserted in IS493 close to one end. Tn5099 transposes in S. griseofuscus giving operon fusions in some cases that drive expression of the xylE gene product, catechol deoxygenase, giving yellow colonies in the presence of catechol. We have also developed plasmid vectors that can be transduced into many streptomycete species by bacteriophage FP43. We describe the characterization of FP43 and mapping of several bacteriophage functions. The region of cloned FP43 DNA essential for plasmid transduction includes the origin for headful packaging.
Journal of Chemical Ecology, 2013
A multiyear effort to identify new natural products was built on a hypothesis that both phytotoxi... more A multiyear effort to identify new natural products was built on a hypothesis that both phytotoxins from plant pathogens and antimicrobial compounds might demonstrate herbicidal activity. The discovery of one such compound, mevalocidin, is described in the current report. Mevalocidin was discovered from static cultures of two unrelated fungal isolates designated Rosellinia DA092917 and Fusarium DA056446. The chemical structure was confirmed by independent synthesis. Mevalocidin demonstrated broad spectrum postemergence activity on grasses and broadleaves and produced a unique set of visual symptoms on treated plants suggesting a novel mode of action. Mevalocidin was rapidly absorbed in a representative grass and broadleaf plant. Translocation occurred from the treated leaf to other plant parts including roots confirming phloem as well as xylem mobility. By 24 hr after application, over 20 % had been redistributed throughout the plant. Mevalocidin is a unique phytotoxin based on its chemistry, with the uncommon attribute of demonstrating both xylem and phloem mobility in grass and broadleaf plants.