PMCC PMCC

Search tips
Search criteria

Advanced
Results 1-8 (8)
 

Clipboard (0)
None

Select a Filter Below

Journals
Year of Publication
Document Types
1.  An erythromycin process improvement using the diethyl methylmalonate responsive (Dmr) phenotype of the Saccharopolyspora erythraea mutB strain 
The Saccharopolyspora erythraea mutB knockout strain, FL2281, having a block in the methylmalonyl-CoA mutase reaction, was found to carry a diethyl methylmalonate-responsive (Dmr) phenotype in an oil-based fermentation medium. The Dmr phenotype confers the ability to increase erythromycin A (erythromycin) production from 250 – 300% when the oil-based medium is supplemented with 15 mM levels of this solvent. Lower concentrations of the solvent stimulated proportionately less erythromycin production, while higher concentrations had no additional benefit. Although the mutB strain is phenotypically a low-level erythromycin producer, diethyl methylmalonate supplementation allowed it to produce up to 30% more erythromycin than the wild type (control) strain--a strain that does not show the Dmr phenotype. The Dmr phenotype represents a new class of strain improvement phenotype. A theory to explain the biochemical mechanism for the Dmr phenotype is proposed. Other phenotypes found to be associated with the mutB knockout were a growth defect and hyper-pigmentation, both of which were restored to normal by exposure to diethyl methylmalonate. Furthermore, mutB fermentations did not significantly metabolize soybean oil in the presence of diethyl methylmalonate. Finally, a novel method is proposed for the isolation of additional mutants with the Dmr phenotype.
doi:10.1007/s00253-011-3650-3
PMCID: PMC3276693  PMID: 22048617
Diethyl methylmalonate; erythromycin; mutB; methylmalonyl-CoA mutase; Dmr; Saccharopolyspora erythraea
2.  Interspecific exchange of avian influenza virus genes in Alaska: the influence of trans-hemispheric migratory tendency and breeding ground sympatry 
Molecular ecology  2010;20(5):1015-1025.
The movement and transmission of avian influenza viral strains via wild migratory birds may vary by host species as a result of migratory tendency and sympatry with other infected individuals. To examine the roles of host migratory tendency and species sympatry on the movement of Eurasian low pathogenic avian influenza (LPAI) genes into North America, we characterized migratory patterns and LPAI viral genomic variation in mallards (Anas platyrhynchos) of Alaska in comparison to LPAI diversity of northern pintails (Anas acuta). A 50-year band recovery data set suggests that unlike northern pintails, mallards rarely make trans-hemispheric migrations between Alaska and Eurasia. Concordantly, fewer (14.5%) of 62 LPAI isolates from mallards contained Eurasian gene segments compared to those from 97 northern pintails (35%), a species with greater intercontinental migratory tendency. Aerial survey and banding data suggest that mallards and northern pintails are largely sympatric throughout Alaska during the breeding season, promoting opportunities for interspecific transmission. Comparisons of full genome isolates confirmed near-complete genetic homology (>99.5%) of seven viruses between mallards and northern pintails. This study found viral segments of Eurasian lineage at a higher frequency in mallards than previous studies, suggesting transmission from other avian species migrating inter-hemispherically or the common occurrence of endemic Alaskan viruses containing segments of Eurasian origin. We conclude that mallards are unlikely to transfer Asian origin viruses directly to North America via Alaska, but that they are likely infected with Asian origin viruses via interspecific transfer from species with regular migrations to the Eastern Hemisphere.
doi:10.1111/j.1365-294X.2010.04908.x
PMCID: PMC3041836  PMID: 21073586
Anas platyrhynchos; avian influenza; migratory; reassortment; transmission
3.  Characterization of frontotemporal dementia and/or amyotrophic lateral sclerosis associated with the GGGGCC repeat expansion in C9ORF72 
Brain  2012;135(3):765-783.
Numerous kindreds with familial frontotemporal dementia and/or amyotrophic lateral sclerosis have been linked to chromosome 9, and an expansion of the GGGGCC hexanucleotide repeat in the non-coding region of chromosome 9 open reading frame 72 has recently been identified as the pathogenic mechanism. We describe the key characteristics in the probands and their affected relatives who have been evaluated at Mayo Clinic Rochester or Mayo Clinic Florida in whom the hexanucleotide repeat expansion were found. Forty-three probands and 10 of their affected relatives with DNA available (total 53 subjects) were shown to carry the hexanucleotide repeat expansion. Thirty-six (84%) of the 43 probands had a familial disorder, whereas seven (16%) appeared to be sporadic. Among examined subjects from the 43 families (n = 63), the age of onset ranged from 33 to 72 years (median 52 years) and survival ranged from 1 to 17 years, with the age of onset <40 years in six (10%) and >60 in 19 (30%). Clinical diagnoses among examined subjects included behavioural variant frontotemporal dementia with or without parkinsonism (n = 30), amyotrophic lateral sclerosis (n = 18), frontotemporal dementia/amyotrophic lateral sclerosis with or without parkinsonism (n = 12), and other various syndromes (n = 3). Parkinsonism was present in 35% of examined subjects, all of whom had behavioural variant frontotemporal dementia or frontotemporal dementia/amyotrophic lateral sclerosis as the dominant clinical phenotype. No subject with a diagnosis of primary progressive aphasia was identified with this mutation. Incomplete penetrance was suggested in two kindreds, and the youngest generation had significantly earlier age of onset (>10 years) compared with the next oldest generation in 11 kindreds. Neuropsychological testing showed a profile of slowed processing speed, complex attention/executive dysfunction, and impairment in rapid word retrieval. Neuroimaging studies showed bilateral frontal abnormalities most consistently, with more variable degrees of parietal with or without temporal changes; no case had strikingly focal or asymmetric findings. Neuropathological examination of 14 patients revealed a range of transactive response DNA binding protein molecular weight 43 pathology (10 type A and four type B), as well as ubiquitin-positive cerebellar granular neuron inclusions in all but one case. Motor neuron degeneration was detected in nine patients, including five patients without ante-mortem signs of motor neuron disease. While variability exists, most cases with this mutation have a characteristic spectrum of demographic, clinical, neuropsychological, neuroimaging and especially neuropathological findings.
doi:10.1093/brain/aws004
PMCID: PMC3286335  PMID: 22366793
frontotemporal dementia; amyotrophic lateral sclerosis; motor neuron disease; TDP-43; neurogenetics; chromosome 9
4.  Clinically relevant doses of chemotherapy agents reversibly block formation of glioblastoma neurospheres 
Cancer letters  2010;296(2):168-177.
Glioblastoma patients have a poor prognosis, even after surgery, radiotherapy, and chemotherapy with temozolomide or 1,3-bis(2-chloroethy)-1-nitrosourea. We developed an in vitro recovery model using neurosphere cultures to analyze the efficacy of chemotherapy treatments, and tested whether glioblastoma neurosphere initiating cells are resistant. Concentrations of chemotherapy drugs that inhibit neurosphere formation are similar to clinically relevant doses. Some lines underwent a transient cell cycle arrest and a robust recovery of neurosphere formation. These results indicate that glioblastoma neurospheres can regrow after treatment with chemotherapy drugs. This neurosphere recovery assay will facilitate studies of chemo-resistant subpopulations and methods to enhance glioblastoma therapy.
doi:10.1016/j.canlet.2010.04.005
PMCID: PMC2914162  PMID: 20435409
chemotherapy; cancer stem cells; DNA damage; temozolomide; BCNU; glioblastoma; neurosphere
5.  Engineering of the methylmalonyl-CoA metabolite node for increased erythromycin production in oil-based fermentations of Saccharopolyspora erythraea 
Metabolic engineering  2007;9(3):293-303.
Engineering of the methylmalonyl-CoA (mmCoA) metabolite node of the Saccharopolyspora erythraea wild type strain (FL2267) through duplication of the mmCoA mutase (MCM) operon led to a 51% (range 40%-64%, 0.95 CI, N = 152) increase in erythromycin production in a high-performance oil-based fermentation medium. The MCM operon was carried on a 6.8 kb DNA fragment in plasmid pFL2212 which was inserted by homologous recombination into the S. erythraea chromosome. The fragment contained one uncharacterized gene, ORF1; three MCM related genes, mutA, mutB, meaB; and one gntR-family regulatory gene, mutR. Additional strains were constructed containing partial duplications of the MCM operon, as well as a knockout of ORF1, none of these strains showed any significant alteration in their erythromycin production profile. The combined results showed that increased erythromycin production only occurred in strain FL2385 containing a duplication of the entire MCM operon including mutR and a predicted stem-loop structure overlapping the 3′ terminus of the mutR coding sequence.
doi:10.1016/j.ymben.2007.02.001
PMCID: PMC2722834  PMID: 17482861
methylmalonyl-CoA mutase (MCM); metabolic engineering; Saccharopolyspora erythraea; erythromycin; precursor; strain improvement
6.  Knockout of the Erythromycin Biosynthetic Cluster Gene, eryBI, Blocks Isoflavone Glucoside Bioconversion during Erythromycin Fermentations in Aeromicrobium erythreum but Not in Saccharopolyspora erythraea▿  
Applied and Environmental Microbiology  2008;74(23):7383-7390.
Isoflavone glucosides are valuable nutraceutical compounds and are present in commercial fermentations, such as the erythromycin fermentation, as constituents of the soy flour in the growth medium. The purpose of this study was to develop a method for recovery of the isoflavone glucosides as value-added coproducts at the end of either Saccharopolyspora erythraea or Aeromicrobium erythreum fermentation. Because the first step in isoflavone metabolism was known to be the conversion of isoflavone glucosides to aglycones by a β-glucosidase, we chose to knock out the only β-glucosidase gene known at the start of the study, eryBI, to see what effect this had on metabolism of isoflavone glucosides in each organism. In the unicellular erythromycin producer A. erythreum, knockout of eryBI was sufficient to block the conversion of isoflavone glucosides to aglycones. In S. erythraea, knockout of eryBI had no effect on this reaction, suggesting that other β-glucosidases are present. Erythromycin production was not significantly affected in either strain as a result of the eryBI knockout. This study showed that isoflavone metabolism could be blocked in A. erythreum by eryBI knockout but that eryBI knockout was not sufficient to block isoflavone metabolism in S. erythraea.
doi:10.1128/AEM.01759-08
PMCID: PMC2592926  PMID: 18836015
7.  Analysis of an 8.1-kb DNA Fragment Contiguous with the Erythromycin Gene Cluster of Saccharopolyspora erythraea in the eryCI-Flanking Region 
Antimicrobial Agents and Chemotherapy  2002;46(12):3892-3899.
An 8.1-kb region of the Saccharopolyspora erythraea genome, significant for its contiguity to the known genes of the erythromycin biosynthetic gene cluster, was mutationally analyzed and its DNA sequence was determined. The region lies immediately adjacent to eryCI. The newly characterized region is notable for a large, 3.0-kb segment, predicted not to be translated, followed by four probable genes: an acetyltransferase gene, a protease inhibitor gene, a methyltransferase gene, and a transposase gene. Because the probable functions of the genes in this region are not required for erythromycin biosynthesis or resistance and because a deletion of a 6.0-kb portion of this region had no effect on erythromycin biosynthesis, this region marks the outside boundary of the erythromycin gene cluster. Therefore, eryCI represents the end of the cluster. These results complete the analysis of the erythromycin gene cluster and eliminate the possibility that additional sought-after pathway-specific structural or regulatory genes might be found within or adjacent to the cluster.
doi:10.1128/AAC.46.12.3892-3899.2002
PMCID: PMC132777  PMID: 12435693
8.  Transcriptional Organization of the Erythromycin Biosynthetic Gene Cluster of Saccharopolyspora erythraea 
Journal of Bacteriology  1999;181(22):7098-7106.
The transcriptional organization of the erythromycin biosynthetic gene (ery) cluster of Saccharopolyspora erythraea has been examined by a variety of methods, including S1 nuclease protection assays, Northern blotting, Western blotting, and bioconversion analysis of erythromycin intermediates. The analysis was facilitated by the construction of novel mutants containing a S. erythraea transcriptional terminator within the eryAI, eryAIII, eryBIII, eryBIV, eryBV, eryBVI, eryCIV, and eryCVI genes and additionally by an eryAI −10 promoter mutant. All mutant strains demonstrated polar effects on the transcription of downstream ery biosynthetic genes. Our results demonstrate that the ery gene cluster contains four major polycistronic transcriptional units, the largest one extending approximately 35 kb from eryAI to eryG. Two overlapping polycistronic transcripts extending from eryBIV to eryBVII were identified. In addition, seven ery cluster promoter transcription start sites, one each beginning at eryAI, eryBI, eryBIII, eryBVI, and eryK and two beginning at eryBIV, were determined.
PMCID: PMC94186  PMID: 10559177

Results 1-8 (8)