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Evaluation of Nostoc Strain ATCC 53789 as a Potential Source of Natural Pesticides. Natascia Biondi, 2004.The cyanobacterium Nostoc strain ATCC 53789, a known cryptophycin producer, was tested for its potential as a source of natural pesticides . The antibacterial, antifungal, insecticidal, nematocidal, and cytotoxic activities of methanolic extracts of the cyanobacterium were evaluated . Among the target organisms, nine fungi (Armillaria sp., Fusarium oxysporum f . sp . melonis, Penicillium expansum, Phytophthora cambivora, P . cinnamomi, Rhizoctonia solani, Rosellinia, sp., Sclerotinia sclerotiorum, and Verticillium albo-atrum) were growth inhibited and one insect (Helicoverpa armigera) was killed by the extract, as well as the two model organisms for nematocidal (Caenorhabditis elegans) and cytotoxic (Artemia salina) activity . No antibacterial activity was detected . The antifungal activity against S . sclerotiorum was further studied with both extracts and biomass of the cyanobacterium in a system involving tomato as a host plant . Finally, the herbicidal activity of Nostoc strain ATCC 53789 was evaluated against a grass mixture . To fully exploit the potential of this cyanobacterium in agriculture as a source of pesticides, suitable application methods to overcome its toxicity toward plants and nontarget organisms must be developed . Effects of Inactivation and Constitutive Expression of the Unfolded- Protein Response Pathway on Protein Production in the Yeast Saccharomyces cerevisiae. Mari Valkonen, 2003.One strategy to obtain better yields of secreted proteins has been overexpression of single endoplasmic reticulum-resident foldases or chaperones . We report here that manipulation of the unfolded-protein response (UPR) pathway regulator, HAC1, affects production of both native and foreign proteins in the yeast Saccharomyces cerevisiae . The effects of HAC1 deletion and overexpression on the production of a native protein, invertase, and two foreign proteins, Bacillus amyloliquefaciens  -amylase and Trichoderma reesei endoglucanase EGI, were studied . Disruption of HAC1 caused decreases in the secretion of both
-amylase (70 to 75% reduction) and EGI (40 to 50% reduction) compared to the secretion by the parental strain . Constitutive overexpression of HAC1 caused a 70% increase in
-amylase secretion but had no effect on EGI secretion . The invertase levels were twofold higher in the strain overexpressing HAC1 . Also, the effect of the active form of T . reesei hac1 was tested in S . cerevisiae . hac1 expression caused a 2.4-fold increase in the secretion of
-amylase in S . cerevisiae and also slight increases in invertase and total protein production . Overexpression of both S . cerevisiae HAC1 and T . reesei hac1 caused an increase in the expression of the known UPR target gene KAR2 at early time points during cultivation .
High-Level Production of Porphyrins in Metabolically Engineered Escherichia coli: Systematic Extension of a Pathway Assembled from Overexpressed Genes Involved in Heme Biosynthesis. Seok Joon Kwon, 2003.Due to their spectroscopic properties porphyrins are of special interest for a variety of applications, ranging from drug development or targeting to material sciences and chemical and biological sensors . Since chemical syntheses are limited in terms of regio- and stereoselective functionalization of porphyrins, a biosynthetic approach with tailored enzyme catalysts offers a promising alternative . In this paper, we describe assembly of the entire heme biosynthetic pathway in a three-plasmid system and overexpression of the corresponding genes with Escherichia coli as a host . Without further optimization, this approach yielded remarkable porphyrin production levels, up to 90 µmol/liter, which is close to industrial vitamin B12 production levels . Different combinations of the genes were used to produce all major porphyrins that occur as intermediates in heme biosynthesis . All these porphyrin intermediates were obtained in high yields . The product spectrum was analyzed and quantified by using high-performance liquid chromatography . Intriguingly, although protoporphyrin IX could be produced at high levels, overexpressed Bacillus subtilis ferrochelatase could not convert this substrate appreciably into heme . However, further investigation clearly revealed a high level of expression of the ferrochelatase and a high level of activity in vitro . These results may indicate that heme has a regulatory impact on the iron uptake of E . coli or that the ferrochelatase is inactive in vivo due to an incompatible enzyme interaction .
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