Effect of photoreactivating light on survival of ultraviolet-light-irradiated Streptomyces lividans 66Mortelmans, Kristien
doi: 10.1007/BF01569687pmid: N/A
Biological systems can repair damage induced in their DNA by ultraviolet light (UV). Most cells contain at least three DNA repair pathways, each of which has a marked effect on UV survival. Excision repair and recombinational (postreplication) repair are light-independent whereas photoreactivation (PR), whether enzyzmatic or photochemical, is light-dependent. The specificity of photoreactivation for UV-induced DNA damage allows it to be used as a tool for examining whether premutational DNA lesions are preferred sites for photoreversal; it therefore plays an important role in mutagenesis studies. Evidence is presented here that PR occurs in a time-dependent fashion in three strains of Streptomyces lividans 66. The effect appears to be independent of temperature and is observed only when PR treatment is given after UV irradiation. The present experiments do not discriminate between enzymatic and photochemical protection.
Growth of Zymomonas on lactose: Gene cloning in combination with mutagenesisBuchholz, Steven; Dooley, Margaret; Eveleigh, Douglas
doi: 10.1007/BF01569689pmid: N/A
Wild-type strains of Zymomonas mobilis have a limited substrate range of glucose, fructose and sucrose. In order to expand this substrate range, transconjugants of Z. mobilis containing Lac + plasmids have been constructed. Although β-galactosidase is expressed in such strains, they lack the ability to grow on lactose. We now report the development of Z. mobilis strains capable of growth on lactose. This was achieved in two stages. First, a broad host range plasmid was constructed (pRUT102) which contained the lactose operon under the control of a Z. mobilis promoter plus genes for galactose utilization. Z. mobilis CP4.45 containing pRUT102 was then subjected to mutagenesis combined with continued selection pressure for growth on lactose. One strain, Z. mobilis SB6, produced a turbid culture that yielded 0.25% ethanol from 5% lactose (plus 2% yeast extract) in 15 days.
Metabolism of chlorinated methanes, ethanes, and ethylenes by a mixed bacterial culture growing on methaneHenson, J.; Yates, Marylynn; Cochran, Jack
doi: 10.1007/BF01569690pmid: N/A
Soil was taken from the top 10 cm of a soil column that removed halogenated aliphatic hydrocarbons in the presence of natural gas. This soil was used as an enrichment inoculum to determine that the removals seen in the soil column were in fact of a microbiological nature. Methane served as the source of carbon and energy and was consumed immediately by the enrichments. After several transfers of the enrichments, a stable consortium of at least three bacterial types was obtained. The predominant bacterium was a non-motile, gram-negative coccus. This stable consortium was able to remove chlorinated methanes, ethanes, and ethylenes when grown with methane and oxygen in the headspace. Methane was required for the removals to be observed. Acetylene inhibited the removals, which further suggests the involvement of methanotrophs. Benzene and toluene were removed by the mixed culture with or without methane in the headspace. Fatty acid analysis of the mixed culture resulted in a profile that indicated that the predominant organism was a type II methanotroph. This study provides further evidence that methanotrophic bacteria are capable of cometabolizing a wide range of chlorinated methanes, ethanes, and ethylenes.
Secretion of the sweet-tasting plant protein thaumatin by Streptomyces lividansIllingworth, Charles; Larson, Gregg; Hellekant, Goran
doi: 10.1007/BF01569691pmid: N/A
To produce and direct the export in Streptomyces lividans of the sweet plant protein thaumatin, thaumatin II cDNA was fused in the correct reading frame to the β-galactosidase leader peptide, under the control of the β-galactosidase promoter and ribosome binding site. The export of the recombinant thaumatin may allow the correct formation of the thaumatin disulfide bonds. The recombinant thaumatin was purified from the medium on an S-Sepharose column and detected with western blots by sheep α-thaumatin antibodies. The recombinant thaumatin was the same size as authentic thaumatin and changed position on an acrylamide gel in response to reduction by 2-mercaptoethanol in the same manner.
A peptide binding chromogenic assay for detecting glycopeptide antibioticsMahoney, David; Baisden, Diana; Yao, Raymond
doi: 10.1007/BF01569692pmid: N/A
A solid-phase peptide binding assay, based on the mechanism of action of glycopeptide antibiotics, was developed for detecting this chemical class of metabolites. Utilizing a pentapeptide ( l -alanyl- d -isoglutaminyl- l -lysyl- d -alanyl- d -alanine)-bovine serum albumin conjugate immobilized on the wall of microtiter wells, the binding of the vancomycin-alkaline phosphatase to the peptide could be demonstrated by subsequently monitoring the enzyme activity. The presence of glycopeptides in fermentation broths could be detected and quantified with a competitive binding assay. Peptides with a d -alanyl- d -alanine carboxyl terminus were necessary for the binding of these glycopeptides, thus confirming the mode of action of this class of antibiotics.
Biotransformation of aromatic aldehydes by Saccharomyces cerevisiae : Investigation of reaction ratesLong, A.; Ward, O.
doi: 10.1007/BF01569693pmid: N/A
The rate of production of l -phenylacetyl carbinol by Saccharomyces cerevisiae in reaction mixtures containing benzaldehyde with sucrose or pyruvate as cosubstrate was investigated in short 1 h incubations. The effect of yeast dose rate, sucrose and benzaldehyde concentration and pH on the rate of reaction was determined. Maximum biotransformation rates were obtained with concentrations of benzaldehyde, sucrose and yeast of 6 g, 40 g and 60 g/l, respectively. Negligible biotransformation rates were observed at a concentration of 8 g/l benzaldehyde. The reaction had a pH optimum of 4.0–4.5. Rates of bioconversion of benzaldehyde and selected substituted aromatic aldehydes using both sucrose and sodium pyruvate as cosubstrate were compared. The rate of aromatic alcohol production was much higher when sucrose was used rather than pyruvate. o -Tolualdehyde and 1-chlorobenzaldehyde were poor substrates for aromatic carbinol formation although the latter produced significant aromatic alcohol in sucrose-containing media. Yields of 2.74 and 3.80 g/l phenylacetyl carbinol were produced from sucrose and pyruvate, respectively, in a 1 h reaction period.
Improved strains for production of xanthan gum by fermentation of Xanthomonas campestrisMarquet, Magda; Mikolajczak, Marcia; Thorne, Linda; Pollock, Thomas
doi: 10.1007/BF01569694pmid: N/A
Two classes of mutants of Xanthomonas campestris B1459 were isolated that accumulate more xanthan gum than the parental wild-type in culture broths of shake flask cultures and both batch and fed-batch fermentations. The first mutant class was resistant to the antibiotic rifampicin and accumulated, on average, about 20% more xanthan gum than wild-type. The second mutant class, a derivative of the first, was resistant to both bacitracin and rifampicin, and accumulated about 10% more xanthan than its parent. On a weight basis, the viscosities of the polysaccharides made by each strain were not distinguishable. Only a subset of the drug-resistant mutants were overproducers of xanthan. The biochemical basis for the overproduction of xanthan by the mutant strains has not been determined. Both new strains served as recipients for recombinant plasmids bearing ‘xanthan’ genes and further augmented the effects of multiple copies of those genes on xanthan productivity.
Lactic acid production by batch fermentation of whey permeate: A mathematical modelLeh, Mel; Charles, Marvin
doi: 10.1007/BF01569695pmid: N/A
The batch fermentation of whey permeate to lactic acid was improved by supplementing the broth with enzyme-hydrolyzed whey protein. A mathematical model based on laboratory results predicts to a 99% confidence limit the kinetics of this fermentation. Cell growth, acid production and protein and sugar use rates are defined in quantifiable terms related to the state of cell metabolism. The model shows that the constants of the Leudeking-Piret model are not true constants, but must vary with the medium composition, and especially the peptide average molecular weight. The kinetic mechanism on which the model is based also is presented.