Amelioration of spinal cord injury in rats by blocking peroxynitrite/calpain activity.

BACKGROUND: Spinal cord injury (SCI) is one of the leading causes of disability and chronic pain. In SCI-induced pathology, homeostasis of the nitric oxide (NO) metabolome is lost. Major NO metabolites such as S-nitrosoglutathione (GSNO) and peroxynitrite are reported to play pivotal roles in regulating the activities of key cysteine proteases, calpains. While peroxynitrite (a metabolite of NO and superoxide) up regulates the activities of calpains leading to neurodegeneration, GSNO (a metabolite of NO and glutathione) down regulates the activities of calpains leading to neuroprotection. In this study, effect of GSNO on locomotor function and pain threshold and their relationship with the levels of peroxynitrite and the activity of calpain in the injured spinal cord were investigated using a 2-week rat model of contusion SCI. RESULTS: SCI animals were initially treated with GSNO at 2 h after the injury followed by a once daily dose of GSNO for 14 days. Locomotor function was evaluated by "Basso Beattie and Bresnahan (BBB) locomotor rating scale" and pain by mechanical allodynia. Peroxynitrite level, as expression of 3-nitrotyrosine (3-NT), calpain activity, as the degradation products of calpain substrate alpha II spectrin, and nNOS activity, as the expression phospho nNOS, were measured by western blot analysis. Treatment with GSNO improved locomotor function and mitigated pain. The treatment also reduced the levels of peroxynitrite (3-NT) and decreased activity of calpains. Reduced levels of peroxynitrite resulted from the GSNO-mediated inhibition of aberrant activity of neuronal nitric oxide synthase (nNOS). CONCLUSIONS: The data indicates that higher levels of 3-NT and aberrant activities of nNOS and calpains correlated with SCI pathology and functional deficits. Treatment with GSNO improved locomotor function and mitigated mechanical allodynia acutely post-injury. Because GSNO shows potential to ameliorate experimental SCI, we discuss implications for GSNO therapy in clinical SCI research.

Enhancing the Production of D-Mannitol by an Artificial Mutant of Penicillium sp. T2-M10.

D-Mannitol belongs to a linear polyol with six-carbon and has indispensable usage in medicine and industry. In order to obtain more efficient D-mannitol producer, this study has screened out a stable mutant Penicillium sp. T2-M10 that was isolated from the initial D-mannitol-produced strain Penicillium sp.T2-8 via UV irradiation as well as nitrosoguanidine (NTG) induction. The mutant had a considerable enhancement in yield of D-mannitol based on optimizing fermentation. The production condition was optimized as the PDB medium with 24 g/L glucose for 9 days. The results showed that the production of D-mannitol from the mutant strain T2-M10 increased 125% in contrast with the parental strain. Meanwhile, the fact that D-mannitol is the main product in the mutant simplified the process of purification. Our finding revealed the potential value of the mutant strain Penicillium sp. T2-M10 to be a D-mannitol-producing strain.

A Lactobacillus mutant capable of accumulating long-chain polyphosphates that enhance intestinal barrier function.

Inorganic polyphosphate (polyP) was previously identified as a probiotic-derived substance that enhances intestinal barrier function. PolyP-accumulating bacteria are expected to have beneficial effects on the human gastrointestinal tract. In this study, we selected Lactobacillus paracasei JCM 1163 as a strain with the potential to accumulate polyP, because among the probiotic bacteria stored in our laboratory, it had the largest amount of polyP. The chain length of polyP accumulated in L. paracasei JCM 1163 was approximately 700 phosphate (Pi) residues. L. paracasei JCM 1163 accumulated polyP when Pi was added to Pi-starved cells. We further improved the ability of L. paracasei JCM 1163 to accumulate polyP by nitrosoguanidine mutagenesis. The mutant accumulated polyP at a level of 1500 nmol/mg protein-approximately 190 times that of the wild-type strain. PolyP extracted from the L. paracasei JCM 1163 significantly suppressed the oxidant-induced intestinal permeability in mouse small intestine. In conclusion, we have succeeded in breeding the polyP-accumulating Lactobacillus mutant that is expected to enhance intestinal barrier function.

Improvement of microbial strain and fermentation process of rapamycin biosynthesis.

The purpose of this investigation is to enhance the production of the immunosuppressant drug rapamycin by subjecting the strain CBS 773.23 to ultraviolet (UV) and N-methyl-N'-nitro-N-nitroso guanidine (NTG) mutations. Among all the mutants tested, MTCC 5681 (NRC-CM03/SH) obtained by NTG mutagenesis of strain CBS 773.72 showed the highest activity, 210 mg/L. The effect of different factors including medium composition, pH, temperature, and intensity of mixing on rapamycin production was studied. Based on the study, the optimal concentrations of soluble starch and dry yeast granules were found to be 50 g/L and 1.5 g/L, respectively. Furthermore, optimal values for pH, temperature, and shaking speed were found to be 6.0, 28°C, and 220 rpm, respectively. The production of rapamycin increased 1.6-fold, to 360 mg/L, in shake-flask culture using the optimal combination of factors observed compared with basal cultivation medium using MTCC 5681 mutant strain.

Isolation of Streptomyces globisporus and Blakeslea trispora mutants with increased carotenoid content.

Hyperpigmented mutants of Streptomyces globisporus 1912-Hp7 and Blakeslea trispora 18(+), 184(-) were isolated by action of hydrogen peroxide and nitrosoguanidine, correspondingly, from initial strains S. globisporus 1912-4Lcp and B. trispora 72(-), 198(+). The carotenoids of dry biomass of obtained strains, rubbed thoroughly with glass powder by a pestle in porcelain mortar were extracted by acetone and purified by TLC. Identification of the individual carotenoids was performed by means of HPLC and LC/MS spectrometry. It was shown that strain S. globisporus 1912-4Crt produced beta-carotene/lycopene (6.91/3.24 mg/L), mutants 1912-4Lcp and 1912-7Hp synthesized only lycopene (26.05 and 50.9 mg/L, respectively), and strains B. trispora 18(+) and 184(-)-beta-carotene (6.2% in dry biomass or more 2.5 g/L) without illumination in shake flasks. It is the first example of high constitutive production of the carotenoids by the representative of genus Streptomyces without photoinduction or increased synthesis of sigma factor The improved strains of B. trispora 18(+) and 184(-) can be used for biotechnological production of beta-carotene in industrial conditions.

[Genetic variability of synthesis feature of carotenoids in Streptomyces globisporus 1912].

Seventeen spontaneous and induced mutants, that acquired a new characteristic--the synthesis of beta-carotene and lycopene, were obtained from strain Streptomyces globisporus 1912. It was found that spontaneous mutants inherited more stably the acquired carotenogenesis as compared to induced ones. Synthesis of carotenoids by all isolated Crt+ Lcp+ cultures is a constitutive feature. It was shown that Crt(+)-mutants (4Crt, 6Crt, 7Crt, RVCrt and R3Crt) synthesized beta-carotene and lycopene, while Lcp(+)-mutants (TpS16-1, TpS16-2, 4Lcp and R3Lcp)--only lycopene. The obtained mutants and transformants of S. globisporus 1912, synthesizing carotene were characterized by a simultaneous change of two or three phenotypic characteristics: synthesis of the antibiotic landomycin E. sporullation and carotenogenesis. It can be assumed that the high instability of this characteristic (carotenogenesis) in strain S. globisporus 1912 was caused by localization of the crt-genes cluster close to a TIR-element in a chromosome terminal region, frequent structural reorganization of DNA here were reported in the literature.

Enhanced ß-galactosidase production from whey powder by a mutant of the psychrotolerant yeast Guehomyces pullulans 17-1 for hydrolysis of lactose.

In order to isolate ß-galactosidase overproducers of the psychrotolerant yeast Guehomyces pullulans 17-1, its cells were mutated by using nitrosoguanidine (NTG). One mutant (NTG-133) with enhanced ß-galactosidase production was obtained. The mutant grown in the production medium with 30.0 g/l lactose and 2.0 g/l glucose could produce more ß-galactosidase than the same mutant grown in the production medium with only 30.0 g/l lactose while ß-galactosidase production by its wild type was sensitive to the presence of glucose in the medium. It was found that 40.0 g/l of the whey powder was the most suitable for ß-galactosidase production by the mutant. After optimization of the medium and cultivation conditions, the mutant could produce 29.2 U/ml of total ß-galactosidase activity within 132 h at the flask level while the mutant could produce 48.1 U/ml of total ß-galactosidase activity within 144 h in 2-l fermentor. Over 77.1% of lactose in the whey powder (5.0% w/v) was hydrolyzed in the presence of the ß-galactosidase activity of 280 U/g of lactose within 9 h while over 77.0% of lactose in the whey was hydrolyzed in the presence of ß-galactosidase activity of 280 U/g of lactose within 6 h. This was the first time to show that the ß-galactosidase produced by the psychrotolerant yeast could be used for hydrolysis of lactose in the whey powder and whey.

Synergistic cytotoxicity of N-methyl-N'-nitro-N-nitrosoguanidine and absence of poly(ADP-ribose) glycohydrolase involves chromatin decondensation.

DNA-alkylating agents in combination with poly (ADP-ribose) (PAR) synthesis inhibitors are a promising treatment for cancer. In search of other efficacious alternatives, we hypothesized that the absence of poly(ADP-ribose) glycohydrolase (PARG), which leads to the inhibition of PAR hydrolysis, would lead to increased DNA alkylation after treatment with low doses of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). At a sublethal dose, MNNG shows synergistic cytotoxicity in PARG-null embryonic trophoblast stem (TS) cells. The PAR modifications of histone H1 and histone H2B are much more pronounced in PARG null-TS cells exposed to MNNG, suggesting their relevance in the efficacy of this combination therapy. Because the PAR modification of these chromatin binding proteins leads to chromatin remodeling, a possible mechanism for the observed synergistic effects involves the subsequent decondensation of chromatin, which may cause the genomic DNA to be more accessible to MNNG alkylation. Further analysis demonstrated chromatin decondensation in PARG null-TS cells as visualized by electron microscopy. In addition, treatment with MNNG led to an increase in O6- methylguanine levels in PARG null-TS cells compared to wild-type, which demonstrates increased DNA alkylation in the absence of PARG. Taken together, we provide compelling evidence that the absence of PARG leads to chromatin decondensation, which in turn leads to increased amounts of DNA alkylation and cell death induced by low doses of MNNG. Therefore, combination therapy of PARG inhibition and a DNA- alkylating agent is a potential treatment to induce the death of cancer cells.

[Genetic improvement of technological characteristics of starters for fermented milk products].

Possibility for improvement of technological characteristics of lactobacilli using mutations of resistance to rifampicin (rif(r)) and streptomycin (str(r)) was studied. Using starter model of Narine Lactobacillus acidophilus INMIA-9602 Armenian diet milk product, it was showed that a possibility for selecting strains with increased rate of milk fermentation and acid production is higher in Rif(r) and Str(r) mutants induced by nitrosoguanidine than in cultures sensitive to antibiotics. The milk products obtained using Rif(r) and Str(r) strains had high viscosity, improved texture, increased amount of alive cells and good organoleptic features.

Isolation and characterization of a nitrosoguanidine-induced Enterococcus faecium MTCC 5153 mutant defective in enterocin biosynthesis.

Enterocin A (EntA) is a low molecular weight, heat-stable, chromosomally encoded class IIa bacteriocin produced by several strains of Enterococcus faecium. In this study, a mutated strain of E. faecium MTCC 5153 was characterized for its sensitivity to EntA, immunity function and for the production of induction factor. Nucleotide sequencing of the putative promoter of the entA operon suggested point mutations upstream of the entA gene. The mutant was sensitive to several class IIa bacteriocins and was found to adsorb 20% more bacteriocin compared to its wild-type counterpart.

Signature gene expression profile of triclosan-resistant Escherichia coli.

OBJECTIVES: To gain further insight into the defence mechanisms against triclosan in a mutant derived from an Escherichia coli strain carrying the triclosan-resistant target enzyme, FabI(G93V). METHODS: An E. coli imp4231 FabI(G93V) strain was constructed by replacing intact fabI with a linear DNA cassette, fabI(G93V)-CmR, that contains a single mutation, GGT to GTT, at codon 93 of fabI(G93V) and a chloramphenicol resistance gene (CmR) as a marker for the mutant allele by a Red-mediated recombination system. Using this E. coli imp4231 FabI(G93V) strain, nitrosoguanidine (NTG) mutagenesis was performed to generate E. coli IFNs [imp4231 FabI(G93V) treated with NTG] displaying higher MICs of triclosan than its parent strain. The genes overexpressed in E. coli IFN4 were identified by DNA microarray analysis. RESULTS: An E. coli imp4231 FabI(G93V) strain displays approximately 400-fold increased MICs of triclosan (MIC approximately 8 mg/L) compared with the parent strain (MIC approximately 0.02 mg/L). Furthermore, E. coli IFN4 has the highest MIC of triclosan (MIC approximately 80 mg/L). DNA microarray analysis of E. coli IFN4 shows that many genes involved in the biosynthesis of membrane proteins, including transporters, reductases/dehydrogenases and stress response regulators, were highly expressed in the mutant. CONCLUSIONS: These results strongly indicate that E. coli IFN cells might protect themselves from triclosan by activating various defence mechanisms, such as (i) changing efflux activities; (ii) capturing the triclosan; and (iii) increasing the expression of important regulators or metabolic enzymes.

Monotherapy with a tumor-targeting mutant of S. typhimurium inhibits liver metastasis in a mouse model of pancreatic cancer.

Cancer of the exocrine pancreas is the fourth leading cause of cancer deaths in the United States. Currently, surgical resection is the only hope for cure. The majority of patients present with locally-advanced or metastatic disease. The most common site for distant metastasis is the liver. We report here a modified auxotrophic strain of S. typhimurium that can target and inhibit the growth of liver metastasis in a mouse model of pancreatic cancer. This strain of S. typhimurium is auxotrophic (leucine-arginine dependent) but apparently receives sufficient nutritional support from tumor tissue. To increase tumor targeting ability and tumor killing efficacy, this strain was further modified by re-isolation from a tumor growing in a nude mouse and termed A1-R. In the present study, we demonstrate the efficacy of locally- as well as systemically-administered A1-R on liver metastasis of pancreatic cancer. Mice treated with A1-R given locally via intrasplenic injection or systemically via tail vein injection had a much lower hepatic and splenic tumor burden compared with control mice. Systemic treatment with intravenous A1-R also increased survival time. All results were statistically significant. This study suggests the clinical potential of bacterial treatment of a critical metastatic target of pancreatic cancer.

Indigenous and environmental modulation of frequencies of mutation in Lactobacillus plantarum.

Reliability of microbial (starter) strains in terms of quality, functional properties, growth performance, and robustness is essential for industrial applications. In an industrial fermentation process, the bacterium should be able to successfully withstand various adverse conditions during processing, such as acid, osmotic, temperature, and oxidative stresses. Besides the evolved defense mechanisms, stress-induced mutations participate in adaptive evolution for survival under stress conditions. However, this may lead to accumulation of mutant strains, which may be accompanied by loss of desired functional properties. Defining the effects of specific fermentation or processing conditions on the mutation frequency is an important step toward preventing loss of genome integrity and maintaining the productivity of industrial strains. Therefore, a set of Lactobacillus plantarum mutator reporter strains suitable for qualitative and quantitative analysis of low-frequency mutation events was developed. The mutation reporter system constructed was validated by using chemical mutagenesis (N-methyl-N'-nitro-N-nitrosoguanidine) and by controlled expression of endogenous candidate mutator genes (e.g., a truncated derivative of the L. plantarum hexA gene). Growth at different temperatures, under low-pH conditions, at high salt concentrations, or under starvation conditions did not have a significant effect on the mutation frequency. However, incubation with sublethal levels of hydrogen peroxide resulted in a 100-fold increase in the mutation frequency compared to the background mutation frequency. Importantly, when cells of L. plantarum were adapted to 42 degrees C prior to treatment with sublethal levels of hydrogen peroxide, there was a 10-fold increase in survival after peroxide treatment, and there was a concomitant 50-fold decrease in the mutation frequency. These results show that specific environmental conditions encountered by bacteria may significantly influence the genetic stability of strains, while protection against mutagenic conditions may be obtained by pretreatment of cultures with other, nonmutagenic stress conditions.

Enhanced degradation of TNT by genome-shuffled Stenotrophomonas maltophilia OK-5.

In this study, the enhanced degradation of TNT using cultures of genome-shuffled Stenotrophomonas maltophilia OK-5 mt-3 has been examined and the proteome of shuffled strain was compared to the wild-type OK-5 strain. Genome shuffling of S. maltophilia OK-5 was used to achieve a rapid enhancement of TNT degradation. The initial mutant population was generated by NTG treatment and UV irradiation. The wild-type OK-5 strain was able to degrade 0.2 mM TNT within 6 days, yet barely tolerated 0.5 mM TNT while the shuffled OK-5 mt-3 was capable of completely degrading 0.5 mM TNT within 8 days, and 1.2 mM within 24 days. The proteomic analysis of the shuffled OK-5 mt-3 demonstrated the changes in the expression levels of certain proteins compared to wild-type OK-5. These results provide clues for understanding TNT tolerance and improved TNT degradation by shuffled S. maltophilia OK-5 mt-3 and have possible applications in the processing of industrial waste containing relatively high TNT concentrations.

Enhancement of carotenoids by mutation and stress induced carotenogenic genes in Haematococcus pluvialis mutants.

Growing culture of green alga Haematococcus was exposed to mutagens such as UV, ethyl methane sulphonate (EMS) and 1-methyl 3-nitro 1-nitrosoguanidine (NTG), and further screened over herbicide - glufosinate. The survival rate of cells decreased with increasing concentration of mutagens and herbicides. The mutants exhibited 23-59% increase in total carotenoid and astaxanthin contents. The NTG treated glufosinate resistant mutant showed increased (2.2% to 3.8% w/w) astaxanthin content. The transcript levels of phytoene synthase, phytoene desaturase, lycopene cyclase, beta-carotene ketolase and beta-carotene hydroxylase enzymes in the mutant cultures were found to be 13-18, 14-17, 3, 3-22 and 6-20 fold higher respectively compared to wild type. The mutant obtained by UV irradiation showed highest lycopene cyclase activity (458 nmole beta-carotene formed/mg protein/h) followed by NTG mutant (315 nmole beta-carotene formed/mg protein/h) when compared to that of parent strain (105 nmole beta-carotene formed/mg protein/h). Expression analysis of carotenoid biosynthetic genes in the mutants exhibited increase in transcript levels compared to wild type.

Genome shuffling enhanced L-lactic acid production by improving glucose tolerance of Lactobacillus rhamnosus.

Genome shuffling is a powerful strategy for rapid engineering of microbial strains for desirable industrial phenotypes. Here we applied the genome shuffling to improve the glucose tolerance of Lactobacillus rhamnosus ATCC 11443 while simultaneously enhancing the L-lactic acid production. The starting population was generated by ultraviolet irradiation and nitrosoguanidine mutagenesis and then subjected for the recursive protoplast fusion. The positive colonies from library created by fusing the inactivated protoplasts were more likely to be screened on plates containing different concentrations of high glucose and 2% CaCO(3). Characterization of all mutants and wild-type strain in the shake flask indicated the compatibility of two optimal phenotypes of glucose tolerance and lactic acid enhancement. The lactic acid production, cell growth and glucose consumption of the best performing strain from the second round genome shuffled populations were 71.4%, 44.9% and 62.2% higher than those of the wild type at the initial glucose concentration of 150 g/l in the 16l bioreactor. Furthermore, the higher lactic acid concentrations were obtained when the initial glucose concentrations increased to 160 and 200 g/l in batch fermentation.

[Biosorption ability of mutants of Rhodotorula mucilaginosa UCM Y-1776].

Twenty stable mutants with various coloration intensity have been allocated in carotene-synthesizing natural strain Rhodotorula mucilaginosa UCM Y-1776 (wild type) after nitrosoguanidine action. Two brightly orange mutants 4L and 11 and one non-pigmented mutant 2 were chosen for the further researches. The ultraviolet was inefficient as a mutagen. Resistance to high concentration of copper ions (up to 200 mg/g), high sorption ability (Qmax = 9.1 mmol/g) was characteristic of R. mucilaginosa UCM Y-1776. Concentration of copper ions 50 mg/l was toxic for mutants 4L, 11 and 2, which sorption ability was lower in comparison with carotene pigmented R. mucilaginosa UCM Y-1776. It was shown, for the first time that there was a direct dependence between the presence of carotenoid pigments, resistance to high concentration of copper ions and sorption ability for yeast R. mucilaginosa UCM Y-1776.

Genome shuffling of Streptomyces sp. U121 for improved production of hydroxycitric acid.

(2S, 3R)-Hydroxycitric acid (HCA) from Hibiscus subdariffa inhibits pancreatic alpha-amylase and intestine alpha-glucosidase, leading to reduction of carbohydrate metabolism. In our previous study, Streptomyces sp. U121 was identified as a producer of (2S, 3R)-HCA [Hida et al. (2005) Bioscience, Biotechnology, and Biochemistry 69:1555-1561]. Here, we applied genome shuffling of Streptomyces sp. U121 to achieve rapid improvement of HCA production. The initial mutant population was generated by nitrosoguanidine treatment of the spores, and an improved population producing fivefold more HCA over wild type was obtained by three rounds of genome shuffling. For efficient screening of the mutant library, trans-epoxyaconitic acid (EAA), an antibiotic analog of HCA, was utilized. EAA inhibited the regeneration of nonfused protoplasts, resulting in selective screening of shuffled strains. Mutant strains with enhanced EAA resistance exhibited significantly higher HCA production in liquid media. Furthermore, the best mutant showed increased cell growth in flask culture, as well as increased HCA production.

The apoptosis inhibitory domain of FE65-like protein 1 regulates both apoptotic and caspase-independent programmed cell death mediated by tumor necrosis factor.

Tumor necrosis factor (TNF) can induce caspase-dependent (apoptotic) and caspase-independent pathways to programmed cell death (PCD). Here, we demonstrate that stable transfection of a cDNA encompassing the C-terminal apoptosis inhibitory domain (AID) of FE65-like protein 1 into mouse L929 fibrosarcoma cells protects from caspase-independent as well as from apoptotic PCD induced by TNF. We show that the AID does not protect from caspase-independent PCD elicited by 1-methyl-3-nitro-1-nitrosoguanidine, suggesting that the AID might prevent cell death by affecting assembly of the death inducing signaling complex of the 55 kDa TNF receptor or clustering of the receptor itself. Interference with caspase-independent PCD mediated by the sphingolipid ceramide further increases protection conferred by the AID, as does the antioxidant butylated hydroxyanisole, implicating ceramide and reactive oxygen species as potential factors interacting with caspase-independent PCD regulated by the AID.

Analysis of the Escherichia coli Alp phenotype: heat shock induction in ssrA mutants.

The major phenotypes of lon mutations, UV sensitivity and overproduction of capsule, are due to the stabilization of two substrates, SulA and RcsA. Inactivation of transfer mRNA (tmRNA) (encoded by ssrA), coupled with a multicopy kanamycin resistance determinant, suppressed both lon phenotypes and restored the rapid degradation of SulA. This novel protease activity was named Alp but was never identified further. We report here the identification, mapping, and characterization of a chromosomal mutation, faa (for function affecting Alp), that leads to full suppression of a Deltalon ssrA::cat host and thus bypasses the requirement for multicopy Kan(r); faa and ssrA mutants are additive in their ability to suppress lon mutants. The faa mutation was mapped to the C terminus of dnaJ(G232); dnaJ null mutants have similar effects. The identification of a lon suppressor in dnaJ suggested the possible involvement of heat shock. We find that ssrA mutants alone significantly induce the heat shock response. The suppression of UV sensitivity, both in the original Alp strain and in faa mutants, is reversed by mutations in clpY, encoding a subunit of the heat shock-induced ClpYQ protease that is known to degrade SulA. However, capsule synthesis is not restored by clpY mutants, probably because less RcsA accumulates in the Alp strain and because the RcsA that does accumulate is inactive. Both ssrA effects are partially relieved by ssrA derivatives encoding protease-resistant tags, implicating ribosome stalling as the primary defect. Thus, ssrA and faa each suppress two lon mutant phenotypes but by somewhat different mechanisms, with heat shock induction playing a major role.