bims-polyam Biomed News
on Polyamines
Issue of 2019‒11‒03
fourteen papers selected by
Alexander Ivanov
Engelhardt Institute of Molecular Biology
  1. Bacterial Pathogens Hijack the Innate Immune Response by Activation of the Reverse Transsulfuration Pathway.
  2. PGC-1α inhibits polyamine metabolism in Cyclin E1-driven ovarian cancer.
  3. Modeling Snyder-Robinson Syndrome in multipotent stromal cells reveals impaired mitochondrial function as a potential cause for deficient osteogenesis.
  4. A general approach for the liquid phase fragment synthesis of orthogonally protected naturally occurring polyamines and applications thereof.
  5. An arginase-based system for selection of transfected CHO cells without the use of toxic chemicals.
  6. Hepatocellular Adenoma in a Patient with Ornithine Transcarbamylase Deficiency.
  7. Enhanced accumulation of gibberellins rendered rice seedlings sensitive to ammonium toxicity.
  8. Sphingobium fluviale sp. nov., isolated from a river.
  9. Sphingomonas paeninsulae sp. nov., isolated from soil sampled at Fildes Peninsula, Antarctica.
  10. Flavobacterium ustbae sp. nov., isolated from rhizosphere soil of Alhagi sparsifolia.
  11. Effect of L-Ornithine application on improving drought tolerance in sugar beet plants.
  12. Hydrogenophaga borbori sp. nov., isolated from activated sludge.
  13. The multifunctional enzyme S-adenosylhomocysteine / methylthioadenosine nucleosidase is a key metabolic enzyme in the virulence of Salmonella enterica var Typhimurium.
  14. Growth and metabolic characteristics of fastidious meat-derived Lactobacillus algidus strains.
  1. MBio. 2019 Oct 29. pii: e02174-19. [Epub ahead of print]10(5):
    Bacterial Pathogens Hijack the Innate Immune Response by Activation of the Reverse Transsulfuration Pathway.
    Alain P Gobert, Yvonne L Latour, Mohammad Asim, Jordan L Finley, Thomas G Verriere, Daniel P Barry, Ginger L Milne, Paula B Luis, Claus Schneider, Emilio S Rivera, Kristie Lindsey-Rose, Kevin L Schey, Alberto G Delgado, Johanna C Sierra, M Blanca Piazuelo, Keith T Wilson.
      The reverse transsulfuration pathway is the major route for the metabolism of sulfur-containing amino acids. The role of this metabolic pathway in macrophage response and function is unknown. We show that the enzyme cystathionine γ-lyase (CTH) is induced in macrophages infected with pathogenic bacteria through signaling involving phosphatidylinositol 3-kinase (PI3K)/MTOR and the transcription factor SP1. This results in the synthesis of cystathionine, which facilitates the survival of pathogens within myeloid cells. Our data demonstrate that the expression of CTH leads to defective macrophage activation by (i) dysregulation of polyamine metabolism by depletion of S-adenosylmethionine, resulting in immunosuppressive putrescine accumulation and inhibition of spermidine and spermine synthesis, and (ii) increased histone H3K9, H3K27, and H3K36 di/trimethylation, which is associated with gene expression silencing. Thus, CTH is a pivotal enzyme of the innate immune response that disrupts host defense. The induction of the reverse transsulfuration pathway by bacterial pathogens can be considered an unrecognized mechanism for immune escape.IMPORTANCE Macrophages are professional immune cells that ingest and kill microbes. In this study, we show that different pathogenic bacteria induce the expression of cystathionine γ-lyase (CTH) in macrophages. This enzyme is involved in a metabolic pathway called the reverse transsulfuration pathway, which leads to the production of numerous metabolites, including cystathionine. Phagocytized bacteria use cystathionine to better survive in macrophages. In addition, the induction of CTH results in dysregulation of the metabolism of polyamines, which in turn dampens the proinflammatory response of macrophages. In conclusion, pathogenic bacteria can evade the host immune response by inducing CTH in macrophages.
    Keywords:  Helicobacter pylori ; immune evasion; immunometabolism; innate immunity; macrophages; pathogenic bacteria; polyamines
    DOI:  https://doi.org/10.1128/mBio.02174-19
  2. Cancer Med. 2019 Oct 27.
    PGC-1α inhibits polyamine metabolism in Cyclin E1-driven ovarian cancer.
    Ting Guo, Bin Li, Chao Gu, Xiuying Chen, Mengxin Han, Xiaocheng Liu, Congjian Xu.
      AIM: Cyclin E1-driven ovarian cancer (OvCa) is characterized with metabolic shift. In this study, we aim to pinpoint the metabolic pathway altered and assess its therapeutic potential.METHODS: In silico reproduction of TCGA ovarian cancer dataset and functional annotation using GSEA was performed. Candidate metabolic pathway was validated using in vitro and in vivo assays.
    RESULTS: From TCGA database, we found that polyamine metabolism was significantly enriched in Cyclin E1-driven OvCa. Expressions of SMS, SRM, and ODC1 were positively correlated with that of CCNE1, respectively. ODC1 and SMS expressions were significantly correlated with decreased immune infiltrates. PGC-1α silencing significantly decreased invasion and migration in both OvCa cell lines. Both spermidine and spermine levels were significantly increased when PGC-1α was silenced. Targeting SRM significantly decreased spermine level in OVCAR3 cells, which was rescued when PGC-1α was silenced. Silencing of PGC-1α resulted in increased SRM in both OvCa cells. Dinaciclib significantly decreased invasion and migration of OVCAR3 cells. Expressions of PD-L1 and PD-L2 were predominantly in tumor-infiltrating lymphocytes. Dinaciclib showed no notable effect of PD-1 yet substantially induced the increased levels of PD-L1 and PD-L2.
    CONCLUSION: Cyclin E1-driven OvCa is characterized with activated polyamine synthesis, which is associated with decreased cancer immunity. Targeting polyamine and CDK2 may therefore sensitize this genotype to immune checkpoint blockade.
    Keywords:  CCNE1; High-grade serous ovarian cancer; polyamine metabolism
    DOI:  https://doi.org/10.1002/cam4.2637
  3. Sci Rep. 2019 Oct 28. 9(1): 15395
    Modeling Snyder-Robinson Syndrome in multipotent stromal cells reveals impaired mitochondrial function as a potential cause for deficient osteogenesis.
    Ashley L Ramsay, Vivian Alonso-Garcia, Cutter Chaboya, Brian Radut, Bryan Le, Jose Florez, Cameron Schumacher, Fernando A Fierro.
      Patients with Snyder-Robinson Syndrome (SRS) exhibit deficient Spermidine Synthase (SMS) gene expression, which causes neurodevelopmental defects and osteoporosis, often leading to extremely fragile bones. To determine the underlying mechanism for impaired bone formation, we modelled the disease by silencing SMS in human bone marrow - derived multipotent stromal cells (MSCs) derived from healthy donors. We found that silencing SMS in MSCs led to reduced cell proliferation and deficient bone formation in vitro, as evidenced by reduced mineralization and decreased bone sialoprotein expression. Furthermore, transplantation of MSCs in osteoconductive scaffolds into immune deficient mice shows that silencing SMS also reduces ectopic bone formation in vivo. Tag-Seq Gene Expression Profiling shows that deficient SMS expression causes strong transcriptome changes, especially in genes related to cell proliferation and metabolic functions. Similarly, metabolome analysis by mass spectrometry, shows that silencing SMS strongly impacts glucose metabolism. This was consistent with observations using electron microscopy, where SMS deficient MSCs show high levels of mitochondrial fusion. In line with these findings, SMS deficiency causes a reduction in glucose consumption and increase in lactate secretion. Our data also suggests that SMS deficiency affects iron metabolism in the cells, which we hypothesize is linked to deficient mitochondrial function. Altogether, our studies suggest that SMS deficiency causes strong transcriptomic and metabolic changes in MSCs, which are likely associated with the observed impaired osteogenesis both in vitro and in vivo.
    DOI:  https://doi.org/10.1038/s41598-019-51868-5
  4. J Org Chem. 2019 Oct 28.
    A general approach for the liquid phase fragment synthesis of orthogonally protected naturally occurring polyamines and applications thereof.
    Stefania Kalantzi, Constantinos M Athanassopoulos, Raili Ruonala, Yrjo Helariutta, Dionissios Papaioannou.
      Orthogonally protected polyamines (PAs) have been synthesized using α,ω-diamines and ω-aminoalcohols as N-Cx-N and N-Cy synthons, respectively, and the Mitsunobou reaction as the key reaction for the assembly of the PA skeleta. The Trt, Dde and Phth groups have been employed for protecting the primary amino functions and the Ns group for activating the primary amino functions towards alkylation and secondary amino function protection. The approach has been readily extended to ac-commodate the total synthesis of the spider toxins Agel 416 and HO-416b incorporat-ing the 3-4-3-3 and the 3-3-3-4 PA skeleton, respectively.
    DOI:  https://doi.org/10.1021/acs.joc.9b02066
  5. J Biol Chem. 2019 Oct 30. pii: jbc.RA119.011162. [Epub ahead of print]
    An arginase-based system for selection of transfected CHO cells without the use of toxic chemicals.
    Berta Capella Roca, Nga Lao, Niall Barron, Padraig Doolan, Martin Clynes.
      Polyamines have essential roles in cell proliferation, DNA replication, transcription, and translation processes, with intracellular depletion of putrescine, spermidine, and spermine resulting in cellular growth arrest and eventual death. Serum-free media for CHO-K1 cells require putrescine supplementation, as these cells lack the first enzyme of the polyamine production pathway, arginase. On the basis of this phenotype, we developed an arginase-based selection system. We transfected CHO-K1 cells with a bicistronic vector co-expressing GFP and arginase and selected cells in media devoid of L-ornithine and putrescine, resulting in mixed populations stably expressing GFP. Moreover, single clones in these selective media stably expressed GFP for a total of 42 generations. Using this polyamine starvation method, we next generated recombinant CHO-K1 cells co-expressing arginase and human erythropoietin (EPO), which also displayed stable expression and healthy growth. The EPO-expressing clones grew in commercial media, such as BalanCD and CHO-S SFM-II, as well as in a defined serum-free, putrescine-containing medium for at least nine passages (27 generations), with a minimal decrease in EPO titer by the end of the culture. We observed lack of arginase activity also in several CHO cell strains (CHO-DP12, CHO-S, and DUXB11) and other mammalian cell lines, including BHK21, suggesting broader utility of this selection system. In conclusion, we have established an easy-to-apply alternative selection system that effectively generates mammalian cell clones expressing biopharmaceutically relevant or other recombinant proteins without the need for any toxic selective agents. We propose that this system is applicable to mammalian cell lines that lack arginase activity.
    Keywords:  Chinese Hamster Ovary (CHO); arginase; cloning; erythropoietin; mammal; polyamine; putrescine; recombinant protein expression; selection system
    DOI:  https://doi.org/10.1074/jbc.RA119.011162
  6. Case Reports Hepatol. 2019 ;2019 2313791
    Hepatocellular Adenoma in a Patient with Ornithine Transcarbamylase Deficiency.
    Lin Cheng, Yajuan Liu, Wenjing Wang, J L Merritt, Matthew Yeh.
      Ornithine transcarbamylase (OTC) deficiency is an X-linked recessive disorder that leads to hyperammonemia and liver damage. Hepatocellular adenoma in OTC deficiency patients has not been previously described. Here we report the first such case to be described in the English language scientific literature.
    DOI:  https://doi.org/10.1155/2019/2313791
  7. J Exp Bot. 2019 Oct 31. pii: erz492. [Epub ahead of print]
    Enhanced accumulation of gibberellins rendered rice seedlings sensitive to ammonium toxicity.
    Baolan Wang, Haifang Wei, Zhang Hui, Wen-Hao Zhang.
      Ammonium (NH4+) phytotoxicity is a worldwide phenomenon, but its primary toxic mechanisms are still controversial. In the present study, we investigated the physiological function of gibberellins (GA) in response of rice plants to ammonium toxicity and polyamine accumulation using GA biosynthesis-related rice mutants. Exposure to NH4+ significantly decreased GA4 production in shoots of wild-type (WT) plants. Both exogenous GA application to WT and increases in endogenous GA level in eui1 mutants rendered them more sensitive to NH4+ toxicity. By contrast, growth of GA-deficient mutants sd1 was more tolerant to NH4+ toxicity than that of their WT counterparts. The role of polyamines was evaluated in the GA-mediated NH4+ toxicity using WT rice plants and their GA-related mutants. The eui1 mutants with GA overproduction displayed a higher endogenous putrescine (Put) accumulation than WT plants, leading to an enhanced Put/(spermidine + spermine) ratio in their shoots. In contrast, the mutation of SD1 gene encoding a defective enzyme in the GA-biosynthesis resulted in a significant increase in spermidine (Spd) and spermine (Spm) production, and reduction in Put/(Spd+Spm) ratio when exposed to high NH4+ medium. Exogenous application of Put exacerbated symptoms associated with NH4+ toxicity in rice shoots, while the symptoms were alleviated by inhibitor of Put biosynthesis. These findings highlight the involvement of GA in ammonium toxicity, and that GA-induced Put accumulation is responsible for the increased sensitivity to ammonium toxicity in rice plants.
    Keywords:  Ammonium toxicity; gibberellins; nitrate; polyamines; putrescine; rice (Oryza sativa L.)
    DOI:  https://doi.org/10.1093/jxb/erz492
  8. Int J Syst Evol Microbiol. 2019 Nov 01.
    Sphingobium fluviale sp. nov., isolated from a river.
    Shih-Yi Sheu, Ya-Ping Guo, Soon-Wo Kwon, Wen-Ming Chen.
      A Gram-stain-negative, rod-shaped, non-motile, poly-β-hydroxybutyrate-accumulating and aerobic bacterial strain, designated CHR27T, was isolated and characterized by using the polyphasic taxonomy approach. The results of phylogenetic analyses based on 16S rRNA gene sequences and coding sequences of an up-to-date bacterial core gene set (92 protein clusters) indicated that strain CHR27T is affiliated with species in the genus Sphingobium. 16S rRNA gene sequence similarity results indicated that strain CHR27T was closely related to species of the genus Sphingobium (94.3-97.0 %), and had the highest sequence similarity to Sphingobium qiguonii X23T (97.0 %). Strain CHR27T showed 19.4-22.1 % digital DNA-DNA hybridization values and 73.2-74.8 % average nucleotide identity values with the strains of other Sphingobium species. Optimal growth occurred at 25 °C, pH 7.5 and in the absence of NaCl. The major fatty acids of strain CHR27T were C18 : 1ω7c and summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c). The predominant hydroxy fatty acid was C14 : 0 2-OH. The polar lipid profile consisted of a mixture of phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, phosphatidylmonomethylethanolamine, phosphatidyldimethylethanolamine, two unidentified sphingoglycolipids and an unidentified aminophospholipid. Strain CHR27T contained spermidine as the major polyamine and putrescine as a minor component. The only isoprenoid quinone was ubiquinone-10. The genomic DNA G+C content of strain CHR27Twas 61.8 mol%. On the basis of the phylogenetic inference and phenotypic data, strain CHR27T was considered a representative of a novel species within the genus Sphingobium. The name Sphingobium fluviale sp. nov. is proposed, with strain CHR27T (=BCRC 81121T=LMG 30596T=KCTC 62510T) as the type strain.
    Keywords:  Alphaproteobacteria; Sphingobium fluviale sp. nov.; Sphingomonadaceae; Sphingomonadales
    DOI:  https://doi.org/10.1099/ijsem.0.003835
  9. Int J Syst Evol Microbiol. 2019 Oct 31.
    Sphingomonas paeninsulae sp. nov., isolated from soil sampled at Fildes Peninsula, Antarctica.
    Yingchao Geng, Yumin Zhang, Kun Qin, Jia Liu, Jin Tian, Yao Huang, Ziyan Wei, Fang Zhang, Fang Peng.
      Strain YZ-8T, isolated from soil sampled at Fildes Peninsula, Antarctica, was found to be a Gram-stain-negative, yellow-pigmented, oxidase- and catalase-positive, non-motile, non-spore-forming, rod-shaped and aerobic bacterium. Strain YZ-8T grewoptimally at pH 7.0 and 20 °C. Tolerance to NaCl was up to 0.3 % (w/v) with optimum growth in the absence of NaCl. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain YZ-8T belonged to the family Sphingomonas. Strain YZ-8T showed the highest sequence similarities to Sphingomonas molluscorum KMM 3882T (94.4 %), Sphingomonas oligophenolica JCM 12082T (94.4 %), Sphingomonas gotjawalisoli SN6-9T (94.3 %) and Sphingomonas aquatica W1-2-1T (94.3 %). The predominant respiratory isoprenoid quinone and polyamine components were identified as ubiquinone Q-10 and sym-homospermidine, respectively. In addition, carotenoid were also found. The polar lipid profile of the strain YZ-8T was found to contain one phosphatidylethanolamine, an unidentified phospholipid, one diphosphatidylglycerol, one phosphatidylglycerol, two sphingophosphonolipids, one phosphatidylcholine and two unidentified alkali-stable lipids. The G+C content of the genomic DNA was determined to be 58.8 mol%. The main fatty acids were summed feature 8 (comprising C18 : 1ω7c and/or C18 : 1ω6c; 35.4 %), summed feature 3 (comprising C16 : 1ω7c and/or C16 : 1ω6c; 32.6 %) and C14 : 0 2-OH (7.7 %). On the basis of the evidence presented in this study, a novel species of the genus Sphingomonas, Sphingomonaspaeninsulae sp. nov., is proposed, with the type strain YZ-8T (=CCTCC AB 2017137T=LMG 31027T).
    Keywords:  Sphingomonas paeninsulae; novel species; phylogenetic analysis; taxonomy
    DOI:  https://doi.org/10.1099/ijsem.0.003504
  10. Int J Syst Evol Microbiol. 2019 Oct 30.
    Flavobacterium ustbae sp. nov., isolated from rhizosphere soil of Alhagi sparsifolia.
    Yang Liu, Ho Le Han, Yuanyuan Zou, Song-Gun Kim.
      A yellow-pigmented bacterial strain, designated T13T, was isolated from the rhizosphere soil of Alhagi sparsifolia collected from Xinjiang, PR China. Cells were rod-shaped, Gram-stain-negative, aerobic and gliding. Strain T13T grew optimally at 25-30 °C and pH 7.0-8.0 with a NaCl tolerance of 0-2 % on Reasoner's 2A agar. Phylogenetic analysis based on the 16S rRNA gene sequence showed that strain T13T belonged to the genus Flavobacterium within the family Flavobacteriaceae and was closely related to Flavobacterium nitrogenifigens KCTC 42884T with a similarity value of 97.4 %. The major polar lipid was phosphatidylethanolamine; the only respiratory quinone was MK-6, and the polyamine profile contained sym-homospermidine as the major polyamine and a trace amount of spermidine. The major fatty acids were iso-C15 : 0, C16 :  1ω7c and summed feature 3 (comprising C16 : 1ω7c or C16 : 1ω6c). The G+C content of the genomic DNA was 34.1 mol%. It is concluded from the phenotypic and genotypic data that strain T13T represents a novel species of the genus Flavobacterium, for which the name Flavobacteriumustbae sp. nov. with the type strain T13T (=KCTC 62874T=ACCC 60126T) is proposed.
    Keywords:  16S rRNA gene; Alhagi sparsifolia; Bacteroidetes
    DOI:  https://doi.org/10.1099/ijsem.0.003717
  11. Heliyon. 2019 Oct;5(10): e02631
    Effect of L-Ornithine application on improving drought tolerance in sugar beet plants.
    Hebat-Allah A Hussein, B B Mekki, Marwa E Abd El-Sadek, Ezzat Ebd El Lateef.
      The objective of this research was to determine the foliar application of L-ornithine (0.0, 0.30 and 0.60 mM) as a precursor of polyamines, at vegetative stage was on antioxidant defense and growth of drought stressed sugar beet plants grown under clay and sandy soil conditions. Two water irrigation treatments (80% and 40% Field capacity) were carried out on sugar beet plants grown in pots under greenhouse conditions. Water stress resulted in significantly decrement in growth parameters including root diameter, root and shoot weights per plant compared with corresponding control plants. The results showed that drought stress significantly affected most biochemical characteristics of plants. Photosynthetic pigments contents, free amino acids and peroxidase enzyme activity were decreased, while catalase enzyme activity and lipid peroxidation was increased with drought stress. On the other hand, foliar application of L-ornithine effectively alleviated harmful effects caused by drought stress on root length, root and shoot weights of sugar beet plants, especially under sandy soil conditions. The results cleared that ameliorating the negative effects of drought stress through exogenously applied L-ornithine associated with improved photosynthetic pigments, protein profile, lipid peroxidation, antioxidant enzymes; catalase and peroxidase, total soluble sugars and total amino led to increasing drought tolerance of sugar beet plants.
    Keywords:  Agricultural science; Biochemistry; Clay soil; Drought; Ornithine; Plant biology; Sandy soil; Sugar beet
    DOI:  https://doi.org/10.1016/j.heliyon.2019.e02631
  12. Int J Syst Evol Microbiol. 2019 Oct 29.
    Hydrogenophaga borbori sp. nov., isolated from activated sludge.
    Gyu-Min Choi, Soon Youl Lee, Sang Yong Kim, Ji-Hyang Wee, Wan-Taek Im.
      A novel Gram-stain-negative, yellowish-pigmented bacterial strain, designated LA-38T, was isolated from activated sludge of wastewater treatment plants in Hanam city, South Korea. Cell of LA-38T were rod-shaped, aerobic, motile and non-spore-forming. In phylogenetic analyses based on 16S rRNA genes, LA-38T clustered with species of the genus Hydrogenophaga and appeared closely related to Hydrogenophaga intermedia DSM 5680T (99.2 % similarity), Hydrogenophaga palleronii DSM 63T (98.2 %), Hydrogrenophaga laconesensis KCTC 42478T (98.1 %), Hydrogenophaga. atypica DSM 15342T (98.1 %), Hydrogenophaga defluvii DSM 15341T (98.0 %) and Hydrogenophaga taeniospiralis DSM 2082T (97.2 %). The average nucleotide identities between LA-38T and the closely related strains were 79.3-88.5 %, indicating that LA-38T represents a novel species of the genus Hydrogenophaga. The DNA G+C content of the genomic DNA was 69.9 mol% and ubiquinone Q-8 was the predominant respiratory quinone. The major cellular fatty acids (>5 %) were C16 : 0, cyclo-C19 : 0, C16 : 1ω7c and/or C16 : 1ω6c (summed feature 3), and C18 : 1ω7c and/or C18 : 1ω6c (summed feature 8). The major polar lipids consisted of phosphatidylglycerol, diphosphatidylglycerol and phosphatidylethanolamine, the major polyamines were 2-hydroxyputrescine and putrescine. ANI calculation, physiological and biochemical characteristics indicated that LA-38T represents a novel species of the genus Hydrogenophaga, for which the name Hydrogenophaga borbori sp. nov. is proposed. The type strain is LA-38T (=KACC 19730T=LMG 30805T).
    Keywords:  16S rRNA gene sequence; Hydrogenophaga borbori; genome sequence; polyphasic taxonomy; sludge
    DOI:  https://doi.org/10.1099/ijsem.0.003787
  13. Biochem J. 2019 Nov 01. pii: BCJ20190297. [Epub ahead of print]
    The multifunctional enzyme S-adenosylhomocysteine / methylthioadenosine nucleosidase is a key metabolic enzyme in the virulence of Salmonella enterica var Typhimurium.
    Asma U Husna, Nancy Wang, Jonathan J Wilksch, Hayley J Newton, Dianna M Hocking, Iain D Hay, Simon A Cobbold, Mark R Davies, Malcolm J McConville, Trevor Lithgow, Richard A Strugnell.
      Key physiological differences between bacterial and mammalian metabolism provide opportunities for the development of novel antimicrobials.  We examined the role of the multifunctional enzyme S-adenosylhomocysteine/Methylthioadenosine (SAH/MTA) nucleosidase (Pfs) in the virulence of S. enterica var Typhimurium (S. Typhimurium) in mice, using a defined Pfs deletion mutant (i.e. Δpfs).  Pfs was essential for growth of S. Typhimurium in M9 minimal medium, in tissue cultured cells, and in mice.  Studies to resolve which of the three known functions of Pfs were key to murine virulence suggested that downstream production of auto-inducer 2, spermidine and methylthioribose were non-essential for Salmonella virulence in a highly sensitive murine model. Mass spectrometry revealed the accumulation of SAH in S. Typhimurium Δpfs and complementation of the Pfs mutant with the specific SAH hydrolase from Legionella pneumophila reduced SAH levels, fully restored growth ex vivo and the virulence of S. Typhimurium Δpfs for mice.  The data suggest that Pfs may be a legitimate target for antimicrobial development, and that the key role of Pfs in bacterial virulence may be in reducing the toxic accumulation of SAH which, in turn, suppresses an undefined methyltransferase.
    Keywords:  Pfs; Salmonella; activated methyl cycle; antimicrobial target; metabolism
    DOI:  https://doi.org/10.1042/BCJ20190297
  14. Int J Food Microbiol. 2019 Oct 23. pii: S0168-1605(19)30309-5. [Epub ahead of print]313 108379
    Growth and metabolic characteristics of fastidious meat-derived Lactobacillus algidus strains.
    Elina Säde, Per Johansson, Tytti Heinonen, Jenni Hultman, Johanna Björkroth.
      Lactobacillus algidus is a meat spoilage bacterium often dominating the bacterial communities on chilled, packaged meat. Yet, L. algidus strains are rarely recovered from meat, and only few studies have focused on this species. The main reason limiting detailed studies on L. algidus is related to its poor growth on the media routinely used for culturing food spoilage bacteria. Thus, our study sought to develop reliable culture media for L. algidus to enable its recovery from meat, and to allow subculturing and phenotypic analyses of the strains. We assessed the growth of meat-derived L. algidus strains on common culture media and their modifications, and explored the suitability of potential media for the recovery of L. algidus from meat. Moreover, we determined whether 12 meat-derived L. algidus strains selected from our culture collection produce biogenic amines that may compromise safety or quality of meat, and finally, sequenced de novo and annotated the genomes of two meat-derived L. algidus strains to uncover genes and metabolic pathways relevant for phenotypic traits observed. MRS agar supplemented with complex substances (peptone, meat and yeast extract, liver digest) supported the growth of L. algidus, and allowed the recovery of new L. algidus isolates from meat. However, most strains grew poorly on standard MRS agar and on general-purpose media. In MRS broth, most strains grew well but a subset of strains required supplementation of MRS broth with additional cysteine. Supplementation of MRS broth with catalase allowed growth in aerated cultures suggesting that the strains produced hydrogen peroxide when grown aerobically. The strains tested (n = 12) produced ornithine from arginine and putrescine from agmatine, and two strains produced tyramine from tyrosine. Our findings reveal that L. algidus populations are underestimated if routine culture protocols are applied, and prompt concerns that L. algidus may generate tyramine or putrescine in meat or fermented meat products.
    Keywords:  Biogenic amines; Lactobacillus algidus; MRS medium; Meat spoilage; Putrescine; Tyramine
    DOI:  https://doi.org/10.1016/j.ijfoodmicro.2019.108379
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