Relative Incidence of Alteromonas putrefaciens and Pseudomonas putrefaciens in Ground Beef

Of 65 H₂S-producing isolates from seven samples of ground beef, 64 were found to be Alteromonas putrefaciens. Isolates of Pseudomonas putrefaciens were not encountered. The mean guanine-plus-cytosine content of DNAs from 10 of the representative isolates, obtained from thermal denaturation determinations, was 46.5 ± 1.0 mol%, which is consistent with the designation A. putrefaciens.     

The effect of hydroxycinnamic acids and potassium sorbate on the growth of 11 strains of spoilage yeasts

D. STEAD. 1995. Hydroxycinnamic acids and their derivatives occur widely in plants, fruits and wine. The effect of the common hydroxycinnamic acids (caffeic, coumaric and ferulic acids), at concentrations of 100 and 500 mg 1^-1, on growth of 11 strains of spoilage yeasts was measured spectrophotometrically and compared with that of potassium sorbate. Ferulic acid was the most generally inhibitory hydroxycinnamic acid. At 500 mg 1^-1 it appreciably inhibited Pichia anomala, Debaryomyces hansenii and Saccharomyces cerevisiae and prevented detectable growth of one strain each of P. anomala and D. hansenii. Caffeic acid was the least inhibitory compound and coumaric acid had an intermediate effect. The more resistant strains of yeast were P. membranaefaciens, Saccharomycodes ludwigii and Zygosaccharomyces bailii. Sensitivity to hydroxycinnamic acid was, in general, associated with sensitivity to potassium sorbate; at a given concentration potassium sorbate was more inhibitory than were any of the hydroxycinnamic acids.     

A note on the effect of dilution and temperature on the bactericidal activity of potassium sorbate

O ragui , J.I. M ara , D.D.1984. A note on a modified membrane-Bovis agar for the enumeration of Streptococcus bovis by membrane filtration. Journal of Applied Bacteriology 56 , 179–181.
A modified membrane-Bovis agar, containing a reduced quantity of sodium azide, for the isolation and enumeration of Streptococcus bovis is described and evaluated. Higher counts, with larger colonies, were obtained from water and sewage samples with this medium than with the original formulation.     

Phospholipid and fatty acid compositions of Alteromonas putrefaciens and A. haloplanktis

The phospholipid and fatty acid composition of Alteromonas putrefaciens S29 (non-halophilic type) and A. haloplanktis S5B (halophilic type) was determined. Major phospholipids of both strains were the same when they were grown in media containing optimum salt concentrations. However, the fatty acid composition of phos-pholipids in strain S29 was remarkably different from that of strain S5B. Strain S29 contained iso-C15: 0 and eicosapentaenoic acid (20: 5) as constituent fatty acids of phospholipids and also contained sterol ester and wax as neutral lipids. In contrast, strain S5B did not contain branched and polyunsaturated fatty acids, and neither sterol ester nor wax were detected.     

Reversible effect of potassium sorbate on Balanus amphitrite larvae. Potential use as antifoulant

Marine biofouling constitutes a major worldwide technical and economic problem. International regulations concerning the protection of both the environment and industrial workers have prompted paint manufacturers and end users to look for suitable replacements for traditional antifouling (AF) pigments. For this reason, the potential AF activity of potassium sorbate (KS) on nauplii and cyprids of Balanus amphitrite was tested in laboratory and field trials. Larval bioassays demonstrated a marked inhibitory and reversible effect. The values obtained for EC₅₀ and LC₅₀ were 9.91 mM and 36.73 mM, respectively, and the therapeutic ratio was 3.71, indicating that KS acts via a non-toxic mechanism. After 60 days in the sea, a varnish coating incorporating KS showed a substantial decrease in micro- and macrofouling density and diversity. This investigation indicated that KS is a promising AF agent for replacing the traditional toxic compounds.     

Amino acid and lactate catabolism in trimethylamine oxide respiration of Alteromonas putrefaciens NCMB 1735

The nonfermentative Alteromonas putrefaciens NCMB 1735 grew anaerobically in defined media with trimethylamine oxide as external electron acceptor. All amino acids tested, except taurine and those with a cyclic or aromatic side chain, were utilized during trimethylamine oxide-dependent anaerobic growth. Lactate, serine, and cysteine (which are easily converted to pyruvate) and glutamate and aspartate (which are easily converted to tricarboxylic acid cycle intermediates) were metabolized at the fastest rate. Growth with lactate as growth-limiting substrate gave rise to the formation of 40 mol% acetate, whereas serine and cysteine were nearly completely oxidized to CO2. Molar growth yields with the latter substrates were the same and were 50% higher than with lactate. This showed that more ATP was formed when acetyl coenzyme A entered the tricarboxylic acid cycle than when it was converted via acetyl phosphate to acetate. Also, growth with formate as substrate indicated that the reduction of trimethylamine oxide to trimethylamine was coupled with energy conservation by a respiratory mechanism.     

Hydrogen and Formate Oxidation Coupled to Dissimilatory Reduction of Iron or Manganese by Alteromonas putrefaciens

The ability of Alteromonas putrefaciens to obtain energy for growth by coupling the oxidation of various electron donors to dissimilatory Fe(III) or Mn(IV) reduction was investigated. A. putrefaciens grew with hydrogen, formate, lactate, or pyruvate as the sole electron donor and Fe(III) as the sole electron acceptor. Lactate and pyruvate were oxidized to acetate, which was not metabolized further. With Fe(III) as the electron acceptor, A. putrefaciens had a high affinity for hydrogen and formate and metabolized hydrogen at partial pressures that were 25-fold lower than those of hydrogen that can be metabolized by pure cultures of sulfate reducers or methanogens. The electron donors for Fe(III) reduction also supported Mn(IV) reduction. The electron donors for Fe(III) and Mn(IV) reduction and the inability of A. putrefaciens to completely oxidize multicarbon substrates to carbon dioxide distinguish A. putrefaciens from GS-15, the only other organism that is known to obtain energy for growth by coupling the oxidation of organic compounds to the reduction of Fe(III) or Mn(IV). The ability of A. putrefaciens to reduce large quantities of Fe(III) and to grow in a defined medium distinguishes it from a Pseudomonas sp., which is the only other known hydrogen-oxidizing, Fe(III)-reducing microorganism. Furthermore, A. putrefaciens is the first organism that is known to grow with hydrogen as the electron donor and Mn(IV) as the electron acceptor and is the first organism that is known to couple the oxidation of formate to the reduction of Fe(III) or Mn(IV). Thus, A. putrefaciens provides a much needed microbial model for key reactions in the oxidation of sediment organic matter coupled to Fe(III) and Mn(IV) reduction.     

Amino acid and lactate catabolism in trimethylamine oxide respiration of Alteromonas putrefaciens NCMB 1735.

The nonfermentative Alteromonas putrefaciens NCMB 1735 grew anaerobically in defined media with trimethylamine oxide as external electron acceptor. All amino acids tested, except taurine and those with a cyclic or aromatic side chain, were utilized during trimethylamine oxide-dependent anaerobic growth. Lactate, serine, and cysteine (which are easily converted to pyruvate) and glutamate and aspartate (which are easily converted to tricarboxylic acid cycle intermediates) were metabolized at the fastest rate. Growth with lactate as growth-limiting substrate gave rise to the formation of 40 mol% acetate, whereas serine and cysteine were nearly completely oxidized to CO2. Molar growth yields with the latter substrates were the same and were 50% higher than with lactate. This showed that more ATP was formed when acetyl coenzyme A entered the tricarboxylic acid cycle than when it was converted via acetyl phosphate to acetate. Also, growth with formate as substrate indicated that the reduction of trimethylamine oxide to trimethylamine was coupled with energy conservation by a respiratory mechanism.     

Effects of natamycin and potassium sorbate on growth and aflatoxin production in olives

Aspergillus flavus NRRL 6555 was inoculated onto whole olives and olive paste samples containing variable amounts of either natamycin or potassium sorbate and incubated at 15 degrees, 25 degrees, and 35 degrees C for 7, 14 and 21 days for whole olives and at 15 degrees and 25 degrees C for 8 and 16 days for olive pastes. The initiation time of growth was parallel to the concentrations of either preservatives applied. However, at 15 degrees C, natamycin at 160 and 320 micrograms/g (ppm) completely inhibited the growth of mold on whole olives for 21 days and olive paste for 7 and 15 days, respectively. All levels of potassium sorbate inhibited mold growth at 15 degrees C, but at 25 degrees C, 6000 micrograms/g (ppm) only, delayed growth for 15 days. The extent of growth at the end of the incubation periods was parallel to the temperatures of incubation. The analyses for aflatoxin B1 production in all samples at all levels of preservatives and control were negative.     

Prevention of surface mold growth on Italian dry sausage by natamycin and potassium sorbate

Inhibition of uncontrolled mold growth on three types of raw cured Italian dry salami was studied under commercial production conditions. Salami were dipped or sprayed with natamycin (pimaricin) or were given a combined organic acid-plus-potassium sorbate treatment. Acetic and citric acids potentiated the inhibitory effects of potassium sorbate significantly, but lactic and succinic acids showed little or no effect. Treatment of salami by dipping in 2.5% (wt/vol) potassium sorbate or 2,000 ppm (mg/liter) of pimaricin did not successfully prevent the growth of surface molds. At 10% potassium sorbate on all types of salami and at 2.5% sorbate on Casalingo salami, visual inhibition of mold growth was observed, but numbers of viable fungi on all salami types treated with 2.5% sorbate were not significantly (95% confidence) different from numbers found in the untreated controls. Pimaricin spray (2 X 1,000 ppm) was as good as or slightly better than 2.5% potassium sorbate, but greater concentrations of each were required to satisfactorily inhibit surface mold growth during the 25- to 50-day ripening period.     

Prevention of surface mold growth on Italian dry sausage by natamycin and potassium sorbate.

Inhibition of uncontrolled mold growth on three types of raw cured Italian dry salami was studied under commercial production conditions. Salami were dipped or sprayed with natamycin (pimaricin) or were given a combined organic acid-plus-potassium sorbate treatment. Acetic and citric acids potentiated the inhibitory effects of potassium sorbate significantly, but lactic and succinic acids showed little or no effect. Treatment of salami by dipping in 2.5% (wt/vol) potassium sorbate or 2,000 ppm (mg/liter) of pimaricin did not successfully prevent the growth of surface molds. At 10% potassium sorbate on all types of salami and at 2.5% sorbate on Casalingo salami, visual inhibition of mold growth was observed, but numbers of viable fungi on all salami types treated with 2.5% sorbate were not significantly (95% confidence) different from numbers found in the untreated controls. Pimaricin spray (2 X 1,000 ppm) was as good as or slightly better than 2.5% potassium sorbate, but greater concentrations of each were required to satisfactorily inhibit surface mold growth during the 25- to 50-day ripening period.     

Consequences of glycan truncation on Fc structural integrity

Effective characterization of protein-based therapeutic candidates such as monoclonal antibodies (mAbs) is important to facilitate their successful progression from early discovery and development stages to marketing approval. One challenge relevant to biopharmaceutical development is, understanding how the stability of a protein is affected by the presence of an attached oligosaccharide, termed a glycan. To explore the utility of molecular dynamics simulations as a complementary technique to currently available experimental methods, the Fc fragment was employed as a model system to improve our understanding of protein stabilization by glycan attachment. Long molecular dynamics simulations were performed on three Fc glycoform variants modeled using the crystal structure of a human IgG1 mAb. Two of these three glycoform variants have their glycan carbohydrates partially or completely removed. Structural differences among the glycoform variants during simulations suggest that glycan truncation and/or removal can cause quaternary structural deformation of the Fc as a result of the loss or disruption of a significant number of inter-glycan contacts that are not formed in the human IgG1 crystal structure, but do form during simulations described here. Glycan truncation/removal can also increase the tertiary structural deformation of C_H2 domains, demonstrating the importance of specific carbohydrates toward stabilizing individual C_H2 domains. At elevated temperatures, glycan truncation can also differentially affect structural deformation in locations (Helix-1 and Helix-2) that are far from the oligosaccharide attachment point. Deformation of these helices, which form part of the FcRn, could affect binding if these regions are unable to refold after temperature normalization. During elevated temperature simulations of the deglycosylated variant, C_H2 domains collapsed onto C_H3 domains. Observations from these glycan truncation/removal simulations have improved our understanding on how glycan composition can affect mAb stability.     

Trimethylamine oxide respiration of Alteromonas putrefaciens NCMB 1735: Na+-stimulated anaerobic transport in cells and membrane vesicles.

Alteromonas putrefaciens NCMB 1735 required the presence of NaCl for anaerobic growth with serine, cysteine, and formate as substrate and trimethylamine oxide ( TMAO ) as external electron acceptor. When lactate was substrate, the organism grew equally well in the absence of NaCl. Anaerobic uptake of glutamate, aspartate, serine, cysteine, and lactate in resting cells was strongly stimulated with NaCl, and cytoplasmic membrane vesicles energized by electron transfer from formate to TMAO displayed active Na+-dependent uptake of serine. The data suggested that participation in transport processes was the only vital function of Na+ in A. putrefaciens. Formate- and TMAO -dependent anaerobic serine uptake in vesicles was sensitive to the protonophore carbonyl cyanide m-chlorophenyl-hydrazone and the ionophores valinomycin and gramicidin. Transport-active vesicles contained cytochromes of b and c type, and both serine uptake and TMAO reduction with formate were inhibited with the electron transfer inhibitor 2-heptyl-4-hydroxyquinoline N-oxide. Thus, reduction of TMAO to trimethylamine in A. putrefaciens appeared to be coupled with a chemiosmotic mechanism of energy conversion.     

Sensitization of thermally injured spores of Bacillus stearothermophilus to sodium benzoate and potassium sorbate

The effects of sodium benzoate and potassium sorbate added to the recovery medium, at different pH values (6·5, 6·0 and 5·0), on the recovery rates and heat resistance of Bacillus stearothermophilus spores (ATCC 12980, 7953, 15951 and 15952) were investigated. Heated spores of strains 12980 and 7953 were inhibited by sorbate concentrations over 0·05%. Potassium sorbate at concentrations as low as 0·025%, and sodium benzoate at 0·1%, were very effective inhibitory agents for heat-damaged spores. Their effectiveness always increased at pH 5·0, at which no growth occurred, with sodium benzoate for strains 7953, 15951 and 15952, and with potassium sorbate for strains 15951 and 15952. Decimal reduction times, whenever recovery was possible, were not significantly ( P  > 0·05) affected. None of these compounds modified the z -values obtained for the spores of the four strains, which had a mean value of 7·53 ± 0·28.     

The effect of lactoperoxidase-catalyzed iodination on the integrity of mitochondrial membranes.

The effect of lactoperoxidase-catalyzed iodination on rat liver mitochondria was investigated. A change from the condensed to the swollen conformation is observed by electron microscopy after extensive iodination of the mitochondria. The outer membrane breaks after incorporation of 0.2 nmol or more iodine atoms per mg of mitochondrial protein releasing adenylate kinase, a soluble enzyme located in the intermembrane space. Further iodination of the mitochondria ruptures the inner membrane, releasing proteins such as glutamic dehydrogenase from the matrix space. Lipid peroxides and I₂ are not intermediates in the disruptive effect of extensive lactoperoxidase-catalyzed iodination on the membranes. During iodination at pH 6.5 almost no release of protein or glutamic dehydrogenase activity is detectable and the loss of adenylate kinase activity from the particulate is diminished. The effect of extensive iodination on mitochondrial membranes limits the amount of iodide which can be incorporated with the lactoperoxidase membrane-labeling procedure when this technique is used as a surface probe of mitochondrial membranes.