Showing papers in "Fems Microbiology Letters in 1985"
TL;DR: The concept of photochemical sterilization was introduced in this article, where microorganisms were killed photoelectrochemically with semiconductor powder (platinum-loaded titanium oxide, TiO2/Pt).
Abstract: We report the novel concept of photochemical sterilization. Microbial cells were killed photoelectrochemically with semiconductor powder (platinum-loaded titanium oxide, TiO2/Pt). Coenzyme A, (CoA) in the whole cells was photo-electrochemically oxidized and, as a result, the respiration of cells was inhibited. Inhibition of respiratory activity caused death of the cells. Lactobacillus acidophilus, Saccharomyces cerevisiae and Escherichia coli (103 cells/ml respectively) were completely sterilized when they were incubated with TiO2/Pt particles under metal halide lamp irradiation for 60–120 min.
1,317 citations
TL;DR: Phospholipid, ester-linked fatty acid profiles showed changes in benthic prokaryotic community structure reflecting culture manipulations that were both quantitative and statistically significant.
Abstract: Phospholipid, ester-linked fatty acid profiles showed changes in benthic prokaryotic community structure reflecting culture manipulations that were both quantitative and statistically significant. Fatty acid structures, including the position and cis/ trans geometry of double bonds, were chemically verified by GC/MS after appropriate derivatization. The fatty acid profiles of independent flasks showed reproducible shifts when manipulated identically and significant differences when manipulated with different treatments. The absence of polyunsaturated fatty acids indicated that the consortia were predominantly prokaryotic. The prokaryotic consortia of different treatments could be differentiated by the proportions of cyclopropyl fatty acids and the proportions and geometry of monounsaturated fatty acids.
692 citations
TL;DR: An extracellular peroxidase was purified by chromatofocusing column chromatography from the growth medium of ligninolytic cultures of the white-rot fungus Phanerochaete chrysosporium Burds BKM-1767 and produced hydrogen peroxide, which could be used as a co-substrate by ligninases such as those that oxidize veratryl alcohol, or by the peroxids itself to oxidize lign
Abstract: An extracellular peroxidase was purified by chromatofocusing column chromatography from the growth medium of ligninolytic cultures of the white-rot fungus Phanerochaete chrysosporium Burds BKM-1767 The enzyme was electrophoretically pure with an Mr of 45 000–47 000 It contained an easily dissociable heme, and required Mn2+ ions for activity In the presence of hydrogen peroxide and Mn2+ it oxidized compounds such as vanillylacetone, 2,6-dimethyloxyphenol, curcumin, syringic acid, guaiacol, syringaldazine, divanillylacetone, and coniferyl alcohol It did not oxidize veratryl alcohol In reactions requiring Mn2+ and O2, but not hydrogen peroxide, the enzyme oxidized glutathione, dithiothreitol, and NADPH with production of hydrogen peroxide The hydrogen peroxide produced could be used as a co-substrate by ligninases such as those that oxidize veratryl alcohol, or by the peroxidase itself to oxidize lignin model compounds
337 citations
TL;DR: In this article, the authors investigated vertical stratified microbial communities of phototrophic bacteria in the upper intertidal zones of the North Sea island of Mellum and concluded that the initial colonization of the sandy sediments was by the cyanobacterium Oscillatoria.
Abstract: Vertically stratified microbial communities of phototrophic bacteria in the upper intertidal zones of the North Sea island of Mellum were investigated. Growth and population dynamics of the cyanobacterial mat were followed over three successive years. It was concluded that the initial colonization of the sandy sediments was by the cyanobacterium Oscillatoria. In well-established mats, however, the dominant organism was Microcoleus chthonoplastes. The observed succession of cyanobacteria during mat development is correlated with nitrogen fixation. Nitrogen fixation is necessary in this low-nutrient environment to ensure colonization by mat-constructing cyanobacteria. Under certain conditions, a red layer of purple sulfur bacteria developed underneath the cyanobacterial mat in which Chromatium and Thiocapsa spp. dominated, but Thiopedia and Ectothiorhodospira spp. have also been observed. Measurements of light penetrating the cyanobacterial mat indicated that sufficient light is available for the photosynthetic growth of purple sulfur bacteria. Profiles of oxygen, sulfide and redox potential within the microbial mat were measured using microelectrodes. Maximum oxygen concentrations, measured at a depth of 0.7 mm, reached levels more than twice the normal air saturation. Dissolved sulfide was not detected by the microelectrodes. Determination of acid-distilled sulfide, however, revealed appreciable amounts of bound sulfide in the mat. Redox profiles measured in the mat led to the conclusion that the upper 10 mm of the sedimentary sequence is in a relatively oxidized state.
267 citations
TL;DR: With respect to bacterial membranes, ample evidence supports the notion that most ions and 'large' polar molecules (M r approx. 100 or more) are transported by specific carriers, while lipophilic and small, uncharged compounds (e.g., CO z, H20, CH4, H2, 02, N2, NH3) rapidly pass membranes by unspecific diffusion.
Abstract: With few exceptions (e.g., extracellular degradation of macromolecules) the metabolism of a compound starts with its transport across the cell membrane, mediated in most cases by specific transport proteins or carriers. As the starting point of a metabolic pathway, uptake is frequently strictly regulated, both on the activity and on the genetic level. Regulation of transport is almost impossible if a compound crosses the membrane by unspecific diffusion, because regulation of permeability--if occurring at all in biological systems -is only possible by biologically uncontrollable parameters (osmotic strength, temperature) and by a lengthy degradation and new synthesis of membrane lipids. With respect to bacterial membranes, ample evidence supports the notion that most ions and 'large' polar molecules (M r approx. 100 or more) are transported by specific carriers, while lipophilic and small, uncharged compounds (e.g., CO z, H20, CH4, H2, 02, N2, NH3) rapidly pass membranes by unspecific diffusion. Of course, dependent on their solubility in the membrane, some diffusion of otherwise specifically transported molecules must also occur, but in general this is very slow in comparison to specific transport and can be considered as biologically insignificant. Several bacterial nutrients or metabolites with a low M r are weak acids and bases, and thus occur in both a charged and uncharged form, e.g.:
254 citations
TL;DR: In this article, the authors studied the production and emission of methane from submerged paddy soil in laboratory rice cultures and in Italian paddy fields and found that up to 80% of the CH4 produced in the paddy soils did not reach the atmosphere but was apparently oxidized in the rhizosphere.
Abstract: Production and emission of methane from submerged paddy soil was studied in laboratory rice cultures and in Italian paddy fields. Up to 80% of the CH4 produced in the paddy soil did not reach the atmosphere but was apparently oxidized in the rhizosphere. CH4 emission through the rice plants was inhibited by an atmosphere of pure O2 but was stimulated by an atmosphere of pure N2 or an atmosphere containing 5% acetylene. Gas bubbles taken from the submerged soil contained up to 60% CH4, but only 0.15% sea salt (0.01% sulfate) resulted in a strong inhibition of the rates of methanogenesis and a decrease in the rates of CH4 emission. This result explains the observation of relatively low CH4 emission rates in rice paddy areas flooded with brackish water.
254 citations
TL;DR: The processes of protein export are most extensively characterised in Escherichia coli, where recent advances have been made in the identification of genes involved in forming the export machinery.
Abstract: A wide variety of proteins are exported or secreted by a range of morphologically distinct bacteria. The processes of protein export are most extensively characterised in Escherichia coli, where recent advances have been made in the identification of genes involved in forming the export machinery. Both Gram-positive and Gram-negative bacteria secrete proteins into the medium. Gram-negative bacteria have adopted a variety of approaches in order to overcome the additional permeability of the outer membrane.
248 citations
TL;DR: Acetylene was shown to bind to proteins which are associated with methane-oxidising activity and it is proposed that acetylene acts as a suicide substrate.
Abstract: Acetylene was shown to be an inhibitor of cell-free methane monooxygenase (MMO) activity in Methylococcus capsulatus (Bath). Inhibition was demonstrated for both the soluble and particulate forms of the enzyme and was dependent on the presence of both NADH and oxygen. Inactivation of the enzyme complex was irreversible and was due to binding of the acetylene to specific proteins of the enzyme complex. The use of radiolabelled [14C]acetylene provided a method for visualisation of the bound inhibitor: protein complex on sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis (PAGE). Acetylene was shown to bind to proteins which are associated with methane-oxidising activity and it is proposed that acetylene acts as a suicide substrate.
233 citations
TL;DR: Research will need to be conducted on the extent of metal resistance in bacteria, the relationship between metal and antibiotic resistance, mechanisms specified by the plasmids, and the ecology, physiology, and genetics of gene transfer in the natural environment.
Abstract: Bacteria have been examined that have developed very efficient and different mechanisms for tolerating heavy metals. Often normal toxic levels of metals have no effect on cell growth of resistant strains. In many organisms, the genes controlling metal resistance are carried on plasmids, which provide the bacteria with a competitive advantage over other organisms when metals are present. Not all metal-resistant bacteria contain plasmids. For example, a Pseudomonas sp. (research at the Canada Centre for Inland Waters and the University of Guelph) resistant to 1000 μg/ml lead, also displays multiple antibiotic resistance. Vertical and horizontal agarose gel electrophoresis of cleared lysates revealed that plasmids were not present, even though the organism was tolerant to extremely high concentrations of lead.
Plasmid-encoded resistance may provide organisms with efflux and bypass mechanisms, enzymes which catalyze the transformation of metals to volatile forms, or make the bacterial cell wall impermeable to the metal(s).
A problem still remains in actually defining the concentrations that distinguish metal-resistant from metal-sensitive bacteria. Some researchers have proposed mathematical equations, and used statistical analysis to solve this problem. Nevertheless, standard concentrations have not been universally proposed and/or accepted by the scientific community. This task is complicated by the various forms of metals used, the effect of media components, pH, and culture conditions, which have the capability of influencing the toxicity of the metal.
Research on metal–bacteria interactions is in some ways still in its early stages of development. Nevertheless, significant advances in scientific knowledge have been achieved over the last 20 years. To fill the existing gaps in knowledge, research will need to be conducted on the extent of metal resistance in bacteria, the relationship between metal and antibiotic resistance, mechanisms specified by the plasmids, and the ecology, physiology, and genetics of gene transfer in the natural environment.
Since some microorganisms are responsible for environmental metal transformations, they may also serve as bioassay indicator organisms in polluted and non-polluted environments. Moreover, there may be potential biotechnological applications for metal-resistant bacteria in the area of toxic metal control in waste-water treatment.
217 citations
TL;DR: The survival after oxygen stress was studied with eight species of sulfate-reducing bacteria and reducing agents did not protect the vegetative cells of this strain against oxygen toxicity, and sulfhydryl group-containing agents increased the oxygen sensitivity considerably.
Abstract: Summary The survival after oxygen stress was studied with eight species of sulfate-reducing bacteria. In the absence of sulfide all species tolerated 6 min of aeration without loss of viability. Even after 3 h of aeration the viability of four species ( Desulfovibrio vulgaris, D. desulfuricans, D. salexigens and Desulfobacter postgatei ) was not impaired. Four other species were sensitive to 3 h of aeration: the surviving fractions of Desulfotomaculum ruminis, D. nigrificans and Desulfococcus multivorans were about 1%, that of Desulfotomaculum orientis about 0.01%. Formation of spores resulted in oxygen resistance of D. orientis . Reducing agents did not protect the vegetative cells of this strain against oxygen toxicity. In contrast, sulfhydryl group-containing agents increased the oxygen sensitivity considerably. Growth of sulfate- and sulfur-reducing bacteria in oxygen-sulfide gradients in agar tubes was studied. In the gradients these strictly anaerobic bacteria revealed oxygen-dependent growth in sulfate- and sulfur-free medium. Three sulfate-reducing bacteria that could not use thiosulfate or sulfur as electron acceptor failed to grow in oxygen-sulfide gradients. Obviously, not directly molecular oxygen, but oxidation products of sulfide, such as thiosulfate or sulfur, were used as electron acceptors and were continuously regenerated in a cycling process from sulfide by autoxidation. The conceivable ecological significance of a short sulfur cycle driven by autoxidation of sulfide is discussed.
208 citations
TL;DR: It was found that a photorepellent system other than photosystem 370 (PS370) also controls the behavior of Halobacterium halobium and a mutant strain showed the repellent response due to the new photosystem.
Abstract: It was found that a photorepellent system other than photosystem 370 (PS370) also controls the behavior of Halobacterium halobium. Both the dependence of background illumination and wavelength where the response showed maximum action distinguished that photosystem from PS370 whose photoreceptor pigment is thought to be an intermediate of s-rhodopsin (sR). A mutant strain that has no detectable activity in PS370 and in photoattractant response was isolated. This mutant strain showed the repellent response due to the new photosystem.
TL;DR: In this article, the extractable ester-linked and the lipopolysaccharide (LPS) normal and hydroxy fatty acids of the methylotrophic bacteria Methylosinus trichosporium 0B3B, Methylobacterium organophilum XX, grown on methane and methanol, Mb. organophilus RG and Methylomonas sp. were analysed by capillary gas chromotography-mass spectrometry (GC-MS).
Abstract: The extractable ester-linked and the lipopolysaccharide (LPS) normal and hydroxy fatty acids of the methylotrophic bacteria Methylosinus trichosporium 0B3B, Methylobacterium organophilum XX, grown on methane and methanol, Mb. organophilum RG and Methylomonas sp. were analysed by capillary gas chromotography-mass spectrometry (GC-MS). Precise monounsaturated double bond position and geometry was determined by GC-MS analysis of the derivatized fatty acids. The three species were readily distinguished based on the extractable fatty acid and LPS hydroxy acid profiles. Type I and Type II methylotrophs can be separated based on the presence of 16-carbon and 18-carbon monoenoic fatty acids in the two groups of organisms, respectively. Relatively novel components, 18 : 1ω8c, 18 : 1ω8t, 18 : 1ω7t and 18 : 1ω6c were present in Ms. trichosporium , and 16 : 1ω8c, 16 : 1ω8t, 16 : 1ω7t, 16 : 1ω5c and 16 : 1ω5t were detected in Methylomonas sp. These specific lipids may be used, together with other components, as signatures for these methylotrophic bacteria in manipulated laboratory and environmental samples.
TL;DR: In this paper, the acetylene blocking technique was used to measure denitrification by accumulation of nitrous oxide, while reduction of nitrate to nitrite and ammonium was also measured.
Abstract: Experiments were carried out with slurries of saltmarsh sediment to which varying concentrations of nitrate were added. The acetylene blocking technique was used to measure denitrification by accumulation of nitrous oxide, while reduction of nitrate to nitrite and ammonium was also measured. There was good recovery of reduced nitrate and at the smallest concentration of nitrate used (250 μM) there was approximately equal reduction to either ammonium or nitrous oxide (denitrification). Nitrite was only a minor end-product of nitrate reduction. As the nitrate concentration was increased the proportion of the nitrate which was denitrified to nitrous oxide increased, to 83% at the greatest nitrate concentration used (2 mM), while reduction to ammonium correspondingly decreased. This change was attributed either to a greater competitiveness by the denitrifiers for nitrate as the ratio of electron donor to electron acceptor decreased; or to the increased production of nitrite rather than ammonium by fermentative bacteria under high nitrate, the nitrite then being reduced to nitrous oxide by denitrifying bacteria.
TL;DR: Ten distinct Eco RI fragments of Clostridum thermocellum DNA have been cloned in Escherichia coli and shown to express enzymatic activities related to cellulose degradation, hinting that they may express three different cellobiohydrolase genes.
Abstract: Ten distinct Eco RI fragments of Clostridum thermocellum DNA have been cloned in Escherichia coli and shown to express enzymatic activities related to cellulose degradation. Two of the cloned fragments appeared to carry the previously characterized celA and celB genes, which code for the endoglucanases (EG) A and B. Five other cloned fragments code for hitherto unidentified EGs, which can be detected by the Congo red test for hydrolysis of carboxymethylcellulose (CMC). In addition, three separate clones hydrolyzed methylumbelliferyl-β-cellobioside (MUC) but not CMC, hinting that they may express three different cellobiohydrolase genes.
TL;DR: The biodegradability of hydrocarbons under anaerobic conditions was studied in enrichment cultures using mineral media inoculated with sewage sludge or sediment samples of limnic and marine origin this article.
Abstract: The biodegradability of hydrocarbons under anaerobic conditions was studied in enrichment cultures using mineral media inoculated with sewage sludge or sediment samples of limnic and marine origin No indication of methanogenic degradation was obtained with either n-hexane, n-hexadecane, n-heptadecane, 1-hexene, cis-2-hexene, trans-2-hexene, isoprene, 1-hexine, benzene, toluene, xylene, cyclohexene, cycloheptatriene, cyclopentadiene, styrene, naphthalene, azulene, or β-carotene Squalene was incompletely converted to methane and carbon dioxide Complete degradation was observed with 1-hexadecene Methanogenic subcultures were maintained on 1-hexadecene and squalene Both enrichments contained after several transfers Methanospirillum hungatei and Methanothrix soehngenii as prevalent methanogenic bacteria Acetate (⩽80 μM) was the only intermediary product detected indicating that degradation proceeded via hydrogen-dependent syntrophic β-oxidations Short rods on hexadecene and cocci on squalene were found to be associated with substrate degradation The results indicate that terminal double bonds can be sufficient to allow methanogenic degradation of hydrocarbons whereas branching and terminal ring closures may significantly contribute to hydrocarbon stability in anoxic environments
TL;DR: A strain of the anaerobic phycomycetous fungus Neocallimastix frontalis isolated from the rumen of a sheep had a high proteolytic activity which became predominantly extracellular during growth.
Abstract: A strain of the anaerobic phycomycetous fungus Neocallimastix frontalis isolated from the rumen of a sheep had a high proteolytic activity which became predominantly extracellular during growth. Proteolytic activity appeared to be due to a metalloprotease, as it was inhibited by 1,10-phenanthroline, EDTA and other chelators but not by phenylmethylsulphonyl fluoride (PMSF). Inhibition by EDTA was fully reversed by the addition of Zn2+, Ca2+ or Co2+, whereas addition of metal ions in the presence of 1,10-phenanthroline restored only a little activity. p-Chloromercuribenzoate (PCMB) was also inhibitory in dialysed supernatant fluid. N-α-p-Tosyl-l-lysine chloromethylketone (TLCK) inhibited proteolysis, suggesting that the protease(s) has a trypsin-like specificity, but benzoylarginine p-nitroanilide was not hydrolysed. Protease activity has a broad pH profile with a maximum at pH 7.5. Gel fractionation indicated that most of the activity was in a high-Mr form.
TL;DR: The mean annual biomass of planktonic bacteria showed large variations both within and between lakes, and the lowest bacterial biomass was found in acidified lakes (7.8-12.1 μg C · 1−1), and tended to increase with increasing water colour (up to 44.1% of the total bacterial biomass as discussed by the authors ).
Abstract: The mean annual biomass of planktonic bacteria showed large variations both within and between lakes. The lowest bacterial biomass was found in acidified lakes (7.8–12.1 μg C · 1−1), and tended to increase with increasing water colour (up to 44.1 μg C · 1−1). The highest recorded bacterial biomass was 138 μg C · 1−1. The mean annual bacterial biomass equalled 23–45% of the algal biomass. Zooplankton biomass was high, compared to algal biomass (40–50%). Multiple regression analysis of 10 variables showed a strong positive correlation between bacterial biomass and humic content ( r = 0.74, P < 0.001), while other parameters, except pH, showed no correlation. The observation thus strongly supports the role of humic compounds in aquatic secondary production.
TL;DR: It is demonstrated that several inorganic and organic solutes are involved in osmotic adjustment in this cyanobacterium, with sequential changes in the relative importance of each solute following transfer to a saline medium.
Abstract: Transfer of Synechocystis PCC6714 from a freshwater medium to a saline medium caused the cells to shrink; rapid entry of NaCl resulted in a partial recovery of cellular volume within 2 min. Active extrusion of internal Na+ in exchange for extracellular K+ then occurred (within 20 min). Finally, the low-Mr carbohydrates sucrose and glucosylglycerol were accumulated and internal KC1 levels declined. In long-term growth experiments, the relative importance of sucrose as a component of the low-Mr organic solute fraction decreased and glucosylglycerol became the single most important intracellular solute. These observations demonstrate that several inorganic and organic solutes are involved in osmotic adjustment in this cyanobacterium, with sequential changes in the relative importance of each solute following transfer to a saline medium.
TL;DR: Some strains exhibited high cellulase activity, constant for 5–7 days, but inhibition by glucose was a common feature for almost all isolates, and all strains were shown to degrade soluble and insoluble cellulose.
Abstract: Cellulolytic actinomycetes were isolated from the hindgut of four different termites: Macrotermes, Armitermes, Odontotermes and Microcerotermes spp. The isolated actinomycetes ( Streptomyces sp. and Micromonospora sp.) were grown on cellulosic substrates and their extracellular cellulase (C l , C x and cellobiase) activity evaluated; using filter paper as a substrate for C l , carboxymethylcellulose (CMC) for C x and d -cellobiose for cellobiase, all strains were shown to degrade soluble and insoluble cellulose; optimum pH for growth was 6.2–6.7 at 28°C; three strains could grow at 48°C on cellulosic substrates. Some strains exhibited high cellulase activity, constant for 5–7 days, but inhibition by glucose was a common feature for almost all isolates.
TL;DR: Differential sensitivity of copper protein nitrite reductase activity to DDC could provide the simple assay method needed for determination of the distribution of two types of nitrite reducectase producers among populations of denitrifiers in nature.
Abstract: Gas chromatographic analyses revealed that rates of release of nitrous oxide from nitrite or nitric oxide in extracts of the c , d 1 cytochrome nitrite reductase-producing denitrifiers, Paracoccus denitrificans and Pseudomonas perfectomarina , were unaffected by preincubation with the metal chelator, diethyldithiocarbamate (DDC). In contrast, preincubation with DDC completely inhibited generation of nitrous oxide from nitrite in extracts of copper protein nitrite reductase-producing denitrifiers, “ Achromobacter cycloclastes ” and Rhodopseudomonas sphaeroides forma species denitrificans . Pre-exposure to DDC lessened but did not completely inhibit nitric oxide reduction in extracts of the copper protein nitrite reductase-producing denitrifiers. Proton consumption values resulting from pulsing with nitrite were similarly completely inhibited by preincubation with DDC of extracts of the two copper protein-producing denitrifiers. Uptake values related to pulsing with nitric oxide were also lessened but not completely inhibited by prior exposure to DDC. As anticipated, proton consumption was not affected by preincubation with DDC in extracts of P. denitrificans pulsed with nitrite or nitric oxide. Differential sensitivity of copper protein nitrite reductase activity to DDC could provide the simple assay method needed for determination of the distribution of two types of nitrite reductase producers among populations of denitrifiers in nature.
TL;DR: A 3.8 kb DNA fragment from plasmid pBD64, which encoded chloramphenicol and kanamycin resistance genes, but had no replication region, was used as a replicator probe to select for the replication region of the cryptic lactic streptococcal plasmide pSH71 using Bacillus subtilis as host.
Abstract: A 3.8 kb DNA fragment from plasmid pBD64 which encoded chloramphenicol and kanamycin resistance genes, but had no replication region, was used as a replicator probe to select for the replication region of the cryptic lactic streptococcal plasmid pSH71 using Bacillus subtilis as host. Three of the resultant recombinant plasmids, pCK1, pCK17 and pCK21 are described. They are vectors in Streptococcus lactis and can be used to clone BglII-compatible fragments into their kanamycin resistance gene. All the plasmids have single sites for restriction endonucleases AvaI, BamHI, EcoRI, PvuII and XbaI, while plasmids pCK17 and pCK21 have single sites for ClaI.
TL;DR: Two marine strains of Desulfovibrio were able to use alanine, serine and glycine as good growth substrates; aspartate, cysteine, threonine and branched-chain amino acids supported only slow growth.
Abstract: Summary Two marine strains of Desulfovibrio were able to use alanine, serine and glycine as good growth substrates; aspartate, cysteine, threonine and branched-chain amino acids supported only slow growth.
TL;DR: Listeriolysin, an SH-activated haemolysin probably involved in Listeria pathogenicity, has been cloned into the cosmid vector pHC79 and was expressed in Escherichia coli HB101 cells.
Abstract: Listeriolysin, an SH-activated haemolysin probably involved in Listeria pathogenicity, has been cloned into the cosmid vector pHC79 and was expressed in Escherichia coli HB101 cells. Chromosomal DNA of Listeria monocytogenes serovar 12 was partially digested with MboI and ligated to the BamHI cleaved cosmid. From 2000 recombinant clones examined, 12 (0.6%) produced haemolysin in solid and liquid media. All of them contained chromosome fragments of Listeria of about 40 kb. The cloning of the listeriolysin determinant will lead to a better understanding of the basis of Listeria pathogenicity.
TL;DR: The results revealed that the pColV-K30-specified receptor protein might be synthesized as a precursor, with a signal sequence of 25 amino acid residues, and the mature protein has an M r of 77 345.
Abstract: The cloacin DF13/aerobactin receptor protein from Escherichia coli (pFS8) and from Klebsiella edwardsii were isolated by repeated Triton X-100 extractions and purified by affinity chromatography. Both receptor proteins ran as a single protein band on SDS-PAGE. Their apparent M r values were 74 000 and 76 000, respectively. The binding constants of the purified receptor proteins from E. coli (pFS8) and K. edwardsii and cloacin DF13 were determined. Values of 2.0 × 10 8 M −1 and 1.0 × 10 9 M −1 , respectively, were found. The nucleotide sequence of the pColV-K30 gene, contained on pFS8 and encoding the cloacin DF13/aerobactin receptor protein, was determined and the primary structure of the protein as well as its secondary structure were deduced. The results revealed that the pColV-K30-specified receptor protein might be synthesized as a precursor, with a signal sequence of 25 amino acid residues. The mature protein has an M r of 77 345.
TL;DR: Most of the moderately thermophilic, acidophilic iron-oxidizing bacteria which have been isolated required a source of reduced sulphur for growth on iron, but one isolate utilized sulphate as the sole source of sulphur.
Abstract: Most of the moderately thermophilic, acidophilic iron-oxidizing bacteria which have been isolated required a source of reduced sulphur for growth on iron. One isolate (strain ALV) utilized sulphate as the sole source of sulphur. All of the isolates were capable of chemolitho-heterotrophin growth on iron in the presence of yeast extract. Autotrophic growth has been confirmed in all strains except one previously described, but now re-isolated, moderate thermophile (TH3).
TL;DR: A new locus required for mediating the binding of type 1 piliated Escherichia coli cells to guinea pig erythrocytes is identified and hemagglutination experiments using partially purified pili supported this suggestion.
Abstract: We have identified a new locus required for mediating the binding of type 1 piliated Escherichia coli cells to guinea pig erythrocytes. This locus, pilE, was discovered after restrition site mutagenesis of a cloned segment of DNA containing the chromosomal pil region from a clinical strain of E. coli. pilE Mutants failed to agglutinate guinea pig erythrocytes but expressed pili were morphologically and antigenically indistinguishable from the parental (pilE+) strain. Construction of a chromosomal pilE mutation in E. coli K-12 was accomplished by introducing a restriction fragment containing a pilE lesion into the chromosome of a recBC sbcB host strain. Mutations in pilE could be complimented in trans by the addition of a cloned segment of DNA containing the parental pilE locus. Lesions in any of the genes required for pilus assembly also produced a hemagglutination minus phenotype suggesting that both the product(s) specified by the pilE locus and pili were required for hemagglutination. Hemagglutination experiments using partially purified pili also supported this suggestion.
TL;DR: 3 new spectrophotometric enzyme assays were developed for the study of microbial lignin-degrading enzymes and led to the discovery of an extracellular, aromatic methyl ether demethylase produced by the white-rot fungus Phanerochaete chrysosporium.
Abstract: 3 New spectrophotometric enzyme assays were developed for the study of microbial lignin-degrading enzymes The conversion of 2-methoxy-3-phenylbenzoic acid to 2-hydroxy-3-phenylbenzoic acid led to the discovery of an extracellular, aromatic methyl ether demethylase produced by the white-rot fungus Phanerochaete chrysosporium The conversion of methyl 2-hydroxy-3-phenylbenzoate to 2-hydroxy-3-phenylbenzoic acid allowed the identification of an extracellular, aromatic methyl ester esterase produced by this fungus The Phanerochaete sp also excreted an enzyme complex that oxidized 4-(4-hydroxy-3-methoxyphenyl)-3-buten-2-one, probably to aliphatic products All 3 novel enzyme activities were produced together with, and probably comprise a part of, the Phanerochaete ligninolytic enzyme complex Unlike previously known ligninases, these enzymes did not oxidize 3,4-dimethoxybenzyl alcohol All 3 were H2O2-dependent and were activated by Mn2+ ions
TL;DR: Extracellular H2O2-dependent ligninase activity of Phanerochaete chrysosporium was produced in agitated culture conditions when veratryl alcohol or veratraldehyde were added to the cultures indicating that true protein synthesis occurred.
Abstract: Extracellular H2O2-dependent ligninase activity of Phanerochaete chrysosporium was produced in agitated culture conditions when veratryl alcohol or veratraldehyde were added to the cultures. The enzyme production was suppressed by cycloheximide indicating that true protein synthesis occurred. The activated cultures were also able to degrade synthetic lignin. Reduction of veratraldehyde to corresponding alcohol during secondary metabolism was a good indicator of the effect of agitation on cell metabolism. Too high agitation speed led to complete inhibition of both the reduction reaction and the ligninolytic activity.
TL;DR: An improved salt aggregation test (improved SAT) was developed to sensitize the determination of bacterial cell-surface hydrophobicity as discussed by the authors, where one drop of a fresh bacterial suspension standardized to an A1cm540 of 20 (equivalent to 5 × 109 cfu/ml), and one drop each of ammonium sulphate solutions stained with methylene blue, were mixed on a white hydrophobic paper card using toothpicks.
Abstract: An improved salt aggregation test (improved SAT) was developed to sensitize the determination of bacterial cell-surface hydrophobicity. One drop of a fresh bacterial suspension standardized to an A1cm540 of 20 (equivalent to 5 × 109 cfu/ml), and one drop each of ammonium sulphate solutions stained with methylene blue, were mixed on a white hydrophobic paper card using toothpicks. The bacterial suspensions, methylene blue stock solutions and the ammonium sulphate solutions (0.01–4.0 M) were made in 0.02 M sodium phosphate buffer, pH 6.8. Bacterial aggregations were read immediately after mixing the salt/bacterial suspensions while the card was gently rocked. Readings were also confirmed the next day on dried preparations. The results proved independent of reading time and mixture conditions (wet or dry preparations). The improved SAT technique is very rapid and sensitive, the reaction is easily read with the naked eye, and the paper cards can be stored for documentation of aggregation patterns after drying. In the improved SAT, the Staphylococcus cells of different species aggregated in 5 ways: tiny, medial, flaky granular, particulated and macrofilamentous forms; Salmonella strains aggregated in flaky granular, particulated and macrofilamentous forms.
TL;DR: After growth in medium containing 50 mM glucose, C. tropicalis and C. parapsilosis were significantly more adherent to acrylic than glucose-grown yeasts of the pathogenic Candida species, including C. albicans.
Abstract: Growth in medium containing 500 mM galactose is known to promote the adhesion of Candida albicans to buccal epithelial cells or to acrylic in vitro. Of 5 other Candida species tested, only C. tropicalis (one strain) showed substantially increased adhesion to buccal cells (but not to acrylic) after growth under these conditions. A second strain of C. tropicalis as well as C. stellatoidea, C. parapsilosis, C. pseudotropicalis, C. guilliermondii and Saccharomyces cerevisiae showed little or no increased adhesion to either surface. However, after growth in medium containing 50 mM glucose, C. tropicalis and C. parapsilosis were significantly more adherent to acrylic than glucose-grown yeasts of the other species, including C. albicans. These results are discussed in relation to the colonization and infection potential of the pathogenic Candida species.