Cepabactin from Pseudomonas cepacia, a new type of siderophore

In iron-deficient conditions of growth Pseudomonas cepacia ATCC 25416 excreted both pyochelin and a low-molecular-mass compound which strongly chelated iron(III), and facilitated iron translocation as demonstrated by growth and uptake experiments. The name cepabactin is proposed for this new siderophore. Comparisons of UV-visible spectra and chromatographic behaviour, together with 1H-NMR spectra, led to the conclusion that cepabactin is 1-hydroxy-5-methoxy-6-methyl-2(1H)-pyridinone, a compound which can be considered as a cyclic hydroxamate, but also as a heterocyclic analogue of catechol. This pyridinone has already been described by other workers as an antibiotic produced by Pseudomonas alcaligenes, and by a soil isolate closely related to Pseudomonas cepacia. Thus, cepabactin appears to act as a siderophore for more than one species of non-fluorescent pseudomonad.     

A physical genome map of the Burkholderia cepacia type strain

Burkholderia cepacia (basonym Pseudomonas cepaci a), the type speciesof the new genus Burkholderia , is of interest, not only because of its broad catabolic capacity and its ability to antagonize soil-borne plant pathogens, but also because of its causative role in infections in man, which are particularly evident in patients with cystic fibrosis. A physical map of the 8.1 Mb genome of the B. cepacia type-strain ATCC 25416 was constructed by applying two-dimensional pulsed-field gel electrophoresis techniques. Placed onto the macrorestriction map were 38 Spel , 11 Swal , 11 Pacl , 11 Pmel and six l-Ceul sites, resulting in an average resolution of 1O5 kbp. Random single-hit linearization by irradiation and restriction mapping uncovered the presence of four circular replicons of 3.65 Mb, 3.17 Mb, 1.07 Mb and 200 kbp in size. The largest replicon harbours four rrn operons while the other two Megabase-size replicons each contain a single rrn operon, suggesting that the genome has three chromosomes and a large plasmid. Within the beta subdivision of proteobacteria, the existence of multiple replicons is not confined to B. cepacia . The phylogenetically related species Burkholderia glumae , Burkholderia pickettii , Burkholderia solanacearum , Alcaligenes eutrophus and the so far unassigned Pseudomonas glathei were also found to harbour more than one Megabase-size replicon.     

Purification of allantoicase fromPseudomonas aeruginosa

Cells ofPseudomonas aeruginosa were grown in a synthetic medium containing allantoin as the sole source of carbon, nitrogen and energy. The specific activity of allantoicase in the cell-free extract amounted to 7 units/mg protein. The enzyme was purified 190 times by treatment of the extract at 72 C in the presence of Mn²⁺ions and chromatography on Ecteola-cellulose.     

A constitutive maltotetraose-producing amylase fromPseudomonas sp. IMD 353

Pseudomonas sp. IMD 353, secretes an extracellular maltotetraose-producing amylase. One of the most outstanding features of this enzyme is that it is produced constitutively (29 units/ml), using glucose (3%, w/v) as the carbon source. The amylase was purified to homogeneity and its enzymic properties examined. It had maxima for activity at pH 7.0 and 50°C, a relative molecular mass of 63,000 and an isoelectric point at pH 5.0. Specific amylase inhibitors, tendamistat and -amylase wheat inhibitor, activated the enzyme. Starch was hydrolysed from the non-reducing chain ends, by an endo-acting mechanism, producing maltotetraose in the -anomeric form. Yields of 65% (w/v), and 62% (w/v) were obtained on hydrolysis of starch (1%, w/v) and dextrin (15%, w/v), respectively. This enzyme failed to hydrolyse mmaltotetraose, even on prolonged incubation.     

Structure of a novel glucosamine-containing phosphoglycolipid from Deinococcus radiodurans

The structure of a major novel lipid from Deinococcus radiodurans has been determined to be 2'-O-(1,2-diacyl-sn-glycero-3-phospho)-3'-O-(alpha-N-acetylglucosaminyl) -N- glyceroyl alkylamine. The lipid was shown to contain a phosphatidic acid backbone by digestion with phospholipase A2 and by hydrolysis with hydrofluoric acid. Using a combination of chemical and NMR spectroscopic techniques, the structure of this lipid was elucidated and compared with that of a similar phosphoglycolipid reported earlier (Anderson, R., and Hansen, K. (1985) J. Biol. Chem. 260, 12219-12223) in which galactose was found in place of N-acetylglucosamine. The fatty acid compositions of the two lipids were similar.     

Structure of a novel phosphoglycolipid from Deinococcus radiodurans

The chemical structure of a major phosphoglycolipid from Deinococcus radiodurans has been shown to be 2'-O-(1,2-diacyl-sn-glycero-3-phospho)-3'-O-(alpha-galactosyl)-N-D-gl yceroyl alkylamine. By infrared spectroscopy, the lipid was shown to contain both carbonyl ester and amide linkages. Chemical analysis demonstrated a molar ratio of fatty acid, carbohydrate, and phosphorus of 2:1:1. The lipid was shown to contain an sn-3-phosphatidic acid backbone by digestion with phospholipase A2. Phosphodiester bond cleavage of the lipid with hydrofluoric acid liberated a component which contained galactose, glyceric acid, and alkylamines. Using NMR and permethylation/hydrolysis procedures, galactose was shown to be linked alpha-glycosidically to the 3-O-position of glyceric acid.     

Purification and characterization of pyocins R fromPseudomonas aeruginosa

Five types of pyocins were found in Pseudomonas aeruginosa strain 112. Production of these types was induced by UV irradiation. The pyocin activity was found to be resistant to trypsin treatment. Their molar mass was found to be 282, 251, 112, 89.1 and 54.9 kg/mol, respectively. The pyocins obtained were different from any known type (such as R, S, F) in their chemical and physical properties.     

Purification and characterization of dihydroorotase fromPseudomonas putida

Dihydroorotase was purified to homogeneity fromPseudomonas putida. The relative molecular mass of the native enzyme was 82 kDa and the enzyme consisted of two identical subunits with a relative molecular mass of 41 kDa. The enzyme only hydrolyzed dihydro-l-orotate and its methyl ester, and the reactions were reversible. The apparentK _m andV _max values for dihydro-l-orotate hydrolysis (at pH 7.4) were 0.081 mM and 18 μmol min⁻¹ mg⁻¹, respectively; and those forN-carbamoyl-dl-aspartate (at pH 6.0) were 2.2 mM and 68 μmol min⁻¹ mg⁻¹, respectively. The enzyme was inhibited by metal ion chelators and activated by Zn²⁺. However, excessive Zn²⁺ was inhibitory. The enzyme was inhibited by sulfhydryl reagents, and competitively inhibited byN-carbamoylamino acids such asN-carbamoylglycine, with aK _i value of 2.7 mM. The enzyme was also inhibited noncompetitively by pyrimidine-metabolism intermediates such as dihydrouracil and orotate, with aK _i value of 3.4 and 0.75 mM, respectively, suggesting that the enzyme activity is regulated by pyrimidine-metabolism intermediates and that dihydroorotase plays a role in the control of pyrimidine biosynthesis.     

A new stomatal type inChenopodiaceae

A new stomatal type—paracytic mesoperigenous—which has not been separated from the paracytic mesogenous type in previous studies of theChenopodiaceae, is described. The frequent occurrence of this previously unknown paracytic mesoperigenous type in this family is demonstrated. As a result a new phylogenetic pathway between anisocytic mesoperigenous and paracytic mesogenous types may be drawn.     

Production of hydantoinase fromPseudomonas fluorescens strain DSM 84

Summary Pseudomonas fluorescens strain DSM 84 was selected as a good hydantoinase (dihydropyrimidinase E.C. 3.5.2.2.) producer from a screening involving 60 collection strains. Optimization of the culture and growth conditions were performed in order to increase the enzyme production. A mineral medium supplemented with 10 g/l of yeast extract having an initial pH of 7.1±0.1 but containing no additional carbon source or inducer was devised. The strain DSM 84 was found to produce the maximal level of hydantoinase in the defined mineral medium within 15 h of incubation at 27°C. When using 5-isopropylhydantoin as substrate, N-carbamyl-valine was detected as the end product of the crude hydantoinase. Conditions leading to the isolation and conservation of a crude hydantoinase as well as its temperature and pH stability are described.     

A new type of zooplankton sampler

This paper describes a new, simple zooplankton sampler for quantitativesampling and studying the microdistribution of the mesozooplankton.     

A new type of arthropod photoreceptor

A new type of photoreceptor for the phylum Arthropoda, found in the class Collembola (Arthropoda, Hexapoda) is reported. This new light-sensitive structure consists of a pair of interocular vesicles present in the genus Vesicephalus Richards, 1964 and is anatomically related to the cluster of ommatidia. The absence of a lens, the presence of a rabdome in the upper part of the vesicle and the reflection and refraction of light by a hemolymph bubble with incidence to the rhabdomeric structure are the main traits of this new photoreceptor.     

一类新型的抗菌活性肽——生物防御素（Defensin）

生物防御素（ｄｅｆｅｎｓｉｎ）是近年来发现的一组新型抗菌活性肽。它们通常都是由３５～５０个氨基酸残基组成,且分子内富含二硫键。由于其具有牢固的分子骨架、广泛的分布以及生物活性功能,因而对它们的研究已成为当前国际学术界中一个引人关注的研究热点。本文将简述有关生物防御素的分布、分子结构特征、生物活性及其可能的作用机制等方面的研究概括及展望。