An amber map of Salmonella phage P22

Summary Forty five amber mutants of Salmonella phage P22 were assigned to 12 complementation groups. Two amber mutants could not be classified into any one particular group.Ten of the complementation groups were mapped by two-factor crosses. The map is circular and about 65 units long.The remaining two complementation groups each consist of a single member which form very small plaques. Attempts to map these two mutants by two-factor crosses were unsuccessful.     

Repression of ant synthesis early in the lytic cycle of phage P22

Summary Using SDS-polyacrylamide gel electrophoresis to study the early expression of P22 genes we show that early expression of the ant-gene (imm I region) is turned off after 6–8 min, independent of the late acting mnt-repressor. A semi-clear mutant called cir5 is defective for this early ant turn-off. The mutation cir5 maps in the imm I region of P22 between genes mnt and ant. P22 cir5 mutants are defective for a repressor which acts in trans to regulate early ant synthesis. There appears to be no absolute requirement of the cir5 allele for the establishment of lysogeny. The overproduction of ant in the P22 cir5 mutant leads to a marked increase in abortive infections, killing the infected cells. The cir5-phenotype can be suppressed by an ant ^- mutation.     

Biodegradable plastics from renewable sources

Plastic waste disposal is a huge ecotechnological problem and one of the approaches to solving this problem is the development of biodegradable plastics. This review summarizes data on their use, biodegradability, commercial reliability and production from renewable resources. Some commercially successful biodegradable plastics are based on chemical synthesis (i.e. polyglycolic acid, polylactic acid, polycaprolactone, and polyvinyl alcohol). Others are products of microbial fermentations (i.e. polyesters and neutral polysaccharides) or are prepared from chemically modified natural products (e.g., starch, cellulose, chitin or soy protein).     

Degradation Pathway of Bisphenol A: Does ipso Substitution Apply to Phenols Containing a Quaternary α-Carbon Structure in the para Position?

The degradation of bisphenol A and nonylphenol involves the unusual rearrangement of stable carbon-carbon bonds. Some nonylphenol isomers and bisphenol A possess a quaternary α-carbon atom as a common structural feature. The degradation of nonylphenol in Sphingomonas sp. strain TTNP3 occurs via a type II ipso substitution with the presence of a quaternary α-carbon as a prerequisite. We report here a new degradation pathway of bisphenol A. Consequent to the hydroxylation at position C-4, according to a type II ipso substitution mechanism, the C-C bond between the phenolic moiety and the isopropyl group of bisphenol A is broken. Besides the formation of hydroquinone and 4-(2-hydroxypropan-2-yl)phenol as the main metabolites, further compounds resulting from molecular rearrangements consistent with a carbocationic intermediate were identified. Assays with resting cells or cell extracts of Sphingomonas sp. strain TTNP3 under an ¹⁸O₂ atmosphere were performed. One atom of ¹⁸O₂ was present in hydroquinone, resulting from the monooxygenation of bisphenol A and nonylphenol. The monooxygenase activity was dependent on both NADPH and flavin adenine dinucleotide. Various cytochrome P450 inhibitors had identical inhibition effects on the conversion of both xenobiotics. Using a mutant of Sphingomonas sp. strain TTNP3, which is defective for growth on nonylphenol, we demonstrated that the reaction is catalyzed by the same enzymatic system. In conclusion, the degradation of bisphenol A and nonylphenol is initiated by the same monooxygenase, which may also lead to ipso substitution in other xenobiotics containing phenol with a quaternary α-carbon.     

A role for MCP-1/CCR2 in interstitial lung disease in children

Background

Particulate matter (PM) can exacerbate allergic airway diseases. Although health effects of PM with a diameter of less than 100 nm have been focused, few studies have elucidated the correlation between the sizes of particles and aggravation of allergic diseases. We investigated the effects of nano particles with a diameter of 14 nm or 56 nm on antigen-related airway inflammation.

Methods

ICR mice were divided into six experimental groups. Vehicle, two sizes of carbon nano particles, ovalbumin (OVA), and OVA + nano particles were administered intratracheally. Cellular profile of bronchoalveolar lavage (BAL) fluid, lung histology, expression of cytokines, chemokines, and 8-hydroxy-2'-deoxyguanosine (8-OHdG), and immunoglobulin production were studied.

Results

Nano particles with a diameter of 14 nm or 56 nm aggravated antigen-related airway inflammation characterized by infiltration of eosinophils, neutrophils, and mononuclear cells, and by an increase in the number of goblet cells in the bronchial epithelium. Nano particles with antigen increased protein levels of interleukin (IL)-5, IL-6, and IL-13, eotaxin, macrophage chemoattractant protein (MCP)-1, and regulated on activation and normal T cells expressed and secreted (RANTES) in the lung as compared with antigen alone. The formation of 8-OHdG, a proper marker of oxidative stress, was moderately induced by nano particles or antigen alone, and was markedly enhanced by antigen plus nano particles as compared with nano particles or antigen alone. The aggravation was more prominent with 14 nm of nano particles than with 56 nm of particles in overall trend. Particles with a diameter of 14 nm exhibited adjuvant activity for total IgE and antigen-specific IgG₁ and IgE.

Conclusion

Nano particles can aggravate antigen-related airway inflammation and immunoglobulin production, which is more prominent with smaller particles. The enhancement may be mediated, at least partly, by the increased local expression of IL-5 and eotaxin, and also by the modulated expression of IL-13, RANTES, MCP-1, and IL-6.     

BacA Is Essential for Bacteroid Development in Nodules of Galegoid,but not Phaseoloid,Legumes

BacA is an integral membrane protein, the mutation of which leads to increased resistance to the antimicrobial peptides bleomycin and Bac7_1-35 and a greater sensitivity to SDS and vancomycin in Rhizobium leguminosarum bv. viciae, R. leguminosarum bv. phaseoli, and Rhizobium etli. The growth of Rhizobium strains on dicarboxylates as a sole carbon source was impaired in bacA mutants but was overcome by elevating the calcium level. While bacA mutants elicited indeterminate nodule formation on peas, which belong to the galegoid tribe of legumes, bacteria lysed after release from infection threads and mature bacteroids were not formed. Microarray analysis revealed almost no change in a bacA mutant of R. leguminosarum bv. viciae in free-living culture. In contrast, 45 genes were more-than 3-fold upregulated in a bacA mutant isolated from pea nodules. Almost half of these genes code for cell membrane components, suggesting that BacA is crucial to alterations that occur in the cell envelope during bacteroid development. In stark contrast, bacA mutants of R. leguminosarum bv. phaseoli and R. etli elicited the formation of normal determinate nodules on their bean host, which belongs to the phaseoloid tribe of legumes. Bacteroids from these nodules were indistinguishable from the wild type in morphology and nitrogen fixation. Thus, while bacA mutants of bacteria that infect galegoid or phaseoloid legumes have similar phenotypes in free-living culture, BacA is essential only for bacteroid development in indeterminate galegoid nodules.Bacteria of the family Rhizobiaceae are alphaproteobacteria, which form a species-specific symbiotic relationship with leguminous plants. Plants release flavonoids that typically induce the synthesis of lipochitooligosaccharides by rhizobia, which in turn initiate a signaling cascade in the plant, leading to nodule formation (34). Rhizobia become trapped by curling root hairs, which they enter via infection threads that grow and ramify into the root cortex, where newly induced meristematic cells form the nodule (34). Bacteria are released from infection threads and engulfed by a plant-derived symbiosome membrane. In galegoid legumes (a clade in the subfamily Papilionoideae, such as Medicago, Pisum, or Vicia), which form indeterminate nodules that have a persistent meristem, bacteria undergo the endoreduplication of their chromosome, resulting in dramatic increases in size, shape, and DNA content to become terminally differentiated bacteroids (32). However, in phaseoloid legumes (e.g., lotus, bean, and soybean), which form determinate nodules with a transient meristem, bacteria do not undergo endoreduplication and therefore do not enlarge substantially. These bacteroids retain a normal DNA content and can regrow after isolation from nodules (32). The endoreduplication of bacteroids is controlled by the plant, and it is believed that nodule-specific cysteine-rich (NCR) peptides, which are made in indeterminate, but not in determinate, nodules, may be responsible for inducing and maintaining bacteroid development (31, 32). Finally, mature bacteroids receive dicarboxylic acids from the plant, which they use as a carbon, reductant, and energy source for the reduction of N₂ to ammonia (38). The ammonia is secreted to the plant, where it is assimilated into amino acids or ureides, depending on the legume, for export to the shoot.Sinorhizobium meliloti BacA protein was the first bacterial factor identified to be essential for bacteroid development (15). More recently, it also has been shown to be essential for the Mesorhizobium-Astragalus symbiosis (42). S. meliloti elicits the formation of indeterminate nodules on alfalfa, and while S. meliloti bacA null mutants induce nodule formation, bacteria lyse soon after endocytosis but prior to bacteroid differentiation (15, 20). BacA is a cytoplasmic membrane protein that shares 64% identity with SbmA from Escherichia coli (15, 25). SbmA/BacA proteins belong to the ATP binding cassette (ABC) superfamily and share sequence similarity with a family of eukaryotic peroxisomal membrane proteins, including the human adrenoleukodystrophy protein, which is required for the efficient transport of very-long-chain fatty acids (VLCFAs) out of the cytoplasm (9). Consistent with this, S. meliloti BacA is required for the complete modification of lipid A with VLCFAs (9). However, since S. meliloti mutants, which are directly involved in the biosynthesis of VLCFA-modified lipid A, show bacteroid abnormalities but still can form a successful alfalfa symbiosis, the effect of BacA on lipid A VLCFA modification does not fully account for its essential role in bacteroid development (10, 11, 16). Strains mutated in bacA also have an increased resistance to the glycopeptide bleomycin, a low-level resistance to aminoglycoside antibiotics, and an increased sensitivity to ethanol, sodium dodecyl sulfate (SDS), and deoxycholate relative to the sensitivities of the parent strain (12, 18, 25). More recently it has been shown that an S. meliloti bacA null mutant has an increased resistance to a truncated form of a eukaryotic proline-rich peptide, Bac7_1-16, and was unable to accumulate a fluorescently labeled form of this peptide (28). This finding, combined with the increased resistance of an S. meliloti bacA null mutant to bleomycin, led to the hypothesis that BacA is itself a putative peptide transporter (BacA mediated) or able to alter the activity of such a transporter (BacA influenced) (11, 15, 18, 28).As the increased resistance of the S. meliloti bacA null mutant to bleomycin and Bac7_1-16 appears to be independent of the VLCFA modification of lipid A (11, 28), this suggested that either BacA-mediated or BacA-influenced peptide uptake into S. meliloti plays a role in bacteroid development. Since indeterminate galegoid nodules contain hundreds of NCR peptides, whereas determinate phaseoloid nodules lack these host peptides (31), we considered it important to assess the role of BacA in bacteroid development during the formation of both nodule types.Here, we show that bacA mutants of Rhizobium leguminosarum bv. viciae strains 3841 and A34 failed to develop bacteroids and did not fix nitrogen in indeterminate pea (Pisum sativum) nodules. However, bacA mutants of both R. leguminosarum bv. phaseoli 4292 and Rhizobium etli CE3 formed normal bacteroids and fixed nitrogen at wild-type rates in determinate bean (Phaseolus vulgaris) nodules. This is consistent with BacA being a key component of bacteroid development in indeterminate galegoid nodules that is not required for functional bacteroid formation in determinate phaseoloid nodules.     

Die Nichtosmotische Harnstoffaufnahme und Ihre Beziehung zur Wasserbilanz Plasmolysierter Zellen

Ohne ZusammenfassungMit 7 Textabbildungen.     

Der Einfluß der Infektionsmultiplizität auf die Lysogenisierung im System Salmonella typhimurium — Phage P 22

Summary The increase of lysogenization in phage infected cells has been investigated with increasing multiplicities of infection in the system Salmonella thyphimurium-phage P 22. The increase of infection resp. lysis and lysogenization with multiplicity follows first order reaction kinetics as concluded from multiplicities<0.3. Under the experimental conditions employed, the probability per phage is 0.57 for lysogenization and 0.43 for lysis. If multiplicity is>0.3 and cells are infected with more than one phage, the lysogenizations increase according to one hit kinetics, whereas the lysis of cells decreases. It is concluded, that lytic reactions in multicomplexes, which can be initiated independently by every one of the infecting phage particles will be suppressed by lysogenic reactions initiated by other independently infecting phages of the complex. Our experiments suggest, that immunity of the prelysogenic condition is the process responsible for the suppression of the lytic reaction. Therefore, in multicomplexes the immunity induced by one of the infecting phages is superimposed upon the one hit lytic infection causing the percentage of lysogenization increasing with multiplicity.