The frequency of MMS-induced,umuDC-dependent,mutations declines during starvation in Escherichia coli

It has been found that the level of methyl methanesulfonate (MMS)-induced mutation in Escherichia coli is dependent on the level of UmuD(D′)C proteins. The frequency of argE(ochre)→Arg⁺ mutations (which occur predominantly by AT→TA transversions) and Rif^S→Rif^R mutations is much higher when UmuDC or UmuD'C are overproduced in the cell. When MMS-treated bacteria were starved for progressively longer times and hence the expression of mutations delayed, the level of mutations observed progressively declined. This same treatment had no effect on the degree of SOS induction. Examination of plasmid DNAs, isolated from MMS-treated cells, for their sensitivity to the specific endonucleases Fpg and Nth revealed that MMS causes formation of abasic sites, which are repaired during cell starvation. It is assumed that, in non-dividing cells, apurinic sites are mostly repaired by RecA-mediated recombinational repair. This pathway, which is error-free, is compared with the processing pathway in metabolically active cells, where translesion synthesis by the UmuD′₂C-RecA-DNA polymerase III holoenzyme complex occurs; this latter pathway is error-prone.     

Structural and evolutionary bioinformatics of the SPOUT superfamily of methyltransferases

Background  

SPOUT methyltransferases (MTases) are a large class of S-adenosyl-L-methionine-dependent enzymes that exhibit an unusual alpha/beta fold with a very deep topological knot. In 2001, when no crystal structures were available for any of these proteins, Anantharaman, Koonin, and Aravind identified homology between SpoU and TrmD MTases and defined the SPOUT superfamily. Since then, multiple crystal structures of knotted MTases have been solved and numerous new homologous sequences appeared in the databases. However, no comprehensive comparative analysis of these proteins has been carried out to classify them based on structural and evolutionary criteria and to guide functional predictions.     

Are seeds suitable for flow cytometric estimation of plant genome size?

BACKGROUND: Nuclear DNA content in plants is commonly estimated using flow cytometry (FCM). Plant material suitable for FCM measurement should contain the majority of its cells arrested in the G0/G1 phase of the cell cycle. Usually young, rapidly growing leaves are used for analysis. However, in some cases seeds would be more convenient because they can be easily transported and analyzed without the delays and additional costs required to raise seedlings. Using seeds would be particularly suitable for species that contain leaf cytosol compounds affecting fluorochrome accessibility to the DNA. Therefore, the usefulness of seeds or their specific tissues for FCM genome size estimation was investigated, and the results are presented here. METHODS: The genome size of six plant species was determined by FCM using intercalating fluorochrome propidium iodide for staining isolated nuclei. Young leaves and different seed tissues were used as experimental material. Pisum sativum cv. Set (2C = 9.11 pg) was used as an internal standard. For isolation of nuclei from species containing compounds that interfere with propidium iodide intercalation and/or fluorescence, buffers were used supplemented with reductants. RESULTS: For Anethum graveolens, Beta vulgaris, and Zea mays, cytometrically estimated genome size was the same in seeds and leaves. For Helianthus annuus, different values for DNA amounts in seeds and in leaves were obtained when using all but one of four nuclei isolation buffers. For Brassica napus var. oleifera, none of the applied nuclei isolation buffers eliminated differences in genome size determined in the seeds and leaves. CONCLUSIONS: The genome size of species that do not contain compounds that influence fluorochrome accessibility appears to be the same when estimated using specific seed tissues and young leaves. Seeds can be more suitable than leaves, especially for species containing staining inhibitors in the leaf cytosol. Thus, use of seeds for FCM nuclear DNA content estimation is recommended, although for some species a specific seed tissue (usually the radicle) should be used. Protocols for preparation of samples from endospermic and endospermless seeds have been developed.     

Phytoplankton composition and cell carbon distribution in Prydz Bay, Antarctica: relation to organic particulate matter and its {delta}13C values

In January-February 1991, in Prydz Bay, phytoplankton bloomwas evident in the inner shelf area with the dominant diatomsbeing represented mainly by pennate species of the Nitzschia-Fragilariopsisgroup. Dinoflagellates and naked flagellates were most abundantin the centre of the bay; however, larger heterotrophic speciesprevailed at the southern stations. Cell carbon values (average317 µg l^–1; range 92-1048 µg l^–1) foundin the bloom in the south were chiefly due to pennate diatomsand larger heterotrophic dinoflagellates. Much lower carbonvalues (average 51 µg l^–1; range 7-147 µgl^–1) in the outer shelf region were mainly contributedby large centric diatoms (70-110 mu;m) and small dinoflagellates(5-25 µm). Wide ranges of algal cell sizes were observedin both southern and northern communities; the overlapping ofsizes of diatoms and flagellates, the latter containing heterotrophs,suggested complex trophic relationships within the planktonand an enhanced heterotrophic activity in the south. North-to-southvariations in surface     

Inside Cover: Localization of PD‐L1 on single cancer cells by iSERS microscopy with Au/Au core/satellite nanoparticles (J. Biophotonics 3/2020)

iSERS (SERS=surface‐enhanced Raman scattering) microscopy is an emerging Raman‐based staining technique for the selective localization of target proteins on cells and tissues using antibody‐ SERS nanotag conjugates. In this contribution we demonstrate the feasibility of iSERS for imaging of programmed cell death‐ligand 1 (PD‐L1), an important predictive biomarker, on single SkBr‐3 breast cancer cells. Further details can be found in the article by Elzbieta Stepula, Matthias König, Xin‐Ping Wang, et al. ( e201960034 ).

     

Polypeptides from maize seedlings with protein kinase functions

Low molecular weight protein kinase from maize seedlings was isolated. The molecular weight of the enzyme was below 10 000. The enzyme preferentially utilized ATP and casein as donor and acceptor of phosphorus, respectively. Casein kinase was a cyclic nucleotide-independent, heparin-sensitive enzyme. The low molecular weight casein kinase was resolved into basic, neutral and slightly acidic peaks of activity by chromatofocussing.     

Serum alkaline phosphatase polymorphism in pigs1

Genetic variants of serum alkaline phosphatase were studied by the method of starch gel electrophoresis in the Zlotnicka Pstra breed of pigs. Two regions of alkaline phosphatase migration were observed. A single fraction in region I and four different phenotypes: AB, B, BC and BD in region II, were found. For AB, B and BC phenotypes the genetic control by three alleles AkpA, AkpB and AkpC in suggested. The observed segregation ratios in some cases deviated significantly from the expected ones.