Central carbon metabolism influences fidelity of DNA replication in Escherichia coli

Recent studies indicated that there is a direct link between central carbon metabolism (CCM) and initiation and elongation of DNA replication in Eschericha coli. Namely, effects of certain mutations in genes coding for replication proteins (dnaA, dnaB, dnaE, dnaG, and dnaN) could be specifically suppressed by deletions of some genes, whose products are involved in CCM reactions (pta, ackA, pgi, tktB, and gpmA). Here, we demonstrate that the link between CCM and DNA synthesis can be extended to the DNA replication fidelity, as we report changes of the mutator phenotypes of E. coli dnaQ49 and dnaX36 mutants (either suppression or enhancement) by dysfunctions of zwf, pta, ackA, acnB, and icdA genes. Overexpression of appropriate wild-type CCM genes in double mutants resulted in reversions to the initial mutator phenotypes, indicating that the effects were specific. Moreover, the observed suppression and enhancement effects were not caused by changes in bacterial growth rates. These results suggest that there is a genetic correlation between CCM and DNA replication fidelity in E. coli, apart from the already documented link between CCM and DNA replication initiation control and elongation efficiency.     

Ovary architecture of two branchiobdellid species and Acanthobdella peledina (Annelida, Clitellata)

The aim of this study was to present data about ovary organization and oogenesis in two small groups of clitellate annelids, i.e. in representatives of Acanthobdellida (Acanthobdella peledina) and Branchiobdellida (Branchiobdella pentodonta and Branchiobdella parasitica), and to compare them to ovaries known from true leeches and oligochaetous clitellates. In A. peledina, the ovaries have the form of elongated cords, termed ovary cords, and are enveloped by coelomic sacs, the so-called ovisacs. The ovisacs are paired and each one contains only one ovary cord. The morphology and structure of the ovary cords depend on the maturity level of the animal. In young specimens the ovary cords are short and contain mainly oogonial cells and germ cells entering meiosis. Oogonia divide mitotically without full cytokineses, and as a result germ-line cysts are formed. As the animals grow, the cords become more elongated and the germ cells within the cords differentiate into nurse cells and oocytes. Oocytes gather cell organelles and, finally, detach from the ovary cord and float freely in the ovisac lumen.In both examined branchiobdellidans the ovaries are also paired. They are short and conical and are not enclosed within ovisacs. The narrow end of each ovary is connected to the intersegmental septum via a ligament, whereas the outermost (broad) end of the ovary extends freely into the coelom. The ovaries are polarized. Their narrow ends contain oogonia, whereas nurse cells and growing oocytes, gradually projecting from the ovary, can be found in their middle and outermost parts. Early vitellogenic oocytes detach from the ovary and float freely in the coelom.In all of the species studied, the ovaries are made up of germ-line cysts associated with somatic (follicular) cells. The architecture of a germ-line cyst is exactly the same as in other clitellate annelids that have been studied to date. Each germ cell in a cyst has one stable cytoplasmic bridge connecting it with a central anuclear cytoplasmic mass, a cytophore. The fate of germ cells constituting cysts is diverse. The majority of the cells withdraw from meiosis and become nurse cells; only a few continue meiosis, grow and become oocytes. The meroistic mode of oogenesis is suggested. We suggest also that the formation of germ-line cysts and ovary meroism should be regarded as basal conditions for all Clitellata. The occurrence of ovisacs enveloping the ovaries in A. peledina and Hirudinida is regarded as a synapomorphy of both groups, whereas ovaries found in B. pentodonta and B. parasitica have no ovisacs and resemble ovaries described in Oligochaeta sensu stricto.     

Is callose a barrier for lead ions entering <Emphasis Type="Italic">Lemna minor</Emphasis> L. root cells?

Plants have developed a range of strategies for resisting environmental stresses. One of the most common is the synthesis and deposition of callose, which functions as a barrier against stress factor penetration. The aim of our study was to examine whether callose forms an efficient barrier against Pb penetration in the roots of Lemna minor L. exposed to this metal. The obtained results showed that Pb induced callose synthesis in L. minor roots, but it was not deposited regularly in all tissues and cells. Callose occurred mainly in the protoderm and in the centre of the root tip (procambial central cylinder). Moreover, continuous callose bands, which could form an efficient barrier for Pb penetration, were formed only in the newly formed and anticlinal cell walls (CWs); while in other CWs, callose formed only small clusters or incomplete bands. Such an arrangement of callose within root CWs inefficiently protected the protoplast from Pb penetration. As a result, Pb was commonly present inside the root cells. In the light of the results, the barrier role of callose against metal ion penetration appears to be less obvious than previously believed. It was indicated that induction of callose synthesis is not enough for a successful blockade of the stress factor penetration. Furthermore, it would appear that the pattern of callose distribution has an important role in this defence strategy.     

Antiproliferative activity of salinomycin and its derivatives

Antiproliferative activity of seven amides and one benzotriazole ester derivative of salinomycin, a polyether ionophore antibiotic, with recently reported antibacterial activity, are herein described. Salinomycin and the majority of derivatives exhibit potent antiproliferative activity against the drug-resistant cancer cell lines. Moreover almost all derivatives show stronger activity against LoVo/DX cell line than that of unmodified salinomycin.     

Organelle evolution: Paulinella breaks a paradigm

It is commonly assumed that transformations of endosymbionts into organelles are exceptionally rare evolutionary events because of hypothetical difficulties in the origin of an import apparatus for nuclear-encoded, organelle-targeted proteins along with their targeting signals. A challenge to this view comes from recent studies of protein import into the cyanobacterial endosymbionts/organelles of Paulinella chromatophora.     

Microbotryum heliospermae, a new anther smut fungus parasitic on Heliosperma pusillum in the mountains of the European Alpine System

The members of the smut genus Microbotryum are pathogens of a wide range of host plant species from nine dicotyledonous families. Within the genus, the species sporulating in anthers of Caryophyllaceae form a monophyletic group that in recent years attracted much interest in various biological studies. The phylogenetic framework developed for species delimitation within Microbotryum revealed that high level host-specificity is a major feature of most caryophyllaceous anther smuts. However, the great number of anther smut specimens on diverse host plant species reported worldwide has still not been included in phylogenetic analyses due to the inaccessibility of recently collected specimens, and thus many species remain still undiscovered. In this study, anther smut specimens on Heliosperma pusillum originating from all main mountain ranges of the European Alpine System were examined using partial rDNA sequence and/or morphological analyses. The investigation revealed that all specimens are morphologically uniform and phylogenetically represent a monophyletic lineage, sister to Microbotryum lagerheimii complex on Atocion rupestre/Silene lacera/Silene vulgaris/Viscaria vulgaris. This lineage cannot be attributed to any of the previously described species, and therefore the smut in anthers of H. pusillum is described and illustrated here as a new species, Microbotryum heliospermae. The species is known from subalpine zone of the Alps, the Carpathians, the Dinaric Alps, and the Pyrenees, inhabiting host plants growing in open spring communities or semihumid mountain meadows.     

Long-term changes in numbers of geese stopping over and wintering in south-western Poland

South-western Poland belongs to the key staging areas for geese in Europe, supporting some 100000 birds in recent years. We compared goose counts conducted in the 1970s, 1990s and during 2009–2011 in this region, and linked the findings to the recent assessments of trends in the flyway-populations. Numbers increased several dozen times between the first two counts and have stabilized to the present. More than 14% of the flyway Tundra Bean Goose (Anser fabalis rossicus) stopped over in SW Poland on passage. Smaller numbers of White-fronted Goose (A. albifrons), Greylag Goose (A. anser), and four other rarer species, have all increased since the 1970s. The likely factors responsible for these changes are mild weather conditions, increased availability of large water bodies and shifts in winter ranges of particular species. Temporal mismatch between SW Poland and the total flyways in Bean and White-fronted Geese was recorded when we compared the long-term and the short-term population trends. Increasing reports of other species in SW Poland match the general tendencies in Europe. These data document that regional trends are not a simple reflection of those in flyways as a whole. To understand changes in goose populations a re-established international count network is desired.