Regulation of colony morphology and biofilm formation in Shewanella algae

Bacterial colony morphology can reflect different physiological stages such as virulence or biofilm formation. In this work we used transposon mutagenesis to identify genes that alter colony morphology and cause differential Congo Red (CR) and Brilliant Blue G (BBG) binding in Shewanella algae, a marine indigenous bacterium and occasional human pathogen. Microscopic analysis of colonies formed by the wild-type strain S. algae CECT 5071 and three transposon integration mutants representing the diversity of colony morphotypes showed production of biofilm extracellular polymeric substances (EPS) and distinctive morphological alterations. Electrophoretic and chemical analyses of extracted EPS showed differential patterns between strains, although the targets of CR and BBG binding remain to be identified. Galactose and galactosamine were the preponderant sugars in the colony biofilm EPS of S. algae. Surface-associated biofilm formation of transposon integration mutants was not directly correlated with a distinct colony morphotype. The hybrid sensor histidine kinase BarA abrogated surface-associated biofilm formation. Ectopic expression of the kinase and mutants in the phosphorelay cascade partially recovered biofilm formation. Altogether, this work provides the basic analysis to subsequently address the complex and intertwined networks regulating colony morphology and biofilm formation in this poorly understood species.     

Invasion of tissue culture cells by diarrhoeagenic strains of Escherichia coli which lack the enteroinvasive inv gene

Abstract Invasive Escherichia coli strains of certain serotypes invade by the same mechanism as the Shigella sp. It has been proposed that invasion of epithelial cells by EPEC strains may also occur; this is a previously overlooked property. In the present study E. coli strains isolated from patients with diarrhoea or ulcerative colitis, lacking the inv plasmid mediating classical invasion, but hybridizing with probes for different adhesins, were analyzed for their ability to invade HeLa and Caco-2 cells. The majority of strains invaded Caco-2 cells to a higher extent than HeLa cells. Adhesion to Caco-2 cells was a prerequisite for subsequent invasion of the cells but EAF, eae , EAgg and other known virulence factors were not sufficient to mediate invasion. In 8/9 E. coli strains invasion was enhanced after growth under iron restriction. Growth during anaerobic conditions did not influence subsequent invasion by E. coli strains whereas 6/9 strains had their invasive ability significantly decreased after growth in the presence of 1% glucose. The invasive process was inhibited by mannose but not by lactose, fucose or galactose. Our data indicate that strains of E. coli may invade Caco-2 cells by novel mechanisms which require adhesion to the cells but which differ from those of Salmonella sp., Yersinia sp., Shigella sp. and classical enteroinvasive E. coli .     

Sesquiterpene lactone from Wunderlichia crulsiana inhibits the respiratory burst of leukocytes triggered by distinct biochemical pathways

The sesquiterpene lactone tubiferin was chemically purified from the brazilian native plant Wunderlichia crulsiana and identified by NMR and GC/MS data. Its ability to inhibit the respiratory burst of peritoneal inflammatory polymorphonuclear leukocytes (PMN) stimulated upon addition of phorbol miristate acetate (PMA), opsonized zymosan (OZ), and N-formyl-methionyl-leucyl-phenylalanine (fMLP) was evaluated. The tubiferin inhibition was more pronounced when PMN were stimulated through the protein kinase C pathway (PMA) compared to the alternative complement pathway (OZ). The inhibition when PMN were triggered by a chemoattractant stimulus (fMLP) was similar to that achieved with OZ-stimulated phagocytes. Tubiferin showed dose-dependent effects on the PMN respiratory burst triggered by the three different substances, and also decreased substantially the carrageenan-induced mice paw edema.     

Inhibition by sodium bromide of acetylcholine release and synaptic transmission in the superior cervical ganglion of the rat

In the superior cervical ganglion (SCG) of rats, the interaction of sodium bromide (NaBr) with various drugs which interfere with the GABA system, such as 3-(4-chlorophenyl)-4-aminobutyrate [( + )baclofen, Bac], ( + )bicuculline (Bic), picrotoxin (Pic) and chlorpromazine (CPZ), and the effects of NaBr on the K⁺-induced release of [³H]acetylcholine ([³H]ACh) were studied in vitro. The effects on the evoked potentials induced by preganglionic stimulation were analysed in situ. The in vitro experiments revealed that 1 mM NaBr inhibits both the basal and the K⁺-induced release of [³H]ACh in a Ca²⁺-dependent manner. This NaBr effect was additive with the similar effect of the GABA agonist Bac, but it could not be blocked with any of the drugs applied. In vivo, 1 mM NaBr depressed the amplitude of the evoked potentials in the SCG. It is concluded that, in the SCG of rats, NaBr interacts with the presynaptic and postsynaptic membranes. The inhibitory effects of NaBr on both the [³H]ACh release and the potentials evoked by preganglionic stimulation cannot be attributed to a direct interference with GABA receptor complexes; some other binding site/s on the presynaptic and postsynaptic membranes might be responsible for the bromide-induced reduction of the synaptic transmission in the SCG of rats.     

Predation on artificial,solitary and aggregated wader nests on farmland

Predation rates on artificial wader nests, solitary curlew (Numenius arquata) and lapwing (Vanellus vanellus) nests and lapwing nests in colonies were studied on a farmland site in central Sweden. Predation rates were highest on artificial wader nests, intermediate on solitary curlew and lapwing nests and lowest on lapwing nests in colonies, probably because of active defence of adults at real nests and/or because of selection of nest sites with lower predation risk by breeding birds. A comparison of nests close to (50 m) and far away from (200 m) forest edges revealed no increased predation risk close to edges for any of the studied nest types. Predation risk changed during the season for artificial nests (highest in the middle of May), while predation rates on lapwing and curlew nests were more stable. Artificial nests seem to be inappropriate for measuring actual predation rates and temporal differences in predation rates on real nests, but they might be suitable for use as an index of spatial differences.     

Expression of DNA methyltransferases is involved in Quercus suber cork quality

Cork oak (Quercus suber) is an important Portuguese species, mainly due to the economic value of the cork it produces. Cork results from phellogen, a meristematic tissue, which can locally produce lenticels or have discontinuities, originating “defects”: pores and nail inclusions that are detrimental to cork industrial use. Epigenetic processes control plant development and its deregulation can lead to altered phenotypes; therefore, the study of epigenetic players in the phellogen is important to understand the emergence of cork's defects. DNA methyltransferases (DNMTs) and one protein associated to MET1 (DMAP1) were characterized in Q. suber, and their gene expression was analyzed in phellogen and contiguous differentiating cell layers of trees producing high and low quality cork, after the evaluation of their defects by physical and image analysis methods. All classes of DNMTs (MET, DRM, and CMT) with the respective canonical motifs were identified in Q. suber. The expression analyses of these genes showed that QsDRM2 was the most active methyltransferases in the cells analyzed, and that all the genes were differentially expressed in trees with distinct cork quality, with a tendency for higher expression levels in low quality producers. Interestingly, the global methylation level was higher in cells with low expression of DNA methyltransferases. A positive and significant correlation was obtained between QsDMAP1 gene expression and the percentage of cork defects. This work provides the first evidence that cork quality in Q. suber is likely influenced by epigenetic mechanisms.     

Species-Rich Scandinavian Grasslands are Inherently Open to Invasion

Invasion of native habitats by alien or generalist species is recognized worldwide as one of the major causes behind species decline and extinction. One mechanism determining community invasibility, i.e. the susceptibility of a community to invasion, which has been supported by recent experimental studies, is species richness and functional diversity acting as barriers to invasion. We used Scandinavian semi-natural grasslands, exceptionally species-rich at small spatial scales, to examine this mechanism, using three grassland generalists and one alien species as experimental invaders. Removal of two putative functional groups, legumes and dominant non-legume forbs, had no effect on invasibility except a marginally insignificant effect of non-legume forb removal. The amount of removed biomass and original plot species richness had no effect on invasibility. Actually, invasibility was high already in the unmanipulated community, leading us to further examine the relationship between invasion and propagule pressure, i.e. the inflow of seeds into the community. Results from an additional experiment suggested that these species-rich grasslands are effectively open to invasion and that diversity may be immigration driven. Thus, species richness is no barrier to invasion. The high species diversity is probably in itself a result of the community being highly invasible, and species have accumulated at small scales during centuries of grassland management.     

Duplicability of self-interacting human genes

Background  

There is increasing interest in the evolution of protein-protein interactions because this should ultimately be informative of the patterns of evolution of new protein functions within the cell. One model proposes that the evolution of new protein-protein interactions and protein complexes proceeds through the duplication of self-interacting genes. This model is supported by data from yeast. We examined the relationship between gene duplication and self-interaction in the human genome.     

Microplate-based high throughput screening procedure for the isolation of lipid-rich marine microalgae

Background

Termites are highly effective at degrading lignocelluloses, and thus can be used as a model for studying plant cell-wall degradation in biological systems. However, the process of lignin deconstruction and/or degradation in termites is still not well understood.

Methods

We investigated the associated structural modification caused by termites in the lignin biomolecular assembly in softwood tissues crucial for cell-wall degradation. We conducted comparative studies on the termite-digested (i.e. termite feces) and native (control) softwood tissues with the aid of advanced analytical techniques: ¹³C crosspolarization magic angle spinning and nuclear magnetic resonance (CP-MAS-NMR) spectroscopy, flash pyrolysis with gas chromatography mass spectrometry (Py-GC/MS), and Py-GC-MS in the presence of tetramethylammonium hydroxide (Py-TMAH)-GC/MS.

Results

The ¹³C CP/MAS NMR spectroscopic analysis revealed an increased level of guaiacyl-derived (G unit) polymeric framework in the termite-digested softwood (feces), while providing specific evidence of cellulose degradation. The Py-GC/MS data were in agreement with the ¹³C CP/MAS NMR spectroscopic studies, thus indicating dehydroxylation and modification of selective intermonomer side-chain linkages in the lignin in the termite feces. Moreover, Py-TMAH-GC/MS analysis showed significant differences in the product distribution between control and termite feces. This strongly suggests that the structural modification in lignin could be associated with the formation of additional condensed interunit linkages.

Conclusion

Collectively, these data further establish: 1) that the major β-O-4' (β-aryl ether) was conserved, albeit with substructure degeneracy, and 2) that the nature of the resulting polymer in termite feces retained most of its original aromatic moieties (G unit-derived). Overall, these results provide insight into lignin-unlocking mechanisms for understanding plant cell-wall deconstruction, which could be useful in development of new enzymatic pretreatment processes mimicking the termite system for biochemical conversion of lignocellulosic biomass to fuels and chemicals.