Legionella pneumophila induces IFNbeta in lung epithelial cells via IPS-1 and IRF3, which also control bacterial replication

Legionella pneumophila, a Gram-negative facultative intracellular bacterium, causes severe pneumonia (Legionnaires' disease). Type I interferons (IFNs) were so far associated with antiviral immunity, but recent studies also indicated a role of these cytokines in immune responses against (intracellular) bacteria. Here we show that wild-type L. pneumophila and flagellin-deficient Legionella, but not L. pneumophila lacking a functional type IV secretion system Dot/Icm, or heat-inactivated Legionella induced IFNbeta expression in human lung epithelial cells. We found that factor (IRF)-3 and NF-kappaB-p65 translocated into the nucleus and bound to the IFNbeta gene enhancer after L. pneumophila infection of lung epithelial cells. RNA interference demonstrated that in addition to IRF3, the caspase recruitment domain (CARD)-containing adapter molecule IPS-1 (interferon-beta promoter stimulator 1) is crucial for L. pneumophila-induced IFNbeta expression, whereas other CARD-possessing molecules, such as RIG-I (retinoic acid-inducible protein I), MDA5 (melanoma differentiation-associated gene 5), Nod27 (nucleotide-binding oligomerization domain protein 27), and ASC (apoptosis-associated speck-like protein containing a CARD) seemed not to be involved. Finally, bacterial multiplication assays in small interfering RNA-treated cells indicated that IPS-1, IRF3, and IFNbeta were essential for the control of intracellular replication of L. pneumophila in lung epithelial cells. In conclusion, we demonstrated a critical role of IPS-1, IRF3, and IFNbeta in Legionella infection of lung epithelium.     

Distribution analysis of hydrogenases in surface waters of marine and freshwater environments

Background

Surface waters of aquatic environments have been shown to both evolve and consume hydrogen and the ocean is estimated to be the principal natural source. In some marine habitats, H₂ evolution and uptake are clearly due to biological activity, while contributions of abiotic sources must be considered in others. Until now the only known biological process involved in H₂ metabolism in marine environments is nitrogen fixation.

Principal Findings

We analyzed marine and freshwater environments for the presence and distribution of genes of all known hydrogenases, the enzymes involved in biological hydrogen turnover. The total genomes and the available marine metagenome datasets were searched for hydrogenase sequences. Furthermore, we isolated DNA from samples from the North Atlantic, Mediterranean Sea, North Sea, Baltic Sea, and two fresh water lakes and amplified and sequenced part of the gene encoding the bidirectional NAD(P)-linked hydrogenase. In 21% of all marine heterotrophic bacterial genomes from surface waters, one or several hydrogenase genes were found, with the membrane-bound H₂ uptake hydrogenase being the most widespread. A clear bias of hydrogenases to environments with terrestrial influence was found. This is exemplified by the cyanobacterial bidirectional NAD(P)-linked hydrogenase that was found in freshwater and coastal areas but not in the open ocean.

Significance

This study shows that hydrogenases are surprisingly abundant in marine environments. Due to its ecological distribution the primary function of the bidirectional NAD(P)-linked hydrogenase seems to be fermentative hydrogen evolution. Moreover, our data suggests that marine surface waters could be an interesting source of oxygen-resistant uptake hydrogenases. The respective genes occur in coastal as well as open ocean habitats and we presume that they are used as additional energy scavenging devices in otherwise nutrient limited environments. The membrane-bound H₂-evolving hydrogenases might be useful as marker for bacteria living inside of marine snow particles.     

Histochemical analysis of phenylphenalenone-related compounds in <Emphasis Type="Italic">Xiphidium caeruleum</Emphasis> (Haemodoraceae)

Phenylphenalenones represent a typical group of secondary metabolites of the Haemodoraceae. Some of these phenolic compounds show organ-specific distribution within the plant. However, detailed information on cellular localisation is still lacking. To this end, confocal laser-scanning microscopy, microspectral photometry and high-performance liquid chromatography were used to study the tissue localisation of phenylphenalenone-type compounds in Xiphidium caeruleum Aubl. From the autofluorescence potential of these compounds, specific distribution of allophanylglucosides and non-glucosidic compounds of the phenylphenalenone-type in distinct cells of the roots (apical meristem, cortex, cap, epidermis) and the shoot system was revealed. Fluorescence enhancement using "Naturstoff reagent A" (NA) indicated the occurrence of NA-positive natural products in the vacuoles of leaf epidermal cells. The present results provide new insights into the possible functions of phenylphenalenone-related compounds in the context of their localisation. Additionally, the advantages and limitations of the techniques are discussed.     

Organ-specific analysis of phenylphenalenone-related compounds in Xiphidium caeruleum

The distribution pattern of phenylphenalenone-type compounds was investigated in vegetative and reproductive organs of Xiphidium caeruleum. The highest total molar concentration, up to 30 micromol g(-1) fr. wt, was detected in the root tip and the stamen. Accumulation of specific phenylphenalenone-related metabolites including glycosides was found in the hypogeal plant parts, the leaves, and the reproductive organs of the inflorescence. Putative biosynthetic relationships and the role of these compounds in plant defence are discussed.     

Studies on C3 convertases. Inhibition of C5 convertase formation by peptides containing aromatic amino acids.

The influence of various peptides containing the aromatic amino acids phenylalanine and tyrosine on the formation of the enzyme EAC1423 of the complement system from component C3 and enzyme EAC142 was investigated. Kinetic analysis of enzyme EAC1423 formation and studies on the binding of the C3b fragment of 125I-labelled component C3 to enzyme EAC142 both showed that binding of the C3b fragment of component C3 was decreased by the peptides. Kinetic studies on component-C3 turnover in the fluid phase of enzyme EAC142 failed to reveal effects of the peptides. However, an initial lag in component-C3 turnover occurred that at constant component-C3 concentration was inversely proportional to enzyme EAC142 concentration. This lag in enzyme EAC142 activity is considered as an indication that the interaction of enzyme EAC142 with component C3 possibly does not follow simple Michaelis-Menten kinetics, as was previously assumed. It is shown that the stages after enzyme EAC1423 formation are not influenced by the peptides, suggesting a high degree of specificity of the peptides for the inhibition of enzyme EAC1423 formation.     

The Krüppel-like transcriptional factors Zf9 and GKLF coactivate the human keratin 4 promoter and physically interact

A total of 4940 random sequence tags of the dimorphic yeast Yarrowia lipolytica, totalling 4.9 Mb, were analyzed. BLASTX comparisons revealed at least 1229 novel Y. lipolytica genes 1083 genes having homology with Saccharomyces cerevisiae genes and 146 with genes from various other genomes. This confirms the rapid sequence evolution assumed for Y. lipolytica. Functional analysis of newly discovered genes revealed that several enzymatic activities were increased compared to S. cerevisiae, in particular, transport activities, ion homeostasis, and various metabolism pathways. Most of the mitochondrial genes were identified in contigs spanning more than 47 kb. Matches to retrotransposons were observed, including a S. cerevisiae Ty3 and a LINE element. The sequences have been deposited with EMBL under the accession numbers AL409956-AL414895.