The present study provides the first evidence that signaling occurs between B-ephrins and EphB receptors in the adult CNS in response to injury. Specifically, our combined histological and biochemical data indicate that two members of the B-class of ephrins and Eph receptors, ephrin-B2 and EphB2, are expressed by astrocytes and meningeal fibroblasts, respectively, in the adult spinal cord. In response to thoracic spinal cord transection lesions, ephrin-B2 and EphB2 protein levels exhibit an initial decrease (1 d after lesion), followed by a significant increase by day 14. Immunohistochemical data indicate that ephrin-B2 is expressed by reactive CNS astrocytes, and EphB2 is present on fibroblasts invading the lesion site from the adjacent meninges. During the first 3 d after injury, there is intermingling of ephrin-B2-expressing reactive astrocytes at the lesion surface with EphB2-containing fibroblasts that is concurrent with bidirectional activation (phosphorylation) of ephrin-B2 and EphB2. By 7 d, both cell types are establishing restricted cellular domains containing dense networks of cells and interweaving processes. This astroglial-meningeal fibroblast scar is fully developed by day 14 when there is strict segregation of ephrin-B2-expressing astrocytes from EphB2-positive meningeal fibroblasts. These morphological changes are concomitant with a simultaneous decrease in ephrin-B2 and EphB2 activation. These observations provide strong evidence that cell contact-mediated bidirectional signaling between ephrin-B2 on reactive astrocytes and EphB2 on meningeal fibroblasts is an early event in the cellular cascades that result in the development of the glial scar and the exclusion of meningeal fibroblasts from the injured spinal cord.

The mechanisms by which Legionella pneumophila, a facultative intracellular parasite and the agent of Legionnaires' disease, acquires iron are largely unexplained. Several earlier studies indicated that L. pneumophila does not elaborate siderophores. However, we now present evidence that supernatants from L. pneumophila cultures can contain a nonproteinaceous, high-affinity iron chelator. More specifically, when aerobically grown in a low-iron, chemically defined medium (CDM), L. pneumophila secretes a substance that is reactive in the chrome azurol S (CAS) assay. Importantly, the siderophore-like activity was only observed when the CDM cultures were inoculated to relatively high density with bacteria that had been grown overnight to log or early stationary phase in CDM or buffered yeast extract. Inocula derived from late-stationary-phase cultures, despite ultimately growing, consistently failed to result in the elaboration of siderophore-like activity. The Legionella CAS reactivity was detected in the culture supernatants of the serogroup 1 strains 130b and Philadelphia-1, as well as those from representatives of other serogroups and other Legionella species. The CAS-reactive substance was resistant to boiling and protease treatment and was associated with the <1-kDa supernatant fraction. As would also be expected for a siderophore, the addition of 0.5 or 2.0 M iron to the cultures repressed the expression of the CAS-reactive substance. Interestingly, the supernatants were negative in the Arnow, Csáky, and Rioux assays, indicating that the Legionella siderophore was not a classic catecholate or hydroxamate and, hence, might have a novel structure. We have designated the L. pneumophila siderophore legiobactin.The bacterium Legionella pneumophila is a ubiquitous inhabitant of natural and man-made aquatic environments, surviving both free, in biofilms, and as an intracellular parasite of protozoa (1,8,26,49,50). Yet, this gram-negative microbe is best known for being the principal etiologic agent of Legionnaires' disease, a potentially fatal form of human pneumonia (59,95). Within the lung, L. pneumophila flourishes as an intracellular parasite of the alveolar macrophages and perhaps the epithelium (1,8,13,41,63,84). A variety of studies indicate that iron is a key requirement for L. pneumophila extracellular replication, intracellular infection, and virulence (7,9,10,25,31,39,40,44,45,60,65,71,72,76,77,78,86,89,91). Despite this, the molecular basis of Legionella iron acquisition, particularly its earliest stages, is relatively unclear.Among all of the considerations regarding Legionella iron acquisition, it is the issue of siderophore production by L. pneumophila that has been the most controversial. In the early 1980s, shortly after the discovery of the Legionella genus, it was reported that L. pneumophila does not produce siderophores (79). This conclusion was based upon the negative results that were obtained from a standard bioassay, as well as the Arnow and Csáky assays, the customary methods for detecting ...

White-rot fungi (basidiomycetes) play an important role in the degradation of lignin which is, beside cellulose, the major compound of wood. This process is catalyzed by ligninolytic enzymes, which are able to cleave oxidatively aromatic rings in lignin structure. Manganese peroxidase and laccase of white-rot-fungi are the most important of these among the ligninolytic enzymes. In addition, they are able to degrade xenobiotic aromatic polymers, persisting as environmental pollutants. Manganese and aromatic compounds have often been discussed as being inducers, enhancers or mediators of these ligninolytic enzymes. It is known that supplementing the growth medium with either Mn2+, veratryl alcohol or coal-derived humic acids leads to significantly enhanced extracellular ligninolytic activities. Measuring the amount of expressed mRNA of the two enzymes by quantitative RT-PCR provided evidence that the expression of manganese peroxidase was induced in the three tested white-rot fungi, Clitocybula dusenii b11, Nematoloma frowardii b19, and a straw-degrading strain designated i63-2. Laccase, on the other hand, was expressed in all three fungi with a significant basic activity even without inducer added. However, since the level of laccase mRNA was higher in cultures supplemented with any one of the tested inducers, we conclude that both manganese and the aromatic substances also increase the expression of laccase.

Three different mechanisms can be envisaged that are used by fungi to solubilize coal: the production of alkaline substances, the extrusion of chelators and, of special interest in the scope of biotechnology, the action of enzymes. Whether these mechanisms are operating separately or in various combinations has not yet been finally assessed. The two deuteromycetes Fusarium oxysporum and Trichoderma atroviride solubilize coal by synergistic effects of various differnt mechanisms depending on the cell metabolism. F. oxysporum seems to solubilize coal by increasing the pH of the mycelial surroundings and by the action of chelators induced during growth in glutamate-containing media (without involvement of enzymes). T. atroviride, on the other hand, appears to use, in addition to an alkaline pH and a high chelator activity, at least two classes of enzyme activity to attack coal: hydrolytic activity for coal solubilization and ligninolytic activity for degradation of humic acids.

The molecular mechanisms that regulate basal ganglia development are largely unknown. Eph receptor tyrosine kinases are potential participants in this process as they regulate development of other CNS regions and are expressed in basal ganglia nuclei, such as the substantia nigra (SN) and striatum. To address the role of Eph receptors in the development of these nuclei, we analysed anatomical changes in the SN and striatum of mice with null mutations for EphB1. These mice express beta-galactosidase as a marker for cells normally expressing EphB1. In situ hybridization data and a direct comparison of SN neurons expressing tyrosine hydroxylase (TH) and/or the beta-gal marker for EphB1 revealed that EphB1 is not expressed in TH+ neurons of pars compacta (SNc), but is restricted to neurons in pars reticulata (SNr). Consistent with this, we find that EphB1 null mice exhibit a significant decrease in the volume and number of neurons (40% decrease) in SNr, whereas the volume and number of TH+ neurons in SNc is not significantly affected nor are there changes in the distribution of nigrostriatal dopamine neurons. Although EphB1 is expressed in the striatum, EphB1-/- mice exhibit no significant changes in striatal volume and TH fiber density, and have no obvious alterations in striatal patch/matrix organization. Behavioral evaluation of EphB1 null mice in an open-field environment revealed that these mice exhibited spontaneous locomotor hyperactivity. These results suggest that EphB1 is necessary for the proper formation of SNr, and that neuronal loss in SNr is associated with altered locomotor functions.