Lactococcus lactis YfiA is necessary and sufficient for ribosome dimerization

Dimerization and inactivation of ribosomes in Escherichia coli is a two‐step process that involves the binding of ribosome modulation factor (RMF) and hibernation promotion factor (HPF). Lactococcus lactis MG1363 expresses a protein, YfiA^Ll, which associates with ribosomes in the stationary phase of growth and is responsible for dimerization of ribosomes. We show that full‐length YfiA^Ll is necessary and sufficient for ribosome dimerization in L. lactis but also functions heterologously in vitro with E. coli ribosomes. Deletion of the yfiA gene has no effect on the growth rate but diminishes the survival of L. lactis under energy‐starving conditions. The N‐terminal domain of YfiA^Ll is homologous to HPF from E. coli, whereas the C‐terminal domain has no counterpart in E. coli. By assembling ribosome dimers in vitro, we could dissect the roles of the N‐ and C‐terminal domains of YfiA^Ll. It is concluded that the dimerization and inactivation of ribosomes in L. lactis and E. coli differ in several cellular and molecular aspects. In addition, two‐dimensional maps of dimeric ribosomes from L. lactis obtained by single particle electron microscopy show a marked structural difference in monomer association in comparison to the ribosome dimers in E. coli.     

A Comparison of Legionella pneumophila Occurrence in Hot Water Tanks and Instantaneous Devices in Domestic, Nosocomial, and Community Environments

The aim of this study was to compare the occurrence of L. pneumophila in hot water samples from hot water tanks and instantaneous devices. Tanks and devices were all operated by heat exchangers employed in the town's district heating system. Thirty-six out of 171 (21%) hot water samples tested positive for L. pneumophila isolation, with 14.6% belonging to serogroup 1 and 6.4% to serogroups 2–14. The proportion of L. pneumophila detected in hot water reservoirs (30%) was higher than that observed in hot water instantaneous devices (6.2%). Differences in L. pneumophila isolation reflected different temperatures registered at the faucet: ≤50°C for hot water from reservoir devices, and >60°C for hot water from instantaneous devices. These data emphasize the need to control temperature in hot water distribution devices, thus inhibiting the formation of biofilm and L. pneumophila colonization. Received: 4 April 2000 / Accepted: 31 May 2000     

Chemokines plasma levels in preterm newborns of preeclamptic mothers

Information on leukocyte activation in newborn infants of preeclamptic mothers is scarce. IL-8 and GRO-α are the main pro-inflammatory cytokines involved in leukocyte activation. The objective was to evaluate IL-8 and GRO-α plasma levels in preterm newborns infants of preeclamptic mothers. Newborns with gestational age <36 weeks and birth weight <2000 g were included and divided: non-preeclamptic (n = 64) and preeclamptic groups (n = 55). Exclusion criteria were major congenital malformations, inborn errors of metabolism or chromosomal anomalies, congenital infections, death in delivery room, and maternal chronic hypertension without preeclampsia. IL-8 and GRO-α were measured by enzyme immunoassay in the first 48 h. Groups were similar in birth weight, gestational age, Apgar scores at 5 min, sepsis, RDS, mechanical ventilation, TPN, NEC, intraventricular hemorrhage and death. The preeclamptic group had more neutropenia, SGA, cesarean section, and less rupture of membranes >18 h. IL-8 was higher in the non-preeclamptic [157.1 pg/mL (86.4–261.3) and 26.54 pg/mL (3.6–87.2) p < 0.001]. GRO-α levels were similar in both groups [229.5 pg/mL (116.6–321.3) and 185.5 pg/mL (63.9–306.7) p = 0.236]. After multiple regression analysis only absence of preeclampsia was associated with high IL-8 levels. Our data suggest that leukocyte activation may be impaired in infants of preeclamptic mothers.     

Nuclear pore complex assembly and maintenance in POM121- and gp210-deficient cells

So far, POM121 and gp210 are the only known anchoring sites of vertebrate nuclear pore complexes (NPCs) within the lipid bilayer of the nuclear envelope (NE) and, thus, are excellent candidates for initiating the NPC assembly process. Indeed, we demonstrate that POM121 can recruit several nucleoporins, such as Nup62 or Nup358, to ectopic assembly sites. It thus appears to act as a nucleation site for the assembly of NPC substructures. Nonetheless, we observed functional NPCs and intact NEs in severely POM121-depleted cells. Double knockdowns of gp210 and POM121 in HeLa cells, as well as depletion of POM121 from human fibroblasts, which do not express gp210, further suggest that NPCs can assemble or at least persist in a POM121- and gp210-free form. This points to extensive redundancies in protein-protein interactions within NPCs and suggests that vertebrate NPCs contain additional membrane-integral nucleoporins for anchorage within the lipid bilayer of the NE. In Stavru et al., we describe such an additional transmembrane nucleoporin as the metazoan orthologue of yeast Ndc1p.     

Variation of anal fin egg‐spots along an environmental gradient in a haplochromine cichlid fish

Male secondary sexual traits are targets of inter‐ and/or intrasexual selection, but can vary due to a correlation with life‐history traits or as by‐product of adaptation to distinct environments. Trade‐offs contributing to this variation may comprise conspicuousness toward conspecifics versus inconspicuousness toward predators, or between allocating resources into coloration versus the immune system. Here, we examine variation in expression of a carotenoid‐based visual signal, anal‐fin egg‐spots, along a replicate environmental gradient in the haplochromine cichlid fish Astatotilapia burtoni. We quantified egg‐spot number, area, and coloration; applied visual models to estimate the trait's conspicuousness when perceived against the surrounding tissue under natural conditions; and used the lymphocyte ratio as a measure for immune activity. We find that (1) males possess larger and more conspicuous egg‐spots than females, which is likely explained by their function in sexual selection; (2) riverine fish generally feature fewer but larger and/or more intensely colored egg‐spots, which is probably to maintain signal efficiency in intraspecific interactions in long wavelength shifted riverine light conditions; and (3) egg‐spot number and relative area correlate with immune defense, suggesting a trade‐off in the allocation of carotenoids. Taken together, haplochromine egg‐spots feature the potential to adapt to the respective underwater light environment, and are traded off with investment into the immune system.     

The syntheses and properties of cobalt(II), nickel(II) and copper(II) complexes with some heterocyclic dithiocarbamates

New cobalt(II), Nickel(II) and copper(II) dithiocarbamato complexes of the type M(Rdtc)₂ (Rdtc = 4-phenylpiperidinedithiocarbamate and N-phenylpiperazinedithiocarbamate) have been prepared and characterized through elemental analyses, conductivity measurements, spectral (electronic and IR) studies, magnetic moment measurements at different temperatures, e.p.r. techniques and thermal analyses (TG and DTG). The dithioligands exhibit bidentate behaviour in all the complexes. The magnetic moments studies suggest that there is no significant interaction between copper ions, and the e.p.r. data provide parameters typical of sulphur coordination in planar CuS₄ chromophores.     

Matching the proteome to the genome: the microbody of penicillin-producing Penicillium chrysogenum cells

In the filamentous fungus Penicillium chrysogenum, microbodies are essential for penicillin biosynthesis. To better understand the role of these organelles in antibiotics production, we determined the matrix enzyme contents of P. chrysogenum microbodies. Using a novel in silico approach, we first obtained a catalogue of 200 P. chrysogenum proteins with putative microbody targeting signals (PTSs). This included two orthologs of proteins involved in cephalosporin biosynthesis, which we demonstrate to be bona fide microbody matrix constituents. Subsequently, we performed a proteomics based inventory of P. chrysogenum microbody matrix proteins using nano-LC-MS/MS analysis. We identified 89 microbody proteins, 79 with a PTS, including the two known microbody-borne penicillin biosynthesis enzymes, isopenicillin N:acyl CoA acyltransferase and phenylacetyl-CoA ligase. Comparative analysis revealed that 69 out of 79 PTS proteins identified experimentally were in the reference list. A prominent microbody protein was identified as a novel fumarate reductase-cytochrome b5 fusion protein, which contains an internal PTS2 between the two functional domains. We show that this protein indeed localizes to P. chrysogenum microbodies. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.