Identifying ‘firebreaks’ to fragment dispersal networks of a marine parasite

Marine ecosystems are beset by disease outbreaks, and efficient strategies to control dispersal of pathogens are scarce. We tested whether introducing no-farming areas or ‘firebreaks’ could disconnect dispersal networks of a parasitic disease affecting the world’s largest marine fish farming industry (～1000 farms). Larval salmon lice (Lepeophtheirus salmonis) are released from and transported among salmon farms by ocean currents, creating inter-farm networks of louse dispersal. We used a state-of-the-art biophysical model to predict louse movement along the Norwegian coastline and network analysis to identify firebreaks to dispersal. At least one firebreak that fragmented the network into two large unconnected groups of farms was identified for all seasons. During spring, when wild salmon migrate out into the ocean, and louse levels per fish at farms must be minimised, two effective firebreaks were created by removing 13 and 21 farms (1.3% and 2.2% of all farms in the system) at ～61°N and 67°N, respectively. We have demonstrated that dispersal models coupled with network analysis can identify no-farming zones that fragment dispersal networks. Reduced dispersal pathways should lower infection pressure at farms, slow the evolution of resistance to parasite control measures, and alleviate infection pressure on wild salmon populations.     

UV-excited chlorophyll fluorescence as a tool for the assessment of UV-protection by the epidermis of plants

Recently, a new method for estimating epidermal transmission of UV radiation in higher plants has been proposed. The empirical evidence for the usefulness of this method is reviewed here. Direct comparison with spectroscopically determined epidermal transmission yielded equivalent results. A linear correlation to the concentration of epidermal screening compounds has been shown. Relating UV-A and UV-B absorbance allowed some preliminary conclusions about the chemical nature of the screening compounds. A new portable apparatus is presented for the first time, which allows the non-destructive assessment of UV-A screening even under field conditions. Repeated measurements on identical leaves over a time-course of 6 d demonstrated a strong age-dependence in the capacity for the synthesis of UV-A screening compounds upon exposure to UV-B radiation. It is concluded that the new method may provide a valuable tool for the investigation of the acclimation of plants to UV-B radiation and, when accompanied by HPLC analysis, of the reaction of phenolic metabolism to environmental stimuli.     

Structure-function analysis of immunity proteins of pediocin-like bacteriocins: C-terminal parts of immunity proteins are involved in specific recognition of cognate bacteriocins

The immunity proteins of pediocin-like bacteriocins show a high degree of specificity with respect to the pediocin-like bacteriocin they recognize and confer immunity to. The aim of this study was to identify regions of the immunity proteins that are involved in this specific recognition. Six different hybrid immunity proteins were constructed from three different pediocin-like bacteriocin immunity proteins that have similar sequences but confer resistance to different bacteriocins. These hybrid immunity proteins were then tested for their ability to confer immunity to various pediocin-like bacteriocins. The specificities of the hybrid immunity proteins proved to be similar to those of the immunity proteins from which the C-terminal halves were derived, thus revealing that the C-terminal half of immunity proteins for pediocin-like bacteriocins contains a domain that is involved in specific recognition of the bacteriocins they confer immunity to. Moreover, the results also revealed that the effectiveness of an immunity protein is strain dependent and that its functionality thus depends in part on interplay with strain-dependent factors. To further investigate the structure-function relationship of these immunity proteins, the enterocin A and leucocin A immunity proteins (EntA-im and LeuA-im) were purified to homogeneity and structurally analyzed under various conditions by Circular dichroism (CD) spectroscopy. The results revealed that both immunity proteins are alpha-helical and well structured in an aqueous environment, the denaturing temperature being 78.5 degrees C for EntA-im and 58.0 degrees C for LeuA-im. The CD spectra also revealed that there was no further increase in the structuring or alpha-helical content when the immunity proteins were exposed to dodecylphosphocholine micelles or dioleoyl-L-alpha-phosphatidyl-DL-glycerol (DOPG) liposomes, indicating that the immunity proteins, in contrast to the bacteriocins, do not interact extensively with membranes. They may nevertheless be loosely associated with the membrane, possibly as peripheral membrane proteins, thus enabling them to interact with their cognate bacteriocin.     

Naming progastrin-derived peptides

The antral hormone gastrin continues to be in focus, because its hormonal and growth promoting effects are essential both for the function of the normal stomach and for the pathogenesis of major dyspeptic and neoplastic diseases. Deduction of the progastrin structure has improved the insight in the cellular synthesis of gastrin, but has also revealed that the biosynthetic machinery is complex, and, accordingly, that progastrin is processed to a multitude of more or less bioactive fragments. The naming of these fragments has, however, become inconsistent and confusing. Therefore, we propose a systematic nomenclature for progastrin-derived peptides of which there are three classes: (I) The gastrins with the evolutionary preserved tetrapeptide amide (Trp-Met-Asp-PheNH₂) at the C-terminus, which ensures high-affinity binding to the gastrin (CCK-B) receptor. Among the gastrins, gastrin-34 and gastrin-17 constitute the primary forms. (II) Processing intermediates, which are early products of progastrin that contain the structure of the primary gastrins within their sequence, but still cannot bind the gastrin receptor due to insufficient processing at their C-terminus. (III) Flanking fragments from the N- and C-termini of progastrin that do not contain any primary gastrin in their sequence, but nevertheless may undergo posttranslational processing. Each fragment can be specified with suffixes corresponding to the derived sequence in progastrin.     

Plumage colour in nestling blue tits: sexual dichromatism,condition dependence and genetic effects

Sexual-selection theory assumes that there are costs associated with ornamental plumage coloration. While pigment-based ornaments have repeatedly been shown to be condition dependent, this has been more difficult to demonstrate for structural colours. We present evidence for condition dependence of both types of plumage colour in nestling blue tits (Parus caeruleus). Using reflectance spectrometry, we show that blue tit nestlings are sexually dichromatic, with males having more chromatic (more 'saturated') and ultraviolet (UV)-shifted tail coloration and more chromatic yellow breast coloration. The sexual dimorphism in nestling tail coloration is qualitatively similar to that of chick-feeding adults from the same population. By contrast, the breast plumage of adult birds is not sexually dichromatic in terms of chroma. In nestlings, the chroma of both tail and breast feathers is positively associated with condition (body mass on day 14). The UV/blue hue of the tail feathers is influenced by paternally inherited genes, as indicated by a maternal half-sibling comparison. We conclude that the expression of both carotenoid-based and structural coloration seems to be condition dependent in blue tit nestlings, and that there are additional genetic effects on the hue of the UV/blue tail feathers. The signalling or other functions of sexual dichromatism in nestlings remain obscure. Our study shows that nestling blue tits are suitable model organisms for the study of ontogenetic costs and heritability of both carotenoid-based and structural colour in birds.     

Processing of seminal plasma hCAP-18 to ALL-38 by gastricsin: a novel mechanism of generating antimicrobial peptides in vagina

The human cathelicidin, hCAP-18, is expressed both in neutrophils and in epithelial cells. hCAP-18 is processed to the antimicrobial peptide LL-37 by proteinase 3 in neutrophils. hCAP-18 is highly expressed in the epididymis with a subsequent high concentration in seminal plasma where the protein is present in its unprocessed and antimicrobially inactive form. We report here that hCAP-18 in seminal plasma is processed to generate a 38-amino acid antimicrobial peptide ALL-38 by the prostate-derived protease gastricsin when incubated at a pH corresponding to the vaginal pH. In accordance with this, seminal plasma derived hCAP-18 was found in its processed form in the vagina following sexual intercourse. The antimicrobial activity of ALL-38 against a variety of microorganisms tested is equal to that of LL-37. This enzymatic activation of a proantimicrobial substance in seminal plasma following exposure to the vaginal milieu represents a novel mechanism to prevent infection following sexual intercourse.     

Microbial diversity in ikaite tufa columns: an alkaline,cold ecological niche in Greenland

Ikaite tufa columns from the Ikka Fjord in south-western Greenland constitute a natural, stable environment at low temperature and with a pH ranging from neutral at the exterior to very alkaline (pH 10.4) at the interior of the column. Phylogenetic analysis of culturable organisms revealed ten different isolates representing three of the major bacterial divisions. Nine of the isolates showed 94-99% similarity to known sequences, whereas one isolate displayed a low degree of similarity (less than 90%) to a Cyclobacterium species. Seven of the isolates were shown to be cold active alkaliphiles, whereas three isolates showed optimal growth at neutral pH. Phylogenetic analysis of DNA isolated directly from the ikaite material demonstrated the presence of a microbial flora more diverse than the culturable isolates. Whereas approximately half of the phylotypes showed 90-99% similarity to known meso- or thermophilic alkaliphiles, the rest of the sequences displayed less than 90% similarity when compared to known 16S rRNA gene sequences in databases. Thus, in the present paper, we demonstrate that ikaite columns that host a specialized macroscopic flora and fauna also contain a unique, cold active, alkaliphilic microflora.     

In situ exposure to low herbicide concentrations affects microbial population composition and catabolic gene frequency in an aerobic shallow aquifer

The aim of this study was to evaluate how the in situ exposure of a Danish subsurface aquifer to phenoxy acid herbicides at low concentrations (<40 micro g l(-1)) changes the microbial community composition. Sediment and groundwater samples were collected inside and outside the herbicide-exposed area and were analyzed for the presence of general microbial populations, Pseudomonas bacteria, and specific phenoxy acid degraders. Both culture-dependent and culture-independent methods were applied. The abundance of microbial phenoxy acid degraders (10(0) to 10(4) g(-1) sediment) was determined by most probable number assays, and their presence was only detected in herbicide-exposed sediments. Similarly, PCR analysis showed that the 2,4-dichlorophenoxyacetic acid degradation pathway genes tfdA and tfdB (10(2) to 10(3) gene copies g(-1) sediment) were only detected in sediments from contaminated areas of the aquifer. PCR-restriction fragment length polymorphism measurements demonstrated the presence of different populations of tfd genes, suggesting that the in situ herbicide degradation was caused by the activity of a heterogeneous population of phenoxy acid degraders. The number of Pseudomonas bacteria measured by either PCR or plating on selective agar media was higher in sediments subjected to high levels of phenoxy acid. Furthermore, high numbers of CFU compared to direct counting of 4',6-diamidino-2-phenylindole-stained cells in the microscope suggested an increased culturability of the indigenous microbial communities from acclimated sediments. The findings of this study demonstrate that continuous exposure to low herbicide concentrations can markedly change the bacterial community composition of a subsurface aquifer.     

Mice with a targeted deletion of the tetranectin gene exhibit a spinal deformity

Tetranectin is a plasminogen-binding, homotrimeric protein belonging to the C-type lectin family of proteins. Tetranectin has been suggested to play a role in tissue remodeling, due to its ability to stimulate plasminogen activation and its expression in developing tissues such as developing bone and muscle. To test the functional role of tetranectin directly, we have generated mice with a targeted disruption of the gene. We report that the tetranectin-deficient mice exhibit kyphosis, a type of spinal deformity characterized by an increased curvature of the thoracic spine. The kyphotic angles were measured on radiographs. In 6-month-old normal mice (n = 27), the thoracic angle was 73 degrees +/- 2 degrees, while in tetranectin-deficient 6-month-old mice (n = 35), it was 93 degrees +/- 2 degrees (P < 0.0001). In approximately one-third of the mutant mice, X-ray analysis revealed structural changes in the morphology of the vertebrae. Histological analysis of the spines of these mice revealed an apparently asymmetric development of the growth plate and of the intervertebral disks of the vertebrae. In the most advanced cases, the growth plates appeared disorganized and irregular, with the disk material protruding through the growth plate. Tetranectin-null mice had a normal peak bone mass density and were not more susceptible to ovariectomy-induced osteoporosis than were their littermates as determined by dual-emission X-ray absorptiometry scanning. These results demonstrate that tetranectin plays a role in tissue growth and remodeling. The tetranectin-deficient mouse is the first mouse model that resembles common human kyphotic disorders, which affect up to 8% of the population.