Stable-isotope analyses reveal the importance of seagrass beds as feeding areas for juveniles of the speckled worm eel Myrophis punctatus (Teleostei: Ophichthidae) in Florida

The feeding habits and habitats of the speckled worm eel Myrophis punctatus were studied on the mangrove edge of the Indian River Lagoon (IRL, Florida) using gut-content and stable-isotope analyses of carbon (δ(13) C) and nitrogen (δ(15) N). Four taxa were identified through analyses of gut contents, and the index of relative importance suggested that amphipods, microphytobenthos and annelids are the most important food sources in the fish's diet. To assess the feeding habits of the fish after their recruitment to the IRL, these food sources were collected from mangroves and nearby seagrass beds for isotope analyses. Stable isotopes constituted a powerful tool for discriminating fish prey items from mangroves (mean ± s.d.δ(13) C = -20·5 ± 0·6‰) and those from seagrass beds (mean ± s.d.δ(13) C = -16·9 ± 0·6‰), thus providing good evidence of food source origins. The 56 M. punctatus collected [10·0 < total length (L(T) ) < 16·2 cm] had average isotopic signatures of δ(13) C = -16·7 ± 0·2‰ and δ(15) N = 8·2 ± 0·1‰. A significant depletion in (13) C was observed for larger juveniles (15·0 < L(T) < 16·2 cm), suggesting that they found a portion of their food in mangroves. Estimation of the trophic level from stable isotopes (T(Liso)) was similar among different size groups of juvenile fish (T(Liso) = 3·2-3·5); therefore, M. punctatus was considered a secondary consumer, which is consistent with its zoobenthic diet. The concentration-dependent mixing Stable Isotope Analysis in R (SIAR) model revealed the importance of food sources from seagrass beds as carbon sources for all the fish collected, with a significant increase in mangrove prey contributions, such as annelids, in the diet of larger juveniles. This study highlights the importance of seagrass beds as feeding habitats for juveniles of M. punctatus after their recruitment to coastal waters.     

Beta-glucan activates microglia without inducing cytokine production in Dectin-1-dependent manner

Microglia are the resident mononuclear phagocytic cells that are critical for innate and adaptive responses within the CNS. Like other immune cells, microglia recognize and are activated by various pathogen-associated molecular patterns. beta-glucans are pathogen-associated molecular patterns present within fungal cell walls that are known to trigger protective responses in a number of immune cells. In an effort to better understand microglial responses to beta-glucans and the underlying response pathways, we sought to determine whether Dectin-1, a major beta-glucan receptor recently identified in leukocytes, plays a similar role in beta-glucan-induced activation in microglia. In this study, we report that Dectin-1 is indeed expressed on the surface of murine primary microglia, and engagement of the receptor with particulate beta-glucan resulted in an increase in tyrosine phosphorylation of spleen tyrosine kinase, a hallmark feature of the Dectin-1 signaling pathway. Moreover, phagocytosis of beta-glucan particles and subsequent intracellular production of reactive oxygen species were also mediated by Dectin-1. However, unlike in macrophages and dendritic cells, beta-glucan-mediated microglial activation did not result in significant production of cytokines or chemokines; thus, the interaction of microglial Dectin-1 with glucan elicits a unique response. Our results suggest that the Dectin-1 pathway may play an important role in antifungal immunity in the CNS.     

The Drosophila caspase Ice is important for many apoptotic cell deaths and for spermatid individualization, a nonapoptotic process

Caspase family proteases play important roles in the regulation of apoptotic cell death. Initiator caspases are activated in response to death stimuli, and they transduce and amplify these signals by cleaving and thereby activating effector caspases. In Drosophila, the initiator caspase Nc (previously Dronc) cleaves and activates two short-prodomain caspases, Dcp-1 and Ice (previously Drice), suggesting these as candidate effectors of Nc killing activity. dcp-1-null mutants are healthy and possess few defects in normally occurring cell death. To explore roles for Ice in cell death, we generated and characterized an Ice null mutant. Animals lacking Ice show a number of defects in cell death, including those that occur during embryonic development, as well as during formation of adult eyes, arista and wings. Ice mutants exhibit subtle defects in the destruction of larval tissues, and do not prevent destruction of salivary glands during metamorphosis. Cells from Ice animals are also markedly resistant to several stresses, including X-irradiation and inhibition of protein synthesis. Mutations in Ice also suppress cell death that is induced by expression of Rpr, Wrinkled (previously Hid) and Grim. These observations demonstrate that Ice plays an important non-redundant role as a cell death effector. Finally, we demonstrate that Ice participates in, but is not absolutely required for, the non-apoptotic process of spermatid differentiation.     

Microbial diversity of biofilms in dental unit water systems

We investigated the microbial diversity of biofilms found in dental unit water systems (DUWS) by three methods. The first was microscopic examination by scanning electron microscopy (SEM), acridine orange staining, and fluorescent in situ hybridization (FISH). Most bacteria present in the biofilm were viable. FISH detected the beta and gamma, but not the alpha, subclasses of Proteobacteria: In the second method, 55 cultivated biofilm isolates were identified with the Biolog system, fatty acid analysis, and 16S ribosomal DNA (rDNA) sequencing. Only 16S identified all 55 isolates, which represented 13 genera. The most common organisms, as shown by analyses of 16S rDNA, belonged to the genera Afipia (28%) and Sphingomonas (16%). The third method was a culture-independent direct amplification and sequencing of 165 subclones from community biofilm 16S rDNA. This method revealed 40 genera: the most common ones included Leptospira (20%), Sphingomonas (14%), Bacillus (7%), Escherichia (6%), Geobacter (5%), and Pseudomonas (5%). Some of these organisms may be opportunistic pathogens. Our results have demonstrated that a biofilm in a health care setting may harbor a vast diversity of organisms. The results also reflect the limitations of culture-based techniques to detect and identify bacteria. Although this is the greatest diversity reported in DUWS biofilms, other genera may have been missed. Using a technique based on jackknife subsampling, we projected that a 25-fold increase in the number of subclones sequenced would approximately double the number of genera observed, reflecting the richness and high diversity of microbial communities in these biofilms.     

Nuclear choreography: interpretations from living cells

The advent of green fluorescent protein technology, its use in photobleaching experiments and the development of methods to rapidly acquire images and analyze complex datasets have opened the door to unraveling the mechanisms of nuclear functions in living cells. Studies over the past few years have characterized the movement of chromatin, nuclear proteins and nuclear bodies and, in some cases, correlated their dynamics with energy dependence, cell cycle progression, developmental changes, factor targeting and nuclear position. The mechanisms by which nuclear components move or are restrained have important implications for understanding not only the efficacy of nuclear functions but also the regulation of developmental programs and cellular growth.     

A real-time PCR assay for the detection of Campylobacter jejuni in foods after enrichment culture

A real-time PCR assay was developed for the quantitative detection of Campylobacter jejuni in foods after enrichment culture. The specificity of the assay for C. jejuni was demonstrated with a diverse range of Campylobacter species, related organisms, and unrelated genera. The assay had a linear range of quantification over six orders of magnitude, and the limit of detection was approximately 12 genome equivalents. The assay was used to detect C. jejuni in both naturally and artificially contaminated food samples. Ninety-seven foods, including raw poultry meat, offal, raw shellfish, and milk samples, were enriched in blood-free Campylobacter enrichment broth at 37 degrees C for 24 h, followed by 42 degrees C for 24 h. Enrichment cultures were subcultured to Campylobacter charcoal-cefoperazone-deoxycholate blood-free selective agar, and presumptive Campylobacter isolates were identified with phenotypic methods. DNA was extracted from enrichment cultures with a rapid lysis method and used as the template in the real-time PCR assay. A total of 66 samples were positive for C. jejuni by either method, with 57 samples positive for C. jejuni by subculture to selective agar medium and 63 samples positive in the real-time PCR assay. The results of both methods were concordant for 84 of the samples. The total time taken for detection from enrichment broth samples was approximately 3 h for the real-time PCR assay, with the results being available immediately at the end of PCR cycling, compared to 48 h for subculture to selective agar. This assay significantly reduces the total time taken for the detection of C. jejuni in foods and is an important model for other food-borne pathogens.