Jellyfish Body Plans Provide Allometric Advantages beyond Low Carbon Content

Jellyfish form spectacular blooms throughout the world’s oceans. Jellyfish body plans are characterised by high water and low carbon contents which enables them to grow much larger than non-gelatinous animals of equivalent carbon content and to deviate from non-gelatinous pelagic animals when incorporated into allometric relationships. Jellyfish have, however, been argued to conform to allometric relationships when carbon content is used as the metric for comparison. Here we test the hypothesis that differences in allometric relationships for several key functional parameters remain for jellyfish even after their body sizes are scaled to their carbon content. Data on carbon and nitrogen contents, rates of respiration, excretion, growth, longevity and swimming velocity of jellyfish and other pelagic animals were assembled. Allometric relationships between each variable and the equivalent spherical diameters of jellyfish and other pelagic animals were compared before and after sizes of jellyfish were standardised for their carbon content. Before standardisation, the slopes of the allometric relationships for respiration, excretion and growth were the same for jellyfish and other pelagic taxa but the intercepts differed. After standardisation, slopes and intercepts for respiration were similar but excretion rates of jellyfish were 10× slower, and growth rates 2× faster than those of other pelagic animals. Longevity of jellyfish was independent of size. The slope of the allometric relationship of swimming velocity of jellyfish differed from that of other pelagic animals but because they are larger jellyfish operate at Reynolds numbers approximately 10× greater than those of other pelagic animals of comparable carbon content. We conclude that low carbon and high water contents alone do not explain the differences in the intercepts or slopes of the allometric relationships of jellyfish and other pelagic animals and that the evolutionary longevity of jellyfish and their propensity to form blooms is facilitated by their unique body plans.     

Atmospheric water vapor as driver of litter decomposition in Mediterranean shrubland and grassland during rainless seasons

Litter production in many drought‐affected ecosystems coincides with the beginning of an extended season of no or limited rainfall. Because of lack of moisture litter decomposition during such periods has been largely ignored so far, despite potential importance for the overall decay process in such ecosystems. To determine drivers and extent of litter decay in rainless periods, a litterbag study was conducted in Mediterranean shrublands, dwarf shrublands and grasslands. Heterogeneous local and common straw litter was left to decompose in open and shaded patches of various field sites in two study regions. Fresh local litter lost 4–18% of its initial mass over about 4 months without rainfall, which amounted to 15–50% of total annual decomposition. Lab incubations and changes in chemical composition suggested that litter was degraded by microbial activity, enabled by absorption of water vapor from the atmosphere. High mean relative humidity of 85% was measured during 8–9 h of most nights, but the possibility of fog deposition or dew formation at the soil surface was excluded. Over 95% of the variation in mass loss and changes in litter nitrogen were explained by characteristics of water‐vapor uptake by litter. Photodegradation induced by the intense solar radiation was an additional mechanism of litter decomposition as indicated by lignin dynamics. Lignin loss from litter increased with exposure to ultraviolet radiation and with initial lignin concentration, together explaining 90%–97% of the variation in lignin mass change. Our results indicate that water vapor, solar radiation and litter quality controlled decomposition and changes in litter chemistry during rainless seasons. Many regions worldwide experience transient periods without rainfall, and more land area is expected to undergo reductions in rainfall as a consequence of climate change. Therefore, absorption of water vapor might play a role in decomposition and nutrient cycling in an increasing number of ecosystems.     

Genotypic diversity of lactic acid bacteria isolated from African traditional alkaline‐fermented foods

Aim: To identify and compare lactic acid bacteria (LAB) isolated from alkaline fermentations of cassava (Manihot esculenta Crantz) leaves, roselle (Hibiscus sabdariffa) and African locust bean (Parkia biglobosa) seeds for production of, respectively, Ntoba Mbodi, Bikalga and Soumbala. Methods and Results: A total of 121 LAB were isolated, identified and compared by phenotyping and genotyping using PCR amplification of 16S–23S rDNA intergenic transcribed spacer (ITS‐PCR), repetitive sequence‐based PCR (rep‐PCR) and DNA sequencing. The results revealed a diversity of genera, species and subspecies of LAB in African alkaline fermentations. The isolates were characterized as nonmotile (in most cases) Gram‐positive rods, cocci or coccobacilli, catalase and oxidase negative. ITS‐PCR allowed typing mainly at species level, with differentiation of a few bacteria at subspecies level. Rep‐PCR permitted typing at subspecies level and revealed significant genotypic differences between the same species of bacteria from different raw materials. DNA sequencing combined with use of API 50CHL and API 20Strep systems allowed identification of bacteria as Weissella confusa, Weissella cibaria, Lactobacillus plantarum, Pediococcus pentosaceus, Enterococcus casseliflavus, Enterococcus faecium, Enterococcus faecalis, Enterococcus avium and Enterococcus hirae from Ntoba Mbodi; Ent. faecium, Ent. hirae and Pediococcus acidilactici from Bikalga and Soumbala. Conclusion: LAB found in African alkaline‐fermented foods belong to a range of genera, species and subspecies of bacteria and vary considerably according to raw material. Significance and Impact of the Study: Our study confirms that LAB survive in alkaline fermentations, a first crucial stage in determining their significance and possible value as probiotic bacteria.     

The regulatory action of α-actinin on actin filaments is enhanced by cofilin

We have used fluorescence recovery after photobleaching to study the effect of muscle α-actinin on the structure of actin filaments in dilute solutions. Unexpectedly we found that α-actinin partitioned filaments into two types: those with a high mobility and those with low mobility. We have determined that the high mobility (smaller sized) population is too large to be simple monomeric actin:α-actinin complexes. Although it is known that cofilin encourages the transformation of α-actinin:actin gels into large meshworks of inter-digitating actin filament bundles (Maciver et al. 1991), we have found that the presence of cofilin also increases the cross-linking of actin filaments by α-actinin and hypothesize that this is due to cofilin’s ability to alter the filament twist. This effectively makes more potential α-actinin binding sites per unit of actin filament. As expected from previous work, this effect was more marked at pH 6.5 than at pH 8.0. Both effects are likely to operate in cells to deny other actin-binding proteins access to binding these particular filaments and may explain how very different actin cytoskeletal structures may co-exist in the same cell at the same time.     

Effects of temperature,nutrients, organic matter and coral mucus on the survival of the coral pathogen,Serratia marcescens PDL100

Serratia marcescens is an enteric bacterium that causes white pox disease in elkhorn coral, Acropora palmata; however, it remains unclear if the pathogenic strain has adapted to seawater or if it requires a host or reservoir for survival. To begin to address this fundamental issue, the persistence of strain PDL100 was compared among seawater and coral mucus microcosms. Median survival time across all conditions ranged from a low of 15 h in natural seawater [with a first‐order decay constant (k) = ?0.173] at 30°C to a maximum of 120 h in glucose‐amended A. palmata mucus (k = ?0.029) at 30°C. Among seawater and mucus microcosms, median survival time was significantly greater within Siderastrea siderea mucus compared with seawater or mucus of Montastraea faveolata or A. palmata (P < 0.0001). In seawater, the addition of phosphate and especially glucose resulted in significant improvements in survival (P < 0.001), while only the addition of glucose resulted in significant improvement in survival in A. palmata mucus (P < 0.0001). Increasing the temperature of seawater to 35°C resulted in a significantly slower decay than that observed at 30°C (P < 0.0001). The results of this study indicate that PDL100 is not well‐adapted to marine water; however, survival can be improved by increasing temperature, the availability of coral mucus from S. siderea and most notably the presence of dissolved organic carbon.     

Improved preparation and detection of cytochrome P450 isoforms using MS methods

Cytochromes P450 (CYPs) are a superfamily of mixed function oxidases, which in the liver have great significance to the pharmaceutical industry because their expression will determine the fate of most clinical agents. CYPs are also targets for inhibitors of hormone‐dependent diseases and conversion of prodrugs to active agents in normal and cancer tissues. We have applied simple modifications to established methods of isolating CYPs, using 8 M urea to solubilise microsomal proteins and specific molecular weight gel bands for in‐gel digestion in combination with nanoHPLC MALDI MS to acquire peptide MS/MS spectra for database searching. As a consequence of the changes we significantly improved the yield of proteomic data, identifying 26 mouse CYPs (CYP1a2, 2a4, 2a5, 2a12, 2b9, 2c29, 2c37, 2c39, 2c40, 2c50, 2c54, 2c70, 2d9, 2d10, 2d26, 2e1, 2f2, 2j5, 3a11, 3a13, 3a25, 3a41, 4a14, 4f14, 8b1 and 27a1) with an average sequence coverage of 30.1%, including some previously undetected highly homologous isoforms. In addition, other important enzymes in drug metabolism are also identified. There is a divergence of opinion over the expression of CYP1a1 in liver and we could not detect the presence of this isoform. In order to provide definitive evidence of the ability to detect CYP1a1, we analysed CHO cells transfected with human CYP1A1 and identified unique peptides that differentiated this isoform from human CYP1A2.     

Analysis of RuvABC and RecG Involvement in the Escherichia coli Response to the Covalent Topoisomerase-DNA Complex

Topoisomerases form a covalent enzyme-DNA intermediate after initial DNA cleavage. Trapping of the cleavage complex formed by type IIA topoisomerases initiates the bactericidal action of fluoroquinolones. It should be possible also to identify novel antibacterial lead compounds that act with a similar mechanism on type IA bacterial topoisomerases. The cellular response and repair pathways for trapped topoisomerase complexes remain to be fully elucidated. The RuvAB and RecG proteins could play a role in the conversion of the initial protein-DNA complex to double-strand breaks and also in the resolution of the Holliday junction during homologous recombination. Escherichia coli strains with ruvA and recG mutations are found to have increased sensitivity to low levels of norfloxacin treatment, but the mutations had more pronounced effects on survival following the accumulation of covalent complexes formed by mutant topoisomerase I defective in DNA religation. Covalent topoisomerase I and DNA gyrase complexes are converted into double-strand breaks for SOS induction by the RecBCD pathway. SOS induction following topoisomerase I complex accumulation is significantly lower in the ruvA and recG mutants than in the wild-type background, suggesting that RuvAB and RecG may play a role in converting the initial single-strand DNA-protein cleavage complex into a double-strand break prior to repair by homologous recombination. The use of a ruvB mutant proficient in homologous recombination but not in replication fork reversal demonstrated that the replication fork reversal function of RuvAB is required for SOS induction by the covalent complex formed by topoisomerase I.DNA topoisomerases can modulate DNA superhelicity and help overcome topological barriers in cellular processes by cleaving the DNA backbone phosphodiester linkage to allow topological changes in DNA substrates. The ends of the cleaved DNA are covalently linked to an active-site tyrosine on the topoisomerase proteins in cleavage complex intermediates. Covalent protein-DNA complexes exist only transiently during catalysis because the cleaved DNA is rapidly religated. The stabilization of covalent complexes formed by human topoisomerase I or II due to the action of certain anticancer drugs results in the apoptotic death of cancer cells. Quinolone antibiotics are highly bactericidal because they cause the accumulation of covalent complexes formed by bacterial DNA gyrase and topoisomerase IV enzymes. Although a similar topoisomerase poison inhibitor remains to be identified for bacterial type IA topoisomerases, bacterial topoisomerase I complex accumulation due to mutations that inhibit DNA religation has also been shown to cause rapid bacterial cell death (4, 36). The requirement of a DNA cleavage step in the mechanism of action of topoisomerases increases the vulnerability of cells to conditions that would trap the covalent protein-DNA complex. These conditions include the presence of DNA intercalators, toxic metabolites, and DNA lesions, as well as protein thiolation (9, 28-31, 38). Response to and repair of the trapped covalent topoisomerase-DNA complex are thus needed for cell survival. In eukaryotes, 3′-tyrosyl DNA phosphodiesterase (TDP1) and 5′-tyrosyl DNA phosphodiesterase (TDP2), which can cleave the covalent linkage between topoisomerases and DNA, have been identified (8, 15, 27). Tyrosyl DNA phosphodiesterases have not been identified in bacteria. Repair of covalent bacterial topoisomerase-DNA complexes may require the action of endonucleases to remove the DNA-bound topoisomerase proteins, similar to the Rad1-Rad10 repair pathway characterized in yeast (37). In Escherichia coli, covalent topoisomerase I and DNA gyrase complexes have been shown to be processed into double-strand DNA breaks (DSB), which are then repaired via the RecBCD-mediated RecA homologous recombination pathway with induction of the SOS regulon (24, 34). The RuvABC and RecG activities could play significant roles in the response to the covalent topoisomerase complexes. They are both capable of resolving the Holliday junctions following DSB formation in the later stages of homologous recombination repair (11). SbcCD has been shown previously to remove protein from a protein-bound DNA end with nucleolytic activity to create a DSB (7). In addition, it is also possible that RuvAB and RecG might act at arrested forks to process replication forks blocked by the covalently bound topoisomerase proteins and generate DSB substrates for RecBCD (1, 32). Previous studies have not clearly elucidated the roles of RuvABC and RecG in the response to covalent topoisomerase complexes. We examine here the effects of mutations in the ruvA and recG genes on both bacterial survival and SOS induction following the accumulation of covalent topoisomerase I or gyrase complexes with cleaved DNA.     

The gelsolin:calponin complex nucleates actin filaments with distinct morphologies

Gelsolin and calponin are cytoskeletal and signalling proteins that form a tight 1:1 complex (GCC). We show that calponin within the GCC inhibits the rate of gelsolin mediated nucleation of actin polymerization. The actin-binding function of calponin is ablated within the GCC as the actin-binding site overlaps with one of the gelsolin binding sites. The structure of filaments that result from nucleation by GCC are different to those nucleated by gelsolin alone in that they are longer, loosely bundled and stain heterogeneously with phalloidin. GCC nucleated filaments appear contorted and wrap around each to form the loose bundles.     

Prolonged local expression of anti-CD4 antibody by adenovirally transduced allografts can promote long-term graft survival

BACKGROUND: Currently, successful transplantation of allografts requires the systemic use of immunosuppressive drugs. These can cause serious morbidity due to toxicity and increased susceptibility to cancer and infections. Local production of immunosuppressive molecules limited to the graft site would reduce the need for conventional, generalized immunosuppressive therapies and thus educe fewer side effects. This is particularly salient in a disease like type 1 diabetes, which is not immediately life-threatening yet islet allografts can effect a cure. METHODS: We studied the efficacy of locally produced anti-CD4 antibody, mediated by adenovirus (Adv-anti-CD4) transduction of islets, to enhance allograft survival. Adenovirus-transduced islets were transplanted under the kidney capsule of diabetic recipients and graft rejection determined by monitoring blood glucose levels. RESULTS: Adv-anti-CD4 transduction of mouse islets afforded protection against allogeneic rejection after transplantation into fully mismatched recipients. In some recipients, the islet allograft survival was prolonged (persisting for at least 15 weeks), corresponding to the prolonged expression of the anti-CD4 antibody. The effect was local, as absence of CD4+ T lymphocytes was observed primarily at the graft site. CONCLUSIONS: Immunosuppressive effects can be restricted locally by our strategy. Local production of a single antibody against one subset of T lymphocytes can protect mouse islets from allograft rejection during transplantation to treat diabetes. Our findings foreshadow that this strategy may be even more effective when a combination of antibodies are used and that similar strategies may prevent xenograft rejection.