Extending the Cellulosome Paradigm: the Modular Clostridium thermocellum Cellulosomal Serpin PinA Is a Broad-Spectrum Inhibitor of Subtilisin-Like Proteases

Clostridium thermocellum encodes a cellulosomal, modular, and thermostable serine protease inhibitor (serpin), PinA. PinA stability but not inhibitory activity is affected by the Fn(III) and Doc(I) domains, and PinA is a broad inhibitor of subtilisin-like proteases and may play a key role in protecting the cellulosome from protease attack.     

Genome Sequence of Staphylococcus epidermidis Strain AU12-03, Isolated from an Intravascular Catheter

In recent years, Staphylococcus epidermidis has become a major nosocomial pathogen and the most common cause of intravascular catheter-related bacteremia, which can increase morbidity and mortality and significantly affect patient recovery. We report a draft genome sequence of Staphylococcus epidermidis AU12-03, isolated from an intravascular catheter tip.     

Fine structure of Lasaea subviridis and Mysella tumida sperm (Bivalvia,Galeommatacea)

Summary Lasaea subviridis and Mysella tumida sperm resemble the primitive spermatozoan type, but exhibit several unique morphological features. L. subviridis sperm heads vary in shape and size owing to differing degrees of nuclear condensation. A fully mature, heterogenous acrosomal vesicle with an associated axial rod is present. Up to 50% of L. subviridis sperm in developing gonads have conspicuously angled flagella that propel the sperm cells in irregular helical paths. This may represent a penultimate stage in sperm development because the remainder of the sperm cells have posteriorly-directed flagella and swim in a nonhelical anterior direction. A trend toward a reduction in both nuclear condensation and swimming ability may be a long-term consequence of increasing degrees of localized, but non-internal self-fertilization in marine invertebrates that brood. Mysella tumida sperm are monomorphic and possess numerous microvilli (30–60 nm in diameter and up to 5.7 m in length) that resemble stereocilia and radiate from the cell membrane surrounding the basal body. In this species, the sperm cell does not have an axial rod, and the complex acrosomal vesicle contains five distinct zones of varying electron opacity. One of these zones is a transverse, electron-opaque band that is apparently composed of rolled-up membrane. Following acrosomal breakdown, this membrane unfolds to cover the anterior tip of the sperm cell. Although both L. subviridis and M. tumida are hermaphroditic, the relative size of their male investments is conspicuously different. Approximately 40–50% of the M. tumida gonadal volume is testis compared with about 5% of that in L. subviridis.     

Ecological correlates and phylogenetic signal of host use in North American unionid mussels

Mussels in the order Unionoida comprise ～75% of the world’s freshwater bivalve species and are free-living apart from a brief larval stage that parasitizes fish. We investigated the relationships among species of North American unionid mussels and their known host fishes from a macroevolutionary perspective to test whether and how ecological and evolutionary factors correlate with patterns of host use. A subset of 69 mussel species was chosen based on data availability regarding their fish host repertoires, phylogenetic relationships, and ecology. Despite the brevity of their parasitic life stages, the mussels conformed to the right-skewed distribution of host specificity typical of parasitic taxa, in which most species are specialists and a few are generalists. Phylogenetic least squares regression models identified affinity for low-gradient and riffle habitats, and colonization of post-glacial watersheds as the best predictors for the number of fish host species per mussel. However, the second-best model identified citation number as a predictor of the number of hosts, implying that many mussel–host interactions still remain to be identified. A Multiple Regression Mantel test was performed to identify factors associated with the proportion of hosts shared between pairs of mussel species. Range overlap, citations, genetic distance, and similarity in host infection strategy were significantly correlated with the proportion of hosts shared, yet total variation as explained by the best model was low (R²?=?0.14). There was evidence of a topological association between mussels and their hosts (P?=?0.001) and a significant phylogenetic signal of host specificity (λ?=?0.81, P?=?0.003), indicating closely related mussels that overlap in range are more likely to be competing for hosts. Our results provide an initial macroevolutionary framework for studying the evolution of host infection strategies in these mussels but also highlights gaps still remaining in our fundamental ecological knowledge of this endangered clade.     

Genetic diversity of oceanic island Lasaea (Mollusca: Bivalvia) lineages exceeds that of continental populations in the northwestern Atlantic

Direct-developing lineages of the intertidal marine bivalve Lasaea have colonized both upstream mainland (southeastern Florida) and downstream oceanic island (Bermuda) locations in the western North Atlantic. Replicate samples from these two regional populations, separated by about 1500 km of open ocean, were sequenced for a 655-nucleotide portion of the mitochondrial (mt) cytochrome oxidase subunit I gene. Twelve haplotypes (2 Floridian and 10 Bermudan) were obtained that differed by a maximum of four substitutions among pairwise comparisons. Phylogenetic analysis yielded a parsimony network within which the mainland lineages clustered in one of the terminal branches; a mirror image of a priori expectations based on regional surface-current polarity. It is difficult, however, to envisage a plausible countercurrent dispersal mechanism. This tree topology may stem from divergent demographic processes operating on these two evolutionarily recent regional populations. The starlike phylogenetic pattern of Bermudan lineages is consistent with a history of rapid population growth. The restricted genetic repertoire and relative ecological scarcity of Floridian lineages imply either a recent founder event by unstudied Caribbean source populations or else a history of pronounced bottlenecks in population size. Bermuda's impoverished Caribbean marine biota may allow western North Atlantic Lasaea lineages to escape severe competitive interactions impacting other parts of their geographic range.     

The inhibitor profiling of the caspase family of proteases using substrate-derived peptide glyoxals

A series of substrate-based α-keto-β-aldehyde (glyoxal) sequences have been synthesised and evaluated as inhibitors of the caspase family of cysteine proteases. A number of potent inhibitor sequences have been identified. For example, a palmitic acid containing sequence pal-Tyr-Val-Ala-Asp-glyoxal was demonstrated to be an extremely effective inhibitor of caspase-1, inhibiting not only the action of the protease against synthetic fluorogenic substrates (K_i = 0.3 nM) but also blocking its processing of pro-interleukin-1beta (pro-IL-1β). In addition, the peptide Ac-Asp-Glu-Val-Asp-glyoxal, which is based on the consensus cleavage sequence for caspase-3, is a potent inhibitor of this protease (K_i = 0.26 nM) yet only functions as a comparatively modest inhibitor of caspase-1 (K_i = 451 nM). Potent inhibitor sequences were also identified for caspases-6 and -8. However, the degree of discrimination between the family members is limited. The ability of Ac-Asp-Glu-Val-Asp-glyoxal to block caspase-3 like activity in whole cells and to delay the development of apoptosis was assessed. When tested against caspase-3 like activity in cell lysates, Ac-Asp-Glu-Val-Asp-glyoxal displayed effective inhibition similar to that observed against recombinant caspase-3. Treatment of whole cells with this potent caspase-3 inhibitor was however, not sufficient to significantly stall the development of apoptosis in-vitro.