Complete Sucrose Metabolism Requires Fructose Phosphotransferase Activity in Corynebacterium glutamicum To Ensure Phosphorylation of Liberated Fructose

Sucrose uptake by Corynebacterium glutamicum involves a phosphoenolpyruvate-dependent sucrose phosphotransferase (PTS), but in the absence of fructokinase, further metabolism of the liberated fructose requires efflux of the fructose and reassimilation via the fructose PTS. Mutant strains lacking detectable fructose-transporting PTS activity accumulated fructose extracellularly but consumed sucrose at rates comparable to those of the wild-type strain.     

Aerobic treatment of black olive wastewater and the effect of an ozonation stage

The reduction of the pollutant organic matter present in wastewaters generated in the black olive production process is studied by an aerobic degradation, and by the combination of two successive steps: an ozonation pretreatment followed by an aerobic degradation. In the single aerobic process, in addition to the biomass evolution which is followed during each experiment, the removal of the pollutant load is evaluated by means of global parameters which are directly related with the organic matter, as the chemical oxygen demand and the total phenolic compounds content. A kinetic study is performed by using the Monod model, which applied to the experimental data, provides the specific kinetic parameters of this model: the kinetic constant for the substrate decomposition rate, the cellular yield coefficient and the kinetic constant for the biomass decrease during the death phase of microorganisms. In the combined process, an ozonation pretreatment is conducted with experiments where the ozone partial pressure is varied, and an important reduction in the phenolic compounds is achieved. The kinetic parameters of the following aerobic degradation stage are also evaluated, and the effect of the chemical oxidation pretreatment on this biological stage is discussed.     

Benthic ctenophore (Order Platyctenida) reproduction,recruitment, and seasonality in south Florida

Reproductive structures, modes, and seasonal patterns of size–class abundances are examined in two benthic platyctene (Family Coeloplanidae) ctenophore species present in dissimilar shallow marine environments in subtropical southeast Florida. Coeloplana waltoni, a minute (1–3 mm body length) epizoic associate of octocorals, occurs in exposed environments often under turbulent conditions, and Vallicula multiformis (2–10 mm) commonly occurs epiphytically on macroalgae in protected, calm‐water environments. Reproductive activity in C. waltoni is most active during the warm‐water summer season (June–October); gonadal development in V. multiformis occurs year‐round, and is most pronounced during sea‐warming periods in late spring (May) and late summer to early autumn (August–October), with release of cydippid larvae. Both species are hermaphroditic brooders, exhibiting paedogenesis (early gonadal development) at body lengths approximately one‐third (Coeloplana) to one‐sixth (Vallicula) of maximum adult size. Juvenile individuals (<0.6 mm) increased in abundance in C. waltoni during the summer reproductive period, and large (≥1 mm) pink‐colored individuals comprised 50% or more of samples from July through September. Seasonal abundance of gravid individuals and the timing of cydippid larval release in V. multiformis did not correspond closely with juvenile or adult population densities. Asexual fragmentation occurred in both ctenophore species, but was observed more frequently in individuals of V. multiformis. This asexual mode of reproduction probably accounted in part for the discordance between ctenophore abundances and larval recruitment events by sexual means. Morphological structures and behaviors associated with reproduction are described in this study. Uncommon images of reproductive products (gametes, embryos, larvae), spawning events, brooding, and asexual fragmentation are included, some for the first time in the published literature.     

Dietary contributions of the alien zebra mussel Dreissena polymorpha in British freshwater fish suggest low biological resistance to their invasion

Hydrobiologia - Native communities can resist the establishment and invasion of alien species through consumptive and/or competitive interactions. The extent of consumptive resistance from...     

The use of ROI overlays and a semi-automated method for measuring cortical area in ImageJ for histological analysis

A major part of histologic studies is the use of high resolution imaging for data collection and analysis. ImageJ, a freely available software from the NIH designed for image analysis, has many features that are not well-known among bone histologists and can be incredibly beneficial in terms of stream-lining data collection and maximizing limited resources. The aims of this technical note are twofold: (a) to describe methods for image annotation and measurement using region of interest overlays in ImageJ, and (b) to present a new code for a semi-automated method of measuring cortical bone areas from high resolution cross-sectional images also using ImageJ.     

Rickettsia Sca2 Recruits Two Actin Subunits for Nucleation but Lacks WH2 Domains

The Rickettsia ～1800-amino-acid autotransporter protein surface cell antigen 2 (Sca2) promotes actin polymerization on the surface of the bacterium to drive its movement using an actin comet-tail mechanism. Sca2 mimics eukaryotic formins in that it promotes both actin filament nucleation and elongation and competes with capping protein to generate filaments that are long and unbranched. However, despite these functional similarities, Sca2 is structurally unrelated to eukaryotic formins and achieves these functions through an entirely different mechanism. Thus, while formins are dimeric, Sca2 functions as a monomer. However, Sca2 displays intramolecular interactions and functional cooperativity between its N- and C-terminal domains that are crucial for actin nucleation and elongation. Here, we map the interaction of N- and C- terminal fragments of Sca2 and their contribution to actin binding and nucleation. We find that both the N- and C-terminal regions of Sca2 interact with actin monomers but only weakly, whereas the full-length protein binds two actin monomers with high affinity. Moreover, deletions at both ends of the N- and C-terminal regions disrupt their ability to interact with each other, suggesting that they form a contiguous ring-like structure that wraps around two actin subunits, analogous to the formin homology-2 domain. The discovery of Sca2 as an actin nucleator followed the identification of what appeared to be a repeat of three Wiskott-Aldrich syndrome homology 2 (WH2) domains in the middle of the molecule, consistent with the presence of WH2 domains in most actin nucleators. However, we show here that contrary to previous assumptions, Sca2 does not contain WH2 domains. Instead, our analysis indicates that the region containing the putative WH2 domains is folded as a globular domain that cooperates with other parts of the Sca2 molecule for actin binding and nucleation.     

WHAMM links actin assembly via the Arp2/3 complex to autophagy

Macroautophagy (hereafter autophagy) is the process by which cytosolic material destined for degradation is enclosed inside a double-membrane cisterna known as the autophagosome and processed for secretion and/or recycling. This process requires a large collection of proteins that converge on certain sites of the ER membrane to generate the autophagosome membrane. Recently, it was shown that actin accumulates around autophagosome precursors and could play a role in this process, but the mechanism and role of actin polymerization in autophagy were unknown. Here, we discuss our recent finding that the nucleation-promoting factor (NPF) WHAMM recruits and activates the Arp2/3 complex for actin assembly at sites of autophagosome formation on the ER. Using high-resolution, live-cell imaging, we showed that WHAMM forms dynamic puncta on the ER that comigrate with several autophagy markers, and propels the spiral movement of these puncta by an Arp2/3 complex-dependent actin comet tail mechanism. In starved cells, WHAMM accumulates at the interface between neighboring autophagosomes, whose number and size increases with WHAMM expression. Conversely, knocking down WHAMM, inhibiting the Arp2/3 complex or interfering with actin polymerization reduces the size and number of autophagosomes. These findings establish a link between Arp2/3 complex-mediated actin assembly and autophagy.