Bacteriohopanepolyols along redox gradients in the Humboldt Current System off northern Chile

Marine oxygen minimum zones (OMZs) are characterized by the presence of subsurface suboxic or anoxic waters where diverse microbial processes are responsible for the removal of fixed nitrogen. OMZs have expanded over past decades and are expected to continue expanding in response to the changing climate. The implications for marine biogeochemistry, particularly nitrogen cycling, are uncertain. Cell membrane lipids (biomarkers), such as bacterial bacteriohopanepolyols (BHPs) and their degradation products (hopanoids), have distinctive structural attributes that convey information about their biological sources. Since the discovery of fossil hopanoids in ancient sediments, the study of BHPs has been of great biogeochemical interest due to their potential to serve as proxies for bacteria in the geological record. A stereoisomer of bacteriohopanetetrol (BHT), BHT II, has been previously identified in OMZ waters and has as been unequivocally identified in culture enrichments of anammox bacteria, a key group contributing to nitrogen loss in marine OMZs. We tested BHT II as a proxy for suboxia/anoxia and anammox bacteria in suspended organic matter across OMZ waters of the Humboldt Current System off northern Chile, as well as in surface and deeply buried sediments (125–150 ky). The BHT II ratio (BHT II/total BHT) increases as oxygen content decreases through the water column, consistent with previous results from Perú, the Cariaco Basin and the Arabian Sea, and in line with microbiological evidence indicating intense anammox activity in the Chilean OMZ. Notably, BHT II is transported from the water column to surface sediments, and preserved in deeply buried sediments, where the BHT II ratio correlates with changes in δ¹⁵N sediment values during glacial–interglacial transitions. This study suggests that BHT II offers a proxy for past changes in the relative importance of anammox, and fluctuations in nitrogen cycling in response to ocean redox changes through the geological record.     

Ser123 Is Essential for the Water Channel Activity of McPIP2;1 from Mesembryanthemum crystallinum

The increased expression of McPIP2;1 (MipC), a root-specific aquaporin (AQP) from Mesembryanthemum crystallinum, under salt stress has suggested a role for this AQP in the salt tolerance of the plant. However, whether McPIP2;1 transports water or another solute and how its activity is regulated are so far unknown. Therefore, wild type (wt) or mutated McPIP2;1 protein was expressed in Xenopus laevis oocytes. Then, the osmotic water permeability (P_f) of the oocytes membrane was assessed by hypotonic challenges. Selectivity of McPIP2;1 to water was determined by radiolabeled glycerol or urea uptake assays. Moreover, swelling and in vitro phosphorylation assays revealed that both water permeation and phosphorylation status of McPIP2;1 were significantly increased by the phosphorylation agonists okadaic acid (OA), phorbol myristate acetate (PMA), and 8-Br-cAMP, and markedly decreased by the inhibitory peptides PKI 14-22 and PKC 20-28, inhibitors of protein kinases A (PKA) and C (PKC), respectively. Substitution of Ser¹²³ or both, Ser¹²³ and Ser²⁸², abolished the water channel activity of McPIP2;1 while substitution of Ser²⁸² only partially inhibited it (51.9% inhibition). Despite lacking Ser¹²³ and/or Ser²⁸², the McPIP2;1 mutant forms were still phosphorylated in vitro, which suggests that phosphorylation may have a dual role on this AQP. Our results indicate that McPIP2;1 water permeability depends completely on Ser¹²³ and is positively regulated by PKA- and PKC-mediated phosphorylation. Regulation of the phosphorylation status of McPIP2;1 may contribute to control water transport through root cells when the plant is subjected to high salinity conditions.     

Ultrastructural and sequence characterization of Penaeus vannamei nodavirus (PvNV) from Belize

The Penaeus vannamei nodavirus (PvNV), which causes muscle necrosis in Penaeus vannamei from Belize, was identified in 2005. Infected shrimp show clinical signs of white, opaque lesions in the tail muscle. Under transmission electron microscopy, the infected cells exhibit increases in various organelles, including mitochondria, Golgi stacks, and rough endoplasmic reticulum. Cytoplasmic inclusions containing para-crystalline arrays of virions were visualized. The viral particle is spherical in shape and 19 to 27 nm in diameter. A cDNA library was constructed from total RNA extracted from infected shrimp. Through nucleotide sequencing from the cDNA clones and northern blot hybridization, the PvNV genome was shown to consist of 2 segments: RNA1 (3111 bp) and RNA2 (1183 bp). RNA1 contains 2 overlapped open reading frames (ORF A and B), which may encode a RNA-dependent RNA polymerase (RdRp) and a B2 protein, respectively. RNA2 contains a single ORF that may encode the viral capsid protein. Sequence analyses showed the presence of 4 RdRp characteristic motifs and 2 conserved domains (RNA-binding B2 protein and viral coat protein) in the PvNV genome. Phylogenetic analysis based on the translated amino acid sequence of the RdRp reveals that PvNV is a member of the genus Alphanodavirus and closely related to Macrobrachium rosenbergii nodavirus (MrNV). In a study investigating potential PvNV vectors, we monitored the presence of PvNV by RT-PCR in seabird feces and various aquatic organisms collected around a shrimp farm in Belize. PvNV was detected in mosquitofish, seabird feces, barnacles, and zooplankton, suggesting that PvNV can be spread via these carriers.     

Characterization of Vacuolar Malate and K Channels under Physiological Conditions

Patch-clamp techniques were employed to study the electrical properties of vacuoles from sugar beet (Beta vulgaris) cell suspensions at physiological concentrations of cytoplasmic Ca²⁺. Vacuoles exposed to K⁺ malate revealed the activation of instantaneous and time-dependent outward currents by positive membrane potentials. Negative potentials induced only instantaneous inward currents. The time-dependent outward currents were 10 times more selective for malate than for K⁺ and were completely blocked by zinc. Vacuoles exposed to KCl developed instantaneous currents when polarized to positive or negative membrane potentials. The time-dependent outward channels could serve as the route for the movement of malate into the vacuole, whereas K⁺ could move through the time-independent inward and outward channels.     

Neuroinflammation and galectins: a key relationship in neurodegenerative diseases

Glycoconjugate Journal - Neurodegeneration is a pathological condition that is associated with the loss of neuronal function and structure. In neurodegenerative diseases, mounting evidence...     

Anti-inflammatory and anti-necrotic effects of lectins from Canavalia ensiformis and Canavalia brasiliensis in experimental acute pancreatitis

Glycoconjugate Journal - Lectins isolated from Canavalia ensiformis (ConA) and Canavalia brasiliensis (ConBr) are promising molecules to prevent cell death. Acute pancreatitis, characterized by...