Planktonic versus benthic foraminifera response to Milankovitch forcing (Late Jurassic,Betic Cordillera): testing methods for cyclostratigraphic analysis

Foraminiferal assemblages from the Bifurcatus Zone (Oxfordian, Upper Jurassic) are studied in the Navalperal section (Betic Cordillera, southern Spain). A total of 24 sampling stations and around 5,700 specimens of foraminifera were recognized on thin-section analysis and classified into two major categories: planktonic and benthic. The abundance of foraminifera (number of specimens/cm²) was calculated for both categories and the cyclic pattern was studied by spectral analysis, considering the autochthonous and para-autochthonous character of the studied assemblages. The Lomb-Scargle periodogram together with a permutation test were tested for performing the high-resolution spectral analysis, being particularly well suited for working with short time series and uneven sampling. Spectral analysis reveals the influence of orbital-scale Milankovitch cyclicity at the eccentricity, obliquity, and precession bands. Moreover, this incidence is significantly different depending on the analyzed group (benthic versus planktonic). Whereas the long-range eccentricity band is not distinguishable from a trend and the short-range eccentricity band is not statistically significant (at 90% confidence level), the obliquity band is better represented in the planktonic component and the precession band is better developed in the benthic group. Variations in temperature affecting upper waters, determined by obliquity-scale fluctuations, could be responsible for changes in the planktonic foraminiferal assemblage, while changes in nutrient availability and substrate oxygenation, as a consequence of input variations from source areas at the precession-scale cycles, could affect the benthic foraminiferal assemblage.     

Nonlinear process modeling of fructosyltransferase (FTase) using bootstrap re-sampling neural network model

Recently, the increased demand of fructooligosaccharides (FOS) as a functional food has alarmed researchers to screen and identify new strains capable of producing fructosyltransferase (FTase). FTase is the enzyme that converts the substrate (sucrose) to glucose and fructose. The characterization of complex sugar such as table sugar, brown sugar, molasses, etc. will be carried out and the sugar that contained the highest sucrose concentration will be selected as a substrate. Eight species of macro-fungi will be screened for its ability to produce FTase and only one strain with the highest FTase activity will be selected for further studies. In this work, neural networks (NN) have been chosen to model the process based on their excellent ‘resume’ in coping with nonlinear process. Bootstrap re-sampling method has been utilized in re-sampling the data in this work. This method has successfully modeled the process as shown in the results.     

Evolving thermostability in mutant libraries of ligninolytic oxidoreductases expressed in yeast

Background  

In the picture of a laboratory evolution experiment, to improve the thermostability whilst maintaining the activity requires of suitable procedures to generate diversity in combination with robust high-throughput protocols. The current work describes how to achieve this goal by engineering ligninolytic oxidoreductases (a high-redox potential laccase -HRPL- and a versatile peroxidase, -VP-) functionally expressed in Saccharomyces cerevisiae.     

Proteomic analysis revealed the biofilm-degradation abilities of the bacteriophage UPMK_1 and UPMK_2 against Methicillin-resistant Staphylococcus aureus

Biotechnology Letters - The degradation activity of two bacteriophages UPMK_1 and UPMK_2 against methicillin-resistant Staphylococcus aureus phages were examined using gel...     

Rab27a controls HIV-1 assembly by regulating plasma membrane levels of phosphatidylinositol 4,5-bisphosphate

During the late stages of the HIV-1 replication cycle, the viral polyprotein Pr55^Gag is recruited to the plasma membrane (PM), where it binds phosphatidylinositol 4,5-bisphosphate (PI(4,5)P₂) and directs HIV-1 assembly. We show that Rab27a controls the trafficking of late endosomes carrying phosphatidylinositol 4-kinase type 2 α (PI4KIIα) toward the PM of CD4⁺ T cells. Hence, Rab27a promotes high levels of PM phosphatidylinositol 4-phosphate and the localized production of PI(4,5)P₂, therefore controlling Pr55^Gag membrane association. Rab27a also controls PI(4,5)P₂ levels at the virus-containing compartments of macrophages. By screening Rab27a effectors, we identified that Slp2a, Slp3, and Slac2b are required for the association of Pr55^Gag with the PM and that Slp2a cooperates with Rab27a in the recruitment of PI4KIIα to the PM. We conclude that by directing the trafficking of PI4KIIα-positive endosomes toward the PM, Rab27a controls PI(4,5)P₂ production and, consequently, HIV-1 replication.     

ADP Ribosylation Factor 6 (ARF6) Promotes Acrosomal Exocytosis by Modulating Lipid Turnover and Rab3A Activation

Regulated secretion is a central issue for the specific function of many cells; for instance, mammalian sperm acrosomal exocytosis is essential for egg fertilization. ARF6 (ADP-ribosylation factor 6) is a small GTPase implicated in exocytosis, but its downstream effectors remain elusive in this process. We combined biochemical, functional, and microscopy-based methods to show that ARF6 is present in human sperm, localizes to the acrosomal region, and is required for calcium and diacylglycerol-induced exocytosis. Results from pulldown assays show that ARF6 exchanges GDP for GTP in sperm challenged with different exocytic stimuli. Myristoylated and guanosine 5′-3-O-(thio)triphosphate (GTPγS)-loaded ARF6 (active form) added to permeabilized sperm induces acrosome exocytosis even in the absence of extracellular calcium. We explore the ARF6 signaling cascade that promotes secretion. We demonstrate that ARF6 stimulates a sperm phospholipase D activity to produce phosphatidic acid and boosts the synthesis of phosphatidylinositol 4,5-bisphosphate. We present direct evidence showing that active ARF6 increases phospholipase C activity, causing phosphatidylinositol 4,5-bisphosphate hydrolysis and inositol 1,4,5-trisphosphate-dependent intra-acrosomal calcium release. We show that active ARF6 increases the exchange of GDP for GTP on Rab3A, a prerequisite for secretion. We propose that exocytic stimuli activate ARF6, which is required for acrosomal calcium efflux and the assembly of the membrane fusion machinery. This report highlights the physiological importance of ARF6 as a key factor for human sperm exocytosis and fertilization.