Comparative growth,cross stress resistance,transcriptomics of Streptococcus pyogenes cultured under low shear modeled microgravity and normal gravity

Streptococcus pyogenes is commonly found on pharynx, mouth and rarely on skin, lower gastrointestinal tract. It is a potential pathogen causing tonsillitis, pneumonia, endocarditis. The present study was undertaken to study the effects of low shear modeled microgravity on growth, morphology, antibiotic resistance, cross-stress resistance to various stresses and alteration in gene expression of S. pyogenes. The growth analysis performed using UV–Visible spectroscopy indicated decrease in growth of S. pyogenes under low shear modeled microgravity. Morphological analysis by Bio-transmission electron microscopy (TEM), Bio-scanning electron microscopy (SEM) did not reveal much difference between normal and low shear modeled microgravity grown S. pyogenes. The sensitivity of S. pyogenes to antibiotics ampicillin, penicillin, streptomycin, kanamycin, hygromycin, rifampicin indicates that the bacterium is resistant to hygromycin. Further S. pyogenes cultured under low shear modeled microgravity was found to be more sensitive to ampicillin and rifampicin as compared with normal gravity grown S. pyogenes. The bacteria were tested for the acid, osmotic, temperature and oxidative cross stress resistances. The gene expression of S. pyogenes under low shear modeled microgravity analyzed by microarray revealed upregulation of 26 genes and down regulation of 22 genes by a fold change of 1.5.     

Probing the U-Shaped Conformation of Caveolin-1 in a Bilayer

Caveolin induces membrane curvature and drives the formation of caveolae that participate in many crucial cell functions such as endocytosis. The central portion of caveolin-1 contains two helices (H1 and H2) connected by a three-residue break with both N- and C-termini exposed to the cytoplasm. Although a U-shaped configuration is assumed based on its inaccessibility by extracellular matrix probes, caveolin structure in a bilayer remains elusive. This work aims to characterize the structure and dynamics of caveolin-1 (D82–S136; Cav1_82–136) in a DMPC bilayer using NMR, fluorescence emission measurements, and molecular dynamics simulations. The secondary structure of Cav1_82–136 from NMR chemical shift indexing analysis serves as a guideline for generating initial structural models. Fifty independent molecular dynamics simulations (100 ns each) are performed to identify its favorable conformation and orientation in the bilayer. A representative configuration was chosen from these multiple simulations and simulated for 1 μs to further explore its stability and dynamics. The results of these simulations mirror those from the tryptophan fluorescence measurements (i.e., Cav1_82–136 insertion depth in the bilayer), corroborate that Cav1_82–136 inserts in the membrane with U-shaped conformations, and show that the angle between H1 and H2 ranges from 35 to 69°, and the tilt angle of Cav1_82–136 is 27 ± 6°. The simulations also reveal that specific faces of H1 and H2 prefer to interact with each other and with lipid molecules, and these interactions stabilize the U-shaped conformation.     

Moths use multimodal sensory information to adopt adaptive resting orientations

Camouflage conceals animals from predators and depends on the interplay between the morphology and behaviour of animals. Behavioural elements of animals, such as the choice of a resting spot or posture, are important for effective camouflage, as well as the animals’ cryptic appearance. To date, the type of sensory input that mediates resting site choice remains poorly understood. Previously, we showed that bark‐like moths perceive and rely on bark structure to seek out cryptic resting positions and body orientations on tree trunks. In the present study, we investigated the sensory organs through which moths perceive the structure of bark when positioning their bodies in adaptive resting orientations. We amputated (or blocked) each one of the hypothetical sensory organs in moths (antennae, forelegs, wings, and eyes) and tested whether they were still able to perceive bark structure properly and adopt adaptive resting orientations. We found that visual information or stimulation is crucial for adaptively orienting their bodies when resting and tactile information from wings may play an additional role. The present study reveals multimodal information use by moths to achieve visual camouflage and highlights the sensory mechanism that is responsible for the adaptive behaviour of cryptic insects. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 111 , 900–904.     

A Note on Sire Evaluation with Uncertain Paternity

We consider sire evaluation for situations in which paternity is uncertain. We show how mixed models equations can be used to obtain the best linear unbiased predictors for sire evaluation in such situations.     

Nrf2 Negatively Regulates Melanogenesis by Modulating PI3K/Akt Signaling

Nrf2 plays a role in protection of cells against oxidative stress and xenobiotic damage by regulating cytoprotective genes. In this study, we investigated the effect of Nrf2 on melanogenesis in normal human melanocytes (NHMCs). When NHMCs were transduced with a recombinant adenovirus expressing Nrf2, melanin synthesis was significantly decreased. Consistent with this result, overexpression of Nrf2 decreased the expression of tyrosinase and tyrosinase-related protein 1. The inhibitory effect of Nrf2 was reversed by overexpression of Keap1, an intracellular regulator of Nrf2. Interestingly, Nrf2 overexpression resulted in marked activation of PI3K/Akt signaling. Conversely, inhibition of PI3K activity by treatment with wortmannin reversed the depigmentary effects of Nrf2. Taken together, these results strongly suggest that Nrf2 negatively regulates melanogenesis by modulating the PI3K/Akt signaling pathway.     

RecQL4 is required for the association of Mcm10 and Ctf4 with replication origins in human cells

Though RecQL4 was shown to be essential for the initiation of DNA replication in mammalian cells, its role in initiation is poorly understood. Here, we show that RecQL4 is required for the origin binding of Mcm10 and Ctf4, and their physical interactions and association with replication origins are controlled by the concerted action of both CDK and DDK activities. Although RecQL4-dependent binding of Mcm10 and Ctf4 to chromatin can occur in the absence of pre-replicative complex, their association with replication origins requires the presence of the pre-replicative complex and CDK and DDK activities. Their association with replication origins and physical interactions are also targets of the DNA damage checkpoint pathways which prevent initiation of DNA replication at replication origins. Taken together, the RecQL4-dependent association of Mcm10 and Ctf4 with replication origins appears to be the first important step controlled by S phase promoting kinases and checkpoint pathways for the initiation of DNA replication in human cells.     

ABCG transporters export cutin precursors for the formation of the plant cuticle

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Isolation and characterization of human erythrocyte insulin receptors

The noncovalently associated 125I-insulin-receptor complex was isolated from human erythrocyte membranes after allowing 125I-insulin to interact with the membranes followed by extraction of the 125I-insulin-receptor complex with Triton X-102 or, alternatively, by complete solubilization of the membranes with sodium dodecyl sulfate (SDS), removal of SDS, and then treatment of the solubilized sample with 125I-insulin. Sepharose CL-6B column chromatography of the 125I-insulin-receptor complex obtained by both of the above procedures yielded a highly radioactive 140,000-Da complex which was dissociated into small peptides when subjected to SDS-polyacrylamide gel electrophoresis. In contrast, when the 125I-insulin-treated membrane sample was extracted with Triton X-102, purified by DEAE-Sephacel ion exchange chromatography, covalently cross-linked with disuccinimidyl suberate, and then subjected to SDS-polyacrylamide gel electrophoresis, a highly radioactive component with Mr = 53,000 was obtained. On the other hand, when the Triton X-102-solubilized membrane receptor sample was fractionated by DEAE-Sephacel ion exchange chromatography, complexed with 125I-insulin, covalently crosslinked, and then applied to a Sepharose CL-6B column, a 95,000-Da complex with high specific radioactivity was obtained. Upon SDS-polyacrylamide gel electrophoresis, the 95,000-Da complex was dissociated into a 53,000-Da component which appeared identical with that obtained from the receptor complex described above which was obtained by direct interaction of the membranes with 125I-insulin.