Bacterial communities and nitrogen transformation genes in streambank legacy sediments and implications for biogeochemical processing

Streambank legacy sediments may be important sources of sediment and nutrients from Mid-Atlantic watersheds. However, little is known about the nutrient processing roles of microorganisms that inhabit legacy sediments, let alone their composition, diversity, and distributions. In this study, we sampled 15 streambanks at multiple depths throughout four watersheds in the Mid-Atlantic Region of the USA. High throughput sequencing of 16S ribosomal RNA genes indicated that streambank microbial community composition varied within site depth and across contemporary land uses. Collectively, the most abundant microbial taxa in legacy sediments included Acidobacteria (25–45%), Proteobacteria (15–40%), Nitrospirae (2–10%), Chloroflexi (1–5%), and Actinobacteria (1–10%). Bacterial community composition was distinct between agriculture and urban sites as well as suburban and urban sites. There was significant variation in community composition between the top (1–25%), upper-middle (26–50%), and bottom layers (76–100%) of sediments, while the relative abundances differed between layers for only Acidobacteria and Proteobacteria. Several streambank chemistry variables (metals, %TC, and %TN) had weak positive correlations with community composition. Compared to ammonia-oxidizing bacteria, nitrifying archaea were more predominant. This study provides the first insights into detailed microbial composition of legacy sediments and identifies environmental drivers for community structure and nitrogen processing. Future studies should consider exploring the role of this unique microbial environment for nutrient processing and leaching from legacy sediments and its implications for watershed water quality.

     

Sclerotium rolfsii lectin induces opposite effects on normal PBMCs and leukemic Molt-4 cells by recognising TF antigen and its variants as receptors

Glycoconjugate Journal - Sclerotium rolfsii lectin (SRL) exerts apoptotic effect against various cancer cells and an antitumor activity on mice with colon and breast cancer xenografts. The current...     

Dynamics of DNA ejection from bacteriophage

The ejection of DNA from a bacterial virus (i.e., phage) into its host cell is a biologically important example of the translocation of a macromolecular chain along its length through a membrane. The simplest mechanism for this motion is diffusion, but in the case of phage ejection a significant driving force derives from the high degree of stress to which the DNA is subjected in the viral capsid. The translocation is further sped up by the ratcheting and entropic forces associated with proteins that bind to the viral DNA in the host cell cytoplasm. We formulate a generalized diffusion equation that includes these various pushing and pulling effects and make estimates of the corresponding speedups in the overall translocation process. Stress in the capsid is the dominant factor throughout early ejection, with the pull due to binding particles taking over at later stages. Confinement effects are also investigated, in the case where the phage injects its DNA into a volume comparable to the capsid size. Our results suggest a series of in vitro experiments involving the ejection of DNA into vesicles filled with varying amounts of binding proteins from phage whose state of stress is controlled by ambient salt conditions or by tuning genome length.     

Inhibition of Mcl-1 promotes senescence in cancer cells: implications for preventing tumor growth and chemotherapy resistance

Although senescence in oncogenesis has been widely studied, little is known regarding the role of this process in chemotherapy resistance. Thus, from the standpoint of enhancing and improving cancer therapy, a better understanding of the molecular machinery involved in chemotherapy-related senescence is paramount. We show for the first time that Mcl-1, a Bcl-2 family member, plays an important role in preventing chemotherapy-induced senescence (CIS). Overexpression of Mcl-1 in p53⁺ cell lines inhibits CIS. Conversely, downregulation of Mcl-1 makes cells sensitive to CIS. Surprisingly, downregulation of Mcl-1 in p53⁻ cells restored CIS to similar levels as p53⁺ cells. In all cases where senescence can be induced, we observed increased p21 expression. Moreover, we show that the domain of Mcl-1 responsible for its antisenescent effects is distinct from that known to confer its antiapoptotic qualities. In vivo we observe that downregulation of Mcl-1 can almost retard tumor growth regardless of p53 status, while overexpression of Mcl-1 in p53⁺ cells conferred resistance to CIS and promoted tumor outgrowth. In summary, our data reveal that Mcl-1 can inhibit CIS in both a p53-dependent and -independent manner in vitro and in vivo and that this Mcl-1-mediated inhibition can enhance tumor growth in vivo.     

Rudhira/BCAS3 is a cytoskeletal protein that controls Cdc42 activation and directional cell migration during angiogenesis

Cell migration is a common cellular process in angiogenesis and tumor metastasis. Rudhira/BCAS3 (Breast Cancer Amplified Sequence 3) is a conserved protein expressed in the embryonic vasculature and malignant tumors. Here, we show for the first time that Rudhira plays an active role in directional cell migration. Rudhira depletion in endothelial cells inhibits Matrigel-induced tube formation and retards healing of wounded cell monolayers. We demonstrate that during wound healing, Rudhira rapidly re-localizes and promotes Cdc42 activation and recruitment to the leading edge of migrating cells. Rudhira deficient cells show impaired downstream signaling of Cdc42 leading to dramatic changes in actin organization and classic cell polarity defects such as loss of microtubule organizing center (MTOC) and Golgi re-orientation. Biochemical assays and co-localization studies show that Rudhira interacts with microtubules as well as intermediate filaments. Thus, Rudhira could control directional cell migration and angiogenesis by facilitating crosstalk between cytoskeletal elements.     

Triacontanol and Jasmonic Acid Differentially Modulate the Lipid Organization as Evidenced by the Fluorescent Probe Behavior and <Superscript>31</Superscript>P Nuclear Magnetic Resonance Shifts in Model Membranes

Fluorescence resonance energy transfer (FRET), time-resolved fluorescence and anisotropy decays were determined in large unilamellar vesicles (LUVs) of egg phosphatidylcholine with the FRET pair N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)-1,2-dipalmitoyl-sn-glycero-3-phospho-ethanolamine as donor and lissamine rhodamine B 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine as acceptor, using 2-ps pulses from a Ti:sapphire laser on LUVs with incorporated plant growth regulators: triacontanol (TRIA) and jasmonic acid (JA). FRET efficiency, energy transfer rate, rotation correlation time, microviscosity, and diffusion coefficient of lateral diffusion of lipids were calculated from these results. It was observed that TRIA and JA differentially modulated all parameters studied. The effect of JA in such modulations was always partially reversed by TRIA. Also, the generalized polarization of laurdan fluorescence indicated that JA enhances the degree of hydration in lipid bilayers to a larger extent than does TRIA. Solid-state ³¹P magic-angle spinning nuclear magnetic resonance spectra of LUVs showed two chemical shifts, at 0.009 and −11.988 ppm, at low temperatures (20°C), while at increasing temperatures (20–60°C) only one (at −11.988 ppm) was prominent and the other (0.009 ppm) gradually became obscure. However, LUVs with TRIA exhibited only one of the shifts at 0.353 ppm even at lower temperatures and JA did not affect the chemical shifts. An erratum to this article can be found at     

Wip1 phosphatase modulates ATM-dependent signaling pathways

Deletion of Ppm1d, the gene encoding the Wip1 phosphatase, renders cells resistant to transformation and mice resistant to tumor development. Here, we report that deficiency of Wip1 resulted in activation of the ataxia-telangiectasia mutated (ATM) kinase. In turn, overexpression of Wip1 was sufficient to reduce activation of the ATM-dependent signaling cascade after DNA damage. Wip1 dephosphorylated ATM Ser1981, a site critical for ATM monomerization and activation, and was critical for resetting ATM phosphorylation as cells repaired damaged DNA. We propose that the Wip1 phosphatase is an integral component of an ATM-dependent signaling pathway.     

Macromolecular uptake in Drosophila pericardial cells requires rudhira function

The vertebrate reticuloendothelial system (RES) functions to remove potentially damaging macromolecules, such as excess hormones, immune-peptides and -complexes, bacterial-endotoxins, microorganisms and tumor cells. Insect hemocytes and nephrocytes - which include pericardial cells (PCs) and garland cells - are thought to be functionally equivalent to the RES. Although the ability of both vertebrate scavenger endothelial cells (SECs) and PCs to sequester colloidal and soluble macromolecules has been demonstrated the molecular mechanism of this function remains to be investigated. We report here the functional characterization of Drosophila larval PCs with important insights into their cellular uptake pathways. We demonstrate the nephrocyte function of PCs in live animals. We also develop and use live-cell assays to show that PCs take up soluble macromolecules in a Dynamin-dependent manner and colloids by a Dynamin-independent pathway. We had earlier identified Drosophila rudhira (Drudh) as a specific marker for PCs. Using RNAi mediated knock-down we show that Drudh regulates macropinocytic uptake in PCs. Our study establishes important functions for Drosophila PCs, describes methods to identify and study them, provides a genetic handle for further investigation of their role in maintaining homeostasis and demonstrates that they perform key subsets of the roles played by the vertebrate RES.