Mechanisms that promote bacterial fitness in fungal-affected soil microhabitats

Soil represents a very heterogeneous environment for its microbiota. Among the soil inhabitants, bacteria and fungi are important organisms as they are involved in key biogeochemical cycling processes. A main energy source driving the system is formed by plants through the provision of plant-fixed (reduced) carbon to the soil, whereas soil nitrogen and phosphorus may move from the soil back to the plant. The carbonaceous compounds released form the key energy and nutrient sources for the soil microbiota. In the grossly carbon-limited soil, the emergence of plant roots and the formation of their associated mycorrhizae thus create nutritional hot spots for soil-dwelling bacteria. As there is natural (fitness) selection on bacteria in the soil, those bacteria that are best able to benefit from the hot spots have probably been selected. The purpose of this review is to examine the interactions of bacteria with soil fungi in these hot spots and to highlight the key mechanisms involved in the selection of fungal-responsive bacteria. Salient bacterial mechanisms that are involved in these interactions have emerged from this examination. Thus, the efficient acquisition for specific released nutrients, the presence of type-III secretion systems and the capacity of flagellar movement and to form a biofilm are pinpointed as key aspects of bacterial life in the mycosphere. The possible involvement of functions present on plasmid-borne genes is also interrogated

Properties of bacterial endophytes and their proposed role in plant growth

Bacterial endophytes live inside plants for at least part of their life cycle. Studies of the interaction of endophytes with their host plants and their function within their hosts are important to address the ecological relevance of endophytes. The modulation of ethylene levels in plants by bacterially produced 1-aminocyclopropane-1-carboxylate deaminase is a key trait that enables interference with the physiology of the host plant. Endophytes with this capacity might profit from association with the plant, because colonization is enhanced. In turn, host plants benefit by stress reduction and increased root growth. This mechanism leads to the concept of 'competent' endophytes, defined as endophytes that are equipped with genes important for maintenance of plant-endophyte associations. The ecological role of these endophytes and their relevance for plant growth are discussed here.</p

Genetic diversity of bacterial wilt caused by <i>Ralstonia solanacearum</i> as assessed by PCR

The current research was conducted to investigate genetic diversity of Ralstonia solanacearum for comparison of different strains that were collected mainly from Netherlands as well as from Bangladesh, Brazil, Kenya, Egypt, Pakistan and Palma. Forty six strains were included in contemporary studies whereas main biovars for these strains included biovar-2 except GMI1000 that belonged to biovar 3. Genetic diversity of bacterial wilt disease caused by R. solancearum was assessed by focusing mainly on three genes i.e. mutL, cbhA and dps. All the genes seem to be conserved but in case of mutL some strains showed divergence. Multi Locus Sequence Typing (MLST) scheme was used in this contemporary research. It was concluded that polymerized chain reaction (PCR) is the most imperative and appropriate modern tool of molecular biology to find genetic diversity in Ralstonia solanacearum causing bacterial wilt

Modulation of the Effects of Lung Immune Response on Bone Marrow by Oral Antigen Exposure

Allergic airway inflammation is attenuated by oral tolerization (oral exposure to allergen, followed by conventional sensitization and challenge with homologous antigen), which decreases airway allergen challenge-induced eosinophilic infiltration of the lungs and bone marrow eosinophilia. We examined its effects on bone marrow eosinophil and neutrophil production. Mice of wild type (BP-2, BALB/c, and C57BL/6) and mutant strains (lacking iNOS or CD95L) were given ovalbumin (OVA) or water (vehicle) orally and subsequently sensitized and challenged with OVA (OVA/OVA/OVA and H2O/OVA/OVA groups, resp.). Anti-OVA IgG and IgE, bone marrow eosinophil and neutrophil numbers, and eosinophil and neutrophil production ex vivo were evaluated. T lymphocytes from OVA/OVA/OVA or control H2O/OVA/OVA donors were transferred into naïve syngeneic recipients, which were subsequently sensitized/challenged with OVA. Alternatively, T lymphocytes were cocultured with bone marrow eosinophil precursors from histocompatible sensitized/challenged mice. OVA/OVA/OVA mice of the BP-2 and BALB/c strains showed, relative to H2O/OVA/OVA controls, significantly decreased bone marrow eosinophil counts and ex vivo eosinopoiesis/neutropoiesis. Full effectiveness in vivo required sequential oral/subcutaneous/intranasal exposures to the same allergen. Transfer of splenic T lymphocytes from OVA/OVA/OVA donors to naive recipients prevented bone marrow eosinophilia and eosinopoiesis in response to recipient sensitization/challenge and supressed eosinopoiesis upon coculture with syngeneic bone marrow precursors from sensitized/challenged donors

Avaliação do possível impacto de milho geneticamente modificado na ciclagem do nitrogênio em solo de Cerrado.

Fertbio 2012

ras Oncogene Activation Does Not Induce Sensitivity to Natural Killer Cell&mdash;Mediated Lysis in Human Melanoma

An important phenomenon in tumor immunology that has come under recent attention is the impact of oncogene activation in tumor cells on the sensitivity to lysis by immune effector cells. Several studies suggested that transfer of an activated ras oncogene into cultured rodent fibroblasts induces susceptibility to natural killer cell (NK)-mediated lysis. Experiments using human tumor cells, however, have produced conflicting data on the effect of ras activation in this respect. In studying the activation of the oncogene c-myc, which is often overexpressed in human melanoma, we have found that in cell lines expressing high levels of Myc protein, the sensitivity to lysis by NK cells was dramatically increased due to reduced expression of Human Leukocyte Antigen B locus products. Since the N-ras oncogene was found to be activated in 15% of human melanomas, we examined the possibility that in melanoma, in analogy to the murine systems, the mutated ras oncogene may influence NK susceptibility of human melanoma cells. Two N-ras genes harboring frequently found mutations were cloned into an expression vector. Transfection of the IGR39D melanoma cell line with wildtype and mutant N-ras constructs yielded several ras-expressing clones that were tested for NK sensitivity. Neither high expression of the wildtype N-ras protein, nor expression of two mutant proteins (N61-arg, N61-lys) was shown to result in enhanced NK-mediated lysis. We conclude that activation of ras oncogenes does not lead to the induction of an NK-sensitive phenotype in human melanoma cells. J Invest Dermatol 103:117S&ndash;121S, 199

PCR-based detection of mobile genetic elements in total community DNA

A

Understanding signaling cascades in melanoma

Understanding regulatory pathways involved in melanoma development and progression has advanced significantly in recent years. It is now appreciated that melanoma is the result of complex changes in multiple signaling pathways that affect growth control, metabolism, motility and the ability to escape cell death programs. Here we review the major signaling pathways currently known to be deregulated in melanoma with an implication to its development and progression. Among these pathways are Ras, B-Raf, MEK, PTEN, phosphatidylinositol-3 kinase (PI3Ks) and Akt which are constitutively activated in a significant number of melanoma tumors, in most cases due to genomic change. Other pathways discussed in this review include the [Janus kinase/signal transducer and activator of transcription (JAK/STAT), transforming growth factor-beta pathways which are also activated in melanoma, although the underlying mechanism is not yet clear. As a paradigm for remodeled signaling pathways, melanoma also offers a unique opportunity for targeted drug development.Fil: Lopez Bergami, Pablo Roberto. Sanford-burnham Medical Research Institute; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; ArgentinaFil: Fitchmann, B. Sanford-burnham Medical Research Institute; Estados UnidosFil: Ronai, Ze´ev. Sanford-burnham Medical Research Institute; Estados Unido

Modulation of the Effects of Lung Immune Response on Bone Marrow by Oral Antigen Exposure

Allergic airway inflammation is attenuated by oral tolerization (oral exposure to allergen, followed by conventional sensitization and challenge with homologous antigen), which decreases airway allergen challenge-induced eosinophilic infiltration of the lungs and bone marrow eosinophilia. We examined its effects on bone marrow eosinophil and neutrophil production. Mice of wild type (BP-2, BALB/c, and C57BL/6) and mutant strains (lacking iNOS or CD95L) were given ovalbumin (OVA) or water (vehicle) orally and subsequently sensitized and challenged with OVA (OVA/OVA/OVA and H(2)O/OVA/OVA groups, resp.). Anti-OVA IgG and IgE, bone marrow eosinophil and neutrophil numbers, and eosinophil and neutrophil production ex vivo were evaluated. T lymphocytes from OVA/OVA/OVA or control H(2)O/OVA/OVA donors were transferred into naïve syngeneic recipients, which were subsequently sensitized/challenged with OVA. Alternatively, T lymphocytes were cocultured with bone marrow eosinophil precursors from histocompatible sensitized/challenged mice. OVA/OVA/OVA mice of the BP-2 and BALB/c strains showed, relative to H(2)O/OVA/OVA controls, significantly decreased bone marrow eosinophil counts and ex vivo eosinopoiesis/neutropoiesis. Full effectiveness in vivo required sequential oral/subcutaneous/intranasal exposures to the same allergen. Transfer of splenic T lymphocytes from OVA/OVA/OVA donors to naive recipients prevented bone marrow eosinophilia and eosinopoiesis in response to recipient sensitization/challenge and supressed eosinopoiesis upon coculture with syngeneic bone marrow precursors from sensitized/challenged donors