Identification of Motifs of <em>Burkholderia pseudomallei</em> BimA Required for Intracellular Motility, Actin Binding, and Actin Polymerization

Actin-based motility of the melioidosis pathogen Burkholderia pseudomallei requires BimA (Burkholderia intracellular motility A). The mechanism by which BimA mediates actin assembly at the bacterial pole is ill-defined. Toward an understanding of the regions of B. pseudomallei BimA required for intracellular motility and the binding and polymerization of actin, we constructed plasmid-borne bimA variants and glutathione-S-transferase fusion proteins with in-frame deletions of specific motifs. A 13-amino-acid direct repeat and IP(7) proline-rich motif were dispensable for actin binding and assembly in vitro, and expression of the mutated proteins in a B. pseudomallei bimA mutant restored actin-based motility in J774.2 murine macrophage-like cells. However, two WASP homology 2 (WH2) domains were found to be required for actin binding, actin assembly, and plaque formation. A tract of five PDASX direct repeats influenced the polymerization of pyrene-actin monomers in vitro and was required for actin-based motility and intercellular spread, but not actin binding. None of the mutations impaired surface expression or polar targeting of BimA. The number of PDASX repeats varied in natural isolates from two to seven. Such repeats acted additively to promote pyrene-actin polymerization in vitro, with stepwise increases in the rate of polymerization as the number of repeats was increased. No differences in the efficiency of actin tail formation could be discerned between strains expressing BimA variants with two, five, or seven PDASX repeats. The data provide valuable new insights into the role of conserved and variable motifs of BimA in actin-based motility and intercellular spread of B. pseudomallei

Adesão voluntária e comportamento ambiental de empresas transnacionais do setor químico no Brasil Self commitment and environmental behavior of transnational enterprises within the chemical sector in Brazil

Empresas transnacionais estão cada vez mais aderindo a padrões ambientais de conduta. Este artigo aborda as diversas facetas da auto-regulação empresarial em países em desenvolvimento:Ela compensa lacunas na legislação da poluição industrial ou é propaganda enganosa? Um estudo de caso de empresas químicas alemãs no Brasil pesquisa os determinantes de seu comportamento ambiental e aponta para dilemas dos códigos de conduta.<br>Transnational enterprises are increasingly committing theirselves to environmental standards. This article focuses on the multiple aspects of self-regulation in developing countries: Do they counterbalance a lack of legislation or are they greenwashing? A case study about German chemical industries in Brazil asks for the determinants of environmental behavior and point out dilemmas related to industrial codes of conduct