RESUMO
Ubiquitous bacteria from the genus Oleispira drive oil degradation in the largest environment on Earth, the cold and deep sea. Here we report the genome sequence of Oleispira antarctica and show that compared with Alcanivorax borkumensis--the paradigm of mesophilic hydrocarbonoclastic bacteria--O. antarctica has a larger genome that has witnessed massive gene-transfer events. We identify an array of alkane monooxygenases, osmoprotectants, siderophores and micronutrient-scavenging pathways. We also show that at low temperatures, the main protein-folding machine Cpn60 functions as a single heptameric barrel that uses larger proteins as substrates compared with the classical double-barrel structure observed at higher temperatures. With 11 protein crystal structures, we further report the largest set of structures from one psychrotolerant organism. The most common structural feature is an increased content of surface-exposed negatively charged residues compared to their mesophilic counterparts. Our findings are relevant in the context of microbial cold-adaptation mechanisms and the development of strategies for oil-spill mitigation in cold environments.
Assuntos
Adaptação Fisiológica/genética , Proteínas de Bactérias/química , Gammaproteobacteria/genética , Genoma Bacteriano , Chaperonas Moleculares/química , Alcanivoraceae/genética , Alcanivoraceae/metabolismo , Sequência de Aminoácidos , Proteínas de Bactérias/genética , Biodegradação Ambiental , Mapeamento Cromossômico , Temperatura Baixa , Gammaproteobacteria/classificação , Gammaproteobacteria/metabolismo , Transferência Genética Horizontal , Tamanho do Genoma , Óleos Industriais , Chaperonas Moleculares/genética , Dados de Sequência Molecular , Filogenia , Dobramento de Proteína , Salinidade , Análise de Sequência de DNARESUMO
Helicobacter pylori is a bacterial pathogen that colonizes the gastric niche of â¼ 50% of the human population worldwide and is known to cause peptic ulceration and gastric cancer. Pathology of infection strongly depends on a cag pathogenicity island (cagPAI)-encoded type IV secretion system (T4SS). Here, we aimed to identify as yet unknown bacterial factors involved in cagPAI effector function and performed a large-scale screen of an H. pylori transposon mutant library using activation of the pro-inflammatory transcription factor NF-κB in human gastric epithelial cells as a measure of T4SS function. Analysis of â¼ 3000 H. pylori mutants revealed three non-cagPAI genes that affected NF-κB nuclear translocation. Of these, the outer membrane protein HopQ from H. pylori strain P12 was essential for CagA translocation and for CagA-mediated host cell responses such as formation of the hummingbird phenotype and cell scattering. Besides that, deletion of hopQ reduced T4SS-dependent activation of NF-κB, induction of MAPK signalling and secretion of interleukin 8 (IL-8) in the host cells, but did not affect motility or the quantity of bacteria attached to host cells. Hence, we identified HopQ as a non-cagPAI-encoded cofactor of T4SS function.